jrtechs-vis/vis.js

/**
 * vis.js
 * https://github.com/almende/vis
 *
 * A dynamic, browser-based visualization library.
 *
 * @version 0.3.0-SNAPSHOT
 * @date    2014-01-03
 *
 * @license
 * Copyright (C) 2011-2013 Almende B.V, http://almende.com
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy
 * of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
(function(e){if("function"==typeof bootstrap)bootstrap("vis",e);else if("object"==typeof exports)module.exports=e();else if("function"==typeof define&&define.amd)define(e);else if("undefined"!=typeof ses){if(!ses.ok())return;ses.makeVis=e}else"undefined"!=typeof window?window.vis=e():global.vis=e()})(function(){var define,ses,bootstrap,module,exports;
return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);throw new Error("Cannot find module '"+o+"'")}var f=n[o]={exports:{}};t[o][0].call(f.exports,function(e){var n=t[o][1][e];return s(n?n:e)},f,f.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
/*! Hammer.JS - v1.0.5 - 2013-04-07
 * http://eightmedia.github.com/hammer.js
 *
 * Copyright (c) 2013 Jorik Tangelder <j.tangelder@gmail.com>;
 * Licensed under the MIT license */

(function(window, undefined) {
    'use strict';

/**
 * Hammer
 * use this to create instances
 * @param   {HTMLElement}   element
 * @param   {Object}        options
 * @returns {Hammer.Instance}
 * @constructor
 */
var Hammer = function(element, options) {
    return new Hammer.Instance(element, options || {});
};

// default settings
Hammer.defaults = {
    // add styles and attributes to the element to prevent the browser from doing
    // its native behavior. this doesnt prevent the scrolling, but cancels
    // the contextmenu, tap highlighting etc
    // set to false to disable this
    stop_browser_behavior: {
		// this also triggers onselectstart=false for IE
        userSelect: 'none',
		// this makes the element blocking in IE10 >, you could experiment with the value
		// see for more options this issue; https://github.com/EightMedia/hammer.js/issues/241
        touchAction: 'none',
		touchCallout: 'none',
        contentZooming: 'none',
        userDrag: 'none',
        tapHighlightColor: 'rgba(0,0,0,0)'
    }

    // more settings are defined per gesture at gestures.js
};

// detect touchevents
Hammer.HAS_POINTEREVENTS = navigator.pointerEnabled || navigator.msPointerEnabled;
Hammer.HAS_TOUCHEVENTS = ('ontouchstart' in window);

// dont use mouseevents on mobile devices
Hammer.MOBILE_REGEX = /mobile|tablet|ip(ad|hone|od)|android/i;
Hammer.NO_MOUSEEVENTS = Hammer.HAS_TOUCHEVENTS && navigator.userAgent.match(Hammer.MOBILE_REGEX);

// eventtypes per touchevent (start, move, end)
// are filled by Hammer.event.determineEventTypes on setup
Hammer.EVENT_TYPES = {};

// direction defines
Hammer.DIRECTION_DOWN = 'down';
Hammer.DIRECTION_LEFT = 'left';
Hammer.DIRECTION_UP = 'up';
Hammer.DIRECTION_RIGHT = 'right';

// pointer type
Hammer.POINTER_MOUSE = 'mouse';
Hammer.POINTER_TOUCH = 'touch';
Hammer.POINTER_PEN = 'pen';

// touch event defines
Hammer.EVENT_START = 'start';
Hammer.EVENT_MOVE = 'move';
Hammer.EVENT_END = 'end';

// hammer document where the base events are added at
Hammer.DOCUMENT = document;

// plugins namespace
Hammer.plugins = {};

// if the window events are set...
Hammer.READY = false;

/**
 * setup events to detect gestures on the document
 */
function setup() {
    if(Hammer.READY) {
        return;
    }

    // find what eventtypes we add listeners to
    Hammer.event.determineEventTypes();

    // Register all gestures inside Hammer.gestures
    for(var name in Hammer.gestures) {
        if(Hammer.gestures.hasOwnProperty(name)) {
            Hammer.detection.register(Hammer.gestures[name]);
        }
    }

    // Add touch events on the document
    Hammer.event.onTouch(Hammer.DOCUMENT, Hammer.EVENT_MOVE, Hammer.detection.detect);
    Hammer.event.onTouch(Hammer.DOCUMENT, Hammer.EVENT_END, Hammer.detection.detect);

    // Hammer is ready...!
    Hammer.READY = true;
}

/**
 * create new hammer instance
 * all methods should return the instance itself, so it is chainable.
 * @param   {HTMLElement}       element
 * @param   {Object}            [options={}]
 * @returns {Hammer.Instance}
 * @constructor
 */
Hammer.Instance = function(element, options) {
    var self = this;

    // setup HammerJS window events and register all gestures
    // this also sets up the default options
    setup();

    this.element = element;

    // start/stop detection option
    this.enabled = true;

    // merge options
    this.options = Hammer.utils.extend(
        Hammer.utils.extend({}, Hammer.defaults),
        options || {});

    // add some css to the element to prevent the browser from doing its native behavoir
    if(this.options.stop_browser_behavior) {
        Hammer.utils.stopDefaultBrowserBehavior(this.element, this.options.stop_browser_behavior);
    }

    // start detection on touchstart
    Hammer.event.onTouch(element, Hammer.EVENT_START, function(ev) {
        if(self.enabled) {
            Hammer.detection.startDetect(self, ev);
        }
    });

    // return instance
    return this;
};


Hammer.Instance.prototype = {
    /**
     * bind events to the instance
     * @param   {String}      gesture
     * @param   {Function}    handler
     * @returns {Hammer.Instance}
     */
    on: function onEvent(gesture, handler){
        var gestures = gesture.split(' ');
        for(var t=0; t<gestures.length; t++) {
            this.element.addEventListener(gestures[t], handler, false);
        }
        return this;
    },


    /**
     * unbind events to the instance
     * @param   {String}      gesture
     * @param   {Function}    handler
     * @returns {Hammer.Instance}
     */
    off: function offEvent(gesture, handler){
        var gestures = gesture.split(' ');
        for(var t=0; t<gestures.length; t++) {
            this.element.removeEventListener(gestures[t], handler, false);
        }
        return this;
    },


    /**
     * trigger gesture event
     * @param   {String}      gesture
     * @param   {Object}      eventData
     * @returns {Hammer.Instance}
     */
    trigger: function triggerEvent(gesture, eventData){
        // create DOM event
        var event = Hammer.DOCUMENT.createEvent('Event');
		event.initEvent(gesture, true, true);
		event.gesture = eventData;

        // trigger on the target if it is in the instance element,
        // this is for event delegation tricks
        var element = this.element;
        if(Hammer.utils.hasParent(eventData.target, element)) {
            element = eventData.target;
        }

        element.dispatchEvent(event);
        return this;
    },


    /**
     * enable of disable hammer.js detection
     * @param   {Boolean}   state
     * @returns {Hammer.Instance}
     */
    enable: function enable(state) {
        this.enabled = state;
        return this;
    }
};

/**
 * this holds the last move event,
 * used to fix empty touchend issue
 * see the onTouch event for an explanation
 * @type {Object}
 */
var last_move_event = null;


/**
 * when the mouse is hold down, this is true
 * @type {Boolean}
 */
var enable_detect = false;


/**
 * when touch events have been fired, this is true
 * @type {Boolean}
 */
var touch_triggered = false;


Hammer.event = {
    /**
     * simple addEventListener
     * @param   {HTMLElement}   element
     * @param   {String}        type
     * @param   {Function}      handler
     */
    bindDom: function(element, type, handler) {
        var types = type.split(' ');
        for(var t=0; t<types.length; t++) {
            element.addEventListener(types[t], handler, false);
        }
    },


    /**
     * touch events with mouse fallback
     * @param   {HTMLElement}   element
     * @param   {String}        eventType        like Hammer.EVENT_MOVE
     * @param   {Function}      handler
     */
    onTouch: function onTouch(element, eventType, handler) {
		var self = this;

        this.bindDom(element, Hammer.EVENT_TYPES[eventType], function bindDomOnTouch(ev) {
            var sourceEventType = ev.type.toLowerCase();

            // onmouseup, but when touchend has been fired we do nothing.
            // this is for touchdevices which also fire a mouseup on touchend
            if(sourceEventType.match(/mouse/) && touch_triggered) {
                return;
            }

            // mousebutton must be down or a touch event
            else if( sourceEventType.match(/touch/) ||   // touch events are always on screen
                sourceEventType.match(/pointerdown/) || // pointerevents touch
                (sourceEventType.match(/mouse/) && ev.which === 1)   // mouse is pressed
            ){
                enable_detect = true;
            }

            // we are in a touch event, set the touch triggered bool to true,
            // this for the conflicts that may occur on ios and android
            if(sourceEventType.match(/touch|pointer/)) {
                touch_triggered = true;
            }

            // count the total touches on the screen
            var count_touches = 0;

            // when touch has been triggered in this detection session
            // and we are now handling a mouse event, we stop that to prevent conflicts
            if(enable_detect) {
                // update pointerevent
                if(Hammer.HAS_POINTEREVENTS && eventType != Hammer.EVENT_END) {
                    count_touches = Hammer.PointerEvent.updatePointer(eventType, ev);
                }
                // touch
                else if(sourceEventType.match(/touch/)) {
                    count_touches = ev.touches.length;
                }
                // mouse
                else if(!touch_triggered) {
                    count_touches = sourceEventType.match(/up/) ? 0 : 1;
                }

                // if we are in a end event, but when we remove one touch and
                // we still have enough, set eventType to move
                if(count_touches > 0 && eventType == Hammer.EVENT_END) {
                    eventType = Hammer.EVENT_MOVE;
                }
                // no touches, force the end event
                else if(!count_touches) {
                    eventType = Hammer.EVENT_END;
                }

                // because touchend has no touches, and we often want to use these in our gestures,
                // we send the last move event as our eventData in touchend
                if(!count_touches && last_move_event !== null) {
                    ev = last_move_event;
                }
                // store the last move event
                else {
                    last_move_event = ev;
                }

                // trigger the handler
                handler.call(Hammer.detection, self.collectEventData(element, eventType, ev));

                // remove pointerevent from list
                if(Hammer.HAS_POINTEREVENTS && eventType == Hammer.EVENT_END) {
                    count_touches = Hammer.PointerEvent.updatePointer(eventType, ev);
                }
            }

            //debug(sourceEventType +" "+ eventType);

            // on the end we reset everything
            if(!count_touches) {
                last_move_event = null;
                enable_detect = false;
                touch_triggered = false;
                Hammer.PointerEvent.reset();
            }
        });
    },


    /**
     * we have different events for each device/browser
     * determine what we need and set them in the Hammer.EVENT_TYPES constant
     */
    determineEventTypes: function determineEventTypes() {
        // determine the eventtype we want to set
        var types;

        // pointerEvents magic
        if(Hammer.HAS_POINTEREVENTS) {
            types = Hammer.PointerEvent.getEvents();
        }
        // on Android, iOS, blackberry, windows mobile we dont want any mouseevents
        else if(Hammer.NO_MOUSEEVENTS) {
            types = [
                'touchstart',
                'touchmove',
                'touchend touchcancel'];
        }
        // for non pointer events browsers and mixed browsers,
        // like chrome on windows8 touch laptop
        else {
            types = [
                'touchstart mousedown',
                'touchmove mousemove',
                'touchend touchcancel mouseup'];
        }

        Hammer.EVENT_TYPES[Hammer.EVENT_START]  = types[0];
        Hammer.EVENT_TYPES[Hammer.EVENT_MOVE]   = types[1];
        Hammer.EVENT_TYPES[Hammer.EVENT_END]    = types[2];
    },


    /**
     * create touchlist depending on the event
     * @param   {Object}    ev
     * @param   {String}    eventType   used by the fakemultitouch plugin
     */
    getTouchList: function getTouchList(ev/*, eventType*/) {
        // get the fake pointerEvent touchlist
        if(Hammer.HAS_POINTEREVENTS) {
            return Hammer.PointerEvent.getTouchList();
        }
        // get the touchlist
        else if(ev.touches) {
            return ev.touches;
        }
        // make fake touchlist from mouse position
        else {
            return [{
                identifier: 1,
                pageX: ev.pageX,
                pageY: ev.pageY,
                target: ev.target
            }];
        }
    },


    /**
     * collect event data for Hammer js
     * @param   {HTMLElement}   element
     * @param   {String}        eventType        like Hammer.EVENT_MOVE
     * @param   {Object}        eventData
     */
    collectEventData: function collectEventData(element, eventType, ev) {
        var touches = this.getTouchList(ev, eventType);

        // find out pointerType
        var pointerType = Hammer.POINTER_TOUCH;
        if(ev.type.match(/mouse/) || Hammer.PointerEvent.matchType(Hammer.POINTER_MOUSE, ev)) {
            pointerType = Hammer.POINTER_MOUSE;
        }

        return {
            center      : Hammer.utils.getCenter(touches),
            timeStamp   : new Date().getTime(),
            target      : ev.target,
            touches     : touches,
            eventType   : eventType,
            pointerType : pointerType,
            srcEvent    : ev,

            /**
             * prevent the browser default actions
             * mostly used to disable scrolling of the browser
             */
            preventDefault: function() {
                if(this.srcEvent.preventManipulation) {
                    this.srcEvent.preventManipulation();
                }

                if(this.srcEvent.preventDefault) {
                    this.srcEvent.preventDefault();
                }
            },

            /**
             * stop bubbling the event up to its parents
             */
            stopPropagation: function() {
                this.srcEvent.stopPropagation();
            },

            /**
             * immediately stop gesture detection
             * might be useful after a swipe was detected
             * @return {*}
             */
            stopDetect: function() {
                return Hammer.detection.stopDetect();
            }
        };
    }
};

Hammer.PointerEvent = {
    /**
     * holds all pointers
     * @type {Object}
     */
    pointers: {},

    /**
     * get a list of pointers
     * @returns {Array}     touchlist
     */
    getTouchList: function() {
        var self = this;
        var touchlist = [];

        // we can use forEach since pointerEvents only is in IE10
        Object.keys(self.pointers).sort().forEach(function(id) {
            touchlist.push(self.pointers[id]);
        });
        return touchlist;
    },

    /**
     * update the position of a pointer
     * @param   {String}   type             Hammer.EVENT_END
     * @param   {Object}   pointerEvent
     */
    updatePointer: function(type, pointerEvent) {
        if(type == Hammer.EVENT_END) {
            this.pointers = {};
        }
        else {
            pointerEvent.identifier = pointerEvent.pointerId;
            this.pointers[pointerEvent.pointerId] = pointerEvent;
        }

        return Object.keys(this.pointers).length;
    },

    /**
     * check if ev matches pointertype
     * @param   {String}        pointerType     Hammer.POINTER_MOUSE
     * @param   {PointerEvent}  ev
     */
    matchType: function(pointerType, ev) {
        if(!ev.pointerType) {
            return false;
        }

        var types = {};
        types[Hammer.POINTER_MOUSE] = (ev.pointerType == ev.MSPOINTER_TYPE_MOUSE || ev.pointerType == Hammer.POINTER_MOUSE);
        types[Hammer.POINTER_TOUCH] = (ev.pointerType == ev.MSPOINTER_TYPE_TOUCH || ev.pointerType == Hammer.POINTER_TOUCH);
        types[Hammer.POINTER_PEN] = (ev.pointerType == ev.MSPOINTER_TYPE_PEN || ev.pointerType == Hammer.POINTER_PEN);
        return types[pointerType];
    },


    /**
     * get events
     */
    getEvents: function() {
        return [
            'pointerdown MSPointerDown',
            'pointermove MSPointerMove',
            'pointerup pointercancel MSPointerUp MSPointerCancel'
        ];
    },

    /**
     * reset the list
     */
    reset: function() {
        this.pointers = {};
    }
};


Hammer.utils = {
    /**
     * extend method,
     * also used for cloning when dest is an empty object
     * @param   {Object}    dest
     * @param   {Object}    src
	 * @parm	{Boolean}	merge		do a merge
     * @returns {Object}    dest
     */
    extend: function extend(dest, src, merge) {
        for (var key in src) {
			if(dest[key] !== undefined && merge) {
				continue;
			}
            dest[key] = src[key];
        }
        return dest;
    },


    /**
     * find if a node is in the given parent
     * used for event delegation tricks
     * @param   {HTMLElement}   node
     * @param   {HTMLElement}   parent
     * @returns {boolean}       has_parent
     */
    hasParent: function(node, parent) {
        while(node){
            if(node == parent) {
                return true;
            }
            node = node.parentNode;
        }
        return false;
    },


    /**
     * get the center of all the touches
     * @param   {Array}     touches
     * @returns {Object}    center
     */
    getCenter: function getCenter(touches) {
        var valuesX = [], valuesY = [];

        for(var t= 0,len=touches.length; t<len; t++) {
            valuesX.push(touches[t].pageX);
            valuesY.push(touches[t].pageY);
        }

        return {
            pageX: ((Math.min.apply(Math, valuesX) + Math.max.apply(Math, valuesX)) / 2),
            pageY: ((Math.min.apply(Math, valuesY) + Math.max.apply(Math, valuesY)) / 2)
        };
    },


    /**
     * calculate the velocity between two points
     * @param   {Number}    delta_time
     * @param   {Number}    delta_x
     * @param   {Number}    delta_y
     * @returns {Object}    velocity
     */
    getVelocity: function getVelocity(delta_time, delta_x, delta_y) {
        return {
            x: Math.abs(delta_x / delta_time) || 0,
            y: Math.abs(delta_y / delta_time) || 0
        };
    },


    /**
     * calculate the angle between two coordinates
     * @param   {Touch}     touch1
     * @param   {Touch}     touch2
     * @returns {Number}    angle
     */
    getAngle: function getAngle(touch1, touch2) {
        var y = touch2.pageY - touch1.pageY,
            x = touch2.pageX - touch1.pageX;
        return Math.atan2(y, x) * 180 / Math.PI;
    },


    /**
     * angle to direction define
     * @param   {Touch}     touch1
     * @param   {Touch}     touch2
     * @returns {String}    direction constant, like Hammer.DIRECTION_LEFT
     */
    getDirection: function getDirection(touch1, touch2) {
        var x = Math.abs(touch1.pageX - touch2.pageX),
            y = Math.abs(touch1.pageY - touch2.pageY);

        if(x >= y) {
            return touch1.pageX - touch2.pageX > 0 ? Hammer.DIRECTION_LEFT : Hammer.DIRECTION_RIGHT;
        }
        else {
            return touch1.pageY - touch2.pageY > 0 ? Hammer.DIRECTION_UP : Hammer.DIRECTION_DOWN;
        }
    },


    /**
     * calculate the distance between two touches
     * @param   {Touch}     touch1
     * @param   {Touch}     touch2
     * @returns {Number}    distance
     */
    getDistance: function getDistance(touch1, touch2) {
        var x = touch2.pageX - touch1.pageX,
            y = touch2.pageY - touch1.pageY;
        return Math.sqrt((x*x) + (y*y));
    },


    /**
     * calculate the scale factor between two touchLists (fingers)
     * no scale is 1, and goes down to 0 when pinched together, and bigger when pinched out
     * @param   {Array}     start
     * @param   {Array}     end
     * @returns {Number}    scale
     */
    getScale: function getScale(start, end) {
        // need two fingers...
        if(start.length >= 2 && end.length >= 2) {
            return this.getDistance(end[0], end[1]) /
                this.getDistance(start[0], start[1]);
        }
        return 1;
    },


    /**
     * calculate the rotation degrees between two touchLists (fingers)
     * @param   {Array}     start
     * @param   {Array}     end
     * @returns {Number}    rotation
     */
    getRotation: function getRotation(start, end) {
        // need two fingers
        if(start.length >= 2 && end.length >= 2) {
            return this.getAngle(end[1], end[0]) -
                this.getAngle(start[1], start[0]);
        }
        return 0;
    },


    /**
     * boolean if the direction is vertical
     * @param    {String}    direction
     * @returns  {Boolean}   is_vertical
     */
    isVertical: function isVertical(direction) {
        return (direction == Hammer.DIRECTION_UP || direction == Hammer.DIRECTION_DOWN);
    },


    /**
     * stop browser default behavior with css props
     * @param   {HtmlElement}   element
     * @param   {Object}        css_props
     */
    stopDefaultBrowserBehavior: function stopDefaultBrowserBehavior(element, css_props) {
        var prop,
            vendors = ['webkit','khtml','moz','ms','o',''];

        if(!css_props || !element.style) {
            return;
        }

        // with css properties for modern browsers
        for(var i = 0; i < vendors.length; i++) {
            for(var p in css_props) {
                if(css_props.hasOwnProperty(p)) {
                    prop = p;

                    // vender prefix at the property
                    if(vendors[i]) {
                        prop = vendors[i] + prop.substring(0, 1).toUpperCase() + prop.substring(1);
                    }

                    // set the style
                    element.style[prop] = css_props[p];
                }
            }
        }

        // also the disable onselectstart
        if(css_props.userSelect == 'none') {
            element.onselectstart = function() {
                return false;
            };
        }
    }
};

Hammer.detection = {
    // contains all registred Hammer.gestures in the correct order
    gestures: [],

    // data of the current Hammer.gesture detection session
    current: null,

    // the previous Hammer.gesture session data
    // is a full clone of the previous gesture.current object
    previous: null,

    // when this becomes true, no gestures are fired
    stopped: false,


    /**
     * start Hammer.gesture detection
     * @param   {Hammer.Instance}   inst
     * @param   {Object}            eventData
     */
    startDetect: function startDetect(inst, eventData) {
        // already busy with a Hammer.gesture detection on an element
        if(this.current) {
            return;
        }

        this.stopped = false;

        this.current = {
            inst        : inst, // reference to HammerInstance we're working for
            startEvent  : Hammer.utils.extend({}, eventData), // start eventData for distances, timing etc
            lastEvent   : false, // last eventData
            name        : '' // current gesture we're in/detected, can be 'tap', 'hold' etc
        };

        this.detect(eventData);
    },


    /**
     * Hammer.gesture detection
     * @param   {Object}    eventData
     * @param   {Object}    eventData
     */
    detect: function detect(eventData) {
        if(!this.current || this.stopped) {
            return;
        }

        // extend event data with calculations about scale, distance etc
        eventData = this.extendEventData(eventData);

        // instance options
        var inst_options = this.current.inst.options;

        // call Hammer.gesture handlers
        for(var g=0,len=this.gestures.length; g<len; g++) {
            var gesture = this.gestures[g];

            // only when the instance options have enabled this gesture
            if(!this.stopped && inst_options[gesture.name] !== false) {
                // if a handler returns false, we stop with the detection
                if(gesture.handler.call(gesture, eventData, this.current.inst) === false) {
                    this.stopDetect();
                    break;
                }
            }
        }

        // store as previous event event
        if(this.current) {
            this.current.lastEvent = eventData;
        }

        // endevent, but not the last touch, so dont stop
        if(eventData.eventType == Hammer.EVENT_END && !eventData.touches.length-1) {
            this.stopDetect();
        }

        return eventData;
    },


    /**
     * clear the Hammer.gesture vars
     * this is called on endDetect, but can also be used when a final Hammer.gesture has been detected
     * to stop other Hammer.gestures from being fired
     */
    stopDetect: function stopDetect() {
        // clone current data to the store as the previous gesture
        // used for the double tap gesture, since this is an other gesture detect session
        this.previous = Hammer.utils.extend({}, this.current);

        // reset the current
        this.current = null;

        // stopped!
        this.stopped = true;
    },


    /**
     * extend eventData for Hammer.gestures
     * @param   {Object}   ev
     * @returns {Object}   ev
     */
    extendEventData: function extendEventData(ev) {
        var startEv = this.current.startEvent;

        // if the touches change, set the new touches over the startEvent touches
        // this because touchevents don't have all the touches on touchstart, or the
        // user must place his fingers at the EXACT same time on the screen, which is not realistic
        // but, sometimes it happens that both fingers are touching at the EXACT same time
        if(startEv && (ev.touches.length != startEv.touches.length || ev.touches === startEv.touches)) {
            // extend 1 level deep to get the touchlist with the touch objects
            startEv.touches = [];
            for(var i=0,len=ev.touches.length; i<len; i++) {
                startEv.touches.push(Hammer.utils.extend({}, ev.touches[i]));
            }
        }

        var delta_time = ev.timeStamp - startEv.timeStamp,
            delta_x = ev.center.pageX - startEv.center.pageX,
            delta_y = ev.center.pageY - startEv.center.pageY,
            velocity = Hammer.utils.getVelocity(delta_time, delta_x, delta_y);

        Hammer.utils.extend(ev, {
            deltaTime   : delta_time,

            deltaX      : delta_x,
            deltaY      : delta_y,

            velocityX   : velocity.x,
            velocityY   : velocity.y,

            distance    : Hammer.utils.getDistance(startEv.center, ev.center),
            angle       : Hammer.utils.getAngle(startEv.center, ev.center),
            direction   : Hammer.utils.getDirection(startEv.center, ev.center),

            scale       : Hammer.utils.getScale(startEv.touches, ev.touches),
            rotation    : Hammer.utils.getRotation(startEv.touches, ev.touches),

            startEvent  : startEv
        });

        return ev;
    },


    /**
     * register new gesture
     * @param   {Object}    gesture object, see gestures.js for documentation
     * @returns {Array}     gestures
     */
    register: function register(gesture) {
        // add an enable gesture options if there is no given
        var options = gesture.defaults || {};
        if(options[gesture.name] === undefined) {
            options[gesture.name] = true;
        }

        // extend Hammer default options with the Hammer.gesture options
        Hammer.utils.extend(Hammer.defaults, options, true);

        // set its index
        gesture.index = gesture.index || 1000;

        // add Hammer.gesture to the list
        this.gestures.push(gesture);

        // sort the list by index
        this.gestures.sort(function(a, b) {
            if (a.index < b.index) {
                return -1;
            }
            if (a.index > b.index) {
                return 1;
            }
            return 0;
        });

        return this.gestures;
    }
};


Hammer.gestures = Hammer.gestures || {};

/**
 * Custom gestures
 * ==============================
 *
 * Gesture object
 * --------------------
 * The object structure of a gesture:
 *
 * { name: 'mygesture',
 *   index: 1337,
 *   defaults: {
 *     mygesture_option: true
 *   }
 *   handler: function(type, ev, inst) {
 *     // trigger gesture event
 *     inst.trigger(this.name, ev);
 *   }
 * }

 * @param   {String}    name
 * this should be the name of the gesture, lowercase
 * it is also being used to disable/enable the gesture per instance config.
 *
 * @param   {Number}    [index=1000]
 * the index of the gesture, where it is going to be in the stack of gestures detection
 * like when you build an gesture that depends on the drag gesture, it is a good
 * idea to place it after the index of the drag gesture.
 *
 * @param   {Object}    [defaults={}]
 * the default settings of the gesture. these are added to the instance settings,
 * and can be overruled per instance. you can also add the name of the gesture,
 * but this is also added by default (and set to true).
 *
 * @param   {Function}  handler
 * this handles the gesture detection of your custom gesture and receives the
 * following arguments:
 *
 *      @param  {Object}    eventData
 *      event data containing the following properties:
 *          timeStamp   {Number}        time the event occurred
 *          target      {HTMLElement}   target element
 *          touches     {Array}         touches (fingers, pointers, mouse) on the screen
 *          pointerType {String}        kind of pointer that was used. matches Hammer.POINTER_MOUSE|TOUCH
 *          center      {Object}        center position of the touches. contains pageX and pageY
 *          deltaTime   {Number}        the total time of the touches in the screen
 *          deltaX      {Number}        the delta on x axis we haved moved
 *          deltaY      {Number}        the delta on y axis we haved moved
 *          velocityX   {Number}        the velocity on the x
 *          velocityY   {Number}        the velocity on y
 *          angle       {Number}        the angle we are moving
 *          direction   {String}        the direction we are moving. matches Hammer.DIRECTION_UP|DOWN|LEFT|RIGHT
 *          distance    {Number}        the distance we haved moved
 *          scale       {Number}        scaling of the touches, needs 2 touches
 *          rotation    {Number}        rotation of the touches, needs 2 touches *
 *          eventType   {String}        matches Hammer.EVENT_START|MOVE|END
 *          srcEvent    {Object}        the source event, like TouchStart or MouseDown *
 *          startEvent  {Object}        contains the same properties as above,
 *                                      but from the first touch. this is used to calculate
 *                                      distances, deltaTime, scaling etc
 *
 *      @param  {Hammer.Instance}    inst
 *      the instance we are doing the detection for. you can get the options from
 *      the inst.options object and trigger the gesture event by calling inst.trigger
 *
 *
 * Handle gestures
 * --------------------
 * inside the handler you can get/set Hammer.detection.current. This is the current
 * detection session. It has the following properties
 *      @param  {String}    name
 *      contains the name of the gesture we have detected. it has not a real function,
 *      only to check in other gestures if something is detected.
 *      like in the drag gesture we set it to 'drag' and in the swipe gesture we can
 *      check if the current gesture is 'drag' by accessing Hammer.detection.current.name
 *
 *      @readonly
 *      @param  {Hammer.Instance}    inst
 *      the instance we do the detection for
 *
 *      @readonly
 *      @param  {Object}    startEvent
 *      contains the properties of the first gesture detection in this session.
 *      Used for calculations about timing, distance, etc.
 *
 *      @readonly
 *      @param  {Object}    lastEvent
 *      contains all the properties of the last gesture detect in this session.
 *
 * after the gesture detection session has been completed (user has released the screen)
 * the Hammer.detection.current object is copied into Hammer.detection.previous,
 * this is usefull for gestures like doubletap, where you need to know if the
 * previous gesture was a tap
 *
 * options that have been set by the instance can be received by calling inst.options
 *
 * You can trigger a gesture event by calling inst.trigger("mygesture", event).
 * The first param is the name of your gesture, the second the event argument
 *
 *
 * Register gestures
 * --------------------
 * When an gesture is added to the Hammer.gestures object, it is auto registered
 * at the setup of the first Hammer instance. You can also call Hammer.detection.register
 * manually and pass your gesture object as a param
 *
 */

/**
 * Hold
 * Touch stays at the same place for x time
 * @events  hold
 */
Hammer.gestures.Hold = {
    name: 'hold',
    index: 10,
    defaults: {
        hold_timeout	: 500,
        hold_threshold	: 1
    },
    timer: null,
    handler: function holdGesture(ev, inst) {
        switch(ev.eventType) {
            case Hammer.EVENT_START:
                // clear any running timers
                clearTimeout(this.timer);

                // set the gesture so we can check in the timeout if it still is
                Hammer.detection.current.name = this.name;

                // set timer and if after the timeout it still is hold,
                // we trigger the hold event
                this.timer = setTimeout(function() {
                    if(Hammer.detection.current.name == 'hold') {
                        inst.trigger('hold', ev);
                    }
                }, inst.options.hold_timeout);
                break;

            // when you move or end we clear the timer
            case Hammer.EVENT_MOVE:
                if(ev.distance > inst.options.hold_threshold) {
                    clearTimeout(this.timer);
                }
                break;

            case Hammer.EVENT_END:
                clearTimeout(this.timer);
                break;
        }
    }
};


/**
 * Tap/DoubleTap
 * Quick touch at a place or double at the same place
 * @events  tap, doubletap
 */
Hammer.gestures.Tap = {
    name: 'tap',
    index: 100,
    defaults: {
        tap_max_touchtime	: 250,
        tap_max_distance	: 10,
		tap_always			: true,
        doubletap_distance	: 20,
        doubletap_interval	: 300
    },
    handler: function tapGesture(ev, inst) {
        if(ev.eventType == Hammer.EVENT_END) {
            // previous gesture, for the double tap since these are two different gesture detections
            var prev = Hammer.detection.previous,
				did_doubletap = false;

            // when the touchtime is higher then the max touch time
            // or when the moving distance is too much
            if(ev.deltaTime > inst.options.tap_max_touchtime ||
                ev.distance > inst.options.tap_max_distance) {
                return;
            }

            // check if double tap
            if(prev && prev.name == 'tap' &&
                (ev.timeStamp - prev.lastEvent.timeStamp) < inst.options.doubletap_interval &&
                ev.distance < inst.options.doubletap_distance) {
				inst.trigger('doubletap', ev);
				did_doubletap = true;
            }

			// do a single tap
			if(!did_doubletap || inst.options.tap_always) {
				Hammer.detection.current.name = 'tap';
				inst.trigger(Hammer.detection.current.name, ev);
			}
        }
    }
};


/**
 * Swipe
 * triggers swipe events when the end velocity is above the threshold
 * @events  swipe, swipeleft, swiperight, swipeup, swipedown
 */
Hammer.gestures.Swipe = {
    name: 'swipe',
    index: 40,
    defaults: {
        // set 0 for unlimited, but this can conflict with transform
        swipe_max_touches  : 1,
        swipe_velocity     : 0.7
    },
    handler: function swipeGesture(ev, inst) {
        if(ev.eventType == Hammer.EVENT_END) {
            // max touches
            if(inst.options.swipe_max_touches > 0 &&
                ev.touches.length > inst.options.swipe_max_touches) {
                return;
            }

            // when the distance we moved is too small we skip this gesture
            // or we can be already in dragging
            if(ev.velocityX > inst.options.swipe_velocity ||
                ev.velocityY > inst.options.swipe_velocity) {
                // trigger swipe events
                inst.trigger(this.name, ev);
                inst.trigger(this.name + ev.direction, ev);
            }
        }
    }
};


/**
 * Drag
 * Move with x fingers (default 1) around on the page. Blocking the scrolling when
 * moving left and right is a good practice. When all the drag events are blocking
 * you disable scrolling on that area.
 * @events  drag, drapleft, dragright, dragup, dragdown
 */
Hammer.gestures.Drag = {
    name: 'drag',
    index: 50,
    defaults: {
        drag_min_distance : 10,
        // set 0 for unlimited, but this can conflict with transform
        drag_max_touches  : 1,
        // prevent default browser behavior when dragging occurs
        // be careful with it, it makes the element a blocking element
        // when you are using the drag gesture, it is a good practice to set this true
        drag_block_horizontal   : false,
        drag_block_vertical     : false,
        // drag_lock_to_axis keeps the drag gesture on the axis that it started on,
        // It disallows vertical directions if the initial direction was horizontal, and vice versa.
        drag_lock_to_axis       : false,
        // drag lock only kicks in when distance > drag_lock_min_distance
        // This way, locking occurs only when the distance has become large enough to reliably determine the direction
        drag_lock_min_distance : 25
    },
    triggered: false,
    handler: function dragGesture(ev, inst) {
        // current gesture isnt drag, but dragged is true
        // this means an other gesture is busy. now call dragend
        if(Hammer.detection.current.name != this.name && this.triggered) {
            inst.trigger(this.name +'end', ev);
            this.triggered = false;
            return;
        }

        // max touches
        if(inst.options.drag_max_touches > 0 &&
            ev.touches.length > inst.options.drag_max_touches) {
            return;
        }

        switch(ev.eventType) {
            case Hammer.EVENT_START:
                this.triggered = false;
                break;

            case Hammer.EVENT_MOVE:
                // when the distance we moved is too small we skip this gesture
                // or we can be already in dragging
                if(ev.distance < inst.options.drag_min_distance &&
                    Hammer.detection.current.name != this.name) {
                    return;
                }

                // we are dragging!
                Hammer.detection.current.name = this.name;

                // lock drag to axis?
                if(Hammer.detection.current.lastEvent.drag_locked_to_axis || (inst.options.drag_lock_to_axis && inst.options.drag_lock_min_distance<=ev.distance)) {
                    ev.drag_locked_to_axis = true;
                }
                var last_direction = Hammer.detection.current.lastEvent.direction;
                if(ev.drag_locked_to_axis && last_direction !== ev.direction) {
                    // keep direction on the axis that the drag gesture started on
                    if(Hammer.utils.isVertical(last_direction)) {
                        ev.direction = (ev.deltaY < 0) ? Hammer.DIRECTION_UP : Hammer.DIRECTION_DOWN;
                    }
                    else {
                        ev.direction = (ev.deltaX < 0) ? Hammer.DIRECTION_LEFT : Hammer.DIRECTION_RIGHT;
                    }
                }

                // first time, trigger dragstart event
                if(!this.triggered) {
                    inst.trigger(this.name +'start', ev);
                    this.triggered = true;
                }

                // trigger normal event
                inst.trigger(this.name, ev);

                // direction event, like dragdown
                inst.trigger(this.name + ev.direction, ev);

                // block the browser events
                if( (inst.options.drag_block_vertical && Hammer.utils.isVertical(ev.direction)) ||
                    (inst.options.drag_block_horizontal && !Hammer.utils.isVertical(ev.direction))) {
                    ev.preventDefault();
                }
                break;

            case Hammer.EVENT_END:
                // trigger dragend
                if(this.triggered) {
                    inst.trigger(this.name +'end', ev);
                }

                this.triggered = false;
                break;
        }
    }
};


/**
 * Transform
 * User want to scale or rotate with 2 fingers
 * @events  transform, pinch, pinchin, pinchout, rotate
 */
Hammer.gestures.Transform = {
    name: 'transform',
    index: 45,
    defaults: {
        // factor, no scale is 1, zoomin is to 0 and zoomout until higher then 1
        transform_min_scale     : 0.01,
        // rotation in degrees
        transform_min_rotation  : 1,
        // prevent default browser behavior when two touches are on the screen
        // but it makes the element a blocking element
        // when you are using the transform gesture, it is a good practice to set this true
        transform_always_block  : false
    },
    triggered: false,
    handler: function transformGesture(ev, inst) {
        // current gesture isnt drag, but dragged is true
        // this means an other gesture is busy. now call dragend
        if(Hammer.detection.current.name != this.name && this.triggered) {
            inst.trigger(this.name +'end', ev);
            this.triggered = false;
            return;
        }

        // atleast multitouch
        if(ev.touches.length < 2) {
            return;
        }

        // prevent default when two fingers are on the screen
        if(inst.options.transform_always_block) {
            ev.preventDefault();
        }

        switch(ev.eventType) {
            case Hammer.EVENT_START:
                this.triggered = false;
                break;

            case Hammer.EVENT_MOVE:
                var scale_threshold = Math.abs(1-ev.scale);
                var rotation_threshold = Math.abs(ev.rotation);

                // when the distance we moved is too small we skip this gesture
                // or we can be already in dragging
                if(scale_threshold < inst.options.transform_min_scale &&
                    rotation_threshold < inst.options.transform_min_rotation) {
                    return;
                }

                // we are transforming!
                Hammer.detection.current.name = this.name;

                // first time, trigger dragstart event
                if(!this.triggered) {
                    inst.trigger(this.name +'start', ev);
                    this.triggered = true;
                }

                inst.trigger(this.name, ev); // basic transform event

                // trigger rotate event
                if(rotation_threshold > inst.options.transform_min_rotation) {
                    inst.trigger('rotate', ev);
                }

                // trigger pinch event
                if(scale_threshold > inst.options.transform_min_scale) {
                    inst.trigger('pinch', ev);
                    inst.trigger('pinch'+ ((ev.scale < 1) ? 'in' : 'out'), ev);
                }
                break;

            case Hammer.EVENT_END:
                // trigger dragend
                if(this.triggered) {
                    inst.trigger(this.name +'end', ev);
                }

                this.triggered = false;
                break;
        }
    }
};


/**
 * Touch
 * Called as first, tells the user has touched the screen
 * @events  touch
 */
Hammer.gestures.Touch = {
    name: 'touch',
    index: -Infinity,
    defaults: {
        // call preventDefault at touchstart, and makes the element blocking by
        // disabling the scrolling of the page, but it improves gestures like
        // transforming and dragging.
        // be careful with using this, it can be very annoying for users to be stuck
        // on the page
        prevent_default: false,

        // disable mouse events, so only touch (or pen!) input triggers events
        prevent_mouseevents: false
    },
    handler: function touchGesture(ev, inst) {
        if(inst.options.prevent_mouseevents && ev.pointerType == Hammer.POINTER_MOUSE) {
            ev.stopDetect();
            return;
        }

        if(inst.options.prevent_default) {
            ev.preventDefault();
        }

        if(ev.eventType ==  Hammer.EVENT_START) {
            inst.trigger(this.name, ev);
        }
    }
};


/**
 * Release
 * Called as last, tells the user has released the screen
 * @events  release
 */
Hammer.gestures.Release = {
    name: 'release',
    index: Infinity,
    handler: function releaseGesture(ev, inst) {
        if(ev.eventType ==  Hammer.EVENT_END) {
            inst.trigger(this.name, ev);
        }
    }
};

// node export
if(typeof module === 'object' && typeof module.exports === 'object'){
    module.exports = Hammer;
}
// just window export
else {
    window.Hammer = Hammer;

    // requireJS module definition
    if(typeof window.define === 'function' && window.define.amd) {
        window.define('hammer', [], function() {
            return Hammer;
        });
    }
}
})(this);
},{}],2:[function(require,module,exports){
//! moment.js
//! version : 2.2.1
//! authors : Tim Wood, Iskren Chernev, Moment.js contributors
//! license : MIT
//! momentjs.com

(function (undefined) {

    /************************************
        Constants
    ************************************/

    var moment,
        VERSION = "2.2.1",
        round = Math.round, i,
        // internal storage for language config files
        languages = {},

        // check for nodeJS
        hasModule = (typeof module !== 'undefined' && module.exports),

        // ASP.NET json date format regex
        aspNetJsonRegex = /^\/?Date\((\-?\d+)/i,
        aspNetTimeSpanJsonRegex = /(\-)?(?:(\d*)\.)?(\d+)\:(\d+)\:(\d+)\.?(\d{3})?/,

        // format tokens
        formattingTokens = /(\[[^\[]*\])|(\\)?(Mo|MM?M?M?|Do|DDDo|DD?D?D?|ddd?d?|do?|w[o|w]?|W[o|W]?|YYYYY|YYYY|YY|gg(ggg?)?|GG(GGG?)?|e|E|a|A|hh?|HH?|mm?|ss?|SS?S?|X|zz?|ZZ?|.)/g,
        localFormattingTokens = /(\[[^\[]*\])|(\\)?(LT|LL?L?L?|l{1,4})/g,

        // parsing token regexes
        parseTokenOneOrTwoDigits = /\d\d?/, // 0 - 99
        parseTokenOneToThreeDigits = /\d{1,3}/, // 0 - 999
        parseTokenThreeDigits = /\d{3}/, // 000 - 999
        parseTokenFourDigits = /\d{1,4}/, // 0 - 9999
        parseTokenSixDigits = /[+\-]?\d{1,6}/, // -999,999 - 999,999
        parseTokenWord = /[0-9]*['a-z\u00A0-\u05FF\u0700-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]+|[\u0600-\u06FF\/]+(\s*?[\u0600-\u06FF]+){1,2}/i, // any word (or two) characters or numbers including two/three word month in arabic.
        parseTokenTimezone = /Z|[\+\-]\d\d:?\d\d/i, // +00:00 -00:00 +0000 -0000 or Z
        parseTokenT = /T/i, // T (ISO seperator)
        parseTokenTimestampMs = /[\+\-]?\d+(\.\d{1,3})?/, // 123456789 123456789.123

        // preliminary iso regex
        // 0000-00-00 + T + 00 or 00:00 or 00:00:00 or 00:00:00.000 + +00:00 or +0000
        isoRegex = /^\s*\d{4}-\d\d-\d\d((T| )(\d\d(:\d\d(:\d\d(\.\d\d?\d?)?)?)?)?([\+\-]\d\d:?\d\d)?)?/,
        isoFormat = 'YYYY-MM-DDTHH:mm:ssZ',

        // iso time formats and regexes
        isoTimes = [
            ['HH:mm:ss.S', /(T| )\d\d:\d\d:\d\d\.\d{1,3}/],
            ['HH:mm:ss', /(T| )\d\d:\d\d:\d\d/],
            ['HH:mm', /(T| )\d\d:\d\d/],
            ['HH', /(T| )\d\d/]
        ],

        // timezone chunker "+10:00" > ["10", "00"] or "-1530" > ["-15", "30"]
        parseTimezoneChunker = /([\+\-]|\d\d)/gi,

        // getter and setter names
        proxyGettersAndSetters = 'Date|Hours|Minutes|Seconds|Milliseconds'.split('|'),
        unitMillisecondFactors = {
            'Milliseconds' : 1,
            'Seconds' : 1e3,
            'Minutes' : 6e4,
            'Hours' : 36e5,
            'Days' : 864e5,
            'Months' : 2592e6,
            'Years' : 31536e6
        },

        unitAliases = {
            ms : 'millisecond',
            s : 'second',
            m : 'minute',
            h : 'hour',
            d : 'day',
            w : 'week',
            W : 'isoweek',
            M : 'month',
            y : 'year'
        },

        // format function strings
        formatFunctions = {},

        // tokens to ordinalize and pad
        ordinalizeTokens = 'DDD w W M D d'.split(' '),
        paddedTokens = 'M D H h m s w W'.split(' '),

        formatTokenFunctions = {
            M    : function () {
                return this.month() + 1;
            },
            MMM  : function (format) {
                return this.lang().monthsShort(this, format);
            },
            MMMM : function (format) {
                return this.lang().months(this, format);
            },
            D    : function () {
                return this.date();
            },
            DDD  : function () {
                return this.dayOfYear();
            },
            d    : function () {
                return this.day();
            },
            dd   : function (format) {
                return this.lang().weekdaysMin(this, format);
            },
            ddd  : function (format) {
                return this.lang().weekdaysShort(this, format);
            },
            dddd : function (format) {
                return this.lang().weekdays(this, format);
            },
            w    : function () {
                return this.week();
            },
            W    : function () {
                return this.isoWeek();
            },
            YY   : function () {
                return leftZeroFill(this.year() % 100, 2);
            },
            YYYY : function () {
                return leftZeroFill(this.year(), 4);
            },
            YYYYY : function () {
                return leftZeroFill(this.year(), 5);
            },
            gg   : function () {
                return leftZeroFill(this.weekYear() % 100, 2);
            },
            gggg : function () {
                return this.weekYear();
            },
            ggggg : function () {
                return leftZeroFill(this.weekYear(), 5);
            },
            GG   : function () {
                return leftZeroFill(this.isoWeekYear() % 100, 2);
            },
            GGGG : function () {
                return this.isoWeekYear();
            },
            GGGGG : function () {
                return leftZeroFill(this.isoWeekYear(), 5);
            },
            e : function () {
                return this.weekday();
            },
            E : function () {
                return this.isoWeekday();
            },
            a    : function () {
                return this.lang().meridiem(this.hours(), this.minutes(), true);
            },
            A    : function () {
                return this.lang().meridiem(this.hours(), this.minutes(), false);
            },
            H    : function () {
                return this.hours();
            },
            h    : function () {
                return this.hours() % 12 || 12;
            },
            m    : function () {
                return this.minutes();
            },
            s    : function () {
                return this.seconds();
            },
            S    : function () {
                return ~~(this.milliseconds() / 100);
            },
            SS   : function () {
                return leftZeroFill(~~(this.milliseconds() / 10), 2);
            },
            SSS  : function () {
                return leftZeroFill(this.milliseconds(), 3);
            },
            Z    : function () {
                var a = -this.zone(),
                    b = "+";
                if (a < 0) {
                    a = -a;
                    b = "-";
                }
                return b + leftZeroFill(~~(a / 60), 2) + ":" + leftZeroFill(~~a % 60, 2);
            },
            ZZ   : function () {
                var a = -this.zone(),
                    b = "+";
                if (a < 0) {
                    a = -a;
                    b = "-";
                }
                return b + leftZeroFill(~~(10 * a / 6), 4);
            },
            z : function () {
                return this.zoneAbbr();
            },
            zz : function () {
                return this.zoneName();
            },
            X    : function () {
                return this.unix();
            }
        };

    function padToken(func, count) {
        return function (a) {
            return leftZeroFill(func.call(this, a), count);
        };
    }
    function ordinalizeToken(func, period) {
        return function (a) {
            return this.lang().ordinal(func.call(this, a), period);
        };
    }

    while (ordinalizeTokens.length) {
        i = ordinalizeTokens.pop();
        formatTokenFunctions[i + 'o'] = ordinalizeToken(formatTokenFunctions[i], i);
    }
    while (paddedTokens.length) {
        i = paddedTokens.pop();
        formatTokenFunctions[i + i] = padToken(formatTokenFunctions[i], 2);
    }
    formatTokenFunctions.DDDD = padToken(formatTokenFunctions.DDD, 3);


    /************************************
        Constructors
    ************************************/

    function Language() {

    }

    // Moment prototype object
    function Moment(config) {
        extend(this, config);
    }

    // Duration Constructor
    function Duration(duration) {
        var years = duration.years || duration.year || duration.y || 0,
            months = duration.months || duration.month || duration.M || 0,
            weeks = duration.weeks || duration.week || duration.w || 0,
            days = duration.days || duration.day || duration.d || 0,
            hours = duration.hours || duration.hour || duration.h || 0,
            minutes = duration.minutes || duration.minute || duration.m || 0,
            seconds = duration.seconds || duration.second || duration.s || 0,
            milliseconds = duration.milliseconds || duration.millisecond || duration.ms || 0;

        // store reference to input for deterministic cloning
        this._input = duration;

        // representation for dateAddRemove
        this._milliseconds = +milliseconds +
            seconds * 1e3 + // 1000
            minutes * 6e4 + // 1000 * 60
            hours * 36e5; // 1000 * 60 * 60
        // Because of dateAddRemove treats 24 hours as different from a
        // day when working around DST, we need to store them separately
        this._days = +days +
            weeks * 7;
        // It is impossible translate months into days without knowing
        // which months you are are talking about, so we have to store
        // it separately.
        this._months = +months +
            years * 12;

        this._data = {};

        this._bubble();
    }


    /************************************
        Helpers
    ************************************/


    function extend(a, b) {
        for (var i in b) {
            if (b.hasOwnProperty(i)) {
                a[i] = b[i];
            }
        }
        return a;
    }

    function absRound(number) {
        if (number < 0) {
            return Math.ceil(number);
        } else {
            return Math.floor(number);
        }
    }

    // left zero fill a number
    // see http://jsperf.com/left-zero-filling for performance comparison
    function leftZeroFill(number, targetLength) {
        var output = number + '';
        while (output.length < targetLength) {
            output = '0' + output;
        }
        return output;
    }

    // helper function for _.addTime and _.subtractTime
    function addOrSubtractDurationFromMoment(mom, duration, isAdding, ignoreUpdateOffset) {
        var milliseconds = duration._milliseconds,
            days = duration._days,
            months = duration._months,
            minutes,
            hours;

        if (milliseconds) {
            mom._d.setTime(+mom._d + milliseconds * isAdding);
        }
        // store the minutes and hours so we can restore them
        if (days || months) {
            minutes = mom.minute();
            hours = mom.hour();
        }
        if (days) {
            mom.date(mom.date() + days * isAdding);
        }
        if (months) {
            mom.month(mom.month() + months * isAdding);
        }
        if (milliseconds && !ignoreUpdateOffset) {
            moment.updateOffset(mom);
        }
        // restore the minutes and hours after possibly changing dst
        if (days || months) {
            mom.minute(minutes);
            mom.hour(hours);
        }
    }

    // check if is an array
    function isArray(input) {
        return Object.prototype.toString.call(input) === '[object Array]';
    }

    // compare two arrays, return the number of differences
    function compareArrays(array1, array2) {
        var len = Math.min(array1.length, array2.length),
            lengthDiff = Math.abs(array1.length - array2.length),
            diffs = 0,
            i;
        for (i = 0; i < len; i++) {
            if (~~array1[i] !== ~~array2[i]) {
                diffs++;
            }
        }
        return diffs + lengthDiff;
    }

    function normalizeUnits(units) {
        return units ? unitAliases[units] || units.toLowerCase().replace(/(.)s$/, '$1') : units;
    }


    /************************************
        Languages
    ************************************/


    extend(Language.prototype, {

        set : function (config) {
            var prop, i;
            for (i in config) {
                prop = config[i];
                if (typeof prop === 'function') {
                    this[i] = prop;
                } else {
                    this['_' + i] = prop;
                }
            }
        },

        _months : "January_February_March_April_May_June_July_August_September_October_November_December".split("_"),
        months : function (m) {
            return this._months[m.month()];
        },

        _monthsShort : "Jan_Feb_Mar_Apr_May_Jun_Jul_Aug_Sep_Oct_Nov_Dec".split("_"),
        monthsShort : function (m) {
            return this._monthsShort[m.month()];
        },

        monthsParse : function (monthName) {
            var i, mom, regex;

            if (!this._monthsParse) {
                this._monthsParse = [];
            }

            for (i = 0; i < 12; i++) {
                // make the regex if we don't have it already
                if (!this._monthsParse[i]) {
                    mom = moment.utc([2000, i]);
                    regex = '^' + this.months(mom, '') + '|^' + this.monthsShort(mom, '');
                    this._monthsParse[i] = new RegExp(regex.replace('.', ''), 'i');
                }
                // test the regex
                if (this._monthsParse[i].test(monthName)) {
                    return i;
                }
            }
        },

        _weekdays : "Sunday_Monday_Tuesday_Wednesday_Thursday_Friday_Saturday".split("_"),
        weekdays : function (m) {
            return this._weekdays[m.day()];
        },

        _weekdaysShort : "Sun_Mon_Tue_Wed_Thu_Fri_Sat".split("_"),
        weekdaysShort : function (m) {
            return this._weekdaysShort[m.day()];
        },

        _weekdaysMin : "Su_Mo_Tu_We_Th_Fr_Sa".split("_"),
        weekdaysMin : function (m) {
            return this._weekdaysMin[m.day()];
        },

        weekdaysParse : function (weekdayName) {
            var i, mom, regex;

            if (!this._weekdaysParse) {
                this._weekdaysParse = [];
            }

            for (i = 0; i < 7; i++) {
                // make the regex if we don't have it already
                if (!this._weekdaysParse[i]) {
                    mom = moment([2000, 1]).day(i);
                    regex = '^' + this.weekdays(mom, '') + '|^' + this.weekdaysShort(mom, '') + '|^' + this.weekdaysMin(mom, '');
                    this._weekdaysParse[i] = new RegExp(regex.replace('.', ''), 'i');
                }
                // test the regex
                if (this._weekdaysParse[i].test(weekdayName)) {
                    return i;
                }
            }
        },

        _longDateFormat : {
            LT : "h:mm A",
            L : "MM/DD/YYYY",
            LL : "MMMM D YYYY",
            LLL : "MMMM D YYYY LT",
            LLLL : "dddd, MMMM D YYYY LT"
        },
        longDateFormat : function (key) {
            var output = this._longDateFormat[key];
            if (!output && this._longDateFormat[key.toUpperCase()]) {
                output = this._longDateFormat[key.toUpperCase()].replace(/MMMM|MM|DD|dddd/g, function (val) {
                    return val.slice(1);
                });
                this._longDateFormat[key] = output;
            }
            return output;
        },

        isPM : function (input) {
            // IE8 Quirks Mode & IE7 Standards Mode do not allow accessing strings like arrays
            // Using charAt should be more compatible.
            return ((input + '').toLowerCase().charAt(0) === 'p');
        },

        _meridiemParse : /[ap]\.?m?\.?/i,
        meridiem : function (hours, minutes, isLower) {
            if (hours > 11) {
                return isLower ? 'pm' : 'PM';
            } else {
                return isLower ? 'am' : 'AM';
            }
        },

        _calendar : {
            sameDay : '[Today at] LT',
            nextDay : '[Tomorrow at] LT',
            nextWeek : 'dddd [at] LT',
            lastDay : '[Yesterday at] LT',
            lastWeek : '[Last] dddd [at] LT',
            sameElse : 'L'
        },
        calendar : function (key, mom) {
            var output = this._calendar[key];
            return typeof output === 'function' ? output.apply(mom) : output;
        },

        _relativeTime : {
            future : "in %s",
            past : "%s ago",
            s : "a few seconds",
            m : "a minute",
            mm : "%d minutes",
            h : "an hour",
            hh : "%d hours",
            d : "a day",
            dd : "%d days",
            M : "a month",
            MM : "%d months",
            y : "a year",
            yy : "%d years"
        },
        relativeTime : function (number, withoutSuffix, string, isFuture) {
            var output = this._relativeTime[string];
            return (typeof output === 'function') ?
                output(number, withoutSuffix, string, isFuture) :
                output.replace(/%d/i, number);
        },
        pastFuture : function (diff, output) {
            var format = this._relativeTime[diff > 0 ? 'future' : 'past'];
            return typeof format === 'function' ? format(output) : format.replace(/%s/i, output);
        },

        ordinal : function (number) {
            return this._ordinal.replace("%d", number);
        },
        _ordinal : "%d",

        preparse : function (string) {
            return string;
        },

        postformat : function (string) {
            return string;
        },

        week : function (mom) {
            return weekOfYear(mom, this._week.dow, this._week.doy).week;
        },
        _week : {
            dow : 0, // Sunday is the first day of the week.
            doy : 6  // The week that contains Jan 1st is the first week of the year.
        }
    });

    // Loads a language definition into the `languages` cache.  The function
    // takes a key and optionally values.  If not in the browser and no values
    // are provided, it will load the language file module.  As a convenience,
    // this function also returns the language values.
    function loadLang(key, values) {
        values.abbr = key;
        if (!languages[key]) {
            languages[key] = new Language();
        }
        languages[key].set(values);
        return languages[key];
    }

    // Remove a language from the `languages` cache. Mostly useful in tests.
    function unloadLang(key) {
        delete languages[key];
    }

    // Determines which language definition to use and returns it.
    //
    // With no parameters, it will return the global language.  If you
    // pass in a language key, such as 'en', it will return the
    // definition for 'en', so long as 'en' has already been loaded using
    // moment.lang.
    function getLangDefinition(key) {
        if (!key) {
            return moment.fn._lang;
        }
        if (!languages[key] && hasModule) {
            try {
                require('./lang/' + key);
            } catch (e) {
                // call with no params to set to default
                return moment.fn._lang;
            }
        }
        return languages[key] || moment.fn._lang;
    }


    /************************************
        Formatting
    ************************************/


    function removeFormattingTokens(input) {
        if (input.match(/\[.*\]/)) {
            return input.replace(/^\[|\]$/g, "");
        }
        return input.replace(/\\/g, "");
    }

    function makeFormatFunction(format) {
        var array = format.match(formattingTokens), i, length;

        for (i = 0, length = array.length; i < length; i++) {
            if (formatTokenFunctions[array[i]]) {
                array[i] = formatTokenFunctions[array[i]];
            } else {
                array[i] = removeFormattingTokens(array[i]);
            }
        }

        return function (mom) {
            var output = "";
            for (i = 0; i < length; i++) {
                output += array[i] instanceof Function ? array[i].call(mom, format) : array[i];
            }
            return output;
        };
    }

    // format date using native date object
    function formatMoment(m, format) {

        format = expandFormat(format, m.lang());

        if (!formatFunctions[format]) {
            formatFunctions[format] = makeFormatFunction(format);
        }

        return formatFunctions[format](m);
    }

    function expandFormat(format, lang) {
        var i = 5;

        function replaceLongDateFormatTokens(input) {
            return lang.longDateFormat(input) || input;
        }

        while (i-- && (localFormattingTokens.lastIndex = 0,
                    localFormattingTokens.test(format))) {
            format = format.replace(localFormattingTokens, replaceLongDateFormatTokens);
        }

        return format;
    }


    /************************************
        Parsing
    ************************************/


    // get the regex to find the next token
    function getParseRegexForToken(token, config) {
        switch (token) {
        case 'DDDD':
            return parseTokenThreeDigits;
        case 'YYYY':
            return parseTokenFourDigits;
        case 'YYYYY':
            return parseTokenSixDigits;
        case 'S':
        case 'SS':
        case 'SSS':
        case 'DDD':
            return parseTokenOneToThreeDigits;
        case 'MMM':
        case 'MMMM':
        case 'dd':
        case 'ddd':
        case 'dddd':
            return parseTokenWord;
        case 'a':
        case 'A':
            return getLangDefinition(config._l)._meridiemParse;
        case 'X':
            return parseTokenTimestampMs;
        case 'Z':
        case 'ZZ':
            return parseTokenTimezone;
        case 'T':
            return parseTokenT;
        case 'MM':
        case 'DD':
        case 'YY':
        case 'HH':
        case 'hh':
        case 'mm':
        case 'ss':
        case 'M':
        case 'D':
        case 'd':
        case 'H':
        case 'h':
        case 'm':
        case 's':
            return parseTokenOneOrTwoDigits;
        default :
            return new RegExp(token.replace('\\', ''));
        }
    }

    function timezoneMinutesFromString(string) {
        var tzchunk = (parseTokenTimezone.exec(string) || [])[0],
            parts = (tzchunk + '').match(parseTimezoneChunker) || ['-', 0, 0],
            minutes = +(parts[1] * 60) + ~~parts[2];

        return parts[0] === '+' ? -minutes : minutes;
    }

    // function to convert string input to date
    function addTimeToArrayFromToken(token, input, config) {
        var a, datePartArray = config._a;

        switch (token) {
        // MONTH
        case 'M' : // fall through to MM
        case 'MM' :
            if (input != null) {
                datePartArray[1] = ~~input - 1;
            }
            break;
        case 'MMM' : // fall through to MMMM
        case 'MMMM' :
            a = getLangDefinition(config._l).monthsParse(input);
            // if we didn't find a month name, mark the date as invalid.
            if (a != null) {
                datePartArray[1] = a;
            } else {
                config._isValid = false;
            }
            break;
        // DAY OF MONTH
        case 'D' : // fall through to DD
        case 'DD' :
            if (input != null) {
                datePartArray[2] = ~~input;
            }
            break;
        // DAY OF YEAR
        case 'DDD' : // fall through to DDDD
        case 'DDDD' :
            if (input != null) {
                datePartArray[1] = 0;
                datePartArray[2] = ~~input;
            }
            break;
        // YEAR
        case 'YY' :
            datePartArray[0] = ~~input + (~~input > 68 ? 1900 : 2000);
            break;
        case 'YYYY' :
        case 'YYYYY' :
            datePartArray[0] = ~~input;
            break;
        // AM / PM
        case 'a' : // fall through to A
        case 'A' :
            config._isPm = getLangDefinition(config._l).isPM(input);
            break;
        // 24 HOUR
        case 'H' : // fall through to hh
        case 'HH' : // fall through to hh
        case 'h' : // fall through to hh
        case 'hh' :
            datePartArray[3] = ~~input;
            break;
        // MINUTE
        case 'm' : // fall through to mm
        case 'mm' :
            datePartArray[4] = ~~input;
            break;
        // SECOND
        case 's' : // fall through to ss
        case 'ss' :
            datePartArray[5] = ~~input;
            break;
        // MILLISECOND
        case 'S' :
        case 'SS' :
        case 'SSS' :
            datePartArray[6] = ~~ (('0.' + input) * 1000);
            break;
        // UNIX TIMESTAMP WITH MS
        case 'X':
            config._d = new Date(parseFloat(input) * 1000);
            break;
        // TIMEZONE
        case 'Z' : // fall through to ZZ
        case 'ZZ' :
            config._useUTC = true;
            config._tzm = timezoneMinutesFromString(input);
            break;
        }

        // if the input is null, the date is not valid
        if (input == null) {
            config._isValid = false;
        }
    }

    // convert an array to a date.
    // the array should mirror the parameters below
    // note: all values past the year are optional and will default to the lowest possible value.
    // [year, month, day , hour, minute, second, millisecond]
    function dateFromArray(config) {
        var i, date, input = [], currentDate;

        if (config._d) {
            return;
        }

        // Default to current date.
        // * if no year, month, day of month are given, default to today
        // * if day of month is given, default month and year
        // * if month is given, default only year
        // * if year is given, don't default anything
        currentDate = currentDateArray(config);
        for (i = 0; i < 3 && config._a[i] == null; ++i) {
            config._a[i] = input[i] = currentDate[i];
        }

        // Zero out whatever was not defaulted, including time
        for (; i < 7; i++) {
            config._a[i] = input[i] = (config._a[i] == null) ? (i === 2 ? 1 : 0) : config._a[i];
        }

        // add the offsets to the time to be parsed so that we can have a clean array for checking isValid
        input[3] += ~~((config._tzm || 0) / 60);
        input[4] += ~~((config._tzm || 0) % 60);

        date = new Date(0);

        if (config._useUTC) {
            date.setUTCFullYear(input[0], input[1], input[2]);
            date.setUTCHours(input[3], input[4], input[5], input[6]);
        } else {
            date.setFullYear(input[0], input[1], input[2]);
            date.setHours(input[3], input[4], input[5], input[6]);
        }

        config._d = date;
    }

    function dateFromObject(config) {
        var o = config._i;

        if (config._d) {
            return;
        }

        config._a = [
            o.years || o.year || o.y,
            o.months || o.month || o.M,
            o.days || o.day || o.d,
            o.hours || o.hour || o.h,
            o.minutes || o.minute || o.m,
            o.seconds || o.second || o.s,
            o.milliseconds || o.millisecond || o.ms
        ];

        dateFromArray(config);
    }

    function currentDateArray(config) {
        var now = new Date();
        if (config._useUTC) {
            return [
                now.getUTCFullYear(),
                now.getUTCMonth(),
                now.getUTCDate()
            ];
        } else {
            return [now.getFullYear(), now.getMonth(), now.getDate()];
        }
    }

    // date from string and format string
    function makeDateFromStringAndFormat(config) {
        // This array is used to make a Date, either with `new Date` or `Date.UTC`
        var lang = getLangDefinition(config._l),
            string = '' + config._i,
            i, parsedInput, tokens;

        tokens = expandFormat(config._f, lang).match(formattingTokens);

        config._a = [];

        for (i = 0; i < tokens.length; i++) {
            parsedInput = (getParseRegexForToken(tokens[i], config).exec(string) || [])[0];
            if (parsedInput) {
                string = string.slice(string.indexOf(parsedInput) + parsedInput.length);
            }
            // don't parse if its not a known token
            if (formatTokenFunctions[tokens[i]]) {
                addTimeToArrayFromToken(tokens[i], parsedInput, config);
            }
        }

        // add remaining unparsed input to the string
        if (string) {
            config._il = string;
        }

        // handle am pm
        if (config._isPm && config._a[3] < 12) {
            config._a[3] += 12;
        }
        // if is 12 am, change hours to 0
        if (config._isPm === false && config._a[3] === 12) {
            config._a[3] = 0;
        }
        // return
        dateFromArray(config);
    }

    // date from string and array of format strings
    function makeDateFromStringAndArray(config) {
        var tempConfig,
            tempMoment,
            bestMoment,

            scoreToBeat = 99,
            i,
            currentScore;

        for (i = 0; i < config._f.length; i++) {
            tempConfig = extend({}, config);
            tempConfig._f = config._f[i];
            makeDateFromStringAndFormat(tempConfig);
            tempMoment = new Moment(tempConfig);

            currentScore = compareArrays(tempConfig._a, tempMoment.toArray());

            // if there is any input that was not parsed
            // add a penalty for that format
            if (tempMoment._il) {
                currentScore += tempMoment._il.length;
            }

            if (currentScore < scoreToBeat) {
                scoreToBeat = currentScore;
                bestMoment = tempMoment;
            }
        }

        extend(config, bestMoment);
    }

    // date from iso format
    function makeDateFromString(config) {
        var i,
            string = config._i,
            match = isoRegex.exec(string);

        if (match) {
            // match[2] should be "T" or undefined
            config._f = 'YYYY-MM-DD' + (match[2] || " ");
            for (i = 0; i < 4; i++) {
                if (isoTimes[i][1].exec(string)) {
                    config._f += isoTimes[i][0];
                    break;
                }
            }
            if (parseTokenTimezone.exec(string)) {
                config._f += " Z";
            }
            makeDateFromStringAndFormat(config);
        } else {
            config._d = new Date(string);
        }
    }

    function makeDateFromInput(config) {
        var input = config._i,
            matched = aspNetJsonRegex.exec(input);

        if (input === undefined) {
            config._d = new Date();
        } else if (matched) {
            config._d = new Date(+matched[1]);
        } else if (typeof input === 'string') {
            makeDateFromString(config);
        } else if (isArray(input)) {
            config._a = input.slice(0);
            dateFromArray(config);
        } else if (input instanceof Date) {
            config._d = new Date(+input);
        } else if (typeof(input) === 'object') {
            dateFromObject(config);
        } else {
            config._d = new Date(input);
        }
    }


    /************************************
        Relative Time
    ************************************/


    // helper function for moment.fn.from, moment.fn.fromNow, and moment.duration.fn.humanize
    function substituteTimeAgo(string, number, withoutSuffix, isFuture, lang) {
        return lang.relativeTime(number || 1, !!withoutSuffix, string, isFuture);
    }

    function relativeTime(milliseconds, withoutSuffix, lang) {
        var seconds = round(Math.abs(milliseconds) / 1000),
            minutes = round(seconds / 60),
            hours = round(minutes / 60),
            days = round(hours / 24),
            years = round(days / 365),
            args = seconds < 45 && ['s', seconds] ||
                minutes === 1 && ['m'] ||
                minutes < 45 && ['mm', minutes] ||
                hours === 1 && ['h'] ||
                hours < 22 && ['hh', hours] ||
                days === 1 && ['d'] ||
                days <= 25 && ['dd', days] ||
                days <= 45 && ['M'] ||
                days < 345 && ['MM', round(days / 30)] ||
                years === 1 && ['y'] || ['yy', years];
        args[2] = withoutSuffix;
        args[3] = milliseconds > 0;
        args[4] = lang;
        return substituteTimeAgo.apply({}, args);
    }


    /************************************
        Week of Year
    ************************************/


    // firstDayOfWeek       0 = sun, 6 = sat
    //                      the day of the week that starts the week
    //                      (usually sunday or monday)
    // firstDayOfWeekOfYear 0 = sun, 6 = sat
    //                      the first week is the week that contains the first
    //                      of this day of the week
    //                      (eg. ISO weeks use thursday (4))
    function weekOfYear(mom, firstDayOfWeek, firstDayOfWeekOfYear) {
        var end = firstDayOfWeekOfYear - firstDayOfWeek,
            daysToDayOfWeek = firstDayOfWeekOfYear - mom.day(),
            adjustedMoment;


        if (daysToDayOfWeek > end) {
            daysToDayOfWeek -= 7;
        }

        if (daysToDayOfWeek < end - 7) {
            daysToDayOfWeek += 7;
        }

        adjustedMoment = moment(mom).add('d', daysToDayOfWeek);
        return {
            week: Math.ceil(adjustedMoment.dayOfYear() / 7),
            year: adjustedMoment.year()
        };
    }


    /************************************
        Top Level Functions
    ************************************/

    function makeMoment(config) {
        var input = config._i,
            format = config._f;

        if (input === null || input === '') {
            return null;
        }

        if (typeof input === 'string') {
            config._i = input = getLangDefinition().preparse(input);
        }

        if (moment.isMoment(input)) {
            config = extend({}, input);
            config._d = new Date(+input._d);
        } else if (format) {
            if (isArray(format)) {
                makeDateFromStringAndArray(config);
            } else {
                makeDateFromStringAndFormat(config);
            }
        } else {
            makeDateFromInput(config);
        }

        return new Moment(config);
    }

    moment = function (input, format, lang) {
        return makeMoment({
            _i : input,
            _f : format,
            _l : lang,
            _isUTC : false
        });
    };

    // creating with utc
    moment.utc = function (input, format, lang) {
        return makeMoment({
            _useUTC : true,
            _isUTC : true,
            _l : lang,
            _i : input,
            _f : format
        }).utc();
    };

    // creating with unix timestamp (in seconds)
    moment.unix = function (input) {
        return moment(input * 1000);
    };

    // duration
    moment.duration = function (input, key) {
        var isDuration = moment.isDuration(input),
            isNumber = (typeof input === 'number'),
            duration = (isDuration ? input._input : (isNumber ? {} : input)),
            matched = aspNetTimeSpanJsonRegex.exec(input),
            sign,
            ret;

        if (isNumber) {
            if (key) {
                duration[key] = input;
            } else {
                duration.milliseconds = input;
            }
        } else if (matched) {
            sign = (matched[1] === "-") ? -1 : 1;
            duration = {
                y: 0,
                d: ~~matched[2] * sign,
                h: ~~matched[3] * sign,
                m: ~~matched[4] * sign,
                s: ~~matched[5] * sign,
                ms: ~~matched[6] * sign
            };
        }

        ret = new Duration(duration);

        if (isDuration && input.hasOwnProperty('_lang')) {
            ret._lang = input._lang;
        }

        return ret;
    };

    // version number
    moment.version = VERSION;

    // default format
    moment.defaultFormat = isoFormat;

    // This function will be called whenever a moment is mutated.
    // It is intended to keep the offset in sync with the timezone.
    moment.updateOffset = function () {};

    // This function will load languages and then set the global language.  If
    // no arguments are passed in, it will simply return the current global
    // language key.
    moment.lang = function (key, values) {
        if (!key) {
            return moment.fn._lang._abbr;
        }
        key = key.toLowerCase();
        key = key.replace('_', '-');
        if (values) {
            loadLang(key, values);
        } else if (values === null) {
            unloadLang(key);
            key = 'en';
        } else if (!languages[key]) {
            getLangDefinition(key);
        }
        moment.duration.fn._lang = moment.fn._lang = getLangDefinition(key);
    };

    // returns language data
    moment.langData = function (key) {
        if (key && key._lang && key._lang._abbr) {
            key = key._lang._abbr;
        }
        return getLangDefinition(key);
    };

    // compare moment object
    moment.isMoment = function (obj) {
        return obj instanceof Moment;
    };

    // for typechecking Duration objects
    moment.isDuration = function (obj) {
        return obj instanceof Duration;
    };


    /************************************
        Moment Prototype
    ************************************/


    extend(moment.fn = Moment.prototype, {

        clone : function () {
            return moment(this);
        },

        valueOf : function () {
            return +this._d + ((this._offset || 0) * 60000);
        },

        unix : function () {
            return Math.floor(+this / 1000);
        },

        toString : function () {
            return this.format("ddd MMM DD YYYY HH:mm:ss [GMT]ZZ");
        },

        toDate : function () {
            return this._offset ? new Date(+this) : this._d;
        },

        toISOString : function () {
            return formatMoment(moment(this).utc(), 'YYYY-MM-DD[T]HH:mm:ss.SSS[Z]');
        },

        toArray : function () {
            var m = this;
            return [
                m.year(),
                m.month(),
                m.date(),
                m.hours(),
                m.minutes(),
                m.seconds(),
                m.milliseconds()
            ];
        },

        isValid : function () {
            if (this._isValid == null) {
                if (this._a) {
                    this._isValid = !compareArrays(this._a, (this._isUTC ? moment.utc(this._a) : moment(this._a)).toArray());
                } else {
                    this._isValid = !isNaN(this._d.getTime());
                }
            }
            return !!this._isValid;
        },

        invalidAt: function () {
            var i, arr1 = this._a, arr2 = (this._isUTC ? moment.utc(this._a) : moment(this._a)).toArray();
            for (i = 6; i >= 0 && arr1[i] === arr2[i]; --i) {
                // empty loop body
            }
            return i;
        },

        utc : function () {
            return this.zone(0);
        },

        local : function () {
            this.zone(0);
            this._isUTC = false;
            return this;
        },

        format : function (inputString) {
            var output = formatMoment(this, inputString || moment.defaultFormat);
            return this.lang().postformat(output);
        },

        add : function (input, val) {
            var dur;
            // switch args to support add('s', 1) and add(1, 's')
            if (typeof input === 'string') {
                dur = moment.duration(+val, input);
            } else {
                dur = moment.duration(input, val);
            }
            addOrSubtractDurationFromMoment(this, dur, 1);
            return this;
        },

        subtract : function (input, val) {
            var dur;
            // switch args to support subtract('s', 1) and subtract(1, 's')
            if (typeof input === 'string') {
                dur = moment.duration(+val, input);
            } else {
                dur = moment.duration(input, val);
            }
            addOrSubtractDurationFromMoment(this, dur, -1);
            return this;
        },

        diff : function (input, units, asFloat) {
            var that = this._isUTC ? moment(input).zone(this._offset || 0) : moment(input).local(),
                zoneDiff = (this.zone() - that.zone()) * 6e4,
                diff, output;

            units = normalizeUnits(units);

            if (units === 'year' || units === 'month') {
                // average number of days in the months in the given dates
                diff = (this.daysInMonth() + that.daysInMonth()) * 432e5; // 24 * 60 * 60 * 1000 / 2
                // difference in months
                output = ((this.year() - that.year()) * 12) + (this.month() - that.month());
                // adjust by taking difference in days, average number of days
                // and dst in the given months.
                output += ((this - moment(this).startOf('month')) -
                        (that - moment(that).startOf('month'))) / diff;
                // same as above but with zones, to negate all dst
                output -= ((this.zone() - moment(this).startOf('month').zone()) -
                        (that.zone() - moment(that).startOf('month').zone())) * 6e4 / diff;
                if (units === 'year') {
                    output = output / 12;
                }
            } else {
                diff = (this - that);
                output = units === 'second' ? diff / 1e3 : // 1000
                    units === 'minute' ? diff / 6e4 : // 1000 * 60
                    units === 'hour' ? diff / 36e5 : // 1000 * 60 * 60
                    units === 'day' ? (diff - zoneDiff) / 864e5 : // 1000 * 60 * 60 * 24, negate dst
                    units === 'week' ? (diff - zoneDiff) / 6048e5 : // 1000 * 60 * 60 * 24 * 7, negate dst
                    diff;
            }
            return asFloat ? output : absRound(output);
        },

        from : function (time, withoutSuffix) {
            return moment.duration(this.diff(time)).lang(this.lang()._abbr).humanize(!withoutSuffix);
        },

        fromNow : function (withoutSuffix) {
            return this.from(moment(), withoutSuffix);
        },

        calendar : function () {
            var diff = this.diff(moment().zone(this.zone()).startOf('day'), 'days', true),
                format = diff < -6 ? 'sameElse' :
                diff < -1 ? 'lastWeek' :
                diff < 0 ? 'lastDay' :
                diff < 1 ? 'sameDay' :
                diff < 2 ? 'nextDay' :
                diff < 7 ? 'nextWeek' : 'sameElse';
            return this.format(this.lang().calendar(format, this));
        },

        isLeapYear : function () {
            var year = this.year();
            return (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
        },

        isDST : function () {
            return (this.zone() < this.clone().month(0).zone() ||
                this.zone() < this.clone().month(5).zone());
        },

        day : function (input) {
            var day = this._isUTC ? this._d.getUTCDay() : this._d.getDay();
            if (input != null) {
                if (typeof input === 'string') {
                    input = this.lang().weekdaysParse(input);
                    if (typeof input !== 'number') {
                        return this;
                    }
                }
                return this.add({ d : input - day });
            } else {
                return day;
            }
        },

        month : function (input) {
            var utc = this._isUTC ? 'UTC' : '',
                dayOfMonth;

            if (input != null) {
                if (typeof input === 'string') {
                    input = this.lang().monthsParse(input);
                    if (typeof input !== 'number') {
                        return this;
                    }
                }

                dayOfMonth = this.date();
                this.date(1);
                this._d['set' + utc + 'Month'](input);
                this.date(Math.min(dayOfMonth, this.daysInMonth()));

                moment.updateOffset(this);
                return this;
            } else {
                return this._d['get' + utc + 'Month']();
            }
        },

        startOf: function (units) {
            units = normalizeUnits(units);
            // the following switch intentionally omits break keywords
            // to utilize falling through the cases.
            switch (units) {
            case 'year':
                this.month(0);
                /* falls through */
            case 'month':
                this.date(1);
                /* falls through */
            case 'week':
            case 'isoweek':
            case 'day':
                this.hours(0);
                /* falls through */
            case 'hour':
                this.minutes(0);
                /* falls through */
            case 'minute':
                this.seconds(0);
                /* falls through */
            case 'second':
                this.milliseconds(0);
                /* falls through */
            }

            // weeks are a special case
            if (units === 'week') {
                this.weekday(0);
            } else if (units === 'isoweek') {
                this.isoWeekday(1);
            }

            return this;
        },

        endOf: function (units) {
            units = normalizeUnits(units);
            return this.startOf(units).add((units === 'isoweek' ? 'week' : units), 1).subtract('ms', 1);
        },

        isAfter: function (input, units) {
            units = typeof units !== 'undefined' ? units : 'millisecond';
            return +this.clone().startOf(units) > +moment(input).startOf(units);
        },

        isBefore: function (input, units) {
            units = typeof units !== 'undefined' ? units : 'millisecond';
            return +this.clone().startOf(units) < +moment(input).startOf(units);
        },

        isSame: function (input, units) {
            units = typeof units !== 'undefined' ? units : 'millisecond';
            return +this.clone().startOf(units) === +moment(input).startOf(units);
        },

        min: function (other) {
            other = moment.apply(null, arguments);
            return other < this ? this : other;
        },

        max: function (other) {
            other = moment.apply(null, arguments);
            return other > this ? this : other;
        },

        zone : function (input) {
            var offset = this._offset || 0;
            if (input != null) {
                if (typeof input === "string") {
                    input = timezoneMinutesFromString(input);
                }
                if (Math.abs(input) < 16) {
                    input = input * 60;
                }
                this._offset = input;
                this._isUTC = true;
                if (offset !== input) {
                    addOrSubtractDurationFromMoment(this, moment.duration(offset - input, 'm'), 1, true);
                }
            } else {
                return this._isUTC ? offset : this._d.getTimezoneOffset();
            }
            return this;
        },

        zoneAbbr : function () {
            return this._isUTC ? "UTC" : "";
        },

        zoneName : function () {
            return this._isUTC ? "Coordinated Universal Time" : "";
        },

        hasAlignedHourOffset : function (input) {
            if (!input) {
                input = 0;
            }
            else {
                input = moment(input).zone();
            }

            return (this.zone() - input) % 60 === 0;
        },

        daysInMonth : function () {
            return moment.utc([this.year(), this.month() + 1, 0]).date();
        },

        dayOfYear : function (input) {
            var dayOfYear = round((moment(this).startOf('day') - moment(this).startOf('year')) / 864e5) + 1;
            return input == null ? dayOfYear : this.add("d", (input - dayOfYear));
        },

        weekYear : function (input) {
            var year = weekOfYear(this, this.lang()._week.dow, this.lang()._week.doy).year;
            return input == null ? year : this.add("y", (input - year));
        },

        isoWeekYear : function (input) {
            var year = weekOfYear(this, 1, 4).year;
            return input == null ? year : this.add("y", (input - year));
        },

        week : function (input) {
            var week = this.lang().week(this);
            return input == null ? week : this.add("d", (input - week) * 7);
        },

        isoWeek : function (input) {
            var week = weekOfYear(this, 1, 4).week;
            return input == null ? week : this.add("d", (input - week) * 7);
        },

        weekday : function (input) {
            var weekday = (this._d.getDay() + 7 - this.lang()._week.dow) % 7;
            return input == null ? weekday : this.add("d", input - weekday);
        },

        isoWeekday : function (input) {
            // behaves the same as moment#day except
            // as a getter, returns 7 instead of 0 (1-7 range instead of 0-6)
            // as a setter, sunday should belong to the previous week.
            return input == null ? this.day() || 7 : this.day(this.day() % 7 ? input : input - 7);
        },

        get : function (units) {
            units = normalizeUnits(units);
            return this[units.toLowerCase()]();
        },

        set : function (units, value) {
            units = normalizeUnits(units);
            this[units.toLowerCase()](value);
        },

        // If passed a language key, it will set the language for this
        // instance.  Otherwise, it will return the language configuration
        // variables for this instance.
        lang : function (key) {
            if (key === undefined) {
                return this._lang;
            } else {
                this._lang = getLangDefinition(key);
                return this;
            }
        }
    });

    // helper for adding shortcuts
    function makeGetterAndSetter(name, key) {
        moment.fn[name] = moment.fn[name + 's'] = function (input) {
            var utc = this._isUTC ? 'UTC' : '';
            if (input != null) {
                this._d['set' + utc + key](input);
                moment.updateOffset(this);
                return this;
            } else {
                return this._d['get' + utc + key]();
            }
        };
    }

    // loop through and add shortcuts (Month, Date, Hours, Minutes, Seconds, Milliseconds)
    for (i = 0; i < proxyGettersAndSetters.length; i ++) {
        makeGetterAndSetter(proxyGettersAndSetters[i].toLowerCase().replace(/s$/, ''), proxyGettersAndSetters[i]);
    }

    // add shortcut for year (uses different syntax than the getter/setter 'year' == 'FullYear')
    makeGetterAndSetter('year', 'FullYear');

    // add plural methods
    moment.fn.days = moment.fn.day;
    moment.fn.months = moment.fn.month;
    moment.fn.weeks = moment.fn.week;
    moment.fn.isoWeeks = moment.fn.isoWeek;

    // add aliased format methods
    moment.fn.toJSON = moment.fn.toISOString;

    /************************************
        Duration Prototype
    ************************************/


    extend(moment.duration.fn = Duration.prototype, {

        _bubble : function () {
            var milliseconds = this._milliseconds,
                days = this._days,
                months = this._months,
                data = this._data,
                seconds, minutes, hours, years;

            // The following code bubbles up values, see the tests for
            // examples of what that means.
            data.milliseconds = milliseconds % 1000;

            seconds = absRound(milliseconds / 1000);
            data.seconds = seconds % 60;

            minutes = absRound(seconds / 60);
            data.minutes = minutes % 60;

            hours = absRound(minutes / 60);
            data.hours = hours % 24;

            days += absRound(hours / 24);
            data.days = days % 30;

            months += absRound(days / 30);
            data.months = months % 12;

            years = absRound(months / 12);
            data.years = years;
        },

        weeks : function () {
            return absRound(this.days() / 7);
        },

        valueOf : function () {
            return this._milliseconds +
              this._days * 864e5 +
              (this._months % 12) * 2592e6 +
              ~~(this._months / 12) * 31536e6;
        },

        humanize : function (withSuffix) {
            var difference = +this,
                output = relativeTime(difference, !withSuffix, this.lang());

            if (withSuffix) {
                output = this.lang().pastFuture(difference, output);
            }

            return this.lang().postformat(output);
        },

        add : function (input, val) {
            // supports only 2.0-style add(1, 's') or add(moment)
            var dur = moment.duration(input, val);

            this._milliseconds += dur._milliseconds;
            this._days += dur._days;
            this._months += dur._months;

            this._bubble();

            return this;
        },

        subtract : function (input, val) {
            var dur = moment.duration(input, val);

            this._milliseconds -= dur._milliseconds;
            this._days -= dur._days;
            this._months -= dur._months;

            this._bubble();

            return this;
        },

        get : function (units) {
            units = normalizeUnits(units);
            return this[units.toLowerCase() + 's']();
        },

        as : function (units) {
            units = normalizeUnits(units);
            return this['as' + units.charAt(0).toUpperCase() + units.slice(1) + 's']();
        },

        lang : moment.fn.lang
    });

    function makeDurationGetter(name) {
        moment.duration.fn[name] = function () {
            return this._data[name];
        };
    }

    function makeDurationAsGetter(name, factor) {
        moment.duration.fn['as' + name] = function () {
            return +this / factor;
        };
    }

    for (i in unitMillisecondFactors) {
        if (unitMillisecondFactors.hasOwnProperty(i)) {
            makeDurationAsGetter(i, unitMillisecondFactors[i]);
            makeDurationGetter(i.toLowerCase());
        }
    }

    makeDurationAsGetter('Weeks', 6048e5);
    moment.duration.fn.asMonths = function () {
        return (+this - this.years() * 31536e6) / 2592e6 + this.years() * 12;
    };


    /************************************
        Default Lang
    ************************************/


    // Set default language, other languages will inherit from English.
    moment.lang('en', {
        ordinal : function (number) {
            var b = number % 10,
                output = (~~ (number % 100 / 10) === 1) ? 'th' :
                (b === 1) ? 'st' :
                (b === 2) ? 'nd' :
                (b === 3) ? 'rd' : 'th';
            return number + output;
        }
    });

    /* EMBED_LANGUAGES */

    /************************************
        Exposing Moment
    ************************************/


    // CommonJS module is defined
    if (hasModule) {
        module.exports = moment;
    }
    /*global ender:false */
    if (typeof ender === 'undefined') {
        // here, `this` means `window` in the browser, or `global` on the server
        // add `moment` as a global object via a string identifier,
        // for Closure Compiler "advanced" mode
        this['moment'] = moment;
    }
    /*global define:false */
    if (typeof define === "function" && define.amd) {
        define("moment", [], function () {
            return moment;
        });
    }
}).call(this);

},{}],3:[function(require,module,exports){
/**
 * vis.js module imports
 */

// Try to load dependencies from the global window object.
// If not available there, load via require.
var moment = (typeof window !== 'undefined') && window['moment'] || require('moment');

var Hammer;
if (typeof window !== 'undefined') {
  // load hammer.js only when running in a browser (where window is available)
  Hammer = window['Hammer'] || require('hammerjs');
}
else {
  Hammer = function () {
    throw Error('hammer.js is only available in a browser, not in node.js.');
  }
}


// Internet Explorer 8 and older does not support Array.indexOf, so we define
// it here in that case.
// http://soledadpenades.com/2007/05/17/arrayindexof-in-internet-explorer/
if(!Array.prototype.indexOf) {
  Array.prototype.indexOf = function(obj){
    for(var i = 0; i < this.length; i++){
      if(this[i] == obj){
        return i;
      }
    }
    return -1;
  };

  try {
    console.log("Warning: Ancient browser detected. Please update your browser");
  }
  catch (err) {
  }
}

// Internet Explorer 8 and older does not support Array.forEach, so we define
// it here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/forEach
if (!Array.prototype.forEach) {
  Array.prototype.forEach = function(fn, scope) {
    for(var i = 0, len = this.length; i < len; ++i) {
      fn.call(scope || this, this[i], i, this);
    }
  }
}

// Internet Explorer 8 and older does not support Array.map, so we define it
// here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/map
// Production steps of ECMA-262, Edition 5, 15.4.4.19
// Reference: http://es5.github.com/#x15.4.4.19
if (!Array.prototype.map) {
  Array.prototype.map = function(callback, thisArg) {

    var T, A, k;

    if (this == null) {
      throw new TypeError(" this is null or not defined");
    }

    // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
    var O = Object(this);

    // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
    // 3. Let len be ToUint32(lenValue).
    var len = O.length >>> 0;

    // 4. If IsCallable(callback) is false, throw a TypeError exception.
    // See: http://es5.github.com/#x9.11
    if (typeof callback !== "function") {
      throw new TypeError(callback + " is not a function");
    }

    // 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
    if (thisArg) {
      T = thisArg;
    }

    // 6. Let A be a new array created as if by the expression new Array(len) where Array is
    // the standard built-in constructor with that name and len is the value of len.
    A = new Array(len);

    // 7. Let k be 0
    k = 0;

    // 8. Repeat, while k < len
    while(k < len) {

      var kValue, mappedValue;

      // a. Let Pk be ToString(k).
      //   This is implicit for LHS operands of the in operator
      // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
      //   This step can be combined with c
      // c. If kPresent is true, then
      if (k in O) {

        // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
        kValue = O[ k ];

        // ii. Let mappedValue be the result of calling the Call internal method of callback
        // with T as the this value and argument list containing kValue, k, and O.
        mappedValue = callback.call(T, kValue, k, O);

        // iii. Call the DefineOwnProperty internal method of A with arguments
        // Pk, Property Descriptor {Value: mappedValue, : true, Enumerable: true, Configurable: true},
        // and false.

        // In browsers that support Object.defineProperty, use the following:
        // Object.defineProperty(A, Pk, { value: mappedValue, writable: true, enumerable: true, configurable: true });

        // For best browser support, use the following:
        A[ k ] = mappedValue;
      }
      // d. Increase k by 1.
      k++;
    }

    // 9. return A
    return A;
  };
}

// Internet Explorer 8 and older does not support Array.filter, so we define it
// here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/filter
if (!Array.prototype.filter) {
  Array.prototype.filter = function(fun /*, thisp */) {
    "use strict";

    if (this == null) {
      throw new TypeError();
    }

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun != "function") {
      throw new TypeError();
    }

    var res = [];
    var thisp = arguments[1];
    for (var i = 0; i < len; i++) {
      if (i in t) {
        var val = t[i]; // in case fun mutates this
        if (fun.call(thisp, val, i, t))
          res.push(val);
      }
    }

    return res;
  };
}


// Internet Explorer 8 and older does not support Object.keys, so we define it
// here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/keys
if (!Object.keys) {
  Object.keys = (function () {
    var hasOwnProperty = Object.prototype.hasOwnProperty,
        hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
        dontEnums = [
          'toString',
          'toLocaleString',
          'valueOf',
          'hasOwnProperty',
          'isPrototypeOf',
          'propertyIsEnumerable',
          'constructor'
        ],
        dontEnumsLength = dontEnums.length;

    return function (obj) {
      if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) {
        throw new TypeError('Object.keys called on non-object');
      }

      var result = [];

      for (var prop in obj) {
        if (hasOwnProperty.call(obj, prop)) result.push(prop);
      }

      if (hasDontEnumBug) {
        for (var i=0; i < dontEnumsLength; i++) {
          if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
        }
      }
      return result;
    }
  })()
}

// Internet Explorer 8 and older does not support Array.isArray,
// so we define it here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/isArray
if(!Array.isArray) {
  Array.isArray = function (vArg) {
    return Object.prototype.toString.call(vArg) === "[object Array]";
  };
}

// Internet Explorer 8 and older does not support Function.bind,
// so we define it here in that case.
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Function/bind
if (!Function.prototype.bind) {
  Function.prototype.bind = function (oThis) {
    if (typeof this !== "function") {
      // closest thing possible to the ECMAScript 5 internal IsCallable function
      throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable");
    }

    var aArgs = Array.prototype.slice.call(arguments, 1),
        fToBind = this,
        fNOP = function () {},
        fBound = function () {
          return fToBind.apply(this instanceof fNOP && oThis
              ? this
              : oThis,
              aArgs.concat(Array.prototype.slice.call(arguments)));
        };

    fNOP.prototype = this.prototype;
    fBound.prototype = new fNOP();

    return fBound;
  };
}

// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/create
if (!Object.create) {
  Object.create = function (o) {
    if (arguments.length > 1) {
      throw new Error('Object.create implementation only accepts the first parameter.');
    }
    function F() {}
    F.prototype = o;
    return new F();
  };
}

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind
if (!Function.prototype.bind) {
  Function.prototype.bind = function (oThis) {
    if (typeof this !== "function") {
      // closest thing possible to the ECMAScript 5 internal IsCallable function
      throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable");
    }

    var aArgs = Array.prototype.slice.call(arguments, 1),
        fToBind = this,
        fNOP = function () {},
        fBound = function () {
          return fToBind.apply(this instanceof fNOP && oThis
              ? this
              : oThis,
              aArgs.concat(Array.prototype.slice.call(arguments)));
        };

    fNOP.prototype = this.prototype;
    fBound.prototype = new fNOP();

    return fBound;
  };
}

/**
 * utility functions
 */
var util = {};

/**
 * Test whether given object is a number
 * @param {*} object
 * @return {Boolean} isNumber
 */
util.isNumber = function isNumber(object) {
  return (object instanceof Number || typeof object == 'number');
};

/**
 * Test whether given object is a string
 * @param {*} object
 * @return {Boolean} isString
 */
util.isString = function isString(object) {
  return (object instanceof String || typeof object == 'string');
};

/**
 * Test whether given object is a Date, or a String containing a Date
 * @param {Date | String} object
 * @return {Boolean} isDate
 */
util.isDate = function isDate(object) {
  if (object instanceof Date) {
    return true;
  }
  else if (util.isString(object)) {
    // test whether this string contains a date
    var match = ASPDateRegex.exec(object);
    if (match) {
      return true;
    }
    else if (!isNaN(Date.parse(object))) {
      return true;
    }
  }

  return false;
};

/**
 * Test whether given object is an instance of google.visualization.DataTable
 * @param {*} object
 * @return {Boolean} isDataTable
 */
util.isDataTable = function isDataTable(object) {
  return (typeof (google) !== 'undefined') &&
      (google.visualization) &&
      (google.visualization.DataTable) &&
      (object instanceof google.visualization.DataTable);
};

/**
 * Create a semi UUID
 * source: http://stackoverflow.com/a/105074/1262753
 * @return {String} uuid
 */
util.randomUUID = function randomUUID () {
  var S4 = function () {
    return Math.floor(
        Math.random() * 0x10000 /* 65536 */
    ).toString(16);
  };

  return (
      S4() + S4() + '-' +
          S4() + '-' +
          S4() + '-' +
          S4() + '-' +
          S4() + S4() + S4()
      );
};

/**
 * Extend object a with the properties of object b or a series of objects
 * Only properties with defined values are copied
 * @param {Object} a
 * @param {... Object} b
 * @return {Object} a
 */
util.extend = function (a, b) {
  for (var i = 1, len = arguments.length; i < len; i++) {
    var other = arguments[i];
    for (var prop in other) {
      if (other.hasOwnProperty(prop) && other[prop] !== undefined) {
        a[prop] = other[prop];
      }
    }
  }

  return a;
};

/**
 * Convert an object to another type
 * @param {Boolean | Number | String | Date | Moment | Null | undefined} object
 * @param {String | undefined} type   Name of the type. Available types:
 *                                    'Boolean', 'Number', 'String',
 *                                    'Date', 'Moment', ISODate', 'ASPDate'.
 * @return {*} object
 * @throws Error
 */
util.convert = function convert(object, type) {
  var match;

  if (object === undefined) {
    return undefined;
  }
  if (object === null) {
    return null;
  }

  if (!type) {
    return object;
  }
  if (!(typeof type === 'string') && !(type instanceof String)) {
    throw new Error('Type must be a string');
  }

  //noinspection FallthroughInSwitchStatementJS
  switch (type) {
    case 'boolean':
    case 'Boolean':
      return Boolean(object);

    case 'number':
    case 'Number':
      return Number(object.valueOf());

    case 'string':
    case 'String':
      return String(object);

    case 'Date':
      if (util.isNumber(object)) {
        return new Date(object);
      }
      if (object instanceof Date) {
        return new Date(object.valueOf());
      }
      else if (moment.isMoment(object)) {
        return new Date(object.valueOf());
      }
      if (util.isString(object)) {
        match = ASPDateRegex.exec(object);
        if (match) {
          // object is an ASP date
          return new Date(Number(match[1])); // parse number
        }
        else {
          return moment(object).toDate(); // parse string
        }
      }
      else {
        throw new Error(
            'Cannot convert object of type ' + util.getType(object) +
                ' to type Date');
      }

    case 'Moment':
      if (util.isNumber(object)) {
        return moment(object);
      }
      if (object instanceof Date) {
        return moment(object.valueOf());
      }
      else if (moment.isMoment(object)) {
        return moment(object);
      }
      if (util.isString(object)) {
        match = ASPDateRegex.exec(object);
        if (match) {
          // object is an ASP date
          return moment(Number(match[1])); // parse number
        }
        else {
          return moment(object); // parse string
        }
      }
      else {
        throw new Error(
            'Cannot convert object of type ' + util.getType(object) +
                ' to type Date');
      }

    case 'ISODate':
      if (util.isNumber(object)) {
        return new Date(object);
      }
      else if (object instanceof Date) {
        return object.toISOString();
      }
      else if (moment.isMoment(object)) {
        return object.toDate().toISOString();
      }
      else if (util.isString(object)) {
        match = ASPDateRegex.exec(object);
        if (match) {
          // object is an ASP date
          return new Date(Number(match[1])).toISOString(); // parse number
        }
        else {
          return new Date(object).toISOString(); // parse string
        }
      }
      else {
        throw new Error(
            'Cannot convert object of type ' + util.getType(object) +
                ' to type ISODate');
      }

    case 'ASPDate':
      if (util.isNumber(object)) {
        return '/Date(' + object + ')/';
      }
      else if (object instanceof Date) {
        return '/Date(' + object.valueOf() + ')/';
      }
      else if (util.isString(object)) {
        match = ASPDateRegex.exec(object);
        var value;
        if (match) {
          // object is an ASP date
          value = new Date(Number(match[1])).valueOf(); // parse number
        }
        else {
          value = new Date(object).valueOf(); // parse string
        }
        return '/Date(' + value + ')/';
      }
      else {
        throw new Error(
            'Cannot convert object of type ' + util.getType(object) +
                ' to type ASPDate');
      }

    default:
      throw new Error('Cannot convert object of type ' + util.getType(object) +
          ' to type "' + type + '"');
  }
};

// parse ASP.Net Date pattern,
// for example '/Date(1198908717056)/' or '/Date(1198908717056-0700)/'
// code from http://momentjs.com/
var ASPDateRegex = /^\/?Date\((\-?\d+)/i;

/**
 * Get the type of an object, for example util.getType([]) returns 'Array'
 * @param {*} object
 * @return {String} type
 */
util.getType = function getType(object) {
  var type = typeof object;

  if (type == 'object') {
    if (object == null) {
      return 'null';
    }
    if (object instanceof Boolean) {
      return 'Boolean';
    }
    if (object instanceof Number) {
      return 'Number';
    }
    if (object instanceof String) {
      return 'String';
    }
    if (object instanceof Array) {
      return 'Array';
    }
    if (object instanceof Date) {
      return 'Date';
    }
    return 'Object';
  }
  else if (type == 'number') {
    return 'Number';
  }
  else if (type == 'boolean') {
    return 'Boolean';
  }
  else if (type == 'string') {
    return 'String';
  }

  return type;
};

/**
 * Retrieve the absolute left value of a DOM element
 * @param {Element} elem        A dom element, for example a div
 * @return {number} left        The absolute left position of this element
 *                              in the browser page.
 */
util.getAbsoluteLeft = function getAbsoluteLeft (elem) {
  var doc = document.documentElement;
  var body = document.body;

  var left = elem.offsetLeft;
  var e = elem.offsetParent;
  while (e != null && e != body && e != doc) {
    left += e.offsetLeft;
    left -= e.scrollLeft;
    e = e.offsetParent;
  }
  return left;
};

/**
 * Retrieve the absolute top value of a DOM element
 * @param {Element} elem        A dom element, for example a div
 * @return {number} top        The absolute top position of this element
 *                              in the browser page.
 */
util.getAbsoluteTop = function getAbsoluteTop (elem) {
  var doc = document.documentElement;
  var body = document.body;

  var top = elem.offsetTop;
  var e = elem.offsetParent;
  while (e != null && e != body && e != doc) {
    top += e.offsetTop;
    top -= e.scrollTop;
    e = e.offsetParent;
  }
  return top;
};

/**
 * Get the absolute, vertical mouse position from an event.
 * @param {Event} event
 * @return {Number} pageY
 */
util.getPageY = function getPageY (event) {
  if ('pageY' in event) {
    return event.pageY;
  }
  else {
    var clientY;
    if (('targetTouches' in event) && event.targetTouches.length) {
      clientY = event.targetTouches[0].clientY;
    }
    else {
      clientY = event.clientY;
    }

    var doc = document.documentElement;
    var body = document.body;
    return clientY +
        ( doc && doc.scrollTop || body && body.scrollTop || 0 ) -
        ( doc && doc.clientTop || body && body.clientTop || 0 );
  }
};

/**
 * Get the absolute, horizontal mouse position from an event.
 * @param {Event} event
 * @return {Number} pageX
 */
util.getPageX = function getPageX (event) {
  if ('pageY' in event) {
    return event.pageX;
  }
  else {
    var clientX;
    if (('targetTouches' in event) && event.targetTouches.length) {
      clientX = event.targetTouches[0].clientX;
    }
    else {
      clientX = event.clientX;
    }

    var doc = document.documentElement;
    var body = document.body;
    return clientX +
        ( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) -
        ( doc && doc.clientLeft || body && body.clientLeft || 0 );
  }
};

/**
 * add a className to the given elements style
 * @param {Element} elem
 * @param {String} className
 */
util.addClassName = function addClassName(elem, className) {
  var classes = elem.className.split(' ');
  if (classes.indexOf(className) == -1) {
    classes.push(className); // add the class to the array
    elem.className = classes.join(' ');
  }
};

/**
 * add a className to the given elements style
 * @param {Element} elem
 * @param {String} className
 */
util.removeClassName = function removeClassname(elem, className) {
  var classes = elem.className.split(' ');
  var index = classes.indexOf(className);
  if (index != -1) {
    classes.splice(index, 1); // remove the class from the array
    elem.className = classes.join(' ');
  }
};

/**
 * For each method for both arrays and objects.
 * In case of an array, the built-in Array.forEach() is applied.
 * In case of an Object, the method loops over all properties of the object.
 * @param {Object | Array} object   An Object or Array
 * @param {function} callback       Callback method, called for each item in
 *                                  the object or array with three parameters:
 *                                  callback(value, index, object)
 */
util.forEach = function forEach (object, callback) {
  var i,
      len;
  if (object instanceof Array) {
    // array
    for (i = 0, len = object.length; i < len; i++) {
      callback(object[i], i, object);
    }
  }
  else {
    // object
    for (i in object) {
      if (object.hasOwnProperty(i)) {
        callback(object[i], i, object);
      }
    }
  }
};

/**
 * Update a property in an object
 * @param {Object} object
 * @param {String} key
 * @param {*} value
 * @return {Boolean} changed
 */
util.updateProperty = function updateProp (object, key, value) {
  if (object[key] !== value) {
    object[key] = value;
    return true;
  }
  else {
    return false;
  }
};

/**
 * Add and event listener. Works for all browsers
 * @param {Element}     element    An html element
 * @param {string}      action     The action, for example "click",
 *                                 without the prefix "on"
 * @param {function}    listener   The callback function to be executed
 * @param {boolean}     [useCapture]
 */
util.addEventListener = function addEventListener(element, action, listener, useCapture) {
  if (element.addEventListener) {
    if (useCapture === undefined)
      useCapture = false;

    if (action === "mousewheel" && navigator.userAgent.indexOf("Firefox") >= 0) {
      action = "DOMMouseScroll";  // For Firefox
    }

    element.addEventListener(action, listener, useCapture);
  } else {
    element.attachEvent("on" + action, listener);  // IE browsers
  }
};

/**
 * Remove an event listener from an element
 * @param {Element}     element         An html dom element
 * @param {string}      action          The name of the event, for example "mousedown"
 * @param {function}    listener        The listener function
 * @param {boolean}     [useCapture]
 */
util.removeEventListener = function removeEventListener(element, action, listener, useCapture) {
  if (element.removeEventListener) {
    // non-IE browsers
    if (useCapture === undefined)
      useCapture = false;

    if (action === "mousewheel" && navigator.userAgent.indexOf("Firefox") >= 0) {
      action = "DOMMouseScroll";  // For Firefox
    }

    element.removeEventListener(action, listener, useCapture);
  } else {
    // IE browsers
    element.detachEvent("on" + action, listener);
  }
};


/**
 * Get HTML element which is the target of the event
 * @param {Event} event
 * @return {Element} target element
 */
util.getTarget = function getTarget(event) {
  // code from http://www.quirksmode.org/js/events_properties.html
  if (!event) {
    event = window.event;
  }

  var target;

  if (event.target) {
    target = event.target;
  }
  else if (event.srcElement) {
    target = event.srcElement;
  }

  if (target.nodeType != undefined && target.nodeType == 3) {
    // defeat Safari bug
    target = target.parentNode;
  }

  return target;
};

/**
 * Stop event propagation
 */
util.stopPropagation = function stopPropagation(event) {
  if (!event)
    event = window.event;

  if (event.stopPropagation) {
    event.stopPropagation();  // non-IE browsers
  }
  else {
    event.cancelBubble = true;  // IE browsers
  }
};


/**
 * Cancels the event if it is cancelable, without stopping further propagation of the event.
 */
util.preventDefault = function preventDefault (event) {
  if (!event)
    event = window.event;

  if (event.preventDefault) {
    event.preventDefault();  // non-IE browsers
  }
  else {
    event.returnValue = false;  // IE browsers
  }
};


util.option = {};

/**
 * Convert a value into a boolean
 * @param {Boolean | function | undefined} value
 * @param {Boolean} [defaultValue]
 * @returns {Boolean} bool
 */
util.option.asBoolean = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  if (value != null) {
    return (value != false);
  }

  return defaultValue || null;
};

/**
 * Convert a value into a number
 * @param {Boolean | function | undefined} value
 * @param {Number} [defaultValue]
 * @returns {Number} number
 */
util.option.asNumber = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  if (value != null) {
    return Number(value) || defaultValue || null;
  }

  return defaultValue || null;
};

/**
 * Convert a value into a string
 * @param {String | function | undefined} value
 * @param {String} [defaultValue]
 * @returns {String} str
 */
util.option.asString = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  if (value != null) {
    return String(value);
  }

  return defaultValue || null;
};

/**
 * Convert a size or location into a string with pixels or a percentage
 * @param {String | Number | function | undefined} value
 * @param {String} [defaultValue]
 * @returns {String} size
 */
util.option.asSize = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  if (util.isString(value)) {
    return value;
  }
  else if (util.isNumber(value)) {
    return value + 'px';
  }
  else {
    return defaultValue || null;
  }
};

/**
 * Convert a value into a DOM element
 * @param {HTMLElement | function | undefined} value
 * @param {HTMLElement} [defaultValue]
 * @returns {HTMLElement | null} dom
 */
util.option.asElement = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  return value || defaultValue || null;
};

/**
 * load css from text
 * @param {String} css    Text containing css
 */
util.loadCss = function (css) {
  if (typeof document === 'undefined') {
    return;
  }

  // get the script location, and built the css file name from the js file name
  // http://stackoverflow.com/a/2161748/1262753
  // var scripts = document.getElementsByTagName('script');
  // var jsFile = scripts[scripts.length-1].src.split('?')[0];
  // var cssFile = jsFile.substring(0, jsFile.length - 2) + 'css';

  // inject css
  // http://stackoverflow.com/questions/524696/how-to-create-a-style-tag-with-javascript
  var style = document.createElement('style');
  style.type = 'text/css';
  if (style.styleSheet){
    style.styleSheet.cssText = css;
  } else {
    style.appendChild(document.createTextNode(css));
  }

  document.getElementsByTagName('head')[0].appendChild(style);
};

/**
 * Event listener (singleton)
 */
// TODO: replace usage of the event listener for the EventBus
var events = {
  'listeners': [],

  /**
   * Find a single listener by its object
   * @param {Object} object
   * @return {Number} index  -1 when not found
   */
  'indexOf': function (object) {
    var listeners = this.listeners;
    for (var i = 0, iMax = this.listeners.length; i < iMax; i++) {
      var listener = listeners[i];
      if (listener && listener.object == object) {
        return i;
      }
    }
    return -1;
  },

  /**
   * Add an event listener
   * @param {Object} object
   * @param {String} event       The name of an event, for example 'select'
   * @param {function} callback  The callback method, called when the
   *                             event takes place
   */
  'addListener': function (object, event, callback) {
    var index = this.indexOf(object);
    var listener = this.listeners[index];
    if (!listener) {
      listener = {
        'object': object,
        'events': {}
      };
      this.listeners.push(listener);
    }

    var callbacks = listener.events[event];
    if (!callbacks) {
      callbacks = [];
      listener.events[event] = callbacks;
    }

    // add the callback if it does not yet exist
    if (callbacks.indexOf(callback) == -1) {
      callbacks.push(callback);
    }
  },

  /**
   * Remove an event listener
   * @param {Object} object
   * @param {String} event       The name of an event, for example 'select'
   * @param {function} callback  The registered callback method
   */
  'removeListener': function (object, event, callback) {
    var index = this.indexOf(object);
    var listener = this.listeners[index];
    if (listener) {
      var callbacks = listener.events[event];
      if (callbacks) {
        index = callbacks.indexOf(callback);
        if (index != -1) {
          callbacks.splice(index, 1);
        }

        // remove the array when empty
        if (callbacks.length == 0) {
          delete listener.events[event];
        }
      }

      // count the number of registered events. remove listener when empty
      var count = 0;
      var events = listener.events;
      for (var e in events) {
        if (events.hasOwnProperty(e)) {
          count++;
        }
      }
      if (count == 0) {
        delete this.listeners[index];
      }
    }
  },

  /**
   * Remove all registered event listeners
   */
  'removeAllListeners': function () {
    this.listeners = [];
  },

  /**
   * Trigger an event. All registered event handlers will be called
   * @param {Object} object
   * @param {String} event
   * @param {Object} properties (optional)
   */
  'trigger': function (object, event, properties) {
    var index = this.indexOf(object);
    var listener = this.listeners[index];
    if (listener) {
      var callbacks = listener.events[event];
      if (callbacks) {
        for (var i = 0, iMax = callbacks.length; i < iMax; i++) {
          callbacks[i](properties);
        }
      }
    }
  }
};

/**
 * An event bus can be used to emit events, and to subscribe to events
 * @constructor EventBus
 */
function EventBus() {
  this.subscriptions = [];
}

/**
 * Subscribe to an event
 * @param {String | RegExp} event   The event can be a regular expression, or
 *                                  a string with wildcards, like 'server.*'.
 * @param {function} callback.      Callback are called with three parameters:
 *                                  {String} event, {*} [data], {*} [source]
 * @param {*} [target]
 * @returns {String} id    A subscription id
 */
EventBus.prototype.on = function (event, callback, target) {
  var regexp = (event instanceof RegExp) ?
      event :
      new RegExp(event.replace('*', '\\w+'));

  var subscription = {
    id:       util.randomUUID(),
    event:    event,
    regexp:   regexp,
    callback: (typeof callback === 'function') ? callback : null,
    target:   target
  };

  this.subscriptions.push(subscription);

  return subscription.id;
};

/**
 * Unsubscribe from an event
 * @param {String | Object} filter   Filter for subscriptions to be removed
 *                                   Filter can be a string containing a
 *                                   subscription id, or an object containing
 *                                   one or more of the fields id, event,
 *                                   callback, and target.
 */
EventBus.prototype.off = function (filter) {
  var i = 0;
  while (i < this.subscriptions.length) {
    var subscription = this.subscriptions[i];

    var match = true;
    if (filter instanceof Object) {
      // filter is an object. All fields must match
      for (var prop in filter) {
        if (filter.hasOwnProperty(prop)) {
          if (filter[prop] !== subscription[prop]) {
            match = false;
          }
        }
      }
    }
    else {
      // filter is a string, filter on id
      match = (subscription.id == filter);
    }

    if (match) {
      this.subscriptions.splice(i, 1);
    }
    else {
      i++;
    }
  }
};

/**
 * Emit an event
 * @param {String} event
 * @param {*} [data]
 * @param {*} [source]
 */
EventBus.prototype.emit = function (event, data, source) {
  for (var i =0; i < this.subscriptions.length; i++) {
    var subscription = this.subscriptions[i];
    if (subscription.regexp.test(event)) {
      if (subscription.callback) {
        subscription.callback(event, data, source);
      }
    }
  }
};

/**
 * DataSet
 *
 * Usage:
 *     var dataSet = new DataSet({
 *         fieldId: '_id',
 *         convert: {
 *             // ...
 *         }
 *     });
 *
 *     dataSet.add(item);
 *     dataSet.add(data);
 *     dataSet.update(item);
 *     dataSet.update(data);
 *     dataSet.remove(id);
 *     dataSet.remove(ids);
 *     var data = dataSet.get();
 *     var data = dataSet.get(id);
 *     var data = dataSet.get(ids);
 *     var data = dataSet.get(ids, options, data);
 *     dataSet.clear();
 *
 * A data set can:
 * - add/remove/update data
 * - gives triggers upon changes in the data
 * - can  import/export data in various data formats
 *
 * @param {Object} [options]   Available options:
 *                             {String} fieldId Field name of the id in the
 *                                              items, 'id' by default.
 *                             {Object.<String, String} convert
 *                                              A map with field names as key,
 *                                              and the field type as value.
 * @constructor DataSet
 */
// TODO: add a DataSet constructor DataSet(data, options)
function DataSet (options) {
  this.id = util.randomUUID();

  this.options = options || {};
  this.data = {};                                 // map with data indexed by id
  this.fieldId = this.options.fieldId || 'id';    // name of the field containing id
  this.convert = {};                              // field types by field name

  if (this.options.convert) {
    for (var field in this.options.convert) {
      if (this.options.convert.hasOwnProperty(field)) {
        var value = this.options.convert[field];
        if (value == 'Date' || value == 'ISODate' || value == 'ASPDate') {
          this.convert[field] = 'Date';
        }
        else {
          this.convert[field] = value;
        }
      }
    }
  }

  // event subscribers
  this.subscribers = {};

  this.internalIds = {};            // internally generated id's
}

/**
 * Subscribe to an event, add an event listener
 * @param {String} event        Event name. Available events: 'put', 'update',
 *                              'remove'
 * @param {function} callback   Callback method. Called with three parameters:
 *                                  {String} event
 *                                  {Object | null} params
 *                                  {String | Number} senderId
 */
DataSet.prototype.subscribe = function (event, callback) {
  var subscribers = this.subscribers[event];
  if (!subscribers) {
    subscribers = [];
    this.subscribers[event] = subscribers;
  }

  subscribers.push({
    callback: callback
  });
};

/**
 * Unsubscribe from an event, remove an event listener
 * @param {String} event
 * @param {function} callback
 */
DataSet.prototype.unsubscribe = function (event, callback) {
  var subscribers = this.subscribers[event];
  if (subscribers) {
    this.subscribers[event] = subscribers.filter(function (listener) {
      return (listener.callback != callback);
    });
  }
};

/**
 * Trigger an event
 * @param {String} event
 * @param {Object | null} params
 * @param {String} [senderId]       Optional id of the sender.
 * @private
 */
DataSet.prototype._trigger = function (event, params, senderId) {
  if (event == '*') {
    throw new Error('Cannot trigger event *');
  }

  var subscribers = [];
  if (event in this.subscribers) {
    subscribers = subscribers.concat(this.subscribers[event]);
  }
  if ('*' in this.subscribers) {
    subscribers = subscribers.concat(this.subscribers['*']);
  }

  for (var i = 0; i < subscribers.length; i++) {
    var subscriber = subscribers[i];
    if (subscriber.callback) {
      subscriber.callback(event, params, senderId || null);
    }
  }
};

/**
 * Add data.
 * Adding an item will fail when there already is an item with the same id.
 * @param {Object | Array | DataTable} data
 * @param {String} [senderId] Optional sender id
 * @return {Array} addedIds      Array with the ids of the added items
 */
DataSet.prototype.add = function (data, senderId) {
  var addedIds = [],
      id,
      me = this;

  if (data instanceof Array) {
    // Array
    for (var i = 0, len = data.length; i < len; i++) {
      id = me._addItem(data[i]);
      addedIds.push(id);
    }
  }
  else if (util.isDataTable(data)) {
    // Google DataTable
    var columns = this._getColumnNames(data);
    for (var row = 0, rows = data.getNumberOfRows(); row < rows; row++) {
      var item = {};
      for (var col = 0, cols = columns.length; col < cols; col++) {
        var field = columns[col];
        item[field] = data.getValue(row, col);
      }

      id = me._addItem(item);
      addedIds.push(id);
    }
  }
  else if (data instanceof Object) {
    // Single item
    id = me._addItem(data);
    addedIds.push(id);
  }
  else {
    throw new Error('Unknown dataType');
  }

  if (addedIds.length) {
    this._trigger('add', {items: addedIds}, senderId);
  }

  return addedIds;
};

/**
 * Update existing items. When an item does not exist, it will be created
 * @param {Object | Array | DataTable} data
 * @param {String} [senderId] Optional sender id
 * @return {Array} updatedIds     The ids of the added or updated items
 */
DataSet.prototype.update = function (data, senderId) {
  var addedIds = [],
      updatedIds = [],
      me = this,
      fieldId = me.fieldId;

  var addOrUpdate = function (item) {
    var id = item[fieldId];
    if (me.data[id]) {
      // update item
      id = me._updateItem(item);
      updatedIds.push(id);
    }
    else {
      // add new item
      id = me._addItem(item);
      addedIds.push(id);
    }
  };

  if (data instanceof Array) {
    // Array
    for (var i = 0, len = data.length; i < len; i++) {
      addOrUpdate(data[i]);
    }
  }
  else if (util.isDataTable(data)) {
    // Google DataTable
    var columns = this._getColumnNames(data);
    for (var row = 0, rows = data.getNumberOfRows(); row < rows; row++) {
      var item = {};
      for (var col = 0, cols = columns.length; col < cols; col++) {
        var field = columns[col];
        item[field] = data.getValue(row, col);
      }

      addOrUpdate(item);
    }
  }
  else if (data instanceof Object) {
    // Single item
    addOrUpdate(data);
  }
  else {
    throw new Error('Unknown dataType');
  }

  if (addedIds.length) {
    this._trigger('add', {items: addedIds}, senderId);
  }
  if (updatedIds.length) {
    this._trigger('update', {items: updatedIds}, senderId);
  }

  return addedIds.concat(updatedIds);
};

/**
 * Get a data item or multiple items.
 *
 * Usage:
 *
 *     get()
 *     get(options: Object)
 *     get(options: Object, data: Array | DataTable)
 *
 *     get(id: Number | String)
 *     get(id: Number | String, options: Object)
 *     get(id: Number | String, options: Object, data: Array | DataTable)
 *
 *     get(ids: Number[] | String[])
 *     get(ids: Number[] | String[], options: Object)
 *     get(ids: Number[] | String[], options: Object, data: Array | DataTable)
 *
 * Where:
 *
 * {Number | String} id         The id of an item
 * {Number[] | String{}} ids    An array with ids of items
 * {Object} options             An Object with options. Available options:
 *                              {String} [type] Type of data to be returned. Can
 *                                              be 'DataTable' or 'Array' (default)
 *                              {Object.<String, String>} [convert]
 *                              {String[]} [fields] field names to be returned
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * {Array | DataTable} [data]   If provided, items will be appended to this
 *                              array or table. Required in case of Google
 *                              DataTable.
 *
 * @throws Error
 */
DataSet.prototype.get = function (args) {
  var me = this;

  // parse the arguments
  var id, ids, options, data;
  var firstType = util.getType(arguments[0]);
  if (firstType == 'String' || firstType == 'Number') {
    // get(id [, options] [, data])
    id = arguments[0];
    options = arguments[1];
    data = arguments[2];
  }
  else if (firstType == 'Array') {
    // get(ids [, options] [, data])
    ids = arguments[0];
    options = arguments[1];
    data = arguments[2];
  }
  else {
    // get([, options] [, data])
    options = arguments[0];
    data = arguments[1];
  }

  // determine the return type
  var type;
  if (options && options.type) {
    type = (options.type == 'DataTable') ? 'DataTable' : 'Array';

    if (data && (type != util.getType(data))) {
      throw new Error('Type of parameter "data" (' + util.getType(data) + ') ' +
          'does not correspond with specified options.type (' + options.type + ')');
    }
    if (type == 'DataTable' && !util.isDataTable(data)) {
      throw new Error('Parameter "data" must be a DataTable ' +
          'when options.type is "DataTable"');
    }
  }
  else if (data) {
    type = (util.getType(data) == 'DataTable') ? 'DataTable' : 'Array';
  }
  else {
    type = 'Array';
  }

  // build options
  var convert = options && options.convert || this.options.convert;
  var filter = options && options.filter;
  var items = [], item, itemId, i, len;

  // convert items
  if (id != undefined) {
    // return a single item
    item = me._getItem(id, convert);
    if (filter && !filter(item)) {
      item = null;
    }
  }
  else if (ids != undefined) {
    // return a subset of items
    for (i = 0, len = ids.length; i < len; i++) {
      item = me._getItem(ids[i], convert);
      if (!filter || filter(item)) {
        items.push(item);
      }
    }
  }
  else {
    // return all items
    for (itemId in this.data) {
      if (this.data.hasOwnProperty(itemId)) {
        item = me._getItem(itemId, convert);
        if (!filter || filter(item)) {
          items.push(item);
        }
      }
    }
  }

  // order the results
  if (options && options.order && id == undefined) {
    this._sort(items, options.order);
  }

  // filter fields of the items
  if (options && options.fields) {
    var fields = options.fields;
    if (id != undefined) {
      item = this._filterFields(item, fields);
    }
    else {
      for (i = 0, len = items.length; i < len; i++) {
        items[i] = this._filterFields(items[i], fields);
      }
    }
  }

  // return the results
  if (type == 'DataTable') {
    var columns = this._getColumnNames(data);
    if (id != undefined) {
      // append a single item to the data table
      me._appendRow(data, columns, item);
    }
    else {
      // copy the items to the provided data table
      for (i = 0, len = items.length; i < len; i++) {
        me._appendRow(data, columns, items[i]);
      }
    }
    return data;
  }
  else {
    // return an array
    if (id != undefined) {
      // a single item
      return item;
    }
    else {
      // multiple items
      if (data) {
        // copy the items to the provided array
        for (i = 0, len = items.length; i < len; i++) {
          data.push(items[i]);
        }
        return data;
      }
      else {
        // just return our array
        return items;
      }
    }
  }
};

/**
 * Get ids of all items or from a filtered set of items.
 * @param {Object} [options]    An Object with options. Available options:
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * @return {Array} ids
 */
DataSet.prototype.getIds = function (options) {
  var data = this.data,
      filter = options && options.filter,
      order = options && options.order,
      convert = options && options.convert || this.options.convert,
      i,
      len,
      id,
      item,
      items,
      ids = [];

  if (filter) {
    // get filtered items
    if (order) {
      // create ordered list
      items = [];
      for (id in data) {
        if (data.hasOwnProperty(id)) {
          item = this._getItem(id, convert);
          if (filter(item)) {
            items.push(item);
          }
        }
      }

      this._sort(items, order);

      for (i = 0, len = items.length; i < len; i++) {
        ids[i] = items[i][this.fieldId];
      }
    }
    else {
      // create unordered list
      for (id in data) {
        if (data.hasOwnProperty(id)) {
          item = this._getItem(id, convert);
          if (filter(item)) {
            ids.push(item[this.fieldId]);
          }
        }
      }
    }
  }
  else {
    // get all items
    if (order) {
      // create an ordered list
      items = [];
      for (id in data) {
        if (data.hasOwnProperty(id)) {
          items.push(data[id]);
        }
      }

      this._sort(items, order);

      for (i = 0, len = items.length; i < len; i++) {
        ids[i] = items[i][this.fieldId];
      }
    }
    else {
      // create unordered list
      for (id in data) {
        if (data.hasOwnProperty(id)) {
          item = data[id];
          ids.push(item[this.fieldId]);
        }
      }
    }
  }

  return ids;
};

/**
 * Execute a callback function for every item in the dataset.
 * The order of the items is not determined.
 * @param {function} callback
 * @param {Object} [options]    Available options:
 *                              {Object.<String, String>} [convert]
 *                              {String[]} [fields] filter fields
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 */
DataSet.prototype.forEach = function (callback, options) {
  var filter = options && options.filter,
      convert = options && options.convert || this.options.convert,
      data = this.data,
      item,
      id;

  if (options && options.order) {
    // execute forEach on ordered list
    var items = this.get(options);

    for (var i = 0, len = items.length; i < len; i++) {
      item = items[i];
      id = item[this.fieldId];
      callback(item, id);
    }
  }
  else {
    // unordered
    for (id in data) {
      if (data.hasOwnProperty(id)) {
        item = this._getItem(id, convert);
        if (!filter || filter(item)) {
          callback(item, id);
        }
      }
    }
  }
};

/**
 * Map every item in the dataset.
 * @param {function} callback
 * @param {Object} [options]    Available options:
 *                              {Object.<String, String>} [convert]
 *                              {String[]} [fields] filter fields
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * @return {Object[]} mappedItems
 */
DataSet.prototype.map = function (callback, options) {
  var filter = options && options.filter,
      convert = options && options.convert || this.options.convert,
      mappedItems = [],
      data = this.data,
      item;

  // convert and filter items
  for (var id in data) {
    if (data.hasOwnProperty(id)) {
      item = this._getItem(id, convert);
      if (!filter || filter(item)) {
        mappedItems.push(callback(item, id));
      }
    }
  }

  // order items
  if (options && options.order) {
    this._sort(mappedItems, options.order);
  }

  return mappedItems;
};

/**
 * Filter the fields of an item
 * @param {Object} item
 * @param {String[]} fields     Field names
 * @return {Object} filteredItem
 * @private
 */
DataSet.prototype._filterFields = function (item, fields) {
  var filteredItem = {};

  for (var field in item) {
    if (item.hasOwnProperty(field) && (fields.indexOf(field) != -1)) {
      filteredItem[field] = item[field];
    }
  }

  return filteredItem;
};

/**
 * Sort the provided array with items
 * @param {Object[]} items
 * @param {String | function} order      A field name or custom sort function.
 * @private
 */
DataSet.prototype._sort = function (items, order) {
  if (util.isString(order)) {
    // order by provided field name
    var name = order; // field name
    items.sort(function (a, b) {
      var av = a[name];
      var bv = b[name];
      return (av > bv) ? 1 : ((av < bv) ? -1 : 0);
    });
  }
  else if (typeof order === 'function') {
    // order by sort function
    items.sort(order);
  }
  // TODO: extend order by an Object {field:String, direction:String}
  //       where direction can be 'asc' or 'desc'
  else {
    throw new TypeError('Order must be a function or a string');
  }
};

/**
 * Remove an object by pointer or by id
 * @param {String | Number | Object | Array} id Object or id, or an array with
 *                                              objects or ids to be removed
 * @param {String} [senderId] Optional sender id
 * @return {Array} removedIds
 */
DataSet.prototype.remove = function (id, senderId) {
  var removedIds = [],
      i, len, removedId;

  if (id instanceof Array) {
    for (i = 0, len = id.length; i < len; i++) {
      removedId = this._remove(id[i]);
      if (removedId != null) {
        removedIds.push(removedId);
      }
    }
  }
  else {
    removedId = this._remove(id);
    if (removedId != null) {
      removedIds.push(removedId);
    }
  }

  if (removedIds.length) {
    this._trigger('remove', {items: removedIds}, senderId);
  }

  return removedIds;
};

/**
 * Remove an item by its id
 * @param {Number | String | Object} id   id or item
 * @returns {Number | String | null} id
 * @private
 */
DataSet.prototype._remove = function (id) {
  if (util.isNumber(id) || util.isString(id)) {
    if (this.data[id]) {
      delete this.data[id];
      delete this.internalIds[id];
      return id;
    }
  }
  else if (id instanceof Object) {
    var itemId = id[this.fieldId];
    if (itemId && this.data[itemId]) {
      delete this.data[itemId];
      delete this.internalIds[itemId];
      return itemId;
    }
  }
  return null;
};

/**
 * Clear the data
 * @param {String} [senderId] Optional sender id
 * @return {Array} removedIds    The ids of all removed items
 */
DataSet.prototype.clear = function (senderId) {
  var ids = Object.keys(this.data);

  this.data = {};
  this.internalIds = {};

  this._trigger('remove', {items: ids}, senderId);

  return ids;
};

/**
 * Find the item with maximum value of a specified field
 * @param {String} field
 * @return {Object | null} item  Item containing max value, or null if no items
 */
DataSet.prototype.max = function (field) {
  var data = this.data,
      max = null,
      maxField = null;

  for (var id in data) {
    if (data.hasOwnProperty(id)) {
      var item = data[id];
      var itemField = item[field];
      if (itemField != null && (!max || itemField > maxField)) {
        max = item;
        maxField = itemField;
      }
    }
  }

  return max;
};

/**
 * Find the item with minimum value of a specified field
 * @param {String} field
 * @return {Object | null} item  Item containing max value, or null if no items
 */
DataSet.prototype.min = function (field) {
  var data = this.data,
      min = null,
      minField = null;

  for (var id in data) {
    if (data.hasOwnProperty(id)) {
      var item = data[id];
      var itemField = item[field];
      if (itemField != null && (!min || itemField < minField)) {
        min = item;
        minField = itemField;
      }
    }
  }

  return min;
};

/**
 * Find all distinct values of a specified field
 * @param {String} field
 * @return {Array} values  Array containing all distinct values. If the data
 *                         items do not contain the specified field, an array
 *                         containing a single value undefined is returned.
 *                         The returned array is unordered.
 */
DataSet.prototype.distinct = function (field) {
  var data = this.data,
      values = [],
      fieldType = this.options.convert[field],
      count = 0;

  for (var prop in data) {
    if (data.hasOwnProperty(prop)) {
      var item = data[prop];
      var value = util.convert(item[field], fieldType);
      var exists = false;
      for (var i = 0; i < count; i++) {
        if (values[i] == value) {
          exists = true;
          break;
        }
      }
      if (!exists) {
        values[count] = value;
        count++;
      }
    }
  }

  return values;
};

/**
 * Add a single item. Will fail when an item with the same id already exists.
 * @param {Object} item
 * @return {String} id
 * @private
 */
DataSet.prototype._addItem = function (item) {
  var id = item[this.fieldId];

  if (id != undefined) {
    // check whether this id is already taken
    if (this.data[id]) {
      // item already exists
      throw new Error('Cannot add item: item with id ' + id + ' already exists');
    }
  }
  else {
    // generate an id
    id = util.randomUUID();
    item[this.fieldId] = id;
    this.internalIds[id] = item;
  }

  var d = {};
  for (var field in item) {
    if (item.hasOwnProperty(field)) {
      var fieldType = this.convert[field];  // type may be undefined
      d[field] = util.convert(item[field], fieldType);
    }
  }
  this.data[id] = d;

  return id;
};

/**
 * Get an item. Fields can be converted to a specific type
 * @param {String} id
 * @param {Object.<String, String>} [convert]  field types to convert
 * @return {Object | null} item
 * @private
 */
DataSet.prototype._getItem = function (id, convert) {
  var field, value;

  // get the item from the dataset
  var raw = this.data[id];
  if (!raw) {
    return null;
  }

  // convert the items field types
  var converted = {},
      fieldId = this.fieldId,
      internalIds = this.internalIds;
  if (convert) {
    for (field in raw) {
      if (raw.hasOwnProperty(field)) {
        value = raw[field];
        // output all fields, except internal ids
        if ((field != fieldId) || !(value in internalIds)) {
          converted[field] = util.convert(value, convert[field]);
        }
      }
    }
  }
  else {
    // no field types specified, no converting needed
    for (field in raw) {
      if (raw.hasOwnProperty(field)) {
        value = raw[field];
        // output all fields, except internal ids
        if ((field != fieldId) || !(value in internalIds)) {
          converted[field] = value;
        }
      }
    }
  }

  return converted;
};

/**
 * Update a single item: merge with existing item.
 * Will fail when the item has no id, or when there does not exist an item
 * with the same id.
 * @param {Object} item
 * @return {String} id
 * @private
 */
DataSet.prototype._updateItem = function (item) {
  var id = item[this.fieldId];
  if (id == undefined) {
    throw new Error('Cannot update item: item has no id (item: ' + JSON.stringify(item) + ')');
  }
  var d = this.data[id];
  if (!d) {
    // item doesn't exist
    throw new Error('Cannot update item: no item with id ' + id + ' found');
  }

  // merge with current item
  for (var field in item) {
    if (item.hasOwnProperty(field)) {
      var fieldType = this.convert[field];  // type may be undefined
      d[field] = util.convert(item[field], fieldType);
    }
  }

  return id;
};

/**
 * Get an array with the column names of a Google DataTable
 * @param {DataTable} dataTable
 * @return {String[]} columnNames
 * @private
 */
DataSet.prototype._getColumnNames = function (dataTable) {
  var columns = [];
  for (var col = 0, cols = dataTable.getNumberOfColumns(); col < cols; col++) {
    columns[col] = dataTable.getColumnId(col) || dataTable.getColumnLabel(col);
  }
  return columns;
};

/**
 * Append an item as a row to the dataTable
 * @param dataTable
 * @param columns
 * @param item
 * @private
 */
DataSet.prototype._appendRow = function (dataTable, columns, item) {
  var row = dataTable.addRow();

  for (var col = 0, cols = columns.length; col < cols; col++) {
    var field = columns[col];
    dataTable.setValue(row, col, item[field]);
  }
};

/**
 * DataView
 *
 * a dataview offers a filtered view on a dataset or an other dataview.
 *
 * @param {DataSet | DataView} data
 * @param {Object} [options]   Available options: see method get
 *
 * @constructor DataView
 */
function DataView (data, options) {
  this.id = util.randomUUID();

  this.data = null;
  this.ids = {}; // ids of the items currently in memory (just contains a boolean true)
  this.options = options || {};
  this.fieldId = 'id'; // name of the field containing id
  this.subscribers = {}; // event subscribers

  var me = this;
  this.listener = function () {
    me._onEvent.apply(me, arguments);
  };

  this.setData(data);
}

// TODO: implement a function .config() to dynamically update things like configured filter
// and trigger changes accordingly

/**
 * Set a data source for the view
 * @param {DataSet | DataView} data
 */
DataView.prototype.setData = function (data) {
  var ids, dataItems, i, len;

  if (this.data) {
    // unsubscribe from current dataset
    if (this.data.unsubscribe) {
      this.data.unsubscribe('*', this.listener);
    }

    // trigger a remove of all items in memory
    ids = [];
    for (var id in this.ids) {
      if (this.ids.hasOwnProperty(id)) {
        ids.push(id);
      }
    }
    this.ids = {};
    this._trigger('remove', {items: ids});
  }

  this.data = data;

  if (this.data) {
    // update fieldId
    this.fieldId = this.options.fieldId ||
        (this.data && this.data.options && this.data.options.fieldId) ||
        'id';

    // trigger an add of all added items
    ids = this.data.getIds({filter: this.options && this.options.filter});
    for (i = 0, len = ids.length; i < len; i++) {
      id = ids[i];
      this.ids[id] = true;
    }
    this._trigger('add', {items: ids});

    // subscribe to new dataset
    if (this.data.subscribe) {
      this.data.subscribe('*', this.listener);
    }
  }
};

/**
 * Get data from the data view
 *
 * Usage:
 *
 *     get()
 *     get(options: Object)
 *     get(options: Object, data: Array | DataTable)
 *
 *     get(id: Number)
 *     get(id: Number, options: Object)
 *     get(id: Number, options: Object, data: Array | DataTable)
 *
 *     get(ids: Number[])
 *     get(ids: Number[], options: Object)
 *     get(ids: Number[], options: Object, data: Array | DataTable)
 *
 * Where:
 *
 * {Number | String} id         The id of an item
 * {Number[] | String{}} ids    An array with ids of items
 * {Object} options             An Object with options. Available options:
 *                              {String} [type] Type of data to be returned. Can
 *                                              be 'DataTable' or 'Array' (default)
 *                              {Object.<String, String>} [convert]
 *                              {String[]} [fields] field names to be returned
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * {Array | DataTable} [data]   If provided, items will be appended to this
 *                              array or table. Required in case of Google
 *                              DataTable.
 * @param args
 */
DataView.prototype.get = function (args) {
  var me = this;

  // parse the arguments
  var ids, options, data;
  var firstType = util.getType(arguments[0]);
  if (firstType == 'String' || firstType == 'Number' || firstType == 'Array') {
    // get(id(s) [, options] [, data])
    ids = arguments[0];  // can be a single id or an array with ids
    options = arguments[1];
    data = arguments[2];
  }
  else {
    // get([, options] [, data])
    options = arguments[0];
    data = arguments[1];
  }

  // extend the options with the default options and provided options
  var viewOptions = util.extend({}, this.options, options);

  // create a combined filter method when needed
  if (this.options.filter && options && options.filter) {
    viewOptions.filter = function (item) {
      return me.options.filter(item) && options.filter(item);
    }
  }

  // build up the call to the linked data set
  var getArguments = [];
  if (ids != undefined) {
    getArguments.push(ids);
  }
  getArguments.push(viewOptions);
  getArguments.push(data);

  return this.data && this.data.get.apply(this.data, getArguments);
};

/**
 * Get ids of all items or from a filtered set of items.
 * @param {Object} [options]    An Object with options. Available options:
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * @return {Array} ids
 */
DataView.prototype.getIds = function (options) {
  var ids;

  if (this.data) {
    var defaultFilter = this.options.filter;
    var filter;

    if (options && options.filter) {
      if (defaultFilter) {
        filter = function (item) {
          return defaultFilter(item) && options.filter(item);
        }
      }
      else {
        filter = options.filter;
      }
    }
    else {
      filter = defaultFilter;
    }

    ids = this.data.getIds({
      filter: filter,
      order: options && options.order
    });
  }
  else {
    ids = [];
  }

  return ids;
};

/**
 * Event listener. Will propagate all events from the connected data set to
 * the subscribers of the DataView, but will filter the items and only trigger
 * when there are changes in the filtered data set.
 * @param {String} event
 * @param {Object | null} params
 * @param {String} senderId
 * @private
 */
DataView.prototype._onEvent = function (event, params, senderId) {
  var i, len, id, item,
      ids = params && params.items,
      data = this.data,
      added = [],
      updated = [],
      removed = [];

  if (ids && data) {
    switch (event) {
      case 'add':
        // filter the ids of the added items
        for (i = 0, len = ids.length; i < len; i++) {
          id = ids[i];
          item = this.get(id);
          if (item) {
            this.ids[id] = true;
            added.push(id);
          }
        }

        break;

      case 'update':
        // determine the event from the views viewpoint: an updated
        // item can be added, updated, or removed from this view.
        for (i = 0, len = ids.length; i < len; i++) {
          id = ids[i];
          item = this.get(id);

          if (item) {
            if (this.ids[id]) {
              updated.push(id);
            }
            else {
              this.ids[id] = true;
              added.push(id);
            }
          }
          else {
            if (this.ids[id]) {
              delete this.ids[id];
              removed.push(id);
            }
            else {
              // nothing interesting for me :-(
            }
          }
        }

        break;

      case 'remove':
        // filter the ids of the removed items
        for (i = 0, len = ids.length; i < len; i++) {
          id = ids[i];
          if (this.ids[id]) {
            delete this.ids[id];
            removed.push(id);
          }
        }

        break;
    }

    if (added.length) {
      this._trigger('add', {items: added}, senderId);
    }
    if (updated.length) {
      this._trigger('update', {items: updated}, senderId);
    }
    if (removed.length) {
      this._trigger('remove', {items: removed}, senderId);
    }
  }
};

// copy subscription functionality from DataSet
DataView.prototype.subscribe = DataSet.prototype.subscribe;
DataView.prototype.unsubscribe = DataSet.prototype.unsubscribe;
DataView.prototype._trigger = DataSet.prototype._trigger;

/**
 * @constructor  TimeStep
 * The class TimeStep is an iterator for dates. You provide a start date and an
 * end date. The class itself determines the best scale (step size) based on the
 * provided start Date, end Date, and minimumStep.
 *
 * If minimumStep is provided, the step size is chosen as close as possible
 * to the minimumStep but larger than minimumStep. If minimumStep is not
 * provided, the scale is set to 1 DAY.
 * The minimumStep should correspond with the onscreen size of about 6 characters
 *
 * Alternatively, you can set a scale by hand.
 * After creation, you can initialize the class by executing first(). Then you
 * can iterate from the start date to the end date via next(). You can check if
 * the end date is reached with the function hasNext(). After each step, you can
 * retrieve the current date via getCurrent().
 * The TimeStep has scales ranging from milliseconds, seconds, minutes, hours,
 * days, to years.
 *
 * Version: 1.2
 *
 * @param {Date} [start]         The start date, for example new Date(2010, 9, 21)
 *                               or new Date(2010, 9, 21, 23, 45, 00)
 * @param {Date} [end]           The end date
 * @param {Number} [minimumStep] Optional. Minimum step size in milliseconds
 */
TimeStep = function(start, end, minimumStep) {
  // variables
  this.current = new Date();
  this._start = new Date();
  this._end = new Date();

  this.autoScale  = true;
  this.scale = TimeStep.SCALE.DAY;
  this.step = 1;

  // initialize the range
  this.setRange(start, end, minimumStep);
};

/// enum scale
TimeStep.SCALE = {
  MILLISECOND: 1,
  SECOND: 2,
  MINUTE: 3,
  HOUR: 4,
  DAY: 5,
  WEEKDAY: 6,
  MONTH: 7,
  YEAR: 8
};


/**
 * Set a new range
 * If minimumStep is provided, the step size is chosen as close as possible
 * to the minimumStep but larger than minimumStep. If minimumStep is not
 * provided, the scale is set to 1 DAY.
 * The minimumStep should correspond with the onscreen size of about 6 characters
 * @param {Date} [start]      The start date and time.
 * @param {Date} [end]        The end date and time.
 * @param {int} [minimumStep] Optional. Minimum step size in milliseconds
 */
TimeStep.prototype.setRange = function(start, end, minimumStep) {
  if (!(start instanceof Date) || !(end instanceof Date)) {
    throw  "No legal start or end date in method setRange";
  }

  this._start = (start != undefined) ? new Date(start.valueOf()) : new Date();
  this._end = (end != undefined) ? new Date(end.valueOf()) : new Date();

  if (this.autoScale) {
    this.setMinimumStep(minimumStep);
  }
};

/**
 * Set the range iterator to the start date.
 */
TimeStep.prototype.first = function() {
  this.current = new Date(this._start.valueOf());
  this.roundToMinor();
};

/**
 * Round the current date to the first minor date value
 * This must be executed once when the current date is set to start Date
 */
TimeStep.prototype.roundToMinor = function() {
  // round to floor
  // IMPORTANT: we have no breaks in this switch! (this is no bug)
  //noinspection FallthroughInSwitchStatementJS
  switch (this.scale) {
    case TimeStep.SCALE.YEAR:
      this.current.setFullYear(this.step * Math.floor(this.current.getFullYear() / this.step));
      this.current.setMonth(0);
    case TimeStep.SCALE.MONTH:        this.current.setDate(1);
    case TimeStep.SCALE.DAY:          // intentional fall through
    case TimeStep.SCALE.WEEKDAY:      this.current.setHours(0);
    case TimeStep.SCALE.HOUR:         this.current.setMinutes(0);
    case TimeStep.SCALE.MINUTE:       this.current.setSeconds(0);
    case TimeStep.SCALE.SECOND:       this.current.setMilliseconds(0);
    //case TimeStep.SCALE.MILLISECOND: // nothing to do for milliseconds
  }

  if (this.step != 1) {
    // round down to the first minor value that is a multiple of the current step size
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  this.current.setMilliseconds(this.current.getMilliseconds() - this.current.getMilliseconds() % this.step);  break;
      case TimeStep.SCALE.SECOND:       this.current.setSeconds(this.current.getSeconds() - this.current.getSeconds() % this.step); break;
      case TimeStep.SCALE.MINUTE:       this.current.setMinutes(this.current.getMinutes() - this.current.getMinutes() % this.step); break;
      case TimeStep.SCALE.HOUR:         this.current.setHours(this.current.getHours() - this.current.getHours() % this.step); break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate((this.current.getDate()-1) - (this.current.getDate()-1) % this.step + 1); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() - this.current.getMonth() % this.step);  break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() - this.current.getFullYear() % this.step); break;
      default: break;
    }
  }
};

/**
 * Check if the there is a next step
 * @return {boolean}  true if the current date has not passed the end date
 */
TimeStep.prototype.hasNext = function () {
  return (this.current.valueOf() <= this._end.valueOf());
};

/**
 * Do the next step
 */
TimeStep.prototype.next = function() {
  var prev = this.current.valueOf();

  // Two cases, needed to prevent issues with switching daylight savings
  // (end of March and end of October)
  if (this.current.getMonth() < 6)   {
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:

        this.current = new Date(this.current.valueOf() + this.step); break;
      case TimeStep.SCALE.SECOND:       this.current = new Date(this.current.valueOf() + this.step * 1000); break;
      case TimeStep.SCALE.MINUTE:       this.current = new Date(this.current.valueOf() + this.step * 1000 * 60); break;
      case TimeStep.SCALE.HOUR:
        this.current = new Date(this.current.valueOf() + this.step * 1000 * 60 * 60);
        // in case of skipping an hour for daylight savings, adjust the hour again (else you get: 0h 5h 9h ... instead of 0h 4h 8h ...)
        var h = this.current.getHours();
        this.current.setHours(h - (h % this.step));
        break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate(this.current.getDate() + this.step); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() + this.step); break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() + this.step); break;
      default:                      break;
    }
  }
  else {
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  this.current = new Date(this.current.valueOf() + this.step); break;
      case TimeStep.SCALE.SECOND:       this.current.setSeconds(this.current.getSeconds() + this.step); break;
      case TimeStep.SCALE.MINUTE:       this.current.setMinutes(this.current.getMinutes() + this.step); break;
      case TimeStep.SCALE.HOUR:         this.current.setHours(this.current.getHours() + this.step); break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          this.current.setDate(this.current.getDate() + this.step); break;
      case TimeStep.SCALE.MONTH:        this.current.setMonth(this.current.getMonth() + this.step); break;
      case TimeStep.SCALE.YEAR:         this.current.setFullYear(this.current.getFullYear() + this.step); break;
      default:                      break;
    }
  }

  if (this.step != 1) {
    // round down to the correct major value
    switch (this.scale) {
      case TimeStep.SCALE.MILLISECOND:  if(this.current.getMilliseconds() < this.step) this.current.setMilliseconds(0);  break;
      case TimeStep.SCALE.SECOND:       if(this.current.getSeconds() < this.step) this.current.setSeconds(0);  break;
      case TimeStep.SCALE.MINUTE:       if(this.current.getMinutes() < this.step) this.current.setMinutes(0);  break;
      case TimeStep.SCALE.HOUR:         if(this.current.getHours() < this.step) this.current.setHours(0);  break;
      case TimeStep.SCALE.WEEKDAY:      // intentional fall through
      case TimeStep.SCALE.DAY:          if(this.current.getDate() < this.step+1) this.current.setDate(1); break;
      case TimeStep.SCALE.MONTH:        if(this.current.getMonth() < this.step) this.current.setMonth(0);  break;
      case TimeStep.SCALE.YEAR:         break; // nothing to do for year
      default:                break;
    }
  }

  // safety mechanism: if current time is still unchanged, move to the end
  if (this.current.valueOf() == prev) {
    this.current = new Date(this._end.valueOf());
  }
};


/**
 * Get the current datetime
 * @return {Date}  current The current date
 */
TimeStep.prototype.getCurrent = function() {
  return this.current;
};

/**
 * Set a custom scale. Autoscaling will be disabled.
 * For example setScale(SCALE.MINUTES, 5) will result
 * in minor steps of 5 minutes, and major steps of an hour.
 *
 * @param {TimeStep.SCALE} newScale
 *                               A scale. Choose from SCALE.MILLISECOND,
 *                               SCALE.SECOND, SCALE.MINUTE, SCALE.HOUR,
 *                               SCALE.WEEKDAY, SCALE.DAY, SCALE.MONTH,
 *                               SCALE.YEAR.
 * @param {Number}     newStep   A step size, by default 1. Choose for
 *                               example 1, 2, 5, or 10.
 */
TimeStep.prototype.setScale = function(newScale, newStep) {
  this.scale = newScale;

  if (newStep > 0) {
    this.step = newStep;
  }

  this.autoScale = false;
};

/**
 * Enable or disable autoscaling
 * @param {boolean} enable  If true, autoascaling is set true
 */
TimeStep.prototype.setAutoScale = function (enable) {
  this.autoScale = enable;
};


/**
 * Automatically determine the scale that bests fits the provided minimum step
 * @param {Number} [minimumStep]  The minimum step size in milliseconds
 */
TimeStep.prototype.setMinimumStep = function(minimumStep) {
  if (minimumStep == undefined) {
    return;
  }

  var stepYear       = (1000 * 60 * 60 * 24 * 30 * 12);
  var stepMonth      = (1000 * 60 * 60 * 24 * 30);
  var stepDay        = (1000 * 60 * 60 * 24);
  var stepHour       = (1000 * 60 * 60);
  var stepMinute     = (1000 * 60);
  var stepSecond     = (1000);
  var stepMillisecond= (1);

  // find the smallest step that is larger than the provided minimumStep
  if (stepYear*1000 > minimumStep)        {this.scale = TimeStep.SCALE.YEAR;        this.step = 1000;}
  if (stepYear*500 > minimumStep)         {this.scale = TimeStep.SCALE.YEAR;        this.step = 500;}
  if (stepYear*100 > minimumStep)         {this.scale = TimeStep.SCALE.YEAR;        this.step = 100;}
  if (stepYear*50 > minimumStep)          {this.scale = TimeStep.SCALE.YEAR;        this.step = 50;}
  if (stepYear*10 > minimumStep)          {this.scale = TimeStep.SCALE.YEAR;        this.step = 10;}
  if (stepYear*5 > minimumStep)           {this.scale = TimeStep.SCALE.YEAR;        this.step = 5;}
  if (stepYear > minimumStep)             {this.scale = TimeStep.SCALE.YEAR;        this.step = 1;}
  if (stepMonth*3 > minimumStep)          {this.scale = TimeStep.SCALE.MONTH;       this.step = 3;}
  if (stepMonth > minimumStep)            {this.scale = TimeStep.SCALE.MONTH;       this.step = 1;}
  if (stepDay*5 > minimumStep)            {this.scale = TimeStep.SCALE.DAY;         this.step = 5;}
  if (stepDay*2 > minimumStep)            {this.scale = TimeStep.SCALE.DAY;         this.step = 2;}
  if (stepDay > minimumStep)              {this.scale = TimeStep.SCALE.DAY;         this.step = 1;}
  if (stepDay/2 > minimumStep)            {this.scale = TimeStep.SCALE.WEEKDAY;     this.step = 1;}
  if (stepHour*4 > minimumStep)           {this.scale = TimeStep.SCALE.HOUR;        this.step = 4;}
  if (stepHour > minimumStep)             {this.scale = TimeStep.SCALE.HOUR;        this.step = 1;}
  if (stepMinute*15 > minimumStep)        {this.scale = TimeStep.SCALE.MINUTE;      this.step = 15;}
  if (stepMinute*10 > minimumStep)        {this.scale = TimeStep.SCALE.MINUTE;      this.step = 10;}
  if (stepMinute*5 > minimumStep)         {this.scale = TimeStep.SCALE.MINUTE;      this.step = 5;}
  if (stepMinute > minimumStep)           {this.scale = TimeStep.SCALE.MINUTE;      this.step = 1;}
  if (stepSecond*15 > minimumStep)        {this.scale = TimeStep.SCALE.SECOND;      this.step = 15;}
  if (stepSecond*10 > minimumStep)        {this.scale = TimeStep.SCALE.SECOND;      this.step = 10;}
  if (stepSecond*5 > minimumStep)         {this.scale = TimeStep.SCALE.SECOND;      this.step = 5;}
  if (stepSecond > minimumStep)           {this.scale = TimeStep.SCALE.SECOND;      this.step = 1;}
  if (stepMillisecond*200 > minimumStep)  {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 200;}
  if (stepMillisecond*100 > minimumStep)  {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 100;}
  if (stepMillisecond*50 > minimumStep)   {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 50;}
  if (stepMillisecond*10 > minimumStep)   {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 10;}
  if (stepMillisecond*5 > minimumStep)    {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 5;}
  if (stepMillisecond > minimumStep)      {this.scale = TimeStep.SCALE.MILLISECOND; this.step = 1;}
};

/**
 * Snap a date to a rounded value. The snap intervals are dependent on the
 * current scale and step.
 * @param {Date} date   the date to be snapped
 */
TimeStep.prototype.snap = function(date) {
  if (this.scale == TimeStep.SCALE.YEAR) {
    var year = date.getFullYear() + Math.round(date.getMonth() / 12);
    date.setFullYear(Math.round(year / this.step) * this.step);
    date.setMonth(0);
    date.setDate(0);
    date.setHours(0);
    date.setMinutes(0);
    date.setSeconds(0);
    date.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.MONTH) {
    if (date.getDate() > 15) {
      date.setDate(1);
      date.setMonth(date.getMonth() + 1);
      // important: first set Date to 1, after that change the month.
    }
    else {
      date.setDate(1);
    }

    date.setHours(0);
    date.setMinutes(0);
    date.setSeconds(0);
    date.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.DAY ||
      this.scale == TimeStep.SCALE.WEEKDAY) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 5:
      case 2:
        date.setHours(Math.round(date.getHours() / 24) * 24); break;
      default:
        date.setHours(Math.round(date.getHours() / 12) * 12); break;
    }
    date.setMinutes(0);
    date.setSeconds(0);
    date.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.HOUR) {
    switch (this.step) {
      case 4:
        date.setMinutes(Math.round(date.getMinutes() / 60) * 60); break;
      default:
        date.setMinutes(Math.round(date.getMinutes() / 30) * 30); break;
    }
    date.setSeconds(0);
    date.setMilliseconds(0);
  } else if (this.scale == TimeStep.SCALE.MINUTE) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 15:
      case 10:
        date.setMinutes(Math.round(date.getMinutes() / 5) * 5);
        date.setSeconds(0);
        break;
      case 5:
        date.setSeconds(Math.round(date.getSeconds() / 60) * 60); break;
      default:
        date.setSeconds(Math.round(date.getSeconds() / 30) * 30); break;
    }
    date.setMilliseconds(0);
  }
  else if (this.scale == TimeStep.SCALE.SECOND) {
    //noinspection FallthroughInSwitchStatementJS
    switch (this.step) {
      case 15:
      case 10:
        date.setSeconds(Math.round(date.getSeconds() / 5) * 5);
        date.setMilliseconds(0);
        break;
      case 5:
        date.setMilliseconds(Math.round(date.getMilliseconds() / 1000) * 1000); break;
      default:
        date.setMilliseconds(Math.round(date.getMilliseconds() / 500) * 500); break;
    }
  }
  else if (this.scale == TimeStep.SCALE.MILLISECOND) {
    var step = this.step > 5 ? this.step / 2 : 1;
    date.setMilliseconds(Math.round(date.getMilliseconds() / step) * step);
  }
};

/**
 * Check if the current value is a major value (for example when the step
 * is DAY, a major value is each first day of the MONTH)
 * @return {boolean} true if current date is major, else false.
 */
TimeStep.prototype.isMajor = function() {
  switch (this.scale) {
    case TimeStep.SCALE.MILLISECOND:
      return (this.current.getMilliseconds() == 0);
    case TimeStep.SCALE.SECOND:
      return (this.current.getSeconds() == 0);
    case TimeStep.SCALE.MINUTE:
      return (this.current.getHours() == 0) && (this.current.getMinutes() == 0);
    // Note: this is no bug. Major label is equal for both minute and hour scale
    case TimeStep.SCALE.HOUR:
      return (this.current.getHours() == 0);
    case TimeStep.SCALE.WEEKDAY: // intentional fall through
    case TimeStep.SCALE.DAY:
      return (this.current.getDate() == 1);
    case TimeStep.SCALE.MONTH:
      return (this.current.getMonth() == 0);
    case TimeStep.SCALE.YEAR:
      return false;
    default:
      return false;
  }
};


/**
 * Returns formatted text for the minor axislabel, depending on the current
 * date and the scale. For example when scale is MINUTE, the current time is
 * formatted as "hh:mm".
 * @param {Date} [date] custom date. if not provided, current date is taken
 */
TimeStep.prototype.getLabelMinor = function(date) {
  if (date == undefined) {
    date = this.current;
  }

  switch (this.scale) {
    case TimeStep.SCALE.MILLISECOND:  return moment(date).format('SSS');
    case TimeStep.SCALE.SECOND:       return moment(date).format('s');
    case TimeStep.SCALE.MINUTE:       return moment(date).format('HH:mm');
    case TimeStep.SCALE.HOUR:         return moment(date).format('HH:mm');
    case TimeStep.SCALE.WEEKDAY:      return moment(date).format('ddd D');
    case TimeStep.SCALE.DAY:          return moment(date).format('D');
    case TimeStep.SCALE.MONTH:        return moment(date).format('MMM');
    case TimeStep.SCALE.YEAR:         return moment(date).format('YYYY');
    default:                          return '';
  }
};


/**
 * Returns formatted text for the major axis label, depending on the current
 * date and the scale. For example when scale is MINUTE, the major scale is
 * hours, and the hour will be formatted as "hh".
 * @param {Date} [date] custom date. if not provided, current date is taken
 */
TimeStep.prototype.getLabelMajor = function(date) {
  if (date == undefined) {
    date = this.current;
  }

  //noinspection FallthroughInSwitchStatementJS
  switch (this.scale) {
    case TimeStep.SCALE.MILLISECOND:return moment(date).format('HH:mm:ss');
    case TimeStep.SCALE.SECOND:     return moment(date).format('D MMMM HH:mm');
    case TimeStep.SCALE.MINUTE:
    case TimeStep.SCALE.HOUR:       return moment(date).format('ddd D MMMM');
    case TimeStep.SCALE.WEEKDAY:
    case TimeStep.SCALE.DAY:        return moment(date).format('MMMM YYYY');
    case TimeStep.SCALE.MONTH:      return moment(date).format('YYYY');
    case TimeStep.SCALE.YEAR:       return '';
    default:                        return '';
  }
};

/**
 * @constructor Stack
 * Stacks items on top of each other.
 * @param {ItemSet} parent
 * @param {Object} [options]
 */
function Stack (parent, options) {
  this.parent = parent;

  this.options = options || {};
  this.defaultOptions = {
    order: function (a, b) {
      //return (b.width - a.width) || (a.left - b.left);  // TODO: cleanup
      // Order: ranges over non-ranges, ranged ordered by width, and
      // lastly ordered by start.
      if (a instanceof ItemRange) {
        if (b instanceof ItemRange) {
          var aInt = (a.data.end - a.data.start);
          var bInt = (b.data.end - b.data.start);
          return (aInt - bInt) || (a.data.start - b.data.start);
        }
        else {
          return -1;
        }
      }
      else {
        if (b instanceof ItemRange) {
          return 1;
        }
        else {
          return (a.data.start - b.data.start);
        }
      }
    },
    margin: {
      item: 10
    }
  };

  this.ordered = [];  // ordered items
}

/**
 * Set options for the stack
 * @param {Object} options  Available options:
 *                          {ItemSet} parent
 *                          {Number} margin
 *                          {function} order  Stacking order
 */
Stack.prototype.setOptions = function setOptions (options) {
  util.extend(this.options, options);

  // TODO: register on data changes at the connected parent itemset, and update the changed part only and immediately
};

/**
 * Stack the items such that they don't overlap. The items will have a minimal
 * distance equal to options.margin.item.
 */
Stack.prototype.update = function update() {
  this._order();
  this._stack();
};

/**
 * Order the items. The items are ordered by width first, and by left position
 * second.
 * If a custom order function has been provided via the options, then this will
 * be used.
 * @private
 */
Stack.prototype._order = function _order () {
  var items = this.parent.items;
  if (!items) {
    throw new Error('Cannot stack items: parent does not contain items');
  }

  // TODO: store the sorted items, to have less work later on
  var ordered = [];
  var index = 0;
  // items is a map (no array)
  util.forEach(items, function (item) {
    if (item.visible) {
      ordered[index] = item;
      index++;
    }
  });

  //if a customer stack order function exists, use it.
  var order = this.options.order || this.defaultOptions.order;
  if (!(typeof order === 'function')) {
    throw new Error('Option order must be a function');
  }

  ordered.sort(order);

  this.ordered = ordered;
};

/**
 * Adjust vertical positions of the events such that they don't overlap each
 * other.
 * @private
 */
Stack.prototype._stack = function _stack () {
  var i,
      iMax,
      ordered = this.ordered,
      options = this.options,
      orientation = options.orientation || this.defaultOptions.orientation,
      axisOnTop = (orientation == 'top'),
      margin;

  if (options.margin && options.margin.item !== undefined) {
    margin = options.margin.item;
  }
  else {
    margin = this.defaultOptions.margin.item
  }

  // calculate new, non-overlapping positions
  for (i = 0, iMax = ordered.length; i < iMax; i++) {
    var item = ordered[i];
    var collidingItem = null;
    do {
      // TODO: optimize checking for overlap. when there is a gap without items,
      //  you only need to check for items from the next item on, not from zero
      collidingItem = this.checkOverlap(ordered, i, 0, i - 1, margin);
      if (collidingItem != null) {
        // There is a collision. Reposition the event above the colliding element
        if (axisOnTop) {
          item.top = collidingItem.top + collidingItem.height + margin;
        }
        else {
          item.top = collidingItem.top - item.height - margin;
        }
      }
    } while (collidingItem);
  }
};

/**
 * Check if the destiny position of given item overlaps with any
 * of the other items from index itemStart to itemEnd.
 * @param {Array} items     Array with items
 * @param {int}  itemIndex  Number of the item to be checked for overlap
 * @param {int}  itemStart  First item to be checked.
 * @param {int}  itemEnd    Last item to be checked.
 * @return {Object | null}  colliding item, or undefined when no collisions
 * @param {Number} margin   A minimum required margin.
 *                          If margin is provided, the two items will be
 *                          marked colliding when they overlap or
 *                          when the margin between the two is smaller than
 *                          the requested margin.
 */
Stack.prototype.checkOverlap = function checkOverlap (items, itemIndex,
                                                      itemStart, itemEnd, margin) {
  var collision = this.collision;

  // we loop from end to start, as we suppose that the chance of a
  // collision is larger for items at the end, so check these first.
  var a = items[itemIndex];
  for (var i = itemEnd; i >= itemStart; i--) {
    var b = items[i];
    if (collision(a, b, margin)) {
      if (i != itemIndex) {
        return b;
      }
    }
  }

  return null;
};

/**
 * Test if the two provided items collide
 * The items must have parameters left, width, top, and height.
 * @param {Component} a     The first item
 * @param {Component} b     The second item
 * @param {Number} margin   A minimum required margin.
 *                          If margin is provided, the two items will be
 *                          marked colliding when they overlap or
 *                          when the margin between the two is smaller than
 *                          the requested margin.
 * @return {boolean}        true if a and b collide, else false
 */
Stack.prototype.collision = function collision (a, b, margin) {
  return ((a.left - margin) < (b.left + b.getWidth()) &&
      (a.left + a.getWidth() + margin) > b.left &&
      (a.top - margin) < (b.top + b.height) &&
      (a.top + a.height + margin) > b.top);
};

/**
 * @constructor Range
 * A Range controls a numeric range with a start and end value.
 * The Range adjusts the range based on mouse events or programmatic changes,
 * and triggers events when the range is changing or has been changed.
 * @param {Object} [options]   See description at Range.setOptions
 * @extends Controller
 */
function Range(options) {
  this.id = util.randomUUID();
  this.start = null; // Number
  this.end = null;   // Number

  this.options = options || {};

  this.setOptions(options);
}

/**
 * Set options for the range controller
 * @param {Object} options      Available options:
 *                              {Number} min    Minimum value for start
 *                              {Number} max    Maximum value for end
 *                              {Number} zoomMin    Set a minimum value for
 *                                                  (end - start).
 *                              {Number} zoomMax    Set a maximum value for
 *                                                  (end - start).
 */
Range.prototype.setOptions = function (options) {
  util.extend(this.options, options);

  // re-apply range with new limitations
  if (this.start !== null && this.end !== null) {
    this.setRange(this.start, this.end);
  }
};

/**
 * Test whether direction has a valid value
 * @param {String} direction    'horizontal' or 'vertical'
 */
function validateDirection (direction) {
  if (direction != 'horizontal' && direction != 'vertical') {
    throw new TypeError('Unknown direction "' + direction + '". ' +
        'Choose "horizontal" or "vertical".');
  }
}

/**
 * Add listeners for mouse and touch events to the component
 * @param {Component} component
 * @param {String} event        Available events: 'move', 'zoom'
 * @param {String} direction    Available directions: 'horizontal', 'vertical'
 */
Range.prototype.subscribe = function (component, event, direction) {
  var me = this;

  if (event == 'move') {
    // drag start listener
    component.on('dragstart', function (event) {
      me._onDragStart(event, component);
    });

    // drag listener
    component.on('drag', function (event) {
      me._onDrag(event, component, direction);
    });

    // drag end listener
    component.on('dragend', function (event) {
      me._onDragEnd(event, component);
    });
  }
  else if (event == 'zoom') {
    // mouse wheel
    function mousewheel (event) {
      me._onMouseWheel(event, component, direction);
    }
    component.on('mousewheel', mousewheel);
    component.on('DOMMouseScroll', mousewheel); // For FF

    // pinch
    component.on('touch', function (event) {
      me._onTouch();
    });
    component.on('pinch', function (event) {
      me._onPinch(event, component, direction);
    });
  }
  else {
    throw new TypeError('Unknown event "' + event + '". ' +
        'Choose "move" or "zoom".');
  }
};

/**
 * Event handler
 * @param {String} event       name of the event, for example 'click', 'mousemove'
 * @param {function} callback  callback handler, invoked with the raw HTML Event
 *                             as parameter.
 */
Range.prototype.on = function (event, callback) {
  events.addListener(this, event, callback);
};

/**
 * Trigger an event
 * @param {String} event    name of the event, available events: 'rangechange',
 *                          'rangechanged'
 * @private
 */
Range.prototype._trigger = function (event) {
  events.trigger(this, event, {
    start: this.start,
    end: this.end
  });
};

/**
 * Set a new start and end range
 * @param {Number} [start]
 * @param {Number} [end]
 */
Range.prototype.setRange = function(start, end) {
  var changed = this._applyRange(start, end);
  if (changed) {
    this._trigger('rangechange');
    this._trigger('rangechanged');
  }
};

/**
 * Set a new start and end range. This method is the same as setRange, but
 * does not trigger a range change and range changed event, and it returns
 * true when the range is changed
 * @param {Number} [start]
 * @param {Number} [end]
 * @return {Boolean} changed
 * @private
 */
Range.prototype._applyRange = function(start, end) {
  var newStart = (start != null) ? util.convert(start, 'Number') : this.start,
      newEnd   = (end != null)   ? util.convert(end, 'Number')   : this.end,
      max = (this.options.max != null) ? util.convert(this.options.max, 'Date').valueOf() : null,
      min = (this.options.min != null) ? util.convert(this.options.min, 'Date').valueOf() : null,
      diff;

  // check for valid number
  if (isNaN(newStart) || newStart === null) {
    throw new Error('Invalid start "' + start + '"');
  }
  if (isNaN(newEnd) || newEnd === null) {
    throw new Error('Invalid end "' + end + '"');
  }

  // prevent start < end
  if (newEnd < newStart) {
    newEnd = newStart;
  }

  // prevent start < min
  if (min !== null) {
    if (newStart < min) {
      diff = (min - newStart);
      newStart += diff;
      newEnd += diff;

      // prevent end > max
      if (max != null) {
        if (newEnd > max) {
          newEnd = max;
        }
      }
    }
  }

  // prevent end > max
  if (max !== null) {
    if (newEnd > max) {
      diff = (newEnd - max);
      newStart -= diff;
      newEnd -= diff;

      // prevent start < min
      if (min != null) {
        if (newStart < min) {
          newStart = min;
        }
      }
    }
  }

  // prevent (end-start) < zoomMin
  if (this.options.zoomMin !== null) {
    var zoomMin = parseFloat(this.options.zoomMin);
    if (zoomMin < 0) {
      zoomMin = 0;
    }
    if ((newEnd - newStart) < zoomMin) {
      if ((this.end - this.start) === zoomMin) {
        // ignore this action, we are already zoomed to the minimum
        newStart = this.start;
        newEnd = this.end;
      }
      else {
        // zoom to the minimum
        diff = (zoomMin - (newEnd - newStart));
        newStart -= diff / 2;
        newEnd += diff / 2;
      }
    }
  }

  // prevent (end-start) > zoomMax
  if (this.options.zoomMax !== null) {
    var zoomMax = parseFloat(this.options.zoomMax);
    if (zoomMax < 0) {
      zoomMax = 0;
    }
    if ((newEnd - newStart) > zoomMax) {
      if ((this.end - this.start) === zoomMax) {
        // ignore this action, we are already zoomed to the maximum
        newStart = this.start;
        newEnd = this.end;
      }
      else {
        // zoom to the maximum
        diff = ((newEnd - newStart) - zoomMax);
        newStart += diff / 2;
        newEnd -= diff / 2;
      }
    }
  }

  var changed = (this.start != newStart || this.end != newEnd);

  this.start = newStart;
  this.end = newEnd;

  return changed;
};

/**
 * Retrieve the current range.
 * @return {Object} An object with start and end properties
 */
Range.prototype.getRange = function() {
  return {
    start: this.start,
    end: this.end
  };
};

/**
 * Calculate the conversion offset and scale for current range, based on
 * the provided width
 * @param {Number} width
 * @returns {{offset: number, scale: number}} conversion
 */
Range.prototype.conversion = function (width) {
  return Range.conversion(this.start, this.end, width);
};

/**
 * Static method to calculate the conversion offset and scale for a range,
 * based on the provided start, end, and width
 * @param {Number} start
 * @param {Number} end
 * @param {Number} width
 * @returns {{offset: number, scale: number}} conversion
 */
Range.conversion = function (start, end, width) {
  if (width != 0 && (end - start != 0)) {
    return {
      offset: start,
      scale: width / (end - start)
    }
  }
  else {
    return {
      offset: 0,
      scale: 1
    };
  }
};

// global (private) object to store drag params
var touchParams = {};

/**
 * Start dragging horizontally or vertically
 * @param {Event} event
 * @param {Object} component
 * @private
 */
Range.prototype._onDragStart = function(event, component) {
  // refuse to drag when we where pinching to prevent the timeline make a jump
  // when releasing the fingers in opposite order from the touch screen
  if (touchParams.pinching) return;

  touchParams.start = this.start;
  touchParams.end = this.end;

  var frame = component.frame;
  if (frame) {
    frame.style.cursor = 'move';
  }
};

/**
 * Perform dragging operating.
 * @param {Event} event
 * @param {Component} component
 * @param {String} direction    'horizontal' or 'vertical'
 * @private
 */
Range.prototype._onDrag = function (event, component, direction) {
  validateDirection(direction);

  // refuse to drag when we where pinching to prevent the timeline make a jump
  // when releasing the fingers in opposite order from the touch screen
  if (touchParams.pinching) return;

  var delta = (direction == 'horizontal') ? event.gesture.deltaX : event.gesture.deltaY,
      interval = (touchParams.end - touchParams.start),
      width = (direction == 'horizontal') ? component.width : component.height,
      diffRange = -delta / width * interval;

  this._applyRange(touchParams.start + diffRange, touchParams.end + diffRange);

  // fire a rangechange event
  this._trigger('rangechange');
};

/**
 * Stop dragging operating.
 * @param {event} event
 * @param {Component} component
 * @private
 */
Range.prototype._onDragEnd = function (event, component) {
  // refuse to drag when we where pinching to prevent the timeline make a jump
  // when releasing the fingers in opposite order from the touch screen
  if (touchParams.pinching) return;

  if (component.frame) {
    component.frame.style.cursor = 'auto';
  }

  // fire a rangechanged event
  this._trigger('rangechanged');
};

/**
 * Event handler for mouse wheel event, used to zoom
 * Code from http://adomas.org/javascript-mouse-wheel/
 * @param {Event} event
 * @param {Component} component
 * @param {String} direction    'horizontal' or 'vertical'
 * @private
 */
Range.prototype._onMouseWheel = function(event, component, direction) {
  validateDirection(direction);

  // retrieve delta
  var delta = 0;
  if (event.wheelDelta) { /* IE/Opera. */
    delta = event.wheelDelta / 120;
  } else if (event.detail) { /* Mozilla case. */
    // In Mozilla, sign of delta is different than in IE.
    // Also, delta is multiple of 3.
    delta = -event.detail / 3;
  }

  // If delta is nonzero, handle it.
  // Basically, delta is now positive if wheel was scrolled up,
  // and negative, if wheel was scrolled down.
  if (delta) {
    // perform the zoom action. Delta is normally 1 or -1

    // adjust a negative delta such that zooming in with delta 0.1
    // equals zooming out with a delta -0.1
    var scale;
    if (delta < 0) {
      scale = 1 - (delta / 5);
    }
    else {
      scale = 1 / (1 + (delta / 5)) ;
    }

    // calculate center, the date to zoom around
    var gesture = Hammer.event.collectEventData(this, 'scroll', event),
        pointer = getPointer(gesture.touches[0], component.frame),
        pointerDate = this._pointerToDate(component, direction, pointer);

    this.zoom(scale, pointerDate);
  }

  // Prevent default actions caused by mouse wheel
  // (else the page and timeline both zoom and scroll)
  util.preventDefault(event);
};

/**
 * On start of a touch gesture, initialize scale to 1
 * @private
 */
Range.prototype._onTouch = function () {
  touchParams.start = this.start;
  touchParams.end = this.end;
  touchParams.pinching = false;
  touchParams.center = null;
};

/**
 * Handle pinch event
 * @param {Event} event
 * @param {Component} component
 * @param {String} direction    'horizontal' or 'vertical'
 * @private
 */
Range.prototype._onPinch = function (event, component, direction) {
  touchParams.pinching = true;

  if (event.gesture.touches.length > 1) {
    if (!touchParams.center) {
      touchParams.center = getPointer(event.gesture.center, component.frame);
    }

    var scale = 1 / event.gesture.scale,
        initDate = this._pointerToDate(component, direction, touchParams.center),
        center = getPointer(event.gesture.center, component.frame),
        date = this._pointerToDate(component, direction, center),
        delta = date - initDate; // TODO: utilize delta

    // calculate new start and end
    var newStart = parseInt(initDate + (touchParams.start - initDate) * scale);
    var newEnd = parseInt(initDate + (touchParams.end - initDate) * scale);

    // apply new range
    this.setRange(newStart, newEnd);
  }
};

/**
 * Helper function to calculate the center date for zooming
 * @param {Component} component
 * @param {{x: Number, y: Number}} pointer
 * @param {String} direction    'horizontal' or 'vertical'
 * @return {number} date
 * @private
 */
Range.prototype._pointerToDate = function (component, direction, pointer) {
  var conversion;
  if (direction == 'horizontal') {
    var width = component.width;
    conversion = this.conversion(width);
    return pointer.x / conversion.scale + conversion.offset;
  }
  else {
    var height = component.height;
    conversion = this.conversion(height);
    return pointer.y / conversion.scale + conversion.offset;
  }
};

/**
 * Get the pointer location relative to the location of the dom element
 * @param {{pageX: Number, pageY: Number}} touch
 * @param {Element} element   HTML DOM element
 * @return {{x: Number, y: Number}} pointer
 * @private
 */
function getPointer (touch, element) {
  return {
    x: touch.pageX - vis.util.getAbsoluteLeft(element),
    y: touch.pageY - vis.util.getAbsoluteTop(element)
  };
}

/**
 * Zoom the range the given scale in or out. Start and end date will
 * be adjusted, and the timeline will be redrawn. You can optionally give a
 * date around which to zoom.
 * For example, try scale = 0.9 or 1.1
 * @param {Number} scale      Scaling factor. Values above 1 will zoom out,
 *                            values below 1 will zoom in.
 * @param {Number} [center]   Value representing a date around which will
 *                            be zoomed.
 */
Range.prototype.zoom = function(scale, center) {
  // if centerDate is not provided, take it half between start Date and end Date
  if (center == null) {
    center = (this.start + this.end) / 2;
  }

  // calculate new start and end
  var newStart = center + (this.start - center) * scale;
  var newEnd = center + (this.end - center) * scale;

  this.setRange(newStart, newEnd);
};

/**
 * Move the range with a given delta to the left or right. Start and end
 * value will be adjusted. For example, try delta = 0.1 or -0.1
 * @param {Number}  delta     Moving amount. Positive value will move right,
 *                            negative value will move left
 */
Range.prototype.move = function(delta) {
  // zoom start Date and end Date relative to the centerDate
  var diff = (this.end - this.start);

  // apply new values
  var newStart = this.start + diff * delta;
  var newEnd = this.end + diff * delta;

  // TODO: reckon with min and max range

  this.start = newStart;
  this.end = newEnd;
};

/**
 * Move the range to a new center point
 * @param {Number} moveTo      New center point of the range
 */
Range.prototype.moveTo = function(moveTo) {
  var center = (this.start + this.end) / 2;

  var diff = center - moveTo;

  // calculate new start and end
  var newStart = this.start - diff;
  var newEnd = this.end - diff;

  this.setRange(newStart, newEnd);
};

/**
 * @constructor Controller
 *
 * A Controller controls the reflows and repaints of all visual components
 */
function Controller () {
  this.id = util.randomUUID();
  this.components = {};

  this.repaintTimer = undefined;
  this.reflowTimer = undefined;
}

/**
 * Add a component to the controller
 * @param {Component} component
 */
Controller.prototype.add = function add(component) {
  // validate the component
  if (component.id == undefined) {
    throw new Error('Component has no field id');
  }
  if (!(component instanceof Component) && !(component instanceof Controller)) {
    throw new TypeError('Component must be an instance of ' +
        'prototype Component or Controller');
  }

  // add the component
  component.controller = this;
  this.components[component.id] = component;
};

/**
 * Remove a component from the controller
 * @param {Component | String} component
 */
Controller.prototype.remove = function remove(component) {
  var id;
  for (id in this.components) {
    if (this.components.hasOwnProperty(id)) {
      if (id == component || this.components[id] == component) {
        break;
      }
    }
  }

  if (id) {
    delete this.components[id];
  }
};

/**
 * Request a reflow. The controller will schedule a reflow
 * @param {Boolean} [force]     If true, an immediate reflow is forced. Default
 *                              is false.
 */
Controller.prototype.requestReflow = function requestReflow(force) {
  if (force) {
    this.reflow();
  }
  else {
    if (!this.reflowTimer) {
      var me = this;
      this.reflowTimer = setTimeout(function () {
        me.reflowTimer = undefined;
        me.reflow();
      }, 0);
    }
  }
};

/**
 * Request a repaint. The controller will schedule a repaint
 * @param {Boolean} [force]    If true, an immediate repaint is forced. Default
 *                             is false.
 */
Controller.prototype.requestRepaint = function requestRepaint(force) {
  if (force) {
    this.repaint();
  }
  else {
    if (!this.repaintTimer) {
      var me = this;
      this.repaintTimer = setTimeout(function () {
        me.repaintTimer = undefined;
        me.repaint();
      }, 0);
    }
  }
};

/**
 * Repaint all components
 */
Controller.prototype.repaint = function repaint() {
  var changed = false;

  // cancel any running repaint request
  if (this.repaintTimer) {
    clearTimeout(this.repaintTimer);
    this.repaintTimer = undefined;
  }

  var done = {};

  function repaint(component, id) {
    if (!(id in done)) {
      // first repaint the components on which this component is dependent
      if (component.depends) {
        component.depends.forEach(function (dep) {
          repaint(dep, dep.id);
        });
      }
      if (component.parent) {
        repaint(component.parent, component.parent.id);
      }

      // repaint the component itself and mark as done
      changed = component.repaint() || changed;
      done[id] = true;
    }
  }

  util.forEach(this.components, repaint);

  // immediately reflow when needed
  if (changed) {
    this.reflow();
  }
  // TODO: limit the number of nested reflows/repaints, prevent loop
};

/**
 * Reflow all components
 */
Controller.prototype.reflow = function reflow() {
  var resized = false;

  // cancel any running repaint request
  if (this.reflowTimer) {
    clearTimeout(this.reflowTimer);
    this.reflowTimer = undefined;
  }

  var done = {};

  function reflow(component, id) {
    if (!(id in done)) {
      // first reflow the components on which this component is dependent
      if (component.depends) {
        component.depends.forEach(function (dep) {
          reflow(dep, dep.id);
        });
      }
      if (component.parent) {
        reflow(component.parent, component.parent.id);
      }

      // reflow the component itself and mark as done
      resized = component.reflow() || resized;
      done[id] = true;
    }
  }

  util.forEach(this.components, reflow);

  // immediately repaint when needed
  if (resized) {
    this.repaint();
  }
  // TODO: limit the number of nested reflows/repaints, prevent loop
};

/**
 * Prototype for visual components
 */
function Component () {
  this.id = null;
  this.parent = null;
  this.depends = null;
  this.controller = null;
  this.options = null;

  this.frame = null; // main DOM element
  this.top = 0;
  this.left = 0;
  this.width = 0;
  this.height = 0;
}

/**
 * Set parameters for the frame. Parameters will be merged in current parameter
 * set.
 * @param {Object} options  Available parameters:
 *                          {String | function} [className]
 *                          {EventBus} [eventBus]
 *                          {String | Number | function} [left]
 *                          {String | Number | function} [top]
 *                          {String | Number | function} [width]
 *                          {String | Number | function} [height]
 */
Component.prototype.setOptions = function setOptions(options) {
  if (options) {
    util.extend(this.options, options);

    if (this.controller) {
      this.requestRepaint();
      this.requestReflow();
    }
  }
};

/**
 * Get an option value by name
 * The function will first check this.options object, and else will check
 * this.defaultOptions.
 * @param {String} name
 * @return {*} value
 */
Component.prototype.getOption = function getOption(name) {
  var value;
  if (this.options) {
    value = this.options[name];
  }
  if (value === undefined && this.defaultOptions) {
    value = this.defaultOptions[name];
  }
  return value;
};

/**
 * Get the container element of the component, which can be used by a child to
 * add its own widgets. Not all components do have a container for childs, in
 * that case null is returned.
 * @returns {HTMLElement | null} container
 */
// TODO: get rid of the getContainer and getFrame methods, provide these via the options
Component.prototype.getContainer = function getContainer() {
  // should be implemented by the component
  return null;
};

/**
 * Get the frame element of the component, the outer HTML DOM element.
 * @returns {HTMLElement | null} frame
 */
Component.prototype.getFrame = function getFrame() {
  return this.frame;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
Component.prototype.repaint = function repaint() {
  // should be implemented by the component
  return false;
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
Component.prototype.reflow = function reflow() {
  // should be implemented by the component
  return false;
};

/**
 * Hide the component from the DOM
 * @return {Boolean} changed
 */
Component.prototype.hide = function hide() {
  if (this.frame && this.frame.parentNode) {
    this.frame.parentNode.removeChild(this.frame);
    return true;
  }
  else {
    return false;
  }
};

/**
 * Show the component in the DOM (when not already visible).
 * A repaint will be executed when the component is not visible
 * @return {Boolean} changed
 */
Component.prototype.show = function show() {
  if (!this.frame || !this.frame.parentNode) {
    return this.repaint();
  }
  else {
    return false;
  }
};

/**
 * Request a repaint. The controller will schedule a repaint
 */
Component.prototype.requestRepaint = function requestRepaint() {
  if (this.controller) {
    this.controller.requestRepaint();
  }
  else {
    throw new Error('Cannot request a repaint: no controller configured');
    // TODO: just do a repaint when no parent is configured?
  }
};

/**
 * Request a reflow. The controller will schedule a reflow
 */
Component.prototype.requestReflow = function requestReflow() {
  if (this.controller) {
    this.controller.requestReflow();
  }
  else {
    throw new Error('Cannot request a reflow: no controller configured');
    // TODO: just do a reflow when no parent is configured?
  }
};

/**
 * A panel can contain components
 * @param {Component} [parent]
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]    Available parameters:
 *                              {String | Number | function} [left]
 *                              {String | Number | function} [top]
 *                              {String | Number | function} [width]
 *                              {String | Number | function} [height]
 *                              {String | function} [className]
 * @constructor Panel
 * @extends Component
 */
function Panel(parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  this.options = options || {};
}

Panel.prototype = new Component();

/**
 * Set options. Will extend the current options.
 * @param {Object} [options]    Available parameters:
 *                              {String | function} [className]
 *                              {String | Number | function} [left]
 *                              {String | Number | function} [top]
 *                              {String | Number | function} [width]
 *                              {String | Number | function} [height]
 */
Panel.prototype.setOptions = Component.prototype.setOptions;

/**
 * Get the container element of the panel, which can be used by a child to
 * add its own widgets.
 * @returns {HTMLElement} container
 */
Panel.prototype.getContainer = function () {
  return this.frame;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
Panel.prototype.repaint = function () {
  var changed = 0,
      update = util.updateProperty,
      asSize = util.option.asSize,
      options = this.options,
      frame = this.frame;
  if (!frame) {
    frame = document.createElement('div');
    frame.className = 'panel';

    var className = options.className;
    if (className) {
      if (typeof className == 'function') {
        util.addClassName(frame, String(className()));
      }
      else {
        util.addClassName(frame, String(className));
      }
    }

    this.frame = frame;
    changed += 1;
  }
  if (!frame.parentNode) {
    if (!this.parent) {
      throw new Error('Cannot repaint panel: no parent attached');
    }
    var parentContainer = this.parent.getContainer();
    if (!parentContainer) {
      throw new Error('Cannot repaint panel: parent has no container element');
    }
    parentContainer.appendChild(frame);
    changed += 1;
  }

  changed += update(frame.style, 'top',    asSize(options.top, '0px'));
  changed += update(frame.style, 'left',   asSize(options.left, '0px'));
  changed += update(frame.style, 'width',  asSize(options.width, '100%'));
  changed += update(frame.style, 'height', asSize(options.height, '100%'));

  return (changed > 0);
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
Panel.prototype.reflow = function () {
  var changed = 0,
      update = util.updateProperty,
      frame = this.frame;

  if (frame) {
    changed += update(this, 'top', frame.offsetTop);
    changed += update(this, 'left', frame.offsetLeft);
    changed += update(this, 'width', frame.offsetWidth);
    changed += update(this, 'height', frame.offsetHeight);
  }
  else {
    changed += 1;
  }

  return (changed > 0);
};

/**
 * A root panel can hold components. The root panel must be initialized with
 * a DOM element as container.
 * @param {HTMLElement} container
 * @param {Object} [options]    Available parameters: see RootPanel.setOptions.
 * @constructor RootPanel
 * @extends Panel
 */
function RootPanel(container, options) {
  this.id = util.randomUUID();
  this.container = container;

  this.options = options || {};
  this.defaultOptions = {
    autoResize: true
  };

  this.listeners = {}; // event listeners
}

RootPanel.prototype = new Panel();

/**
 * Set options. Will extend the current options.
 * @param {Object} [options]    Available parameters:
 *                              {String | function} [className]
 *                              {String | Number | function} [left]
 *                              {String | Number | function} [top]
 *                              {String | Number | function} [width]
 *                              {String | Number | function} [height]
 *                              {Boolean | function} [autoResize]
 */
RootPanel.prototype.setOptions = Component.prototype.setOptions;

/**
 * Repaint the component
 * @return {Boolean} changed
 */
RootPanel.prototype.repaint = function () {
  var changed = 0,
      update = util.updateProperty,
      asSize = util.option.asSize,
      options = this.options,
      frame = this.frame;

  if (!frame) {
    frame = document.createElement('div');

    this.frame = frame;

    changed += 1;
  }
  if (!frame.parentNode) {
    if (!this.container) {
      throw new Error('Cannot repaint root panel: no container attached');
    }
    this.container.appendChild(frame);
    changed += 1;
  }

  frame.className = 'vis timeline rootpanel ' + options.orientation;
  var className = options.className;
  if (className) {
    util.addClassName(frame, util.option.asString(className));
  }

  changed += update(frame.style, 'top',    asSize(options.top, '0px'));
  changed += update(frame.style, 'left',   asSize(options.left, '0px'));
  changed += update(frame.style, 'width',  asSize(options.width, '100%'));
  changed += update(frame.style, 'height', asSize(options.height, '100%'));

  this._updateEventEmitters();
  this._updateWatch();

  return (changed > 0);
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
RootPanel.prototype.reflow = function () {
  var changed = 0,
      update = util.updateProperty,
      frame = this.frame;

  if (frame) {
    changed += update(this, 'top', frame.offsetTop);
    changed += update(this, 'left', frame.offsetLeft);
    changed += update(this, 'width', frame.offsetWidth);
    changed += update(this, 'height', frame.offsetHeight);
  }
  else {
    changed += 1;
  }

  return (changed > 0);
};

/**
 * Update watching for resize, depending on the current option
 * @private
 */
RootPanel.prototype._updateWatch = function () {
  var autoResize = this.getOption('autoResize');
  if (autoResize) {
    this._watch();
  }
  else {
    this._unwatch();
  }
};

/**
 * Watch for changes in the size of the frame. On resize, the Panel will
 * automatically redraw itself.
 * @private
 */
RootPanel.prototype._watch = function () {
  var me = this;

  this._unwatch();

  var checkSize = function () {
    var autoResize = me.getOption('autoResize');
    if (!autoResize) {
      // stop watching when the option autoResize is changed to false
      me._unwatch();
      return;
    }

    if (me.frame) {
      // check whether the frame is resized
      if ((me.frame.clientWidth != me.width) ||
          (me.frame.clientHeight != me.height)) {
        me.requestReflow();
      }
    }
  };

  // TODO: automatically cleanup the event listener when the frame is deleted
  util.addEventListener(window, 'resize', checkSize);

  this.watchTimer = setInterval(checkSize, 1000);
};

/**
 * Stop watching for a resize of the frame.
 * @private
 */
RootPanel.prototype._unwatch = function () {
  if (this.watchTimer) {
    clearInterval(this.watchTimer);
    this.watchTimer = undefined;
  }

  // TODO: remove event listener on window.resize
};

/**
 * Event handler
 * @param {String} event       name of the event, for example 'click', 'mousemove'
 * @param {function} callback  callback handler, invoked with the raw HTML Event
 *                             as parameter.
 */
RootPanel.prototype.on = function (event, callback) {
  // register the listener at this component
  var arr = this.listeners[event];
  if (!arr) {
    arr = [];
    this.listeners[event] = arr;
  }
  arr.push(callback);

  this._updateEventEmitters();
};

/**
 * Update the event listeners for all event emitters
 * @private
 */
RootPanel.prototype._updateEventEmitters = function () {
  if (this.listeners) {
    var me = this;
    util.forEach(this.listeners, function (listeners, event) {
      if (!me.emitters) {
        me.emitters = {};
      }
      if (!(event in me.emitters)) {
        // create event
        var frame = me.frame;
        if (frame) {
          //console.log('Created a listener for event ' + event + ' on component ' + me.id); // TODO: cleanup logging
          var callback = function(event) {
            listeners.forEach(function (listener) {
              // TODO: filter on event target!
              listener(event);
            });
          };
          me.emitters[event] = callback;

          if (!me.hammer) {
            me.hammer = Hammer(frame, {
              prevent_default: true
            });
          }
          me.hammer.on(event, callback);
        }
      }
    });

    // TODO: be able to delete event listeners
    // TODO: be able to move event listeners to a parent when available
  }
};

/**
 * A horizontal time axis
 * @param {Component} parent
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]        See TimeAxis.setOptions for the available
 *                                  options.
 * @constructor TimeAxis
 * @extends Component
 */
function TimeAxis (parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  this.dom = {
    majorLines: [],
    majorTexts: [],
    minorLines: [],
    minorTexts: [],
    redundant: {
      majorLines: [],
      majorTexts: [],
      minorLines: [],
      minorTexts: []
    }
  };
  this.props = {
    range: {
      start: 0,
      end: 0,
      minimumStep: 0
    },
    lineTop: 0
  };

  this.options = options || {};
  this.defaultOptions = {
    orientation: 'bottom',  // supported: 'top', 'bottom'
    // TODO: implement timeaxis orientations 'left' and 'right'
    showMinorLabels: true,
    showMajorLabels: true
  };

  this.conversion = null;
  this.range = null;
}

TimeAxis.prototype = new Component();

// TODO: comment options
TimeAxis.prototype.setOptions = Component.prototype.setOptions;

/**
 * Set a range (start and end)
 * @param {Range | Object} range  A Range or an object containing start and end.
 */
TimeAxis.prototype.setRange = function (range) {
  if (!(range instanceof Range) && (!range || !range.start || !range.end)) {
    throw new TypeError('Range must be an instance of Range, ' +
        'or an object containing start and end.');
  }
  this.range = range;
};

/**
 * Convert a position on screen (pixels) to a datetime
 * @param {int}     x    Position on the screen in pixels
 * @return {Date}   time The datetime the corresponds with given position x
 */
TimeAxis.prototype.toTime = function(x) {
  var conversion = this.conversion;
  return new Date(x / conversion.scale + conversion.offset);
};

/**
 * Convert a datetime (Date object) into a position on the screen
 * @param {Date}   time A date
 * @return {int}   x    The position on the screen in pixels which corresponds
 *                      with the given date.
 * @private
 */
TimeAxis.prototype.toScreen = function(time) {
  var conversion = this.conversion;
  return (time.valueOf() - conversion.offset) * conversion.scale;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
TimeAxis.prototype.repaint = function () {
  var changed = 0,
      update = util.updateProperty,
      asSize = util.option.asSize,
      options = this.options,
      orientation = this.getOption('orientation'),
      props = this.props,
      step = this.step;

  var frame = this.frame;
  if (!frame) {
    frame = document.createElement('div');
    this.frame = frame;
    changed += 1;
  }
  frame.className = 'axis';
  // TODO: custom className?

  if (!frame.parentNode) {
    if (!this.parent) {
      throw new Error('Cannot repaint time axis: no parent attached');
    }
    var parentContainer = this.parent.getContainer();
    if (!parentContainer) {
      throw new Error('Cannot repaint time axis: parent has no container element');
    }
    parentContainer.appendChild(frame);

    changed += 1;
  }

  var parent = frame.parentNode;
  if (parent) {
    var beforeChild = frame.nextSibling;
    parent.removeChild(frame); //  take frame offline while updating (is almost twice as fast)

    var defaultTop = (orientation == 'bottom' && this.props.parentHeight && this.height) ?
        (this.props.parentHeight - this.height) + 'px' :
        '0px';
    changed += update(frame.style, 'top', asSize(options.top, defaultTop));
    changed += update(frame.style, 'left', asSize(options.left, '0px'));
    changed += update(frame.style, 'width', asSize(options.width, '100%'));
    changed += update(frame.style, 'height', asSize(options.height, this.height + 'px'));

    // get characters width and height
    this._repaintMeasureChars();

    if (this.step) {
      this._repaintStart();

      step.first();
      var xFirstMajorLabel = undefined;
      var max = 0;
      while (step.hasNext() && max < 1000) {
        max++;
        var cur = step.getCurrent(),
            x = this.toScreen(cur),
            isMajor = step.isMajor();

        // TODO: lines must have a width, such that we can create css backgrounds

        if (this.getOption('showMinorLabels')) {
          this._repaintMinorText(x, step.getLabelMinor());
        }

        if (isMajor && this.getOption('showMajorLabels')) {
          if (x > 0) {
            if (xFirstMajorLabel == undefined) {
              xFirstMajorLabel = x;
            }
            this._repaintMajorText(x, step.getLabelMajor());
          }
          this._repaintMajorLine(x);
        }
        else {
          this._repaintMinorLine(x);
        }

        step.next();
      }

      // create a major label on the left when needed
      if (this.getOption('showMajorLabels')) {
        var leftTime = this.toTime(0),
            leftText = step.getLabelMajor(leftTime),
            widthText = leftText.length * (props.majorCharWidth || 10) + 10; // upper bound estimation

        if (xFirstMajorLabel == undefined || widthText < xFirstMajorLabel) {
          this._repaintMajorText(0, leftText);
        }
      }

      this._repaintEnd();
    }

    this._repaintLine();

    // put frame online again
    if (beforeChild) {
      parent.insertBefore(frame, beforeChild);
    }
    else {
      parent.appendChild(frame)
    }
  }

  return (changed > 0);
};

/**
 * Start a repaint. Move all DOM elements to a redundant list, where they
 * can be picked for re-use, or can be cleaned up in the end
 * @private
 */
TimeAxis.prototype._repaintStart = function () {
  var dom = this.dom,
      redundant = dom.redundant;

  redundant.majorLines = dom.majorLines;
  redundant.majorTexts = dom.majorTexts;
  redundant.minorLines = dom.minorLines;
  redundant.minorTexts = dom.minorTexts;

  dom.majorLines = [];
  dom.majorTexts = [];
  dom.minorLines = [];
  dom.minorTexts = [];
};

/**
 * End a repaint. Cleanup leftover DOM elements in the redundant list
 * @private
 */
TimeAxis.prototype._repaintEnd = function () {
  util.forEach(this.dom.redundant, function (arr) {
    while (arr.length) {
      var elem = arr.pop();
      if (elem && elem.parentNode) {
        elem.parentNode.removeChild(elem);
      }
    }
  });
};


/**
 * Create a minor label for the axis at position x
 * @param {Number} x
 * @param {String} text
 * @private
 */
TimeAxis.prototype._repaintMinorText = function (x, text) {
  // reuse redundant label
  var label = this.dom.redundant.minorTexts.shift();

  if (!label) {
    // create new label
    var content = document.createTextNode('');
    label = document.createElement('div');
    label.appendChild(content);
    label.className = 'text minor';
    this.frame.appendChild(label);
  }
  this.dom.minorTexts.push(label);

  label.childNodes[0].nodeValue = text;
  label.style.left = x + 'px';
  label.style.top  = this.props.minorLabelTop + 'px';
  //label.title = title;  // TODO: this is a heavy operation
};

/**
 * Create a Major label for the axis at position x
 * @param {Number} x
 * @param {String} text
 * @private
 */
TimeAxis.prototype._repaintMajorText = function (x, text) {
  // reuse redundant label
  var label = this.dom.redundant.majorTexts.shift();

  if (!label) {
    // create label
    var content = document.createTextNode(text);
    label = document.createElement('div');
    label.className = 'text major';
    label.appendChild(content);
    this.frame.appendChild(label);
  }
  this.dom.majorTexts.push(label);

  label.childNodes[0].nodeValue = text;
  label.style.top = this.props.majorLabelTop + 'px';
  label.style.left = x + 'px';
  //label.title = title; // TODO: this is a heavy operation
};

/**
 * Create a minor line for the axis at position x
 * @param {Number} x
 * @private
 */
TimeAxis.prototype._repaintMinorLine = function (x) {
  // reuse redundant line
  var line = this.dom.redundant.minorLines.shift();

  if (!line) {
    // create vertical line
    line = document.createElement('div');
    line.className = 'grid vertical minor';
    this.frame.appendChild(line);
  }
  this.dom.minorLines.push(line);

  var props = this.props;
  line.style.top = props.minorLineTop + 'px';
  line.style.height = props.minorLineHeight + 'px';
  line.style.left = (x - props.minorLineWidth / 2) + 'px';
};

/**
 * Create a Major line for the axis at position x
 * @param {Number} x
 * @private
 */
TimeAxis.prototype._repaintMajorLine = function (x) {
  // reuse redundant line
  var line = this.dom.redundant.majorLines.shift();

  if (!line) {
    // create vertical line
    line = document.createElement('DIV');
    line.className = 'grid vertical major';
    this.frame.appendChild(line);
  }
  this.dom.majorLines.push(line);

  var props = this.props;
  line.style.top = props.majorLineTop + 'px';
  line.style.left = (x - props.majorLineWidth / 2) + 'px';
  line.style.height = props.majorLineHeight + 'px';
};


/**
 * Repaint the horizontal line for the axis
 * @private
 */
TimeAxis.prototype._repaintLine = function() {
  var line = this.dom.line,
      frame = this.frame,
      options = this.options;

  // line before all axis elements
  if (this.getOption('showMinorLabels') || this.getOption('showMajorLabels')) {
    if (line) {
      // put this line at the end of all childs
      frame.removeChild(line);
      frame.appendChild(line);
    }
    else {
      // create the axis line
      line = document.createElement('div');
      line.className = 'grid horizontal major';
      frame.appendChild(line);
      this.dom.line = line;
    }

    line.style.top = this.props.lineTop + 'px';
  }
  else {
    if (line && line.parentElement) {
      frame.removeChild(line.line);
      delete this.dom.line;
    }
  }
};

/**
 * Create characters used to determine the size of text on the axis
 * @private
 */
TimeAxis.prototype._repaintMeasureChars = function () {
  // calculate the width and height of a single character
  // this is used to calculate the step size, and also the positioning of the
  // axis
  var dom = this.dom,
      text;

  if (!dom.measureCharMinor) {
    text = document.createTextNode('0');
    var measureCharMinor = document.createElement('DIV');
    measureCharMinor.className = 'text minor measure';
    measureCharMinor.appendChild(text);
    this.frame.appendChild(measureCharMinor);

    dom.measureCharMinor = measureCharMinor;
  }

  if (!dom.measureCharMajor) {
    text = document.createTextNode('0');
    var measureCharMajor = document.createElement('DIV');
    measureCharMajor.className = 'text major measure';
    measureCharMajor.appendChild(text);
    this.frame.appendChild(measureCharMajor);

    dom.measureCharMajor = measureCharMajor;
  }
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
TimeAxis.prototype.reflow = function () {
  var changed = 0,
      update = util.updateProperty,
      frame = this.frame,
      range = this.range;

  if (!range) {
    throw new Error('Cannot repaint time axis: no range configured');
  }

  if (frame) {
    changed += update(this, 'top', frame.offsetTop);
    changed += update(this, 'left', frame.offsetLeft);

    // calculate size of a character
    var props = this.props,
        showMinorLabels = this.getOption('showMinorLabels'),
        showMajorLabels = this.getOption('showMajorLabels'),
        measureCharMinor = this.dom.measureCharMinor,
        measureCharMajor = this.dom.measureCharMajor;
    if (measureCharMinor) {
      props.minorCharHeight = measureCharMinor.clientHeight;
      props.minorCharWidth = measureCharMinor.clientWidth;
    }
    if (measureCharMajor) {
      props.majorCharHeight = measureCharMajor.clientHeight;
      props.majorCharWidth = measureCharMajor.clientWidth;
    }

    var parentHeight = frame.parentNode ? frame.parentNode.offsetHeight : 0;
    if (parentHeight != props.parentHeight) {
      props.parentHeight = parentHeight;
      changed += 1;
    }
    switch (this.getOption('orientation')) {
      case 'bottom':
        props.minorLabelHeight = showMinorLabels ? props.minorCharHeight : 0;
        props.majorLabelHeight = showMajorLabels ? props.majorCharHeight : 0;

        props.minorLabelTop = 0;
        props.majorLabelTop = props.minorLabelTop + props.minorLabelHeight;

        props.minorLineTop = -this.top;
        props.minorLineHeight = Math.max(this.top + props.majorLabelHeight, 0);
        props.minorLineWidth = 1; // TODO: really calculate width

        props.majorLineTop = -this.top;
        props.majorLineHeight = Math.max(this.top + props.minorLabelHeight + props.majorLabelHeight, 0);
        props.majorLineWidth = 1; // TODO: really calculate width

        props.lineTop = 0;

        break;

      case 'top':
        props.minorLabelHeight = showMinorLabels ? props.minorCharHeight : 0;
        props.majorLabelHeight = showMajorLabels ? props.majorCharHeight : 0;

        props.majorLabelTop = 0;
        props.minorLabelTop = props.majorLabelTop + props.majorLabelHeight;

        props.minorLineTop = props.minorLabelTop;
        props.minorLineHeight = Math.max(parentHeight - props.majorLabelHeight - this.top);
        props.minorLineWidth = 1; // TODO: really calculate width

        props.majorLineTop = 0;
        props.majorLineHeight = Math.max(parentHeight - this.top);
        props.majorLineWidth = 1; // TODO: really calculate width

        props.lineTop = props.majorLabelHeight +  props.minorLabelHeight;

        break;

      default:
        throw new Error('Unkown orientation "' + this.getOption('orientation') + '"');
    }

    var height = props.minorLabelHeight + props.majorLabelHeight;
    changed += update(this, 'width', frame.offsetWidth);
    changed += update(this, 'height', height);

    // calculate range and step
    this._updateConversion();

    var start = util.convert(range.start, 'Number'),
        end = util.convert(range.end, 'Number'),
        minimumStep = this.toTime((props.minorCharWidth || 10) * 5).valueOf()
            -this.toTime(0).valueOf();
    this.step = new TimeStep(new Date(start), new Date(end), minimumStep);
    changed += update(props.range, 'start', start);
    changed += update(props.range, 'end', end);
    changed += update(props.range, 'minimumStep', minimumStep.valueOf());
  }

  return (changed > 0);
};

/**
 * Calculate the scale and offset to convert a position on screen to the
 * corresponding date and vice versa.
 * After the method _updateConversion is executed once, the methods toTime
 * and toScreen can be used.
 * @private
 */
TimeAxis.prototype._updateConversion = function() {
  var range = this.range;
  if (!range) {
    throw new Error('No range configured');
  }

  if (range.conversion) {
    this.conversion = range.conversion(this.width);
  }
  else {
    this.conversion = Range.conversion(range.start, range.end, this.width);
  }
};

/**
 * A current time bar
 * @param {Component} parent
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]        Available parameters:
 *                                  {Boolean} [showCurrentTime]
 * @constructor CurrentTime
 * @extends Component
 */

function CurrentTime (parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  this.options = options || {};
  this.defaultOptions = {
    showCurrentTime: false
  };
}

CurrentTime.prototype = new Component();

CurrentTime.prototype.setOptions = Component.prototype.setOptions;

/**
 * Get the container element of the bar, which can be used by a child to
 * add its own widgets.
 * @returns {HTMLElement} container
 */
CurrentTime.prototype.getContainer = function () {
  return this.frame;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
CurrentTime.prototype.repaint = function () {
  var bar = this.frame,
      parent = this.parent,
      parentContainer = parent.parent.getContainer();

  if (!parent) {
    throw new Error('Cannot repaint bar: no parent attached');
  }

  if (!parentContainer) {
    throw new Error('Cannot repaint bar: parent has no container element');
  }

  if (!this.getOption('showCurrentTime')) {
    if (bar) {
      parentContainer.removeChild(bar);
      delete this.frame;
    }

    return;
  }

  if (!bar) {
    bar = document.createElement('div');
    bar.className = 'currenttime';
    bar.style.position = 'absolute';
    bar.style.top = '0px';
    bar.style.height = '100%';

    parentContainer.appendChild(bar);
    this.frame = bar;
  }

  if (!parent.conversion) {
    parent._updateConversion();
  }

  var now = new Date();
  var x = parent.toScreen(now);

  bar.style.left = x + 'px';
  bar.title = 'Current time: ' + now;

  // start a timer to adjust for the new time
  if (this.currentTimeTimer !== undefined) {
    clearTimeout(this.currentTimeTimer);
    delete this.currentTimeTimer;
  }

  var timeline = this;
  var interval = 1 / parent.conversion.scale / 2;

  if (interval < 30) {
    interval = 30;
  }

  this.currentTimeTimer = setTimeout(function() {
    timeline.repaint();
  }, interval);

  return false;
};

/**
 * A custom time bar
 * @param {Component} parent
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]        Available parameters:
 *                                  {Boolean} [showCustomTime]
 * @constructor CustomTime
 * @extends Component
 */

function CustomTime (parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  this.options = options || {};
  this.defaultOptions = {
    showCustomTime: false
  };

  this.listeners = [];
  this.customTime = new Date();
}

CustomTime.prototype = new Component();

CustomTime.prototype.setOptions = Component.prototype.setOptions;

/**
 * Get the container element of the bar, which can be used by a child to
 * add its own widgets.
 * @returns {HTMLElement} container
 */
CustomTime.prototype.getContainer = function () {
  return this.frame;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
CustomTime.prototype.repaint = function () {
  var bar = this.frame,
      parent = this.parent,
      parentContainer = parent.parent.getContainer();

  if (!parent) {
    throw new Error('Cannot repaint bar: no parent attached');
  }

  if (!parentContainer) {
    throw new Error('Cannot repaint bar: parent has no container element');
  }

  if (!this.getOption('showCustomTime')) {
    if (bar) {
      parentContainer.removeChild(bar);
      delete this.frame;
    }

    return;
  }

  if (!bar) {
    bar = document.createElement('div');
    bar.className = 'customtime';
    bar.style.position = 'absolute';
    bar.style.top = '0px';
    bar.style.height = '100%';

    parentContainer.appendChild(bar);

    var drag = document.createElement('div');
    drag.style.position = 'relative';
    drag.style.top = '0px';
    drag.style.left = '-10px';
    drag.style.height = '100%';
    drag.style.width = '20px';
    bar.appendChild(drag);

    this.frame = bar;

    this.subscribe(this, 'movetime');
  }

  if (!parent.conversion) {
    parent._updateConversion();
  }

  var x = parent.toScreen(this.customTime);

  bar.style.left = x + 'px';
  bar.title = 'Time: ' + this.customTime;

  return false;
};

/**
 * Set custom time.
 * @param {Date} time
 */
CustomTime.prototype._setCustomTime = function(time) {
  this.customTime = new Date(time.valueOf());
  this.repaint();
};

/**
 * Retrieve the current custom time.
 * @return {Date} customTime
 */
CustomTime.prototype._getCustomTime = function() {
  return new Date(this.customTime.valueOf());
};

/**
 * Add listeners for mouse and touch events to the component
 * @param {Component} component
 */
CustomTime.prototype.subscribe = function (component, event) {
  var me = this;
  var listener = {
    component: component,
    event: event,
    callback: function (event) {
      me._onMouseDown(event, listener);
    },
    params: {}
  };

  component.on('mousedown', listener.callback);
  me.listeners.push(listener);

};

/**
 * Event handler
 * @param {String} event       name of the event, for example 'click', 'mousemove'
 * @param {function} callback  callback handler, invoked with the raw HTML Event
 *                             as parameter.
 */
CustomTime.prototype.on = function (event, callback) {
  var bar = this.frame;
  if (!bar) {
    throw new Error('Cannot add event listener: no parent attached');
  }

  events.addListener(this, event, callback);
  util.addEventListener(bar, event, callback);
};

/**
 * Start moving horizontally
 * @param {Event} event
 * @param {Object} listener   Listener containing the component and params
 * @private
 */
CustomTime.prototype._onMouseDown = function(event, listener) {
  event = event || window.event;
  var params = listener.params;

  // only react on left mouse button down
  var leftButtonDown = event.which ? (event.which == 1) : (event.button == 1);
  if (!leftButtonDown) {
    return;
  }

  // get mouse position
  params.mouseX = util.getPageX(event);
  params.moved = false;

  params.customTime = this.customTime;

  // add event listeners to handle moving the custom time bar
  var me = this;
  if (!params.onMouseMove) {
    params.onMouseMove = function (event) {
      me._onMouseMove(event, listener);
    };
    util.addEventListener(document, 'mousemove', params.onMouseMove);
  }
  if (!params.onMouseUp) {
    params.onMouseUp = function (event) {
      me._onMouseUp(event, listener);
    };
    util.addEventListener(document, 'mouseup', params.onMouseUp);
  }

  util.stopPropagation(event);
  util.preventDefault(event);
};

/**
 * Perform moving operating.
 * This function activated from within the funcion CustomTime._onMouseDown().
 * @param {Event} event
 * @param {Object} listener
 * @private
 */
CustomTime.prototype._onMouseMove = function (event, listener) {
  event = event || window.event;
  var params = listener.params;
  var parent = this.parent;

  // calculate change in mouse position
  var mouseX = util.getPageX(event);

  if (params.mouseX === undefined) {
    params.mouseX = mouseX;
  }

  var diff = mouseX - params.mouseX;

  // if mouse movement is big enough, register it as a "moved" event
  if (Math.abs(diff) >= 1) {
    params.moved = true;
  }

  var x = parent.toScreen(params.customTime);
  var xnew = x + diff;
  var time = parent.toTime(xnew);
  this._setCustomTime(time);

  // fire a timechange event
  events.trigger(this, 'timechange', {customTime: this.customTime});

  util.preventDefault(event);
};

/**
 * Stop moving operating.
 * This function activated from within the function CustomTime._onMouseDown().
 * @param {event} event
 * @param {Object} listener
 * @private
 */
CustomTime.prototype._onMouseUp = function (event, listener) {
  event = event || window.event;
  var params = listener.params;

  // remove event listeners here, important for Safari
  if (params.onMouseMove) {
    util.removeEventListener(document, 'mousemove', params.onMouseMove);
    params.onMouseMove = null;
  }
  if (params.onMouseUp) {
    util.removeEventListener(document, 'mouseup', params.onMouseUp);
    params.onMouseUp = null;
  }

  if (params.moved) {
    // fire a timechanged event
    events.trigger(this, 'timechanged', {customTime: this.customTime});
  }
};

/**
 * An ItemSet holds a set of items and ranges which can be displayed in a
 * range. The width is determined by the parent of the ItemSet, and the height
 * is determined by the size of the items.
 * @param {Component} parent
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]        See ItemSet.setOptions for the available
 *                                  options.
 * @constructor ItemSet
 * @extends Panel
 */
// TODO: improve performance by replacing all Array.forEach with a for loop
function ItemSet(parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  // one options object is shared by this itemset and all its items
  this.options = options || {};
  this.defaultOptions = {
    type: 'box',
    align: 'center',
    orientation: 'bottom',
    margin: {
      axis: 20,
      item: 10
    },
    padding: 5
  };

  this.dom = {};

  var me = this;
  this.itemsData = null;  // DataSet
  this.range = null;      // Range or Object {start: number, end: number}

  this.listeners = {
    'add': function (event, params, senderId) {
      if (senderId != me.id) {
        me._onAdd(params.items);
      }
    },
    'update': function (event, params, senderId) {
      if (senderId != me.id) {
        me._onUpdate(params.items);
      }
    },
    'remove': function (event, params, senderId) {
      if (senderId != me.id) {
        me._onRemove(params.items);
      }
    }
  };

  this.items = {};    // object with an Item for every data item
  this.queue = {};       // queue with id/actions: 'add', 'update', 'delete'
  this.stack = new Stack(this, Object.create(this.options));
  this.conversion = null;

  // TODO: ItemSet should also attach event listeners for rangechange and rangechanged, like timeaxis
}

ItemSet.prototype = new Panel();

// available item types will be registered here
ItemSet.types = {
  box: ItemBox,
  range: ItemRange,
  rangeoverflow: ItemRangeOverflow,
  point: ItemPoint
};

/**
 * Set options for the ItemSet. Existing options will be extended/overwritten.
 * @param {Object} [options] The following options are available:
 *                           {String | function} [className]
 *                              class name for the itemset
 *                           {String} [type]
 *                              Default type for the items. Choose from 'box'
 *                              (default), 'point', or 'range'. The default
 *                              Style can be overwritten by individual items.
 *                           {String} align
 *                              Alignment for the items, only applicable for
 *                              ItemBox. Choose 'center' (default), 'left', or
 *                              'right'.
 *                           {String} orientation
 *                              Orientation of the item set. Choose 'top' or
 *                              'bottom' (default).
 *                           {Number} margin.axis
 *                              Margin between the axis and the items in pixels.
 *                              Default is 20.
 *                           {Number} margin.item
 *                              Margin between items in pixels. Default is 10.
 *                           {Number} padding
 *                              Padding of the contents of an item in pixels.
 *                              Must correspond with the items css. Default is 5.
 */
ItemSet.prototype.setOptions = Component.prototype.setOptions;

/**
 * Set range (start and end).
 * @param {Range | Object} range  A Range or an object containing start and end.
 */
ItemSet.prototype.setRange = function setRange(range) {
  if (!(range instanceof Range) && (!range || !range.start || !range.end)) {
    throw new TypeError('Range must be an instance of Range, ' +
        'or an object containing start and end.');
  }
  this.range = range;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
ItemSet.prototype.repaint = function repaint() {
  var changed = 0,
      update = util.updateProperty,
      asSize = util.option.asSize,
      options = this.options,
      orientation = this.getOption('orientation'),
      defaultOptions = this.defaultOptions,
      frame = this.frame;

  if (!frame) {
    frame = document.createElement('div');
    frame.className = 'itemset';

    var className = options.className;
    if (className) {
      util.addClassName(frame, util.option.asString(className));
    }

    // create background panel
    var background = document.createElement('div');
    background.className = 'background';
    frame.appendChild(background);
    this.dom.background = background;

    // create foreground panel
    var foreground = document.createElement('div');
    foreground.className = 'foreground';
    frame.appendChild(foreground);
    this.dom.foreground = foreground;

    // create axis panel
    var axis = document.createElement('div');
    axis.className = 'itemset-axis';
    //frame.appendChild(axis);
    this.dom.axis = axis;

    this.frame = frame;
    changed += 1;
  }

  if (!this.parent) {
    throw new Error('Cannot repaint itemset: no parent attached');
  }
  var parentContainer = this.parent.getContainer();
  if (!parentContainer) {
    throw new Error('Cannot repaint itemset: parent has no container element');
  }
  if (!frame.parentNode) {
    parentContainer.appendChild(frame);
    changed += 1;
  }
  if (!this.dom.axis.parentNode) {
    parentContainer.appendChild(this.dom.axis);
    changed += 1;
  }

  // reposition frame
  changed += update(frame.style, 'left',   asSize(options.left, '0px'));
  changed += update(frame.style, 'top',    asSize(options.top, '0px'));
  changed += update(frame.style, 'width',  asSize(options.width, '100%'));
  changed += update(frame.style, 'height', asSize(options.height, this.height + 'px'));

  // reposition axis
  changed += update(this.dom.axis.style, 'left', asSize(options.left, '0px'));
  changed += update(this.dom.axis.style, 'width',  asSize(options.width, '100%'));
  if (orientation == 'bottom') {
    changed += update(this.dom.axis.style, 'top',  (this.height + this.top) + 'px');
  }
  else { // orientation == 'top'
    changed += update(this.dom.axis.style, 'top', this.top + 'px');
  }

  this._updateConversion();

  var me = this,
      queue = this.queue,
      itemsData = this.itemsData,
      items = this.items,
      dataOptions = {
        // TODO: cleanup
        // fields: [(itemsData && itemsData.fieldId || 'id'), 'start', 'end', 'content', 'type', 'className']
      };

  // show/hide added/changed/removed items
  Object.keys(queue).forEach(function (id) {
    //var entry = queue[id];
    var action = queue[id];
    var item = items[id];
    //var item = entry.item;
    //noinspection FallthroughInSwitchStatementJS
    switch (action) {
      case 'add':
      case 'update':
        var itemData = itemsData && itemsData.get(id, dataOptions);

        if (itemData) {
          var type = itemData.type ||
              (itemData.start && itemData.end && 'range') ||
              options.type ||
              'box';
          var constructor = ItemSet.types[type];

          // TODO: how to handle items with invalid data? hide them and give a warning? or throw an error?
          if (item) {
            // update item
            if (!constructor || !(item instanceof constructor)) {
              // item type has changed, hide and delete the item
              changed += item.hide();
              item = null;
            }
            else {
              item.data = itemData; // TODO: create a method item.setData ?
              changed++;
            }
          }

          if (!item) {
            // create item
            if (constructor) {
              item = new constructor(me, itemData, options, defaultOptions);
              changed++;
            }
            else {
              throw new TypeError('Unknown item type "' + type + '"');
            }
          }

          // force a repaint (not only a reposition)
          item.repaint();

          items[id] = item;
        }

        // update queue
        delete queue[id];
        break;

      case 'remove':
        if (item) {
          // remove DOM of the item
          changed += item.hide();
        }

        // update lists
        delete items[id];
        delete queue[id];
        break;

      default:
        console.log('Error: unknown action "' + action + '"');
    }
  });

  // reposition all items. Show items only when in the visible area
  util.forEach(this.items, function (item) {
    if (item.visible) {
      changed += item.show();
      item.reposition();
    }
    else {
      changed += item.hide();
    }
  });

  return (changed > 0);
};

/**
 * Get the foreground container element
 * @return {HTMLElement} foreground
 */
ItemSet.prototype.getForeground = function getForeground() {
  return this.dom.foreground;
};

/**
 * Get the background container element
 * @return {HTMLElement} background
 */
ItemSet.prototype.getBackground = function getBackground() {
  return this.dom.background;
};

/**
 * Get the axis container element
 * @return {HTMLElement} axis
 */
ItemSet.prototype.getAxis = function getAxis() {
  return this.dom.axis;
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
ItemSet.prototype.reflow = function reflow () {
  var changed = 0,
      options = this.options,
      marginAxis = options.margin && options.margin.axis || this.defaultOptions.margin.axis,
      marginItem = options.margin && options.margin.item || this.defaultOptions.margin.item,
      update = util.updateProperty,
      asNumber = util.option.asNumber,
      asSize = util.option.asSize,
      frame = this.frame;

  if (frame) {
    this._updateConversion();

    util.forEach(this.items, function (item) {
      changed += item.reflow();
    });

    // TODO: stack.update should be triggered via an event, in stack itself
    // TODO: only update the stack when there are changed items
    this.stack.update();

    var maxHeight = asNumber(options.maxHeight);
    var fixedHeight = (asSize(options.height) != null);
    var height;
    if (fixedHeight) {
      height = frame.offsetHeight;
    }
    else {
      // height is not specified, determine the height from the height and positioned items
      var visibleItems = this.stack.ordered; // TODO: not so nice way to get the filtered items
      if (visibleItems.length) {
        var min = visibleItems[0].top;
        var max = visibleItems[0].top + visibleItems[0].height;
        util.forEach(visibleItems, function (item) {
          min = Math.min(min, item.top);
          max = Math.max(max, (item.top + item.height));
        });
        height = (max - min) + marginAxis + marginItem;
      }
      else {
        height = marginAxis + marginItem;
      }
    }
    if (maxHeight != null) {
      height = Math.min(height, maxHeight);
    }
    changed += update(this, 'height', height);

    // calculate height from items
    changed += update(this, 'top', frame.offsetTop);
    changed += update(this, 'left', frame.offsetLeft);
    changed += update(this, 'width', frame.offsetWidth);
  }
  else {
    changed += 1;
  }

  return (changed > 0);
};

/**
 * Hide this component from the DOM
 * @return {Boolean} changed
 */
ItemSet.prototype.hide = function hide() {
  var changed = false;

  // remove the DOM
  if (this.frame && this.frame.parentNode) {
    this.frame.parentNode.removeChild(this.frame);
    changed = true;
  }
  if (this.dom.axis && this.dom.axis.parentNode) {
    this.dom.axis.parentNode.removeChild(this.dom.axis);
    changed = true;
  }

  return changed;
};

/**
 * Set items
 * @param {vis.DataSet | null} items
 */
ItemSet.prototype.setItems = function setItems(items) {
  var me = this,
      ids,
      oldItemsData = this.itemsData;

  // replace the dataset
  if (!items) {
    this.itemsData = null;
  }
  else if (items instanceof DataSet || items instanceof DataView) {
    this.itemsData = items;
  }
  else {
    throw new TypeError('Data must be an instance of DataSet');
  }

  if (oldItemsData) {
    // unsubscribe from old dataset
    util.forEach(this.listeners, function (callback, event) {
      oldItemsData.unsubscribe(event, callback);
    });

    // remove all drawn items
    ids = oldItemsData.getIds();
    this._onRemove(ids);
  }

  if (this.itemsData) {
    // subscribe to new dataset
    var id = this.id;
    util.forEach(this.listeners, function (callback, event) {
      me.itemsData.subscribe(event, callback, id);
    });

    // draw all new items
    ids = this.itemsData.getIds();
    this._onAdd(ids);
  }
};

/**
 * Get the current items items
 * @returns {vis.DataSet | null}
 */
ItemSet.prototype.getItems = function getItems() {
  return this.itemsData;
};

/**
 * Handle updated items
 * @param {Number[]} ids
 * @private
 */
ItemSet.prototype._onUpdate = function _onUpdate(ids) {
  this._toQueue('update', ids);
};

/**
 * Handle changed items
 * @param {Number[]} ids
 * @private
 */
ItemSet.prototype._onAdd = function _onAdd(ids) {
  this._toQueue('add', ids);
};

/**
 * Handle removed items
 * @param {Number[]} ids
 * @private
 */
ItemSet.prototype._onRemove = function _onRemove(ids) {
  this._toQueue('remove', ids);
};

/**
 * Put items in the queue to be added/updated/remove
 * @param {String} action     can be 'add', 'update', 'remove'
 * @param {Number[]} ids
 */
ItemSet.prototype._toQueue = function _toQueue(action, ids) {
  var queue = this.queue;
  ids.forEach(function (id) {
    queue[id] = action;
  });

  if (this.controller) {
    //this.requestReflow();
    this.requestRepaint();
  }
};

/**
 * Calculate the scale and offset to convert a position on screen to the
 * corresponding date and vice versa.
 * After the method _updateConversion is executed once, the methods toTime
 * and toScreen can be used.
 * @private
 */
ItemSet.prototype._updateConversion = function _updateConversion() {
  var range = this.range;
  if (!range) {
    throw new Error('No range configured');
  }

  if (range.conversion) {
    this.conversion = range.conversion(this.width);
  }
  else {
    this.conversion = Range.conversion(range.start, range.end, this.width);
  }
};

/**
 * Convert a position on screen (pixels) to a datetime
 * Before this method can be used, the method _updateConversion must be
 * executed once.
 * @param {int}     x    Position on the screen in pixels
 * @return {Date}   time The datetime the corresponds with given position x
 */
ItemSet.prototype.toTime = function toTime(x) {
  var conversion = this.conversion;
  return new Date(x / conversion.scale + conversion.offset);
};

/**
 * Convert a datetime (Date object) into a position on the screen
 * Before this method can be used, the method _updateConversion must be
 * executed once.
 * @param {Date}   time A date
 * @return {int}   x    The position on the screen in pixels which corresponds
 *                      with the given date.
 */
ItemSet.prototype.toScreen = function toScreen(time) {
  var conversion = this.conversion;
  return (time.valueOf() - conversion.offset) * conversion.scale;
};

/**
 * @constructor Item
 * @param {ItemSet} parent
 * @param {Object} data             Object containing (optional) parameters type,
 *                                  start, end, content, group, className.
 * @param {Object} [options]        Options to set initial property values
 * @param {Object} [defaultOptions] default options
 *                                  // TODO: describe available options
 */
function Item (parent, data, options, defaultOptions) {
  this.parent = parent;
  this.data = data;
  this.dom = null;
  this.options = options || {};
  this.defaultOptions = defaultOptions || {};

  this.selected = false;
  this.visible = false;
  this.top = 0;
  this.left = 0;
  this.width = 0;
  this.height = 0;
}

/**
 * Select current item
 */
Item.prototype.select = function select() {
  this.selected = true;
};

/**
 * Unselect current item
 */
Item.prototype.unselect = function unselect() {
  this.selected = false;
};

/**
 * Show the Item in the DOM (when not already visible)
 * @return {Boolean} changed
 */
Item.prototype.show = function show() {
  return false;
};

/**
 * Hide the Item from the DOM (when visible)
 * @return {Boolean} changed
 */
Item.prototype.hide = function hide() {
  return false;
};

/**
 * Repaint the item
 * @return {Boolean} changed
 */
Item.prototype.repaint = function repaint() {
  // should be implemented by the item
  return false;
};

/**
 * Reflow the item
 * @return {Boolean} resized
 */
Item.prototype.reflow = function reflow() {
  // should be implemented by the item
  return false;
};

/**
 * Return the items width
 * @return {Integer} width
 */
Item.prototype.getWidth = function getWidth() {
  return this.width;
}

/**
 * @constructor ItemBox
 * @extends Item
 * @param {ItemSet} parent
 * @param {Object} data             Object containing parameters start
 *                                  content, className.
 * @param {Object} [options]        Options to set initial property values
 * @param {Object} [defaultOptions] default options
 *                                  // TODO: describe available options
 */
function ItemBox (parent, data, options, defaultOptions) {
  this.props = {
    dot: {
      left: 0,
      top: 0,
      width: 0,
      height: 0
    },
    line: {
      top: 0,
      left: 0,
      width: 0,
      height: 0
    }
  };

  Item.call(this, parent, data, options, defaultOptions);
}

ItemBox.prototype = new Item (null, null);

/**
 * Select the item
 * @override
 */
ItemBox.prototype.select = function select() {
  this.selected = true;
  // TODO: select and unselect
};

/**
 * Unselect the item
 * @override
 */
ItemBox.prototype.unselect = function unselect() {
  this.selected = false;
  // TODO: select and unselect
};

/**
 * Repaint the item
 * @return {Boolean} changed
 */
ItemBox.prototype.repaint = function repaint() {
  // TODO: make an efficient repaint
  var changed = false;
  var dom = this.dom;

  if (!dom) {
    this._create();
    dom = this.dom;
    changed = true;
  }

  if (dom) {
    if (!this.parent) {
      throw new Error('Cannot repaint item: no parent attached');
    }

    if (!dom.box.parentNode) {
      var foreground = this.parent.getForeground();
      if (!foreground) {
        throw new Error('Cannot repaint time axis: ' +
            'parent has no foreground container element');
      }
      foreground.appendChild(dom.box);
      changed = true;
    }

    if (!dom.line.parentNode) {
      var background = this.parent.getBackground();
      if (!background) {
        throw new Error('Cannot repaint time axis: ' +
            'parent has no background container element');
      }
      background.appendChild(dom.line);
      changed = true;
    }

    if (!dom.dot.parentNode) {
      var axis = this.parent.getAxis();
      if (!background) {
        throw new Error('Cannot repaint time axis: ' +
            'parent has no axis container element');
      }
      axis.appendChild(dom.dot);
      changed = true;
    }

    // update contents
    if (this.data.content != this.content) {
      this.content = this.data.content;
      if (this.content instanceof Element) {
        dom.content.innerHTML = '';
        dom.content.appendChild(this.content);
      }
      else if (this.data.content != undefined) {
        dom.content.innerHTML = this.content;
      }
      else {
        throw new Error('Property "content" missing in item ' + this.data.id);
      }
      changed = true;
    }

    // update class
    var className = (this.data.className? ' ' + this.data.className : '') +
        (this.selected ? ' selected' : '');
    if (this.className != className) {
      this.className = className;
      dom.box.className = 'item box' + className;
      dom.line.className = 'item line' + className;
      dom.dot.className  = 'item dot' + className;
      changed = true;
    }
  }

  return changed;
};

/**
 * Show the item in the DOM (when not already visible). The items DOM will
 * be created when needed.
 * @return {Boolean} changed
 */
ItemBox.prototype.show = function show() {
  if (!this.dom || !this.dom.box.parentNode) {
    return this.repaint();
  }
  else {
    return false;
  }
};

/**
 * Hide the item from the DOM (when visible)
 * @return {Boolean} changed
 */
ItemBox.prototype.hide = function hide() {
  var changed = false,
      dom = this.dom;
  if (dom) {
    if (dom.box.parentNode) {
      dom.box.parentNode.removeChild(dom.box);
      changed = true;
    }
    if (dom.line.parentNode) {
      dom.line.parentNode.removeChild(dom.line);
    }
    if (dom.dot.parentNode) {
      dom.dot.parentNode.removeChild(dom.dot);
    }
  }
  return changed;
};

/**
 * Reflow the item: calculate its actual size and position from the DOM
 * @return {boolean} resized    returns true if the axis is resized
 * @override
 */
ItemBox.prototype.reflow = function reflow() {
  var changed = 0,
      update,
      dom,
      props,
      options,
      margin,
      start,
      align,
      orientation,
      top,
      left,
      data,
      range;

  if (this.data.start == undefined) {
    throw new Error('Property "start" missing in item ' + this.data.id);
  }

  data = this.data;
  range = this.parent && this.parent.range;
  if (data && range) {
    // TODO: account for the width of the item
    var interval = (range.end - range.start);
    this.visible = (data.start > range.start - interval) && (data.start < range.end + interval);
  }
  else {
    this.visible = false;
  }

  if (this.visible) {
    dom = this.dom;
    if (dom) {
      update = util.updateProperty;
      props = this.props;
      options = this.options;
      start = this.parent.toScreen(this.data.start);
      align = options.align || this.defaultOptions.align;
      margin = options.margin && options.margin.axis || this.defaultOptions.margin.axis;
      orientation = options.orientation || this.defaultOptions.orientation;

      changed += update(props.dot, 'height', dom.dot.offsetHeight);
      changed += update(props.dot, 'width', dom.dot.offsetWidth);
      changed += update(props.line, 'width', dom.line.offsetWidth);
      changed += update(props.line, 'height', dom.line.offsetHeight);
      changed += update(props.line, 'top', dom.line.offsetTop);
      changed += update(this, 'width', dom.box.offsetWidth);
      changed += update(this, 'height', dom.box.offsetHeight);
      if (align == 'right') {
        left = start - this.width;
      }
      else if (align == 'left') {
        left = start;
      }
      else {
        // default or 'center'
        left = start - this.width / 2;
      }
      changed += update(this, 'left', left);

      changed += update(props.line, 'left', start - props.line.width / 2);
      changed += update(props.dot, 'left', start - props.dot.width / 2);
      changed += update(props.dot, 'top', -props.dot.height / 2);
      if (orientation == 'top') {
        top = margin;

        changed += update(this, 'top', top);
      }
      else {
        // default or 'bottom'
        var parentHeight = this.parent.height;
        top = parentHeight - this.height - margin;

        changed += update(this, 'top', top);
      }
    }
    else {
      changed += 1;
    }
  }

  return (changed > 0);
};

/**
 * Create an items DOM
 * @private
 */
ItemBox.prototype._create = function _create() {
  var dom = this.dom;
  if (!dom) {
    this.dom = dom = {};

    // create the box
    dom.box = document.createElement('DIV');
    // className is updated in repaint()

    // contents box (inside the background box). used for making margins
    dom.content = document.createElement('DIV');
    dom.content.className = 'content';
    dom.box.appendChild(dom.content);

    // line to axis
    dom.line = document.createElement('DIV');
    dom.line.className = 'line';

    // dot on axis
    dom.dot = document.createElement('DIV');
    dom.dot.className = 'dot';
  }
};

/**
 * Reposition the item, recalculate its left, top, and width, using the current
 * range and size of the items itemset
 * @override
 */
ItemBox.prototype.reposition = function reposition() {
  var dom = this.dom,
      props = this.props,
      orientation = this.options.orientation || this.defaultOptions.orientation;

  if (dom) {
    var box = dom.box,
        line = dom.line,
        dot = dom.dot;

    box.style.left = this.left + 'px';
    box.style.top = this.top + 'px';

    line.style.left = props.line.left + 'px';
    if (orientation == 'top') {
      line.style.top = 0 + 'px';
      line.style.height = this.top + 'px';
    }
    else {
      // orientation 'bottom'
      line.style.top = (this.top + this.height) + 'px';
      line.style.height = Math.max(this.parent.height - this.top - this.height +
          this.props.dot.height / 2, 0) + 'px';
    }

    dot.style.left = props.dot.left + 'px';
    dot.style.top = props.dot.top + 'px';
  }
};

/**
 * @constructor ItemPoint
 * @extends Item
 * @param {ItemSet} parent
 * @param {Object} data             Object containing parameters start
 *                                  content, className.
 * @param {Object} [options]        Options to set initial property values
 * @param {Object} [defaultOptions] default options
 *                                  // TODO: describe available options
 */
function ItemPoint (parent, data, options, defaultOptions) {
  this.props = {
    dot: {
      top: 0,
      width: 0,
      height: 0
    },
    content: {
      height: 0,
      marginLeft: 0
    }
  };

  Item.call(this, parent, data, options, defaultOptions);
}

ItemPoint.prototype = new Item (null, null);

/**
 * Select the item
 * @override
 */
ItemPoint.prototype.select = function select() {
  this.selected = true;
  // TODO: select and unselect
};

/**
 * Unselect the item
 * @override
 */
ItemPoint.prototype.unselect = function unselect() {
  this.selected = false;
  // TODO: select and unselect
};

/**
 * Repaint the item
 * @return {Boolean} changed
 */
ItemPoint.prototype.repaint = function repaint() {
  // TODO: make an efficient repaint
  var changed = false;
  var dom = this.dom;

  if (!dom) {
    this._create();
    dom = this.dom;
    changed = true;
  }

  if (dom) {
    if (!this.parent) {
      throw new Error('Cannot repaint item: no parent attached');
    }
    var foreground = this.parent.getForeground();
    if (!foreground) {
      throw new Error('Cannot repaint time axis: ' +
          'parent has no foreground container element');
    }

    if (!dom.point.parentNode) {
      foreground.appendChild(dom.point);
      foreground.appendChild(dom.point);
      changed = true;
    }

    // update contents
    if (this.data.content != this.content) {
      this.content = this.data.content;
      if (this.content instanceof Element) {
        dom.content.innerHTML = '';
        dom.content.appendChild(this.content);
      }
      else if (this.data.content != undefined) {
        dom.content.innerHTML = this.content;
      }
      else {
        throw new Error('Property "content" missing in item ' + this.data.id);
      }
      changed = true;
    }

    // update class
    var className = (this.data.className? ' ' + this.data.className : '') +
        (this.selected ? ' selected' : '');
    if (this.className != className) {
      this.className = className;
      dom.point.className  = 'item point' + className;
      changed = true;
    }
  }

  return changed;
};

/**
 * Show the item in the DOM (when not already visible). The items DOM will
 * be created when needed.
 * @return {Boolean} changed
 */
ItemPoint.prototype.show = function show() {
  if (!this.dom || !this.dom.point.parentNode) {
    return this.repaint();
  }
  else {
    return false;
  }
};

/**
 * Hide the item from the DOM (when visible)
 * @return {Boolean} changed
 */
ItemPoint.prototype.hide = function hide() {
  var changed = false,
      dom = this.dom;
  if (dom) {
    if (dom.point.parentNode) {
      dom.point.parentNode.removeChild(dom.point);
      changed = true;
    }
  }
  return changed;
};

/**
 * Reflow the item: calculate its actual size from the DOM
 * @return {boolean} resized    returns true if the axis is resized
 * @override
 */
ItemPoint.prototype.reflow = function reflow() {
  var changed = 0,
      update,
      dom,
      props,
      options,
      margin,
      orientation,
      start,
      top,
      data,
      range;

  if (this.data.start == undefined) {
    throw new Error('Property "start" missing in item ' + this.data.id);
  }

  data = this.data;
  range = this.parent && this.parent.range;
  if (data && range) {
    // TODO: account for the width of the item
    var interval = (range.end - range.start);
    this.visible = (data.start > range.start - interval) && (data.start < range.end);
  }
  else {
    this.visible = false;
  }

  if (this.visible) {
    dom = this.dom;
    if (dom) {
      update = util.updateProperty;
      props = this.props;
      options = this.options;
      orientation = options.orientation || this.defaultOptions.orientation;
      margin = options.margin && options.margin.axis || this.defaultOptions.margin.axis;
      start = this.parent.toScreen(this.data.start);

      changed += update(this, 'width', dom.point.offsetWidth);
      changed += update(this, 'height', dom.point.offsetHeight);
      changed += update(props.dot, 'width', dom.dot.offsetWidth);
      changed += update(props.dot, 'height', dom.dot.offsetHeight);
      changed += update(props.content, 'height', dom.content.offsetHeight);

      if (orientation == 'top') {
        top = margin;
      }
      else {
        // default or 'bottom'
        var parentHeight = this.parent.height;
        top = Math.max(parentHeight - this.height - margin, 0);
      }
      changed += update(this, 'top', top);
      changed += update(this, 'left', start - props.dot.width / 2);
      changed += update(props.content, 'marginLeft', 1.5 * props.dot.width);
      //changed += update(props.content, 'marginRight', 0.5 * props.dot.width); // TODO

      changed += update(props.dot, 'top', (this.height - props.dot.height) / 2);
    }
    else {
      changed += 1;
    }
  }

  return (changed > 0);
};

/**
 * Create an items DOM
 * @private
 */
ItemPoint.prototype._create = function _create() {
  var dom = this.dom;
  if (!dom) {
    this.dom = dom = {};

    // background box
    dom.point = document.createElement('div');
    // className is updated in repaint()

    // contents box, right from the dot
    dom.content = document.createElement('div');
    dom.content.className = 'content';
    dom.point.appendChild(dom.content);

    // dot at start
    dom.dot = document.createElement('div');
    dom.dot.className  = 'dot';
    dom.point.appendChild(dom.dot);
  }
};

/**
 * Reposition the item, recalculate its left, top, and width, using the current
 * range and size of the items itemset
 * @override
 */
ItemPoint.prototype.reposition = function reposition() {
  var dom = this.dom,
      props = this.props;

  if (dom) {
    dom.point.style.top = this.top + 'px';
    dom.point.style.left = this.left + 'px';

    dom.content.style.marginLeft = props.content.marginLeft + 'px';
    //dom.content.style.marginRight = props.content.marginRight + 'px'; // TODO

    dom.dot.style.top = props.dot.top + 'px';
  }
};

/**
 * @constructor ItemRange
 * @extends Item
 * @param {ItemSet} parent
 * @param {Object} data             Object containing parameters start, end
 *                                  content, className.
 * @param {Object} [options]        Options to set initial property values
 * @param {Object} [defaultOptions] default options
 *                                  // TODO: describe available options
 */
function ItemRange (parent, data, options, defaultOptions) {
  this.props = {
    content: {
      left: 0,
      width: 0
    }
  };

  Item.call(this, parent, data, options, defaultOptions);
}

ItemRange.prototype = new Item (null, null);

/**
 * Select the item
 * @override
 */
ItemRange.prototype.select = function select() {
  this.selected = true;
  // TODO: select and unselect
};

/**
 * Unselect the item
 * @override
 */
ItemRange.prototype.unselect = function unselect() {
  this.selected = false;
  // TODO: select and unselect
};

/**
 * Repaint the item
 * @return {Boolean} changed
 */
ItemRange.prototype.repaint = function repaint() {
  // TODO: make an efficient repaint
  var changed = false;
  var dom = this.dom;

  if (!dom) {
    this._create();
    dom = this.dom;
    changed = true;
  }

  if (dom) {
    if (!this.parent) {
      throw new Error('Cannot repaint item: no parent attached');
    }
    var foreground = this.parent.getForeground();
    if (!foreground) {
      throw new Error('Cannot repaint time axis: ' +
          'parent has no foreground container element');
    }

    if (!dom.box.parentNode) {
      foreground.appendChild(dom.box);
      changed = true;
    }

    // update content
    if (this.data.content != this.content) {
      this.content = this.data.content;
      if (this.content instanceof Element) {
        dom.content.innerHTML = '';
        dom.content.appendChild(this.content);
      }
      else if (this.data.content != undefined) {
        dom.content.innerHTML = this.content;
      }
      else {
        throw new Error('Property "content" missing in item ' + this.data.id);
      }
      changed = true;
    }

    // update class
    var className = this.data.className ? (' ' + this.data.className) : '';
    if (this.className != className) {
      this.className = className;
      dom.box.className = 'item range' + className;
      changed = true;
    }
  }

  return changed;
};

/**
 * Show the item in the DOM (when not already visible). The items DOM will
 * be created when needed.
 * @return {Boolean} changed
 */
ItemRange.prototype.show = function show() {
  if (!this.dom || !this.dom.box.parentNode) {
    return this.repaint();
  }
  else {
    return false;
  }
};

/**
 * Hide the item from the DOM (when visible)
 * @return {Boolean} changed
 */
ItemRange.prototype.hide = function hide() {
  var changed = false,
      dom = this.dom;
  if (dom) {
    if (dom.box.parentNode) {
      dom.box.parentNode.removeChild(dom.box);
      changed = true;
    }
  }
  return changed;
};

/**
 * Reflow the item: calculate its actual size from the DOM
 * @return {boolean} resized    returns true if the axis is resized
 * @override
 */
ItemRange.prototype.reflow = function reflow() {
  var changed = 0,
      dom,
      props,
      options,
      margin,
      padding,
      parent,
      start,
      end,
      data,
      range,
      update,
      box,
      parentWidth,
      contentLeft,
      orientation,
      top;

  if (this.data.start == undefined) {
    throw new Error('Property "start" missing in item ' + this.data.id);
  }
  if (this.data.end == undefined) {
    throw new Error('Property "end" missing in item ' + this.data.id);
  }

  data = this.data;
  range = this.parent && this.parent.range;
  if (data && range) {
    // TODO: account for the width of the item. Take some margin
    this.visible = (data.start < range.end) && (data.end > range.start);
  }
  else {
    this.visible = false;
  }

  if (this.visible) {
    dom = this.dom;
    if (dom) {
      props = this.props;
      options = this.options;
      parent = this.parent;
      start = parent.toScreen(this.data.start);
      end = parent.toScreen(this.data.end);
      update = util.updateProperty;
      box = dom.box;
      parentWidth = parent.width;
      orientation = options.orientation || this.defaultOptions.orientation;
      margin = options.margin && options.margin.axis || this.defaultOptions.margin.axis;
      padding = options.padding || this.defaultOptions.padding;

      changed += update(props.content, 'width', dom.content.offsetWidth);

      changed += update(this, 'height', box.offsetHeight);

      // limit the width of the this, as browsers cannot draw very wide divs
      if (start < -parentWidth) {
        start = -parentWidth;
      }
      if (end > 2 * parentWidth) {
        end = 2 * parentWidth;
      }

      // when range exceeds left of the window, position the contents at the left of the visible area
      if (start < 0) {
        contentLeft = Math.min(-start,
            (end - start - props.content.width - 2 * padding));
        // TODO: remove the need for options.padding. it's terrible.
      }
      else {
        contentLeft = 0;
      }
      changed += update(props.content, 'left', contentLeft);

      if (orientation == 'top') {
        top = margin;
        changed += update(this, 'top', top);
      }
      else {
        // default or 'bottom'
        top = parent.height - this.height - margin;
        changed += update(this, 'top', top);
      }

      changed += update(this, 'left', start);
      changed += update(this, 'width', Math.max(end - start, 1)); // TODO: reckon with border width;
    }
    else {
      changed += 1;
    }
  }

  return (changed > 0);
};

/**
 * Create an items DOM
 * @private
 */
ItemRange.prototype._create = function _create() {
  var dom = this.dom;
  if (!dom) {
    this.dom = dom = {};
    // background box
    dom.box = document.createElement('div');
    // className is updated in repaint()

    // contents box
    dom.content = document.createElement('div');
    dom.content.className = 'content';
    dom.box.appendChild(dom.content);
  }
};

/**
 * Reposition the item, recalculate its left, top, and width, using the current
 * range and size of the items itemset
 * @override
 */
ItemRange.prototype.reposition = function reposition() {
  var dom = this.dom,
      props = this.props;

  if (dom) {
    dom.box.style.top = this.top + 'px';
    dom.box.style.left = this.left + 'px';
    dom.box.style.width = this.width + 'px';

    dom.content.style.left = props.content.left + 'px';
  }
};

/**
 * @constructor ItemRangeOverflow
 * @extends ItemRange
 * @param {ItemSet} parent
 * @param {Object} data             Object containing parameters start, end
 *                                  content, className.
 * @param {Object} [options]        Options to set initial property values
 * @param {Object} [defaultOptions] default options
 *                                  // TODO: describe available options
 */
function ItemRangeOverflow (parent, data, options, defaultOptions) {
  this.props = {
    content: {
      left: 0,
      width: 0
    }
  };

  ItemRange.call(this, parent, data, options, defaultOptions);
}

ItemRangeOverflow.prototype = new ItemRange (null, null);

/**
 * Repaint the item
 * @return {Boolean} changed
 */
ItemRangeOverflow.prototype.repaint = function repaint() {
  // TODO: make an efficient repaint
  var changed = false;
  var dom = this.dom;

  if (!dom) {
    this._create();
    dom = this.dom;
    changed = true;
  }

  if (dom) {
    if (!this.parent) {
      throw new Error('Cannot repaint item: no parent attached');
    }
    var foreground = this.parent.getForeground();
    if (!foreground) {
      throw new Error('Cannot repaint time axis: ' +
          'parent has no foreground container element');
    }

    if (!dom.box.parentNode) {
      foreground.appendChild(dom.box);
      changed = true;
    }

    // update content
    if (this.data.content != this.content) {
      this.content = this.data.content;
      if (this.content instanceof Element) {
        dom.content.innerHTML = '';
        dom.content.appendChild(this.content);
      }
      else if (this.data.content != undefined) {
        dom.content.innerHTML = this.content;
      }
      else {
        throw new Error('Property "content" missing in item ' + this.data.id);
      }
      changed = true;
    }

    // update class
    var className = this.data.className ? (' ' + this.data.className) : '';
    if (this.className != className) {
      this.className = className;
      dom.box.className = 'item rangeoverflow' + className;
      changed = true;
    }
  }

  return changed;
};

/**
 * Return the items width
 * @return {Number} width
 */
ItemRangeOverflow.prototype.getWidth = function getWidth() {
  if (this.props.content !== undefined && this.width < this.props.content.width)
    return this.props.content.width;
  else
    return this.width;
};

/**
 * @constructor Group
 * @param {GroupSet} parent
 * @param {Number | String} groupId
 * @param {Object} [options]  Options to set initial property values
 *                            // TODO: describe available options
 * @extends Component
 */
function Group (parent, groupId, options) {
  this.id = util.randomUUID();
  this.parent = parent;

  this.groupId = groupId;
  this.itemset = null;    // ItemSet
  this.options = options || {};
  this.options.top = 0;

  this.props = {
    label: {
      width: 0,
      height: 0
    }
  };

  this.top = 0;
  this.left = 0;
  this.width = 0;
  this.height = 0;
}

Group.prototype = new Component();

// TODO: comment
Group.prototype.setOptions = Component.prototype.setOptions;

/**
 * Get the container element of the panel, which can be used by a child to
 * add its own widgets.
 * @returns {HTMLElement} container
 */
Group.prototype.getContainer = function () {
  return this.parent.getContainer();
};

/**
 * Set item set for the group. The group will create a view on the itemset,
 * filtered by the groups id.
 * @param {DataSet | DataView} items
 */
Group.prototype.setItems = function setItems(items) {
  if (this.itemset) {
    // remove current item set
    this.itemset.hide();
    this.itemset.setItems();

    this.parent.controller.remove(this.itemset);
    this.itemset = null;
  }

  if (items) {
    var groupId = this.groupId;

    var itemsetOptions = Object.create(this.options);
    this.itemset = new ItemSet(this, null, itemsetOptions);
    this.itemset.setRange(this.parent.range);

    this.view = new DataView(items, {
      filter: function (item) {
        return item.group == groupId;
      }
    });
    this.itemset.setItems(this.view);

    this.parent.controller.add(this.itemset);
  }
};

/**
 * Repaint the item
 * @return {Boolean} changed
 */
Group.prototype.repaint = function repaint() {
  return false;
};

/**
 * Reflow the item
 * @return {Boolean} resized
 */
Group.prototype.reflow = function reflow() {
  var changed = 0,
      update = util.updateProperty;

  changed += update(this, 'top',    this.itemset ? this.itemset.top : 0);
  changed += update(this, 'height', this.itemset ? this.itemset.height : 0);

  // TODO: reckon with the height of the group label

  if (this.label) {
    var inner = this.label.firstChild;
    changed += update(this.props.label, 'width', inner.clientWidth);
    changed += update(this.props.label, 'height', inner.clientHeight);
  }
  else {
    changed += update(this.props.label, 'width', 0);
    changed += update(this.props.label, 'height', 0);
  }

  return (changed > 0);
};

/**
 * An GroupSet holds a set of groups
 * @param {Component} parent
 * @param {Component[]} [depends]   Components on which this components depends
 *                                  (except for the parent)
 * @param {Object} [options]        See GroupSet.setOptions for the available
 *                                  options.
 * @constructor GroupSet
 * @extends Panel
 */
function GroupSet(parent, depends, options) {
  this.id = util.randomUUID();
  this.parent = parent;
  this.depends = depends;

  this.options = options || {};

  this.range = null;      // Range or Object {start: number, end: number}
  this.itemsData = null;  // DataSet with items
  this.groupsData = null; // DataSet with groups

  this.groups = {};       // map with groups

  this.dom = {};
  this.props = {
    labels: {
      width: 0
    }
  };

  // TODO: implement right orientation of the labels

  // changes in groups are queued  key/value map containing id/action
  this.queue = {};

  var me = this;
  this.listeners = {
    'add': function (event, params) {
      me._onAdd(params.items);
    },
    'update': function (event, params) {
      me._onUpdate(params.items);
    },
    'remove': function (event, params) {
      me._onRemove(params.items);
    }
  };
}

GroupSet.prototype = new Panel();

/**
 * Set options for the GroupSet. Existing options will be extended/overwritten.
 * @param {Object} [options] The following options are available:
 *                           {String | function} groupsOrder
 *                           TODO: describe options
 */
GroupSet.prototype.setOptions = Component.prototype.setOptions;

GroupSet.prototype.setRange = function (range) {
  // TODO: implement setRange
};

/**
 * Set items
 * @param {vis.DataSet | null} items
 */
GroupSet.prototype.setItems = function setItems(items) {
  this.itemsData = items;

  for (var id in this.groups) {
    if (this.groups.hasOwnProperty(id)) {
      var group = this.groups[id];
      group.setItems(items);
    }
  }
};

/**
 * Get items
 * @return {vis.DataSet | null} items
 */
GroupSet.prototype.getItems = function getItems() {
  return this.itemsData;
};

/**
 * Set range (start and end).
 * @param {Range | Object} range  A Range or an object containing start and end.
 */
GroupSet.prototype.setRange = function setRange(range) {
  this.range = range;
};

/**
 * Set groups
 * @param {vis.DataSet} groups
 */
GroupSet.prototype.setGroups = function setGroups(groups) {
  var me = this,
      ids;

  // unsubscribe from current dataset
  if (this.groupsData) {
    util.forEach(this.listeners, function (callback, event) {
      me.groupsData.unsubscribe(event, callback);
    });

    // remove all drawn groups
    ids = this.groupsData.getIds();
    this._onRemove(ids);
  }

  // replace the dataset
  if (!groups) {
    this.groupsData = null;
  }
  else if (groups instanceof DataSet) {
    this.groupsData = groups;
  }
  else {
    this.groupsData = new DataSet({
      convert: {
        start: 'Date',
        end: 'Date'
      }
    });
    this.groupsData.add(groups);
  }

  if (this.groupsData) {
    // subscribe to new dataset
    var id = this.id;
    util.forEach(this.listeners, function (callback, event) {
      me.groupsData.subscribe(event, callback, id);
    });

    // draw all new groups
    ids = this.groupsData.getIds();
    this._onAdd(ids);
  }
};

/**
 * Get groups
 * @return {vis.DataSet | null} groups
 */
GroupSet.prototype.getGroups = function getGroups() {
  return this.groupsData;
};

/**
 * Repaint the component
 * @return {Boolean} changed
 */
GroupSet.prototype.repaint = function repaint() {
  var changed = 0,
      i, id, group, label,
      update = util.updateProperty,
      asSize = util.option.asSize,
      asElement = util.option.asElement,
      options = this.options,
      frame = this.dom.frame,
      labels = this.dom.labels,
      labelSet = this.dom.labelSet;

  // create frame
  if (!this.parent) {
    throw new Error('Cannot repaint groupset: no parent attached');
  }
  var parentContainer = this.parent.getContainer();
  if (!parentContainer) {
    throw new Error('Cannot repaint groupset: parent has no container element');
  }
  if (!frame) {
    frame = document.createElement('div');
    frame.className = 'groupset';
    this.dom.frame = frame;

    var className = options.className;
    if (className) {
      util.addClassName(frame, util.option.asString(className));
    }

    changed += 1;
  }
  if (!frame.parentNode) {
    parentContainer.appendChild(frame);
    changed += 1;
  }

  // create labels
  var labelContainer = asElement(options.labelContainer);
  if (!labelContainer) {
    throw new Error('Cannot repaint groupset: option "labelContainer" not defined');
  }
  if (!labels) {
    labels = document.createElement('div');
    labels.className = 'labels';
    this.dom.labels = labels;
  }
  if (!labelSet) {
    labelSet = document.createElement('div');
    labelSet.className = 'label-set';
    labels.appendChild(labelSet);
    this.dom.labelSet = labelSet;
  }
  if (!labels.parentNode || labels.parentNode != labelContainer) {
    if (labels.parentNode) {
      labels.parentNode.removeChild(labels.parentNode);
    }
    labelContainer.appendChild(labels);
  }

  // reposition frame
  changed += update(frame.style, 'height', asSize(options.height, this.height + 'px'));
  changed += update(frame.style, 'top',    asSize(options.top, '0px'));
  changed += update(frame.style, 'left',   asSize(options.left, '0px'));
  changed += update(frame.style, 'width',  asSize(options.width, '100%'));

  // reposition labels
  changed += update(labelSet.style, 'top',    asSize(options.top, '0px'));
  changed += update(labelSet.style, 'height', asSize(options.height, this.height + 'px'));

  var me = this,
      queue = this.queue,
      groups = this.groups,
      groupsData = this.groupsData;

  // show/hide added/changed/removed groups
  var ids = Object.keys(queue);
  if (ids.length) {
    ids.forEach(function (id) {
      var action = queue[id];
      var group = groups[id];

      //noinspection FallthroughInSwitchStatementJS
      switch (action) {
        case 'add':
        case 'update':
          if (!group) {
            var groupOptions = Object.create(me.options);
            util.extend(groupOptions, {
              height: null,
              maxHeight: null
            });

            group = new Group(me, id, groupOptions);
            group.setItems(me.itemsData); // attach items data
            groups[id] = group;

            me.controller.add(group);
          }

          // TODO: update group data
          group.data = groupsData.get(id);

          delete queue[id];
          break;

        case 'remove':
          if (group) {
            group.setItems(); // detach items data
            delete groups[id];

            me.controller.remove(group);
          }

          // update lists
          delete queue[id];
          break;

        default:
          console.log('Error: unknown action "' + action + '"');
      }
    });

    // the groupset depends on each of the groups
    //this.depends = this.groups; // TODO: gives a circular reference through the parent

    // TODO: apply dependencies of the groupset

    // update the top positions of the groups in the correct order
    var orderedGroups = this.groupsData.getIds({
      order: this.options.groupOrder
    });
    for (i = 0; i < orderedGroups.length; i++) {
      (function (group, prevGroup) {
        var top = 0;
        if (prevGroup) {
          top = function () {
            // TODO: top must reckon with options.maxHeight
            return prevGroup.top + prevGroup.height;
          }
        }
        group.setOptions({
          top: top
        });
      })(groups[orderedGroups[i]], groups[orderedGroups[i - 1]]);
    }

    // (re)create the labels
    while (labelSet.firstChild) {
      labelSet.removeChild(labelSet.firstChild);
    }
    for (i = 0; i < orderedGroups.length; i++) {
      id = orderedGroups[i];
      label = this._createLabel(id);
      labelSet.appendChild(label);
    }

    changed++;
  }

  // reposition the labels
  // TODO: labels are not displayed correctly when orientation=='top'
  // TODO: width of labelPanel is not immediately updated on a change in groups
  for (id in groups) {
    if (groups.hasOwnProperty(id)) {
      group = groups[id];
      label = group.label;
      if (label) {
        label.style.top = group.top + 'px';
        label.style.height = group.height + 'px';
      }
    }
  }

  return (changed > 0);
};

/**
 * Create a label for group with given id
 * @param {Number} id
 * @return {Element} label
 * @private
 */
GroupSet.prototype._createLabel = function(id) {
  var group = this.groups[id];
  var label = document.createElement('div');
  label.className = 'label';
  var inner = document.createElement('div');
  inner.className = 'inner';
  label.appendChild(inner);

  var content = group.data && group.data.content;
  if (content instanceof Element) {
    inner.appendChild(content);
  }
  else if (content != undefined) {
    inner.innerHTML = content;
  }

  var className = group.data && group.data.className;
  if (className) {
    util.addClassName(label, className);
  }

  group.label = label; // TODO: not so nice, parking labels in the group this way!!!

  return label;
};

/**
 * Get container element
 * @return {HTMLElement} container
 */
GroupSet.prototype.getContainer = function getContainer() {
  return this.dom.frame;
};

/**
 * Get the width of the group labels
 * @return {Number} width
 */
GroupSet.prototype.getLabelsWidth = function getContainer() {
  return this.props.labels.width;
};

/**
 * Reflow the component
 * @return {Boolean} resized
 */
GroupSet.prototype.reflow = function reflow() {
  var changed = 0,
      id, group,
      options = this.options,
      update = util.updateProperty,
      asNumber = util.option.asNumber,
      asSize = util.option.asSize,
      frame = this.dom.frame;

  if (frame) {
    var maxHeight = asNumber(options.maxHeight);
    var fixedHeight = (asSize(options.height) != null);
    var height;
    if (fixedHeight) {
      height = frame.offsetHeight;
    }
    else {
      // height is not specified, calculate the sum of the height of all groups
      height = 0;

      for (id in this.groups) {
        if (this.groups.hasOwnProperty(id)) {
          group = this.groups[id];
          height += group.height;
        }
      }
    }
    if (maxHeight != null) {
      height = Math.min(height, maxHeight);
    }
    changed += update(this, 'height', height);

    changed += update(this, 'top', frame.offsetTop);
    changed += update(this, 'left', frame.offsetLeft);
    changed += update(this, 'width', frame.offsetWidth);
  }

  // calculate the maximum width of the labels
  var width = 0;
  for (id in this.groups) {
    if (this.groups.hasOwnProperty(id)) {
      group = this.groups[id];
      var labelWidth = group.props && group.props.label && group.props.label.width || 0;
      width = Math.max(width, labelWidth);
    }
  }
  changed += update(this.props.labels, 'width', width);

  return (changed > 0);
};

/**
 * Hide the component from the DOM
 * @return {Boolean} changed
 */
GroupSet.prototype.hide = function hide() {
  if (this.dom.frame && this.dom.frame.parentNode) {
    this.dom.frame.parentNode.removeChild(this.dom.frame);
    return true;
  }
  else {
    return false;
  }
};

/**
 * Show the component in the DOM (when not already visible).
 * A repaint will be executed when the component is not visible
 * @return {Boolean} changed
 */
GroupSet.prototype.show = function show() {
  if (!this.dom.frame || !this.dom.frame.parentNode) {
    return this.repaint();
  }
  else {
    return false;
  }
};

/**
 * Handle updated groups
 * @param {Number[]} ids
 * @private
 */
GroupSet.prototype._onUpdate = function _onUpdate(ids) {
  this._toQueue(ids, 'update');
};

/**
 * Handle changed groups
 * @param {Number[]} ids
 * @private
 */
GroupSet.prototype._onAdd = function _onAdd(ids) {
  this._toQueue(ids, 'add');
};

/**
 * Handle removed groups
 * @param {Number[]} ids
 * @private
 */
GroupSet.prototype._onRemove = function _onRemove(ids) {
  this._toQueue(ids, 'remove');
};

/**
 * Put groups in the queue to be added/updated/remove
 * @param {Number[]} ids
 * @param {String} action     can be 'add', 'update', 'remove'
 */
GroupSet.prototype._toQueue = function _toQueue(ids, action) {
  var queue = this.queue;
  ids.forEach(function (id) {
    queue[id] = action;
  });

  if (this.controller) {
    //this.requestReflow();
    this.requestRepaint();
  }
};

/**
 * Create a timeline visualization
 * @param {HTMLElement} container
 * @param {vis.DataSet | Array | DataTable} [items]
 * @param {Object} [options]  See Timeline.setOptions for the available options.
 * @constructor
 */
function Timeline (container, items, options) {
  var me = this;
  var now = moment().hours(0).minutes(0).seconds(0).milliseconds(0);
  this.options = {
    orientation: 'bottom',
    min: null,
    max: null,
    zoomMin: 10,                                // milliseconds
    zoomMax: 1000 * 60 * 60 * 24 * 365 * 10000, // milliseconds
    // moveable: true, // TODO: option moveable
    // zoomable: true, // TODO: option zoomable
    showMinorLabels: true,
    showMajorLabels: true,
    showCurrentTime: false,
    showCustomTime: false,
    autoResize: false
  };

  // controller
  this.controller = new Controller();

  // root panel
  if (!container) {
    throw new Error('No container element provided');
  }
  var rootOptions = Object.create(this.options);
  rootOptions.height = function () {
    // TODO: change to height
    if (me.options.height) {
      // fixed height
      return me.options.height;
    }
    else {
      // auto height
      return (me.timeaxis.height + me.content.height) + 'px';
    }
  };
  this.rootPanel = new RootPanel(container, rootOptions);
  this.controller.add(this.rootPanel);

  // item panel
  var itemOptions = Object.create(this.options);
  itemOptions.left = function () {
    return me.labelPanel.width;
  };
  itemOptions.width = function () {
    return me.rootPanel.width - me.labelPanel.width;
  };
  itemOptions.top = null;
  itemOptions.height = null;
  this.itemPanel = new Panel(this.rootPanel, [], itemOptions);
  this.controller.add(this.itemPanel);

  // label panel
  var labelOptions = Object.create(this.options);
  labelOptions.top = null;
  labelOptions.left = null;
  labelOptions.height = null;
  labelOptions.width = function () {
    if (me.content && typeof me.content.getLabelsWidth === 'function') {
      return me.content.getLabelsWidth();
    }
    else {
      return 0;
    }
  };
  this.labelPanel = new Panel(this.rootPanel, [], labelOptions);
  this.controller.add(this.labelPanel);

  // range
  var rangeOptions = Object.create(this.options);
  this.range = new Range(rangeOptions);
  this.range.setRange(
      now.clone().add('days', -3).valueOf(),
      now.clone().add('days', 4).valueOf()
  );

  // TODO: reckon with options moveable and zoomable
  this.range.subscribe(this.rootPanel, 'move', 'horizontal');
  this.range.subscribe(this.rootPanel, 'zoom', 'horizontal');
  this.range.on('rangechange', function () {
    var force = true;
    me.controller.requestReflow(force);
  });
  this.range.on('rangechanged', function () {
    var force = true;
    me.controller.requestReflow(force);
  });

  // TODO: put the listeners in setOptions, be able to dynamically change with options moveable and zoomable

  // time axis
  var timeaxisOptions = Object.create(rootOptions);
  timeaxisOptions.range = this.range;
  timeaxisOptions.left = null;
  timeaxisOptions.top = null;
  timeaxisOptions.width = '100%';
  timeaxisOptions.height = null;
  this.timeaxis = new TimeAxis(this.itemPanel, [], timeaxisOptions);
  this.timeaxis.setRange(this.range);
  this.controller.add(this.timeaxis);

  // current time bar
  this.currenttime = new CurrentTime(this.timeaxis, [], rootOptions);
  this.controller.add(this.currenttime);

  // custom time bar
  this.customtime = new CustomTime(this.timeaxis, [], rootOptions);
  this.controller.add(this.customtime);

  // create groupset
  this.setGroups(null);

  this.itemsData = null;      // DataSet
  this.groupsData = null;     // DataSet

  // apply options
  if (options) {
    this.setOptions(options);
  }

  // create itemset and groupset
  if (items) {
    this.setItems(items);
  }
}

/**
 * Set options
 * @param {Object} options  TODO: describe the available options
 */
Timeline.prototype.setOptions = function (options) {
  util.extend(this.options, options);

  // force update of range
  // options.start and options.end can be undefined
  //this.range.setRange(options.start, options.end);
  this.range.setRange();

  this.controller.reflow();
  this.controller.repaint();
};

/**
 * Set a custom time bar
 * @param {Date} time
 */
Timeline.prototype.setCustomTime = function (time) {
  this.customtime._setCustomTime(time);
};

/**
 * Retrieve the current custom time.
 * @return {Date} customTime
 */
Timeline.prototype.getCustomTime = function() {
  return new Date(this.customtime.customTime.valueOf());
};

/**
 * Set items
 * @param {vis.DataSet | Array | DataTable | null} items
 */
Timeline.prototype.setItems = function(items) {
  var initialLoad = (this.itemsData == null);

  // convert to type DataSet when needed
  var newItemSet;
  if (!items) {
    newItemSet = null;
  }
  else if (items instanceof DataSet) {
    newItemSet = items;
  }
  if (!(items instanceof DataSet)) {
    newItemSet = new DataSet({
      convert: {
        start: 'Date',
        end: 'Date'
      }
    });
    newItemSet.add(items);
  }

  // set items
  this.itemsData = newItemSet;
  this.content.setItems(newItemSet);

  if (initialLoad && (this.options.start == undefined || this.options.end == undefined)) {
    // apply the data range as range
    var dataRange = this.getItemRange();

    // add 5% space on both sides
    var min = dataRange.min;
    var max = dataRange.max;
    if (min != null && max != null) {
      var interval = (max.valueOf() - min.valueOf());
      if (interval <= 0) {
        // prevent an empty interval
        interval = 24 * 60 * 60 * 1000; // 1 day
      }
      min = new Date(min.valueOf() - interval * 0.05);
      max = new Date(max.valueOf() + interval * 0.05);
    }

    // override specified start and/or end date
    if (this.options.start != undefined) {
      min = util.convert(this.options.start, 'Date');
    }
    if (this.options.end != undefined) {
      max = util.convert(this.options.end, 'Date');
    }

    // apply range if there is a min or max available
    if (min != null || max != null) {
      this.range.setRange(min, max);
    }
  }
};

/**
 * Set groups
 * @param {vis.DataSet | Array | DataTable} groups
 */
Timeline.prototype.setGroups = function(groups) {
  var me = this;
  this.groupsData = groups;

  // switch content type between ItemSet or GroupSet when needed
  var Type = this.groupsData ? GroupSet : ItemSet;
  if (!(this.content instanceof Type)) {
    // remove old content set
    if (this.content) {
      this.content.hide();
      if (this.content.setItems) {
        this.content.setItems(); // disconnect from items
      }
      if (this.content.setGroups) {
        this.content.setGroups(); // disconnect from groups
      }
      this.controller.remove(this.content);
    }

    // create new content set
    var options = Object.create(this.options);
    util.extend(options, {
      top: function () {
        if (me.options.orientation == 'top') {
          return me.timeaxis.height;
        }
        else {
          return me.itemPanel.height - me.timeaxis.height - me.content.height;
        }
      },
      left: null,
      width: '100%',
      height: function () {
        if (me.options.height) {
          // fixed height
          return me.itemPanel.height - me.timeaxis.height;
        }
        else {
          // auto height
          return null;
        }
      },
      maxHeight: function () {
        // TODO: change maxHeight to be a css string like '100%' or '300px'
        if (me.options.maxHeight) {
          if (!util.isNumber(me.options.maxHeight)) {
            throw new TypeError('Number expected for property maxHeight');
          }
          return me.options.maxHeight - me.timeaxis.height;
        }
        else {
          return null;
        }
      },
      labelContainer: function () {
        return me.labelPanel.getContainer();
      }
    });

    this.content = new Type(this.itemPanel, [this.timeaxis], options);
    if (this.content.setRange) {
      this.content.setRange(this.range);
    }
    if (this.content.setItems) {
      this.content.setItems(this.itemsData);
    }
    if (this.content.setGroups) {
      this.content.setGroups(this.groupsData);
    }
    this.controller.add(this.content);
  }
};

/**
 * Get the data range of the item set.
 * @returns {{min: Date, max: Date}} range  A range with a start and end Date.
 *                                          When no minimum is found, min==null
 *                                          When no maximum is found, max==null
 */
Timeline.prototype.getItemRange = function getItemRange() {
  // calculate min from start filed
  var itemsData = this.itemsData,
      min = null,
      max = null;

  if (itemsData) {
    // calculate the minimum value of the field 'start'
    var minItem = itemsData.min('start');
    min = minItem ? minItem.start.valueOf() : null;

    // calculate maximum value of fields 'start' and 'end'
    var maxStartItem = itemsData.max('start');
    if (maxStartItem) {
      max = maxStartItem.start.valueOf();
    }
    var maxEndItem = itemsData.max('end');
    if (maxEndItem) {
      if (max == null) {
        max = maxEndItem.end.valueOf();
      }
      else {
        max = Math.max(max, maxEndItem.end.valueOf());
      }
    }
  }

  return {
    min: (min != null) ? new Date(min) : null,
    max: (max != null) ? new Date(max) : null
  };
};

(function(exports) {
  /**
   * Parse a text source containing data in DOT language into a JSON object.
   * The object contains two lists: one with nodes and one with edges.
   *
   * DOT language reference: http://www.graphviz.org/doc/info/lang.html
   *
   * @param {String} data     Text containing a graph in DOT-notation
   * @return {Object} graph   An object containing two parameters:
   *                          {Object[]} nodes
   *                          {Object[]} edges
   */
  function parseDOT (data) {
    dot = data;
    return parseGraph();
  }

  // token types enumeration
  var TOKENTYPE = {
    NULL : 0,
    DELIMITER : 1,
    IDENTIFIER: 2,
    UNKNOWN : 3
  };

  // map with all delimiters
  var DELIMITERS = {
    '{': true,
    '}': true,
    '[': true,
    ']': true,
    ';': true,
    '=': true,
    ',': true,

    '->': true,
    '--': true
  };

  var dot = '';                   // current dot file
  var index = 0;                  // current index in dot file
  var c = '';                     // current token character in expr
  var token = '';                 // current token
  var tokenType = TOKENTYPE.NULL; // type of the token

  /**
   * Get the first character from the dot file.
   * The character is stored into the char c. If the end of the dot file is
   * reached, the function puts an empty string in c.
   */
  function first() {
    index = 0;
    c = dot.charAt(0);
  }

  /**
   * Get the next character from the dot file.
   * The character is stored into the char c. If the end of the dot file is
   * reached, the function puts an empty string in c.
   */
  function next() {
    index++;
    c = dot.charAt(index);
  }

  /**
   * Preview the next character from the dot file.
   * @return {String} cNext
   */
  function nextPreview() {
    return dot.charAt(index + 1);
  }

  /**
   * Test whether given character is alphabetic or numeric
   * @param {String} c
   * @return {Boolean} isAlphaNumeric
   */
  var regexAlphaNumeric = /[a-zA-Z_0-9.:#]/;
  function isAlphaNumeric(c) {
    return regexAlphaNumeric.test(c);
  }

  /**
   * Merge all properties of object b into object b
   * @param {Object} a
   * @param {Object} b
   * @return {Object} a
   */
  function merge (a, b) {
    if (!a) {
      a = {};
    }

    if (b) {
      for (var name in b) {
        if (b.hasOwnProperty(name)) {
          a[name] = b[name];
        }
      }
    }
    return a;
  }

  /**
   * Set a value in an object, where the provided parameter name can be a
   * path with nested parameters. For example:
   *
   *     var obj = {a: 2};
   *     setValue(obj, 'b.c', 3);     // obj = {a: 2, b: {c: 3}}
   *
   * @param {Object} obj
   * @param {String} path  A parameter name or dot-separated parameter path,
   *                      like "color.highlight.border".
   * @param {*} value
   */
  function setValue(obj, path, value) {
    var keys = path.split('.');
    var o = obj;
    while (keys.length) {
      var key = keys.shift();
      if (keys.length) {
        // this isn't the end point
        if (!o[key]) {
          o[key] = {};
        }
        o = o[key];
      }
      else {
        // this is the end point
        o[key] = value;
      }
    }
  }

  /**
   * Add a node to a graph object. If there is already a node with
   * the same id, their attributes will be merged.
   * @param {Object} graph
   * @param {Object} node
   */
  function addNode(graph, node) {
    var i, len;
    var current = null;

    // find root graph (in case of subgraph)
    var graphs = [graph]; // list with all graphs from current graph to root graph
    var root = graph;
    while (root.parent) {
      graphs.push(root.parent);
      root = root.parent;
    }

    // find existing node (at root level) by its id
    if (root.nodes) {
      for (i = 0, len = root.nodes.length; i < len; i++) {
        if (node.id === root.nodes[i].id) {
          current = root.nodes[i];
          break;
        }
      }
    }

    if (!current) {
      // this is a new node
      current = {
        id: node.id
      };
      if (graph.node) {
        // clone default attributes
        current.attr = merge(current.attr, graph.node);
      }
    }

    // add node to this (sub)graph and all its parent graphs
    for (i = graphs.length - 1; i >= 0; i--) {
      var g = graphs[i];

      if (!g.nodes) {
        g.nodes = [];
      }
      if (g.nodes.indexOf(current) == -1) {
        g.nodes.push(current);
      }
    }

    // merge attributes
    if (node.attr) {
      current.attr = merge(current.attr, node.attr);
    }
  }

  /**
   * Add an edge to a graph object
   * @param {Object} graph
   * @param {Object} edge
   */
  function addEdge(graph, edge) {
    if (!graph.edges) {
      graph.edges = [];
    }
    graph.edges.push(edge);
    if (graph.edge) {
      var attr = merge({}, graph.edge);     // clone default attributes
      edge.attr = merge(attr, edge.attr); // merge attributes
    }
  }

  /**
   * Create an edge to a graph object
   * @param {Object} graph
   * @param {String | Number | Object} from
   * @param {String | Number | Object} to
   * @param {String} type
   * @param {Object | null} attr
   * @return {Object} edge
   */
  function createEdge(graph, from, to, type, attr) {
    var edge = {
      from: from,
      to: to,
      type: type
    };

    if (graph.edge) {
      edge.attr = merge({}, graph.edge);  // clone default attributes
    }
    edge.attr = merge(edge.attr || {}, attr); // merge attributes

    return edge;
  }

  /**
   * Get next token in the current dot file.
   * The token and token type are available as token and tokenType
   */
  function getToken() {
    tokenType = TOKENTYPE.NULL;
    token = '';

    // skip over whitespaces
    while (c == ' ' || c == '\t' || c == '\n' || c == '\r') {  // space, tab, enter
      next();
    }

    do {
      var isComment = false;

      // skip comment
      if (c == '#') {
        // find the previous non-space character
        var i = index - 1;
        while (dot.charAt(i) == ' ' || dot.charAt(i) == '\t') {
          i--;
        }
        if (dot.charAt(i) == '\n' || dot.charAt(i) == '') {
          // the # is at the start of a line, this is indeed a line comment
          while (c != '' && c != '\n') {
            next();
          }
          isComment = true;
        }
      }
      if (c == '/' && nextPreview() == '/') {
        // skip line comment
        while (c != '' && c != '\n') {
          next();
        }
        isComment = true;
      }
      if (c == '/' && nextPreview() == '*') {
        // skip block comment
        while (c != '') {
          if (c == '*' && nextPreview() == '/') {
            // end of block comment found. skip these last two characters
            next();
            next();
            break;
          }
          else {
            next();
          }
        }
        isComment = true;
      }

      // skip over whitespaces
      while (c == ' ' || c == '\t' || c == '\n' || c == '\r') {  // space, tab, enter
        next();
      }
    }
    while (isComment);

    // check for end of dot file
    if (c == '') {
      // token is still empty
      tokenType = TOKENTYPE.DELIMITER;
      return;
    }

    // check for delimiters consisting of 2 characters
    var c2 = c + nextPreview();
    if (DELIMITERS[c2]) {
      tokenType = TOKENTYPE.DELIMITER;
      token = c2;
      next();
      next();
      return;
    }

    // check for delimiters consisting of 1 character
    if (DELIMITERS[c]) {
      tokenType = TOKENTYPE.DELIMITER;
      token = c;
      next();
      return;
    }

    // check for an identifier (number or string)
    // TODO: more precise parsing of numbers/strings (and the port separator ':')
    if (isAlphaNumeric(c) || c == '-') {
      token += c;
      next();

      while (isAlphaNumeric(c)) {
        token += c;
        next();
      }
      if (token == 'false') {
        token = false;   // convert to boolean
      }
      else if (token == 'true') {
        token = true;   // convert to boolean
      }
      else if (!isNaN(Number(token))) {
        token = Number(token); // convert to number
      }
      tokenType = TOKENTYPE.IDENTIFIER;
      return;
    }

    // check for a string enclosed by double quotes
    if (c == '"') {
      next();
      while (c != '' && (c != '"' || (c == '"' && nextPreview() == '"'))) {
        token += c;
        if (c == '"') { // skip the escape character
          next();
        }
        next();
      }
      if (c != '"') {
        throw newSyntaxError('End of string " expected');
      }
      next();
      tokenType = TOKENTYPE.IDENTIFIER;
      return;
    }

    // something unknown is found, wrong characters, a syntax error
    tokenType = TOKENTYPE.UNKNOWN;
    while (c != '') {
      token += c;
      next();
    }
    throw new SyntaxError('Syntax error in part "' + chop(token, 30) + '"');
  }

  /**
   * Parse a graph.
   * @returns {Object} graph
   */
  function parseGraph() {
    var graph = {};

    first();
    getToken();

    // optional strict keyword
    if (token == 'strict') {
      graph.strict = true;
      getToken();
    }

    // graph or digraph keyword
    if (token == 'graph' || token == 'digraph') {
      graph.type = token;
      getToken();
    }

    // optional graph id
    if (tokenType == TOKENTYPE.IDENTIFIER) {
      graph.id = token;
      getToken();
    }

    // open angle bracket
    if (token != '{') {
      throw newSyntaxError('Angle bracket { expected');
    }
    getToken();

    // statements
    parseStatements(graph);

    // close angle bracket
    if (token != '}') {
      throw newSyntaxError('Angle bracket } expected');
    }
    getToken();

    // end of file
    if (token !== '') {
      throw newSyntaxError('End of file expected');
    }
    getToken();

    // remove temporary default properties
    delete graph.node;
    delete graph.edge;
    delete graph.graph;

    return graph;
  }

  /**
   * Parse a list with statements.
   * @param {Object} graph
   */
  function parseStatements (graph) {
    while (token !== '' && token != '}') {
      parseStatement(graph);
      if (token == ';') {
        getToken();
      }
    }
  }

  /**
   * Parse a single statement. Can be a an attribute statement, node
   * statement, a series of node statements and edge statements, or a
   * parameter.
   * @param {Object} graph
   */
  function parseStatement(graph) {
    // parse subgraph
    var subgraph = parseSubgraph(graph);
    if (subgraph) {
      // edge statements
      parseEdge(graph, subgraph);

      return;
    }

    // parse an attribute statement
    var attr = parseAttributeStatement(graph);
    if (attr) {
      return;
    }

    // parse node
    if (tokenType != TOKENTYPE.IDENTIFIER) {
      throw newSyntaxError('Identifier expected');
    }
    var id = token; // id can be a string or a number
    getToken();

    if (token == '=') {
      // id statement
      getToken();
      if (tokenType != TOKENTYPE.IDENTIFIER) {
        throw newSyntaxError('Identifier expected');
      }
      graph[id] = token;
      getToken();
      // TODO: implement comma separated list with "a_list: ID=ID [','] [a_list] "
    }
    else {
      parseNodeStatement(graph, id);
    }
  }

  /**
   * Parse a subgraph
   * @param {Object} graph    parent graph object
   * @return {Object | null} subgraph
   */
  function parseSubgraph (graph) {
    var subgraph = null;

    // optional subgraph keyword
    if (token == 'subgraph') {
      subgraph = {};
      subgraph.type = 'subgraph';
      getToken();

      // optional graph id
      if (tokenType == TOKENTYPE.IDENTIFIER) {
        subgraph.id = token;
        getToken();
      }
    }

    // open angle bracket
    if (token == '{') {
      getToken();

      if (!subgraph) {
        subgraph = {};
      }
      subgraph.parent = graph;
      subgraph.node = graph.node;
      subgraph.edge = graph.edge;
      subgraph.graph = graph.graph;

      // statements
      parseStatements(subgraph);

      // close angle bracket
      if (token != '}') {
        throw newSyntaxError('Angle bracket } expected');
      }
      getToken();

      // remove temporary default properties
      delete subgraph.node;
      delete subgraph.edge;
      delete subgraph.graph;
      delete subgraph.parent;

      // register at the parent graph
      if (!graph.subgraphs) {
        graph.subgraphs = [];
      }
      graph.subgraphs.push(subgraph);
    }

    return subgraph;
  }

  /**
   * parse an attribute statement like "node [shape=circle fontSize=16]".
   * Available keywords are 'node', 'edge', 'graph'.
   * The previous list with default attributes will be replaced
   * @param {Object} graph
   * @returns {String | null} keyword Returns the name of the parsed attribute
   *                                  (node, edge, graph), or null if nothing
   *                                  is parsed.
   */
  function parseAttributeStatement (graph) {
    // attribute statements
    if (token == 'node') {
      getToken();

      // node attributes
      graph.node = parseAttributeList();
      return 'node';
    }
    else if (token == 'edge') {
      getToken();

      // edge attributes
      graph.edge = parseAttributeList();
      return 'edge';
    }
    else if (token == 'graph') {
      getToken();

      // graph attributes
      graph.graph = parseAttributeList();
      return 'graph';
    }

    return null;
  }

  /**
   * parse a node statement
   * @param {Object} graph
   * @param {String | Number} id
   */
  function parseNodeStatement(graph, id) {
    // node statement
    var node = {
      id: id
    };
    var attr = parseAttributeList();
    if (attr) {
      node.attr = attr;
    }
    addNode(graph, node);

    // edge statements
    parseEdge(graph, id);
  }

  /**
   * Parse an edge or a series of edges
   * @param {Object} graph
   * @param {String | Number} from        Id of the from node
   */
  function parseEdge(graph, from) {
    while (token == '->' || token == '--') {
      var to;
      var type = token;
      getToken();

      var subgraph = parseSubgraph(graph);
      if (subgraph) {
        to = subgraph;
      }
      else {
        if (tokenType != TOKENTYPE.IDENTIFIER) {
          throw newSyntaxError('Identifier or subgraph expected');
        }
        to = token;
        addNode(graph, {
          id: to
        });
        getToken();
      }

      // parse edge attributes
      var attr = parseAttributeList();

      // create edge
      var edge = createEdge(graph, from, to, type, attr);
      addEdge(graph, edge);

      from = to;
    }
  }

  /**
   * Parse a set with attributes,
   * for example [label="1.000", shape=solid]
   * @return {Object | null} attr
   */
  function parseAttributeList() {
    var attr = null;

    while (token == '[') {
      getToken();
      attr = {};
      while (token !== '' && token != ']') {
        if (tokenType != TOKENTYPE.IDENTIFIER) {
          throw newSyntaxError('Attribute name expected');
        }
        var name = token;

        getToken();
        if (token != '=') {
          throw newSyntaxError('Equal sign = expected');
        }
        getToken();

        if (tokenType != TOKENTYPE.IDENTIFIER) {
          throw newSyntaxError('Attribute value expected');
        }
        var value = token;
        setValue(attr, name, value); // name can be a path

        getToken();
        if (token ==',') {
          getToken();
        }
      }

      if (token != ']') {
        throw newSyntaxError('Bracket ] expected');
      }
      getToken();
    }

    return attr;
  }

  /**
   * Create a syntax error with extra information on current token and index.
   * @param {String} message
   * @returns {SyntaxError} err
   */
  function newSyntaxError(message) {
    return new SyntaxError(message + ', got "' + chop(token, 30) + '" (char ' + index + ')');
  }

  /**
   * Chop off text after a maximum length
   * @param {String} text
   * @param {Number} maxLength
   * @returns {String}
   */
  function chop (text, maxLength) {
    return (text.length <= maxLength) ? text : (text.substr(0, 27) + '...');
  }

  /**
   * Execute a function fn for each pair of elements in two arrays
   * @param {Array | *} array1
   * @param {Array | *} array2
   * @param {function} fn
   */
  function forEach2(array1, array2, fn) {
    if (array1 instanceof Array) {
      array1.forEach(function (elem1) {
        if (array2 instanceof Array) {
          array2.forEach(function (elem2)  {
            fn(elem1, elem2);
          });
        }
        else {
          fn(elem1, array2);
        }
      });
    }
    else {
      if (array2 instanceof Array) {
        array2.forEach(function (elem2)  {
          fn(array1, elem2);
        });
      }
      else {
        fn(array1, array2);
      }
    }
  }

  /**
   * Convert a string containing a graph in DOT language into a map containing
   * with nodes and edges in the format of graph.
   * @param {String} data         Text containing a graph in DOT-notation
   * @return {Object} graphData
   */
  function DOTToGraph (data) {
    // parse the DOT file
    var dotData = parseDOT(data);
    var graphData = {
      nodes: [],
      edges: [],
      options: {}
    };

    // copy the nodes
    if (dotData.nodes) {
      dotData.nodes.forEach(function (dotNode) {
        var graphNode = {
          id: dotNode.id,
          label: String(dotNode.label || dotNode.id)
        };
        merge(graphNode, dotNode.attr);
        if (graphNode.image) {
          graphNode.shape = 'image';
        }
        graphData.nodes.push(graphNode);
      });
    }

    // copy the edges
    if (dotData.edges) {
      /**
       * Convert an edge in DOT format to an edge with VisGraph format
       * @param {Object} dotEdge
       * @returns {Object} graphEdge
       */
      function convertEdge(dotEdge) {
        var graphEdge = {
          from: dotEdge.from,
          to: dotEdge.to
        };
        merge(graphEdge, dotEdge.attr);
        graphEdge.style = (dotEdge.type == '->') ? 'arrow' : 'line';
        return graphEdge;
      }

      dotData.edges.forEach(function (dotEdge) {
        var from, to;
        if (dotEdge.from instanceof Object) {
          from = dotEdge.from.nodes;
        }
        else {
          from = {
            id: dotEdge.from
          }
        }

        if (dotEdge.to instanceof Object) {
          to = dotEdge.to.nodes;
        }
        else {
          to = {
            id: dotEdge.to
          }
        }

        if (dotEdge.from instanceof Object && dotEdge.from.edges) {
          dotEdge.from.edges.forEach(function (subEdge) {
            var graphEdge = convertEdge(subEdge);
            graphData.edges.push(graphEdge);
          });
        }

        forEach2(from, to, function (from, to) {
          var subEdge = createEdge(graphData, from.id, to.id, dotEdge.type, dotEdge.attr);
          var graphEdge = convertEdge(subEdge);
          graphData.edges.push(graphEdge);
        });

        if (dotEdge.to instanceof Object && dotEdge.to.edges) {
          dotEdge.to.edges.forEach(function (subEdge) {
            var graphEdge = convertEdge(subEdge);
            graphData.edges.push(graphEdge);
          });
        }
      });
    }

    // copy the options
    if (dotData.attr) {
      graphData.options = dotData.attr;
    }

    return graphData;
  }

  // exports
  exports.parseDOT = parseDOT;
  exports.DOTToGraph = DOTToGraph;

})(typeof util !== 'undefined' ? util : exports);

/**
 * Canvas shapes used by the Graph
 */
if (typeof CanvasRenderingContext2D !== 'undefined') {

  /**
   * Draw a circle shape
   */
  CanvasRenderingContext2D.prototype.circle = function(x, y, r) {
    this.beginPath();
    this.arc(x, y, r, 0, 2*Math.PI, false);
  };

  /**
   * Draw a square shape
   * @param {Number} x horizontal center
   * @param {Number} y vertical center
   * @param {Number} r   size, width and height of the square
   */
  CanvasRenderingContext2D.prototype.square = function(x, y, r) {
    this.beginPath();
    this.rect(x - r, y - r, r * 2, r * 2);
  };

  /**
   * Draw a triangle shape
   * @param {Number} x horizontal center
   * @param {Number} y vertical center
   * @param {Number} r   radius, half the length of the sides of the triangle
   */
  CanvasRenderingContext2D.prototype.triangle = function(x, y, r) {
    // http://en.wikipedia.org/wiki/Equilateral_triangle
    this.beginPath();

    var s = r * 2;
    var s2 = s / 2;
    var ir = Math.sqrt(3) / 6 * s;      // radius of inner circle
    var h = Math.sqrt(s * s - s2 * s2); // height

    this.moveTo(x, y - (h - ir));
    this.lineTo(x + s2, y + ir);
    this.lineTo(x - s2, y + ir);
    this.lineTo(x, y - (h - ir));
    this.closePath();
  };

  /**
   * Draw a triangle shape in downward orientation
   * @param {Number} x horizontal center
   * @param {Number} y vertical center
   * @param {Number} r radius
   */
  CanvasRenderingContext2D.prototype.triangleDown = function(x, y, r) {
    // http://en.wikipedia.org/wiki/Equilateral_triangle
    this.beginPath();

    var s = r * 2;
    var s2 = s / 2;
    var ir = Math.sqrt(3) / 6 * s;      // radius of inner circle
    var h = Math.sqrt(s * s - s2 * s2); // height

    this.moveTo(x, y + (h - ir));
    this.lineTo(x + s2, y - ir);
    this.lineTo(x - s2, y - ir);
    this.lineTo(x, y + (h - ir));
    this.closePath();
  };

  /**
   * Draw a star shape, a star with 5 points
   * @param {Number} x horizontal center
   * @param {Number} y vertical center
   * @param {Number} r   radius, half the length of the sides of the triangle
   */
  CanvasRenderingContext2D.prototype.star = function(x, y, r) {
    // http://www.html5canvastutorials.com/labs/html5-canvas-star-spinner/
    this.beginPath();

    for (var n = 0; n < 10; n++) {
      var radius = (n % 2 === 0) ? r * 1.3 : r * 0.5;
      this.lineTo(
          x + radius * Math.sin(n * 2 * Math.PI / 10),
          y - radius * Math.cos(n * 2 * Math.PI / 10)
      );
    }

    this.closePath();
  };

  /**
   * http://stackoverflow.com/questions/1255512/how-to-draw-a-rounded-rectangle-on-html-canvas
   */
  CanvasRenderingContext2D.prototype.roundRect = function(x, y, w, h, r) {
    var r2d = Math.PI/180;
    if( w - ( 2 * r ) < 0 ) { r = ( w / 2 ); } //ensure that the radius isn't too large for x
    if( h - ( 2 * r ) < 0 ) { r = ( h / 2 ); } //ensure that the radius isn't too large for y
    this.beginPath();
    this.moveTo(x+r,y);
    this.lineTo(x+w-r,y);
    this.arc(x+w-r,y+r,r,r2d*270,r2d*360,false);
    this.lineTo(x+w,y+h-r);
    this.arc(x+w-r,y+h-r,r,0,r2d*90,false);
    this.lineTo(x+r,y+h);
    this.arc(x+r,y+h-r,r,r2d*90,r2d*180,false);
    this.lineTo(x,y+r);
    this.arc(x+r,y+r,r,r2d*180,r2d*270,false);
  };

  /**
   * http://stackoverflow.com/questions/2172798/how-to-draw-an-oval-in-html5-canvas
   */
  CanvasRenderingContext2D.prototype.ellipse = function(x, y, w, h) {
    var kappa = .5522848,
        ox = (w / 2) * kappa, // control point offset horizontal
        oy = (h / 2) * kappa, // control point offset vertical
        xe = x + w,           // x-end
        ye = y + h,           // y-end
        xm = x + w / 2,       // x-middle
        ym = y + h / 2;       // y-middle

    this.beginPath();
    this.moveTo(x, ym);
    this.bezierCurveTo(x, ym - oy, xm - ox, y, xm, y);
    this.bezierCurveTo(xm + ox, y, xe, ym - oy, xe, ym);
    this.bezierCurveTo(xe, ym + oy, xm + ox, ye, xm, ye);
    this.bezierCurveTo(xm - ox, ye, x, ym + oy, x, ym);
  };



  /**
   * http://stackoverflow.com/questions/2172798/how-to-draw-an-oval-in-html5-canvas
   */
  CanvasRenderingContext2D.prototype.database = function(x, y, w, h) {
    var f = 1/3;
    var wEllipse = w;
    var hEllipse = h * f;

    var kappa = .5522848,
        ox = (wEllipse / 2) * kappa, // control point offset horizontal
        oy = (hEllipse / 2) * kappa, // control point offset vertical
        xe = x + wEllipse,           // x-end
        ye = y + hEllipse,           // y-end
        xm = x + wEllipse / 2,       // x-middle
        ym = y + hEllipse / 2,       // y-middle
        ymb = y + (h - hEllipse/2),  // y-midlle, bottom ellipse
        yeb = y + h;                 // y-end, bottom ellipse

    this.beginPath();
    this.moveTo(xe, ym);

    this.bezierCurveTo(xe, ym + oy, xm + ox, ye, xm, ye);
    this.bezierCurveTo(xm - ox, ye, x, ym + oy, x, ym);

    this.bezierCurveTo(x, ym - oy, xm - ox, y, xm, y);
    this.bezierCurveTo(xm + ox, y, xe, ym - oy, xe, ym);

    this.lineTo(xe, ymb);

    this.bezierCurveTo(xe, ymb + oy, xm + ox, yeb, xm, yeb);
    this.bezierCurveTo(xm - ox, yeb, x, ymb + oy, x, ymb);

    this.lineTo(x, ym);
  };


  /**
   * Draw an arrow point (no line)
   */
  CanvasRenderingContext2D.prototype.arrow = function(x, y, angle, length) {
    // tail
    var xt = x - length * Math.cos(angle);
    var yt = y - length * Math.sin(angle);

    // inner tail
    // TODO: allow to customize different shapes
    var xi = x - length * 0.9 * Math.cos(angle);
    var yi = y - length * 0.9 * Math.sin(angle);

    // left
    var xl = xt + length / 3 * Math.cos(angle + 0.5 * Math.PI);
    var yl = yt + length / 3 * Math.sin(angle + 0.5 * Math.PI);

    // right
    var xr = xt + length / 3 * Math.cos(angle - 0.5 * Math.PI);
    var yr = yt + length / 3 * Math.sin(angle - 0.5 * Math.PI);

    this.beginPath();
    this.moveTo(x, y);
    this.lineTo(xl, yl);
    this.lineTo(xi, yi);
    this.lineTo(xr, yr);
    this.closePath();
  };

  /**
   * Sets up the dashedLine functionality for drawing
   * Original code came from http://stackoverflow.com/questions/4576724/dotted-stroke-in-canvas
   * @author David Jordan
   * @date 2012-08-08
   */
  CanvasRenderingContext2D.prototype.dashedLine = function(x,y,x2,y2,dashArray){
    if (!dashArray) dashArray=[10,5];
    if (dashLength==0) dashLength = 0.001; // Hack for Safari
    var dashCount = dashArray.length;
    this.moveTo(x, y);
    var dx = (x2-x), dy = (y2-y);
    var slope = dy/dx;
    var distRemaining = Math.sqrt( dx*dx + dy*dy );
    var dashIndex=0, draw=true;
    while (distRemaining>=0.1){
      var dashLength = dashArray[dashIndex++%dashCount];
      if (dashLength > distRemaining) dashLength = distRemaining;
      var xStep = Math.sqrt( dashLength*dashLength / (1 + slope*slope) );
      if (dx<0) xStep = -xStep;
      x += xStep;
      y += slope*xStep;
      this[draw ? 'lineTo' : 'moveTo'](x,y);
      distRemaining -= dashLength;
      draw = !draw;
    }
  };

  // TODO: add diamond shape
}

/**
 * @class Node
 * A node. A node can be connected to other nodes via one or multiple edges.
 * @param {object} properties An object containing properties for the node. All
 *                            properties are optional, except for the id.
 *                              {number} id     Id of the node. Required
 *                              {string} label  Text label for the node
 *                              {number} x      Horizontal position of the node
 *                              {number} y      Vertical position of the node
 *                              {string} shape  Node shape, available:
 *                                              "database", "circle", "ellipse",
 *                                              "box", "image", "text", "dot",
 *                                              "star", "triangle", "triangleDown",
 *                                              "square"
 *                              {string} image  An image url
 *                              {string} title  An title text, can be HTML
 *                              {anytype} group A group name or number
 * @param {Graph.Images} imagelist    A list with images. Only needed
 *                                            when the node has an image
 * @param {Graph.Groups} grouplist    A list with groups. Needed for
 *                                            retrieving group properties
 * @param {Object}               constants    An object with default values for
 *                                            example for the color
 */
function Node(properties, imagelist, grouplist, constants) {
  this.selected = false;

  this.edges = []; // all edges connected to this node
  this.group = constants.nodes.group;

  this.fontSize = constants.nodes.fontSize;
  this.fontFace = constants.nodes.fontFace;
  this.fontColor = constants.nodes.fontColor;

  this.color = constants.nodes.color;

  // set defaults for the properties
  this.id = undefined;
  this.shape = constants.nodes.shape;
  this.image = constants.nodes.image;
  this.x = 0;
  this.y = 0;
  this.xFixed = false;
  this.yFixed = false;
  this.radius = constants.nodes.radius;
  this.radiusFixed = false;
  this.radiusMin = constants.nodes.radiusMin;
  this.radiusMax = constants.nodes.radiusMax;

  this.imagelist = imagelist;
  this.grouplist = grouplist;

  this.setProperties(properties, constants);

  // mass, force, velocity
  this.mass = 50;  // kg (mass is adjusted for the number of connected edges)
  this.fx = 0.0;  // external force x
  this.fy = 0.0;  // external force y
  this.vx = 0.0;  // velocity x
  this.vy = 0.0;  // velocity y
  this.minForce = constants.minForce;
  this.damping = 0.9; // damping factor
};

/**
 * Attach a edge to the node
 * @param {Edge} edge
 */
Node.prototype.attachEdge = function(edge) {
  if (this.edges.indexOf(edge) == -1) {
    this.edges.push(edge);
  }
  this._updateMass();
};

/**
 * Detach a edge from the node
 * @param {Edge} edge
 */
Node.prototype.detachEdge = function(edge) {
  var index = this.edges.indexOf(edge);
  if (index != -1) {
    this.edges.splice(index, 1);
  }
  this._updateMass();
};

/**
 * Update the nodes mass, which is determined by the number of edges connecting
 * to it (more edges -> heavier node).
 * @private
 */
Node.prototype._updateMass = function() {
  this.mass = 50 + 20 * this.edges.length; // kg
};

/**
 * Set or overwrite properties for the node
 * @param {Object} properties an object with properties
 * @param {Object} constants  and object with default, global properties
 */
Node.prototype.setProperties = function(properties, constants) {
  if (!properties) {
    return;
  }

  // basic properties
  if (properties.id != undefined)        {this.id = properties.id;}
  if (properties.label != undefined)     {this.label = properties.label;}
  if (properties.title != undefined)     {this.title = properties.title;}
  if (properties.group != undefined)     {this.group = properties.group;}
  if (properties.x != undefined)         {this.x = properties.x;}
  if (properties.y != undefined)         {this.y = properties.y;}
  if (properties.value != undefined)     {this.value = properties.value;}

  if (this.id === undefined) {
    throw "Node must have an id";
  }

  // copy group properties
  if (this.group) {
    var groupObj = this.grouplist.get(this.group);
    for (var prop in groupObj) {
      if (groupObj.hasOwnProperty(prop)) {
        this[prop] = groupObj[prop];
      }
    }
  }

  // individual shape properties
  if (properties.shape != undefined)          {this.shape = properties.shape;}
  if (properties.image != undefined)          {this.image = properties.image;}
  if (properties.radius != undefined)         {this.radius = properties.radius;}
  if (properties.color != undefined)          {this.color = Node.parseColor(properties.color);}

  if (properties.fontColor != undefined)      {this.fontColor = properties.fontColor;}
  if (properties.fontSize != undefined)       {this.fontSize = properties.fontSize;}
  if (properties.fontFace != undefined)       {this.fontFace = properties.fontFace;}


  if (this.image != undefined) {
    if (this.imagelist) {
      this.imageObj = this.imagelist.load(this.image);
    }
    else {
      throw "No imagelist provided";
    }
  }

  this.xFixed = this.xFixed || (properties.x != undefined);
  this.yFixed = this.yFixed || (properties.y != undefined);
  this.radiusFixed = this.radiusFixed || (properties.radius != undefined);

  if (this.shape == 'image') {
    this.radiusMin = constants.nodes.widthMin;
    this.radiusMax = constants.nodes.widthMax;
  }

  // choose draw method depending on the shape
  switch (this.shape) {
    case 'database':      this.draw = this._drawDatabase; this.resize = this._resizeDatabase; break;
    case 'box':           this.draw = this._drawBox; this.resize = this._resizeBox; break;
    case 'circle':        this.draw = this._drawCircle; this.resize = this._resizeCircle; break;
    case 'ellipse':       this.draw = this._drawEllipse; this.resize = this._resizeEllipse; break;
    // TODO: add diamond shape
    case 'image':         this.draw = this._drawImage; this.resize = this._resizeImage; break;
    case 'text':          this.draw = this._drawText; this.resize = this._resizeText; break;
    case 'dot':           this.draw = this._drawDot; this.resize = this._resizeShape; break;
    case 'square':        this.draw = this._drawSquare; this.resize = this._resizeShape; break;
    case 'triangle':      this.draw = this._drawTriangle; this.resize = this._resizeShape; break;
    case 'triangleDown':  this.draw = this._drawTriangleDown; this.resize = this._resizeShape; break;
    case 'star':          this.draw = this._drawStar; this.resize = this._resizeShape; break;
    default:              this.draw = this._drawEllipse; this.resize = this._resizeEllipse; break;
  }

  // reset the size of the node, this can be changed
  this._reset();
};

/**
 * Parse a color property into an object with border, background, and
 * hightlight colors
 * @param {Object | String} color
 * @return {Object} colorObject
 */
Node.parseColor = function(color) {
  var c;
  if (util.isString(color)) {
    c = {
      border: color,
      background: color,
      highlight: {
        border: color,
        background: color
      }
    };
    // TODO: automatically generate a nice highlight color
  }
  else {
    c = {};
    c.background = color.background || 'white';
    c.border = color.border || c.background;
    if (util.isString(color.highlight)) {
      c.highlight = {
        border: color.highlight,
        background: color.highlight
      }
    }
    else {
      c.highlight = {};
      c.highlight.background = color.highlight && color.highlight.background || c.background;
      c.highlight.border = color.highlight && color.highlight.border || c.border;
    }
  }
  return c;
};

/**
 * select this node
 */
Node.prototype.select = function() {
  this.selected = true;
  this._reset();
};

/**
 * unselect this node
 */
Node.prototype.unselect = function() {
  this.selected = false;
  this._reset();
};

/**
 * Reset the calculated size of the node, forces it to recalculate its size
 * @private
 */
Node.prototype._reset = function() {
  this.width = undefined;
  this.height = undefined;
};

/**
 * get the title of this node.
 * @return {string} title    The title of the node, or undefined when no title
 *                           has been set.
 */
Node.prototype.getTitle = function() {
  return this.title;
};

/**
 * Calculate the distance to the border of the Node
 * @param {CanvasRenderingContext2D}   ctx
 * @param {Number} angle        Angle in radians
 * @returns {number} distance   Distance to the border in pixels
 */
Node.prototype.distanceToBorder = function (ctx, angle) {
  var borderWidth = 1;

  if (!this.width) {
    this.resize(ctx);
  }

  //noinspection FallthroughInSwitchStatementJS
  switch (this.shape) {
    case 'circle':
    case 'dot':
      return this.radius + borderWidth;

    case 'ellipse':
      var a = this.width / 2;
      var b = this.height / 2;
      var w = (Math.sin(angle) * a);
      var h = (Math.cos(angle) * b);
      return a * b / Math.sqrt(w * w + h * h);

    // TODO: implement distanceToBorder for database
    // TODO: implement distanceToBorder for triangle
    // TODO: implement distanceToBorder for triangleDown

    case 'box':
    case 'image':
    case 'text':
    default:
      if (this.width) {
        return Math.min(
            Math.abs(this.width / 2 / Math.cos(angle)),
            Math.abs(this.height / 2 / Math.sin(angle))) + borderWidth;
        // TODO: reckon with border radius too in case of box
      }
      else {
        return 0;
      }

  }

  // TODO: implement calculation of distance to border for all shapes
};

/**
 * Set forces acting on the node
 * @param {number} fx   Force in horizontal direction
 * @param {number} fy   Force in vertical direction
 */
Node.prototype._setForce = function(fx, fy) {
  this.fx = fx;
  this.fy = fy;
};

/**
 * Add forces acting on the node
 * @param {number} fx   Force in horizontal direction
 * @param {number} fy   Force in vertical direction
 * @private
 */
Node.prototype._addForce = function(fx, fy) {
  this.fx += fx;
  this.fy += fy;
};

/**
 * Perform one discrete step for the node
 * @param {number} interval    Time interval in seconds
 */
Node.prototype.discreteStep = function(interval) {
  if (!this.xFixed) {
    var dx   = -this.damping * this.vx;     // damping force
    var ax   = (this.fx + dx) / this.mass;  // acceleration
    this.vx += ax / interval;               // velocity
    this.x  += this.vx / interval;          // position
  }

  if (!this.yFixed) {
    var dy   = -this.damping * this.vy;     // damping force
    var ay   = (this.fy + dy) / this.mass;  // acceleration
    this.vy += ay / interval;               // velocity
    this.y  += this.vy / interval;          // position
  }
};


/**
 * Check if this node has a fixed x and y position
 * @return {boolean}      true if fixed, false if not
 */
Node.prototype.isFixed = function() {
  return (this.xFixed && this.yFixed);
};

/**
 * Check if this node is moving
 * @param {number} vmin   the minimum velocity considered as "moving"
 * @return {boolean}      true if moving, false if it has no velocity
 */
// TODO: replace this method with calculating the kinetic energy
Node.prototype.isMoving = function(vmin) {
  return (Math.abs(this.vx) > vmin || Math.abs(this.vy) > vmin ||
      (!this.xFixed && Math.abs(this.fx) > this.minForce) ||
      (!this.yFixed && Math.abs(this.fy) > this.minForce));
};

/**
 * check if this node is selecte
 * @return {boolean} selected   True if node is selected, else false
 */
Node.prototype.isSelected = function() {
  return this.selected;
};

/**
 * Retrieve the value of the node. Can be undefined
 * @return {Number} value
 */
Node.prototype.getValue = function() {
  return this.value;
};

/**
 * Calculate the distance from the nodes location to the given location (x,y)
 * @param {Number} x
 * @param {Number} y
 * @return {Number} value
 */
Node.prototype.getDistance = function(x, y) {
  var dx = this.x - x,
      dy = this.y - y;
  return Math.sqrt(dx * dx + dy * dy);
};


/**
 * Adjust the value range of the node. The node will adjust it's radius
 * based on its value.
 * @param {Number} min
 * @param {Number} max
 */
Node.prototype.setValueRange = function(min, max) {
  if (!this.radiusFixed && this.value !== undefined) {
    if (max == min) {
      this.radius = (this.radiusMin + this.radiusMax) / 2;
    }
    else {
      var scale = (this.radiusMax - this.radiusMin) / (max - min);
      this.radius = (this.value - min) * scale + this.radiusMin;
    }
  }
};

/**
 * Draw this node in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 */
Node.prototype.draw = function(ctx) {
  throw "Draw method not initialized for node";
};

/**
 * Recalculate the size of this node in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 */
Node.prototype.resize = function(ctx) {
  throw "Resize method not initialized for node";
};

/**
 * Check if this object is overlapping with the provided object
 * @param {Object} obj   an object with parameters left, top, right, bottom
 * @return {boolean}     True if location is located on node
 */
Node.prototype.isOverlappingWith = function(obj) {
  return (this.left          < obj.right &&
      this.left + this.width > obj.left &&
      this.top               < obj.bottom &&
      this.top + this.height > obj.top);
};

Node.prototype._resizeImage = function (ctx) {
  // TODO: pre calculate the image size
  if (!this.width) {  // undefined or 0
    var width, height;
    if (this.value) {
      var scale = this.imageObj.height / this.imageObj.width;
      width = this.radius || this.imageObj.width;
      height = this.radius * scale || this.imageObj.height;
    }
    else {
      width = this.imageObj.width;
      height = this.imageObj.height;
    }
    this.width  = width;
    this.height = height;
  }
};

Node.prototype._drawImage = function (ctx) {
  this._resizeImage(ctx);

  this.left   = this.x - this.width / 2;
  this.top    = this.y - this.height / 2;

  var yLabel;
  if (this.imageObj) {
    ctx.drawImage(this.imageObj, this.left, this.top, this.width, this.height);
    yLabel = this.y + this.height / 2;
  }
  else {
    // image still loading... just draw the label for now
    yLabel = this.y;
  }

  this._label(ctx, this.label, this.x, yLabel, undefined, "top");
};


Node.prototype._resizeBox = function (ctx) {
  if (!this.width) {
    var margin = 5;
    var textSize = this.getTextSize(ctx);
    this.width = textSize.width + 2 * margin;
    this.height = textSize.height + 2 * margin;
  }
};

Node.prototype._drawBox = function (ctx) {
  this._resizeBox(ctx);

  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  ctx.strokeStyle = this.selected ? this.color.highlight.border : this.color.border;
  ctx.fillStyle = this.selected ? this.color.highlight.background : this.color.background;
  ctx.lineWidth = this.selected ? 2.0 : 1.0;
  ctx.roundRect(this.left, this.top, this.width, this.height, this.radius);
  ctx.fill();
  ctx.stroke();

  this._label(ctx, this.label, this.x, this.y);
};


Node.prototype._resizeDatabase = function (ctx) {
  if (!this.width) {
    var margin = 5;
    var textSize = this.getTextSize(ctx);
    var size = textSize.width + 2 * margin;
    this.width = size;
    this.height = size;
  }
};

Node.prototype._drawDatabase = function (ctx) {
  this._resizeDatabase(ctx);
  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  ctx.strokeStyle = this.selected ? this.color.highlight.border : this.color.border;
  ctx.fillStyle = this.selected ? this.color.highlight.background : this.color.background;
  ctx.lineWidth = this.selected ? 2.0 : 1.0;
  ctx.database(this.x - this.width/2, this.y - this.height*0.5, this.width, this.height);
  ctx.fill();
  ctx.stroke();

  this._label(ctx, this.label, this.x, this.y);
};


Node.prototype._resizeCircle = function (ctx) {
  if (!this.width) {
    var margin = 5;
    var textSize = this.getTextSize(ctx);
    var diameter = Math.max(textSize.width, textSize.height) + 2 * margin;
    this.radius = diameter / 2;

    this.width = diameter;
    this.height = diameter;
  }
};

Node.prototype._drawCircle = function (ctx) {
  this._resizeCircle(ctx);
  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  ctx.strokeStyle = this.selected ? this.color.highlight.border : this.color.border;
  ctx.fillStyle = this.selected ? this.color.highlight.background : this.color.background;
  ctx.lineWidth = this.selected ? 2.0 : 1.0;
  ctx.circle(this.x, this.y, this.radius);
  ctx.fill();
  ctx.stroke();

  this._label(ctx, this.label, this.x, this.y);
};

Node.prototype._resizeEllipse = function (ctx) {
  if (!this.width) {
    var textSize = this.getTextSize(ctx);

    this.width = textSize.width * 1.5;
    this.height = textSize.height * 2;
    if (this.width < this.height) {
      this.width = this.height;
    }
  }
};

Node.prototype._drawEllipse = function (ctx) {
  this._resizeEllipse(ctx);
  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  ctx.strokeStyle = this.selected ? this.color.highlight.border : this.color.border;
  ctx.fillStyle = this.selected ? this.color.highlight.background : this.color.background;
  ctx.lineWidth = this.selected ? 2.0 : 1.0;
  ctx.ellipse(this.left, this.top, this.width, this.height);
  ctx.fill();
  ctx.stroke();

  this._label(ctx, this.label, this.x, this.y);
};

Node.prototype._drawDot = function (ctx) {
  this._drawShape(ctx, 'circle');
};

Node.prototype._drawTriangle = function (ctx) {
  this._drawShape(ctx, 'triangle');
};

Node.prototype._drawTriangleDown = function (ctx) {
  this._drawShape(ctx, 'triangleDown');
};

Node.prototype._drawSquare = function (ctx) {
  this._drawShape(ctx, 'square');
};

Node.prototype._drawStar = function (ctx) {
  this._drawShape(ctx, 'star');
};

Node.prototype._resizeShape = function (ctx) {
  if (!this.width) {
    var size = 2 * this.radius;
    this.width = size;
    this.height = size;
  }
};

Node.prototype._drawShape = function (ctx, shape) {
  this._resizeShape(ctx);

  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  ctx.strokeStyle = this.selected ? this.color.highlight.border : this.color.border;
  ctx.fillStyle = this.selected ? this.color.highlight.background : this.color.background;
  ctx.lineWidth = this.selected ? 2.0 : 1.0;

  ctx[shape](this.x, this.y, this.radius);
  ctx.fill();
  ctx.stroke();

  if (this.label) {
    this._label(ctx, this.label, this.x, this.y + this.height / 2, undefined, 'top');
  }
};

Node.prototype._resizeText = function (ctx) {
  if (!this.width) {
    var margin = 5;
    var textSize = this.getTextSize(ctx);
    this.width = textSize.width + 2 * margin;
    this.height = textSize.height + 2 * margin;
  }
};

Node.prototype._drawText = function (ctx) {
  this._resizeText(ctx);
  this.left = this.x - this.width / 2;
  this.top = this.y - this.height / 2;

  this._label(ctx, this.label, this.x, this.y);
};


Node.prototype._label = function (ctx, text, x, y, align, baseline) {
  if (text) {
    ctx.font = (this.selected ? "bold " : "") + this.fontSize + "px " + this.fontFace;
    ctx.fillStyle = this.fontColor || "black";
    ctx.textAlign = align || "center";
    ctx.textBaseline = baseline || "middle";

    var lines = text.split('\n'),
        lineCount = lines.length,
        fontSize = (this.fontSize + 4),
        yLine = y + (1 - lineCount) / 2 * fontSize;

    for (var i = 0; i < lineCount; i++) {
      ctx.fillText(lines[i], x, yLine);
      yLine += fontSize;
    }
  }
};


Node.prototype.getTextSize = function(ctx) {
  if (this.label != undefined) {
    ctx.font = (this.selected ? "bold " : "") + this.fontSize + "px " + this.fontFace;

    var lines = this.label.split('\n'),
        height = (this.fontSize + 4) * lines.length,
        width = 0;

    for (var i = 0, iMax = lines.length; i < iMax; i++) {
      width = Math.max(width, ctx.measureText(lines[i]).width);
    }

    return {"width": width, "height": height};
  }
  else {
    return {"width": 0, "height": 0};
  }
};

/**
 * @class Edge
 *
 * A edge connects two nodes
 * @param {Object} properties     Object with properties. Must contain
 *                                At least properties from and to.
 *                                Available properties: from (number),
 *                                to (number), label (string, color (string),
 *                                width (number), style (string),
 *                                length (number), title (string)
 * @param {Graph} graph A graph object, used to find and edge to
 *                                nodes.
 * @param {Object} constants      An object with default values for
 *                                example for the color
 */
function Edge (properties, graph, constants) {
  if (!graph) {
    throw "No graph provided";
  }
  this.graph = graph;

  // initialize constants
  this.widthMin = constants.edges.widthMin;
  this.widthMax = constants.edges.widthMax;

  // initialize variables
  this.id     = undefined;
  this.fromId = undefined;
  this.toId = undefined;
  this.style  = constants.edges.style;
  this.title  = undefined;
  this.width  = constants.edges.width;
  this.value  = undefined;
  this.length = constants.edges.length;

  this.from = null;   // a node
  this.to = null;     // a node
  this.connected = false;

  // Added to support dashed lines
  // David Jordan
  // 2012-08-08
  this.dash = util.extend({}, constants.edges.dash); // contains properties length, gap, altLength

  this.stiffness   = undefined; // depends on the length of the edge
  this.color       = constants.edges.color;
  this.widthFixed  = false;
  this.lengthFixed = false;

  this.setProperties(properties, constants);
}

/**
 * Set or overwrite properties for the edge
 * @param {Object} properties  an object with properties
 * @param {Object} constants   and object with default, global properties
 */
Edge.prototype.setProperties = function(properties, constants) {
  if (!properties) {
    return;
  }

  if (properties.from != undefined)           {this.fromId = properties.from;}
  if (properties.to != undefined)             {this.toId = properties.to;}

  if (properties.id != undefined)             {this.id = properties.id;}
  if (properties.style != undefined)          {this.style = properties.style;}
  if (properties.label != undefined)          {this.label = properties.label;}
  if (this.label) {
    this.fontSize = constants.edges.fontSize;
    this.fontFace = constants.edges.fontFace;
    this.fontColor = constants.edges.fontColor;
    if (properties.fontColor != undefined)  {this.fontColor = properties.fontColor;}
    if (properties.fontSize != undefined)   {this.fontSize = properties.fontSize;}
    if (properties.fontFace != undefined)   {this.fontFace = properties.fontFace;}
  }
  if (properties.title != undefined)          {this.title = properties.title;}
  if (properties.width != undefined)          {this.width = properties.width;}
  if (properties.value != undefined)          {this.value = properties.value;}
  if (properties.length != undefined)         {this.length = properties.length;}

  // Added to support dashed lines
  // David Jordan
  // 2012-08-08
  if (properties.dash) {
    if (properties.dash.length != undefined)    {this.dash.length = properties.dash.length;}
    if (properties.dash.gap != undefined)       {this.dash.gap = properties.dash.gap;}
    if (properties.dash.altLength != undefined) {this.dash.altLength = properties.dash.altLength;}
  }

  if (properties.color != undefined) {this.color = properties.color;}

  // A node is connected when it has a from and to node.
  this.connect();

  this.widthFixed = this.widthFixed || (properties.width != undefined);
  this.lengthFixed = this.lengthFixed || (properties.length != undefined);
  this.stiffness = 1 / this.length;

  // set draw method based on style
  switch (this.style) {
    case 'line':          this.draw = this._drawLine; break;
    case 'arrow':         this.draw = this._drawArrow; break;
    case 'arrow-center':  this.draw = this._drawArrowCenter; break;
    case 'dash-line':     this.draw = this._drawDashLine; break;
    default:              this.draw = this._drawLine; break;
  }
};

/**
 * Connect an edge to its nodes
 */
Edge.prototype.connect = function () {
  this.disconnect();

  this.from = this.graph.nodes[this.fromId] || null;
  this.to = this.graph.nodes[this.toId] || null;
  this.connected = (this.from && this.to);

  if (this.connected) {
    this.from.attachEdge(this);
    this.to.attachEdge(this);
  }
  else {
    if (this.from) {
      this.from.detachEdge(this);
    }
    if (this.to) {
      this.to.detachEdge(this);
    }
  }
};

/**
 * Disconnect an edge from its nodes
 */
Edge.prototype.disconnect = function () {
  if (this.from) {
    this.from.detachEdge(this);
    this.from = null;
  }
  if (this.to) {
    this.to.detachEdge(this);
    this.to = null;
  }

  this.connected = false;
};

/**
 * get the title of this edge.
 * @return {string} title    The title of the edge, or undefined when no title
 *                           has been set.
 */
Edge.prototype.getTitle = function() {
  return this.title;
};


/**
 * Retrieve the value of the edge. Can be undefined
 * @return {Number} value
 */
Edge.prototype.getValue = function() {
  return this.value;
};

/**
 * Adjust the value range of the edge. The edge will adjust it's width
 * based on its value.
 * @param {Number} min
 * @param {Number} max
 */
Edge.prototype.setValueRange = function(min, max) {
  if (!this.widthFixed && this.value !== undefined) {
    var scale = (this.widthMax - this.widthMin) / (max - min);
    this.width = (this.value - min) * scale + this.widthMin;
  }
};

/**
 * Redraw a edge
 * Draw this edge in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 */
Edge.prototype.draw = function(ctx) {
  throw "Method draw not initialized in edge";
};

/**
 * Check if this object is overlapping with the provided object
 * @param {Object} obj   an object with parameters left, top
 * @return {boolean}     True if location is located on the edge
 */
Edge.prototype.isOverlappingWith = function(obj) {
  var distMax = 10;

  var xFrom = this.from.x;
  var yFrom = this.from.y;
  var xTo = this.to.x;
  var yTo = this.to.y;
  var xObj = obj.left;
  var yObj = obj.top;


  var dist = Edge._dist(xFrom, yFrom, xTo, yTo, xObj, yObj);

  return (dist < distMax);
};


/**
 * Redraw a edge as a line
 * Draw this edge in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Edge.prototype._drawLine = function(ctx) {
  // set style
  ctx.strokeStyle = this.color;
  ctx.lineWidth = this._getLineWidth();

  var point;
  if (this.from != this.to) {
    // draw line
    this._line(ctx);

    // draw label
    if (this.label) {
      point = this._pointOnLine(0.5);
      this._label(ctx, this.label, point.x, point.y);
    }
  }
  else {
    var x, y;
    var radius = this.length / 4;
    var node = this.from;
    if (!node.width) {
      node.resize(ctx);
    }
    if (node.width > node.height) {
      x = node.x + node.width / 2;
      y = node.y - radius;
    }
    else {
      x = node.x + radius;
      y = node.y - node.height / 2;
    }
    this._circle(ctx, x, y, radius);
    point = this._pointOnCircle(x, y, radius, 0.5);
    this._label(ctx, this.label, point.x, point.y);
  }
};

/**
 * Get the line width of the edge. Depends on width and whether one of the
 * connected nodes is selected.
 * @return {Number} width
 * @private
 */
Edge.prototype._getLineWidth = function() {
  if (this.from.selected || this.to.selected) {
    return Math.min(this.width * 2, this.widthMax);
  }
  else {
    return this.width;
  }
};

/**
 * Draw a line between two nodes
 * @param {CanvasRenderingContext2D} ctx
 * @private
 */
Edge.prototype._line = function (ctx) {
  // draw a straight line
  ctx.beginPath();
  ctx.moveTo(this.from.x, this.from.y);
  ctx.lineTo(this.to.x, this.to.y);
  ctx.stroke();
};

/**
 * Draw a line from a node to itself, a circle
 * @param {CanvasRenderingContext2D} ctx
 * @param {Number} x
 * @param {Number} y
 * @param {Number} radius
 * @private
 */
Edge.prototype._circle = function (ctx, x, y, radius) {
  // draw a circle
  ctx.beginPath();
  ctx.arc(x, y, radius, 0, 2 * Math.PI, false);
  ctx.stroke();
};

/**
 * Draw label with white background and with the middle at (x, y)
 * @param {CanvasRenderingContext2D} ctx
 * @param {String} text
 * @param {Number} x
 * @param {Number} y
 * @private
 */
Edge.prototype._label = function (ctx, text, x, y) {
  if (text) {
    // TODO: cache the calculated size
    ctx.font = ((this.from.selected || this.to.selected) ? "bold " : "") +
        this.fontSize + "px " + this.fontFace;
    ctx.fillStyle = 'white';
    var width = ctx.measureText(text).width;
    var height = this.fontSize;
    var left = x - width / 2;
    var top = y - height / 2;

    ctx.fillRect(left, top, width, height);

    // draw text
    ctx.fillStyle = this.fontColor || "black";
    ctx.textAlign = "left";
    ctx.textBaseline = "top";
    ctx.fillText(text, left, top);
  }
};

/**
 * Redraw a edge as a dashed line
 * Draw this edge in the given canvas
 * @author David Jordan
 * @date 2012-08-08
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Edge.prototype._drawDashLine = function(ctx) {
  // set style
  ctx.strokeStyle = this.color;
  ctx.lineWidth = this._getLineWidth();

  // draw dashed line
  ctx.beginPath();
  ctx.lineCap = 'round';
  if (this.dash.altLength != undefined) //If an alt dash value has been set add to the array this value
  {
    ctx.dashedLine(this.from.x,this.from.y,this.to.x,this.to.y,
        [this.dash.length,this.dash.gap,this.dash.altLength,this.dash.gap]);
  }
  else if (this.dash.length != undefined && this.dash.gap != undefined) //If a dash and gap value has been set add to the array this value
  {
    ctx.dashedLine(this.from.x,this.from.y,this.to.x,this.to.y,
        [this.dash.length,this.dash.gap]);
  }
  else //If all else fails draw a line
  {
    ctx.moveTo(this.from.x, this.from.y);
    ctx.lineTo(this.to.x, this.to.y);
  }
  ctx.stroke();

  // draw label
  if (this.label) {
    var point = this._pointOnLine(0.5);
    this._label(ctx, this.label, point.x, point.y);
  }
};

/**
 * Get a point on a line
 * @param {Number} percentage. Value between 0 (line start) and 1 (line end)
 * @return {Object} point
 * @private
 */
Edge.prototype._pointOnLine = function (percentage) {
  return {
    x: (1 - percentage) * this.from.x + percentage * this.to.x,
    y: (1 - percentage) * this.from.y + percentage * this.to.y
  }
};

/**
 * Get a point on a circle
 * @param {Number} x
 * @param {Number} y
 * @param {Number} radius
 * @param {Number} percentage. Value between 0 (line start) and 1 (line end)
 * @return {Object} point
 * @private
 */
Edge.prototype._pointOnCircle = function (x, y, radius, percentage) {
  var angle = (percentage - 3/8) * 2 * Math.PI;
  return {
    x: x + radius * Math.cos(angle),
    y: y - radius * Math.sin(angle)
  }
};

/**
 * Redraw a edge as a line with an arrow halfway the line
 * Draw this edge in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Edge.prototype._drawArrowCenter = function(ctx) {
  var point;
  // set style
  ctx.strokeStyle = this.color;
  ctx.fillStyle = this.color;
  ctx.lineWidth = this._getLineWidth();

  if (this.from != this.to) {
    // draw line
    this._line(ctx);

    // draw an arrow halfway the line
    var angle = Math.atan2((this.to.y - this.from.y), (this.to.x - this.from.x));
    var length = 10 + 5 * this.width; // TODO: make customizable?
    point = this._pointOnLine(0.5);
    ctx.arrow(point.x, point.y, angle, length);
    ctx.fill();
    ctx.stroke();

    // draw label
    if (this.label) {
      point = this._pointOnLine(0.5);
      this._label(ctx, this.label, point.x, point.y);
    }
  }
  else {
    // draw circle
    var x, y;
    var radius = this.length / 4;
    var node = this.from;
    if (!node.width) {
      node.resize(ctx);
    }
    if (node.width > node.height) {
      x = node.x + node.width / 2;
      y = node.y - radius;
    }
    else {
      x = node.x + radius;
      y = node.y - node.height / 2;
    }
    this._circle(ctx, x, y, radius);

    // draw all arrows
    var angle = 0.2 * Math.PI;
    var length = 10 + 5 * this.width; // TODO: make customizable?
    point = this._pointOnCircle(x, y, radius, 0.5);
    ctx.arrow(point.x, point.y, angle, length);
    ctx.fill();
    ctx.stroke();

    // draw label
    if (this.label) {
      point = this._pointOnCircle(x, y, radius, 0.5);
      this._label(ctx, this.label, point.x, point.y);
    }
  }
};



/**
 * Redraw a edge as a line with an arrow
 * Draw this edge in the given canvas
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext("2d");
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Edge.prototype._drawArrow = function(ctx) {
  // set style
  ctx.strokeStyle = this.color;
  ctx.fillStyle = this.color;
  ctx.lineWidth = this._getLineWidth();

  // draw line
  var angle, length;
  if (this.from != this.to) {
    // calculate length and angle of the line
    angle = Math.atan2((this.to.y - this.from.y), (this.to.x - this.from.x));
    var dx = (this.to.x - this.from.x);
    var dy = (this.to.y - this.from.y);
    var lEdge = Math.sqrt(dx * dx + dy * dy);

    var lFrom = this.from.distanceToBorder(ctx, angle + Math.PI);
    var pFrom = (lEdge - lFrom) / lEdge;
    var xFrom = (pFrom) * this.from.x + (1 - pFrom) * this.to.x;
    var yFrom = (pFrom) * this.from.y + (1 - pFrom) * this.to.y;

    var lTo = this.to.distanceToBorder(ctx, angle);
    var pTo = (lEdge - lTo) / lEdge;
    var xTo = (1 - pTo) * this.from.x + pTo * this.to.x;
    var yTo = (1 - pTo) * this.from.y + pTo * this.to.y;

    ctx.beginPath();
    ctx.moveTo(xFrom, yFrom);
    ctx.lineTo(xTo, yTo);
    ctx.stroke();

    // draw arrow at the end of the line
    length = 10 + 5 * this.width; // TODO: make customizable?
    ctx.arrow(xTo, yTo, angle, length);
    ctx.fill();
    ctx.stroke();

    // draw label
    if (this.label) {
      var point = this._pointOnLine(0.5);
      this._label(ctx, this.label, point.x, point.y);
    }
  }
  else {
    // draw circle
    var node = this.from;
    var x, y, arrow;
    var radius = this.length / 4;
    if (!node.width) {
      node.resize(ctx);
    }
    if (node.width > node.height) {
      x = node.x + node.width / 2;
      y = node.y - radius;
      arrow = {
        x: x,
        y: node.y,
        angle: 0.9 * Math.PI
      };
    }
    else {
      x = node.x + radius;
      y = node.y - node.height / 2;
      arrow = {
        x: node.x,
        y: y,
        angle: 0.6 * Math.PI
      };
    }
    ctx.beginPath();
    // TODO: do not draw a circle, but an arc
    // TODO: similarly, for a line without arrows, draw to the border of the nodes instead of the center
    ctx.arc(x, y, radius, 0, 2 * Math.PI, false);
    ctx.stroke();

    // draw all arrows
    length = 10 + 5 * this.width; // TODO: make customizable?
    ctx.arrow(arrow.x, arrow.y, arrow.angle, length);
    ctx.fill();
    ctx.stroke();

    // draw label
    if (this.label) {
      point = this._pointOnCircle(x, y, radius, 0.5);
      this._label(ctx, this.label, point.x, point.y);
    }
  }
};



/**
 * Calculate the distance between a point (x3,y3) and a line segment from
 * (x1,y1) to (x2,y2).
 * http://stackoverflow.com/questions/849211/shortest-distancae-between-a-point-and-a-line-segment
 * @param {number} x1
 * @param {number} y1
 * @param {number} x2
 * @param {number} y2
 * @param {number} x3
 * @param {number} y3
 * @private
 */
Edge._dist = function (x1,y1, x2,y2, x3,y3) { // x3,y3 is the point
  var px = x2-x1,
      py = y2-y1,
      something = px*px + py*py,
      u =  ((x3 - x1) * px + (y3 - y1) * py) / something;

  if (u > 1) {
    u = 1;
  }
  else if (u < 0) {
    u = 0;
  }

  var x = x1 + u * px,
      y = y1 + u * py,
      dx = x - x3,
      dy = y - y3;

  //# Note: If the actual distance does not matter,
  //# if you only want to compare what this function
  //# returns to other results of this function, you
  //# can just return the squared distance instead
  //# (i.e. remove the sqrt) to gain a little performance

  return Math.sqrt(dx*dx + dy*dy);
};

/**
 * Popup is a class to create a popup window with some text
 * @param {Element}  container     The container object.
 * @param {Number} [x]
 * @param {Number} [y]
 * @param {String} [text]
 */
function Popup(container, x, y, text) {
  if (container) {
    this.container = container;
  }
  else {
    this.container = document.body;
  }
  this.x = 0;
  this.y = 0;
  this.padding = 5;

  if (x !== undefined && y !== undefined ) {
    this.setPosition(x, y);
  }
  if (text !== undefined) {
    this.setText(text);
  }

  // create the frame
  this.frame = document.createElement("div");
  var style = this.frame.style;
  style.position = "absolute";
  style.visibility = "hidden";
  style.border = "1px solid #666";
  style.color = "black";
  style.padding = this.padding + "px";
  style.backgroundColor = "#FFFFC6";
  style.borderRadius = "3px";
  style.MozBorderRadius = "3px";
  style.WebkitBorderRadius = "3px";
  style.boxShadow = "3px 3px 10px rgba(128, 128, 128, 0.5)";
  style.whiteSpace = "nowrap";
  this.container.appendChild(this.frame);
};

/**
 * @param {number} x   Horizontal position of the popup window
 * @param {number} y   Vertical position of the popup window
 */
Popup.prototype.setPosition = function(x, y) {
  this.x = parseInt(x);
  this.y = parseInt(y);
};

/**
 * Set the text for the popup window. This can be HTML code
 * @param {string} text
 */
Popup.prototype.setText = function(text) {
  this.frame.innerHTML = text;
};

/**
 * Show the popup window
 * @param {boolean} show    Optional. Show or hide the window
 */
Popup.prototype.show = function (show) {
  if (show === undefined) {
    show = true;
  }

  if (show) {
    var height = this.frame.clientHeight;
    var width =  this.frame.clientWidth;
    var maxHeight = this.frame.parentNode.clientHeight;
    var maxWidth = this.frame.parentNode.clientWidth;

    var top = (this.y - height);
    if (top + height + this.padding > maxHeight) {
      top = maxHeight - height - this.padding;
    }
    if (top < this.padding) {
      top = this.padding;
    }

    var left = this.x;
    if (left + width + this.padding > maxWidth) {
      left = maxWidth - width - this.padding;
    }
    if (left < this.padding) {
      left = this.padding;
    }

    this.frame.style.left = left + "px";
    this.frame.style.top = top + "px";
    this.frame.style.visibility = "visible";
  }
  else {
    this.hide();
  }
};

/**
 * Hide the popup window
 */
Popup.prototype.hide = function () {
  this.frame.style.visibility = "hidden";
};

/**
 * @class Groups
 * This class can store groups and properties specific for groups.
 */
Groups = function () {
  this.clear();
  this.defaultIndex = 0;
};


/**
 * default constants for group colors
 */
Groups.DEFAULT = [
  {border: "#2B7CE9", background: "#97C2FC", highlight: {border: "#2B7CE9", background: "#D2E5FF"}}, // blue
  {border: "#FFA500", background: "#FFFF00", highlight: {border: "#FFA500", background: "#FFFFA3"}}, // yellow
  {border: "#FA0A10", background: "#FB7E81", highlight: {border: "#FA0A10", background: "#FFAFB1"}}, // red
  {border: "#41A906", background: "#7BE141", highlight: {border: "#41A906", background: "#A1EC76"}}, // green
  {border: "#E129F0", background: "#EB7DF4", highlight: {border: "#E129F0", background: "#F0B3F5"}}, // magenta
  {border: "#7C29F0", background: "#AD85E4", highlight: {border: "#7C29F0", background: "#D3BDF0"}}, // purple
  {border: "#C37F00", background: "#FFA807", highlight: {border: "#C37F00", background: "#FFCA66"}}, // orange
  {border: "#4220FB", background: "#6E6EFD", highlight: {border: "#4220FB", background: "#9B9BFD"}}, // darkblue
  {border: "#FD5A77", background: "#FFC0CB", highlight: {border: "#FD5A77", background: "#FFD1D9"}}, // pink
  {border: "#4AD63A", background: "#C2FABC", highlight: {border: "#4AD63A", background: "#E6FFE3"}}  // mint
];


/**
 * Clear all groups
 */
Groups.prototype.clear = function () {
  this.groups = {};
  this.groups.length = function()
  {
    var i = 0;
    for ( var p in this ) {
      if (this.hasOwnProperty(p)) {
        i++;
      }
    }
    return i;
  }
};


/**
 * get group properties of a groupname. If groupname is not found, a new group
 * is added.
 * @param {*} groupname        Can be a number, string, Date, etc.
 * @return {Object} group      The created group, containing all group properties
 */
Groups.prototype.get = function (groupname) {
  var group = this.groups[groupname];

  if (group == undefined) {
    // create new group
    var index = this.defaultIndex % Groups.DEFAULT.length;
    this.defaultIndex++;
    group = {};
    group.color = Groups.DEFAULT[index];
    this.groups[groupname] = group;
  }

  return group;
};

/**
 * Add a custom group style
 * @param {String} groupname
 * @param {Object} style       An object containing borderColor,
 *                             backgroundColor, etc.
 * @return {Object} group      The created group object
 */
Groups.prototype.add = function (groupname, style) {
  this.groups[groupname] = style;
  if (style.color) {
    style.color = Node.parseColor(style.color);
  }
  return style;
};

/**
 * @class Images
 * This class loads images and keeps them stored.
 */
Images = function () {
  this.images = {};

  this.callback = undefined;
};

/**
 * Set an onload callback function. This will be called each time an image
 * is loaded
 * @param {function} callback
 */
Images.prototype.setOnloadCallback = function(callback) {
  this.callback = callback;
};

/**
 *
 * @param {string} url          Url of the image
 * @return {Image} img          The image object
 */
Images.prototype.load = function(url) {
  var img = this.images[url];
  if (img == undefined) {
    // create the image
    var images = this;
    img = new Image();
    this.images[url] = img;
    img.onload = function() {
      if (images.callback) {
        images.callback(this);
      }
    };
    img.src = url;
  }

  return img;
};

/**
 * @constructor Graph
 * Create a graph visualization, displaying nodes and edges.
 *
 * @param {Element} container   The DOM element in which the Graph will
 *                                  be created. Normally a div element.
 * @param {Object} data         An object containing parameters
 *                              {Array} nodes
 *                              {Array} edges
 * @param {Object} options      Options
 */
function Graph (container, data, options) {
  // create variables and set default values
  this.containerElement = container;
  this.width = '100%';
  this.height = '100%';
  this.refreshRate = 50; // milliseconds
  this.stabilize = true; // stabilize before displaying the graph
  this.selectable = true;

  // set constant values
  this.constants = {
    nodes: {
      radiusMin: 5,
      radiusMax: 20,
      radius: 5,
      distance: 100, // px
      shape: 'ellipse',
      image: undefined,
      widthMin: 16, // px
      widthMax: 64, // px
      fontColor: 'black',
      fontSize: 14, // px
      //fontFace: verdana,
      fontFace: 'arial',
      color: {
        border: '#2B7CE9',
        background: '#97C2FC',
        highlight: {
          border: '#2B7CE9',
          background: '#D2E5FF'
        }
      },
      borderColor: '#2B7CE9',
      backgroundColor: '#97C2FC',
      highlightColor: '#D2E5FF',
      group: undefined
    },
    edges: {
      widthMin: 1,
      widthMax: 15,
      width: 1,
      style: 'line',
      color: '#343434',
      fontColor: '#343434',
      fontSize: 14, // px
      fontFace: 'arial',
      //distance: 100, //px
      length: 100,   // px
      dash: {
        length: 10,
        gap: 5,
        altLength: undefined
      }
    },
    minForce: 0.05,
    minVelocity: 0.02,   // px/s
    maxIterations: 1000  // maximum number of iteration to stabilize
  };

  var graph = this;
  this.nodes = {};            // object with Node objects
  this.edges = {};            // object with Edge objects
  // TODO: create a counter to keep track on the number of nodes having values
  // TODO: create a counter to keep track on the number of nodes currently moving
  // TODO: create a counter to keep track on the number of edges having values

  this.nodesData = null;      // A DataSet or DataView
  this.edgesData = null;      // A DataSet or DataView

  // create event listeners used to subscribe on the DataSets of the nodes and edges
  var me = this;
  this.nodesListeners = {
    'add': function (event, params) {
      me._addNodes(params.items);
      me.start();
    },
    'update': function (event, params) {
      me._updateNodes(params.items);
      me.start();
    },
    'remove': function (event, params) {
      me._removeNodes(params.items);
      me.start();
    }
  };
  this.edgesListeners = {
    'add': function (event, params) {
      me._addEdges(params.items);
      me.start();
    },
    'update': function (event, params) {
      me._updateEdges(params.items);
      me.start();
    },
    'remove': function (event, params) {
      me._removeEdges(params.items);
      me.start();
    }
  };

  this.groups = new Groups(); // object with groups
  this.images = new Images(); // object with images
  this.images.setOnloadCallback(function () {
    graph._redraw();
  });

  // properties of the data
  this.moving = false;    // True if any of the nodes have an undefined position

  this.selection = [];
  this.timer = undefined;

  // create a frame and canvas
  this._create();

  // apply options
  this.setOptions(options);

  // draw data
  this.setData(data);
}

/**
 * Set nodes and edges, and optionally options as well.
 *
 * @param {Object} data    Object containing parameters:
 *                         {Array | DataSet | DataView} [nodes] Array with nodes
 *                         {Array | DataSet | DataView} [edges] Array with edges
 *                         {String} [dot] String containing data in DOT format
 *                         {Options} [options] Object with options
 */
Graph.prototype.setData = function(data) {
  if (data && data.dot && (data.nodes || data.edges)) {
    throw new SyntaxError('Data must contain either parameter "dot" or ' +
        ' parameter pair "nodes" and "edges", but not both.');
  }

  // set options
  this.setOptions(data && data.options);

  // set all data
  if (data && data.dot) {
    // parse DOT file
    if(data && data.dot) {
      var dotData = vis.util.DOTToGraph(data.dot);
      this.setData(dotData);
      return;
    }
  }
  else {
    this._setNodes(data && data.nodes);
    this._setEdges(data && data.edges);
  }

  // find a stable position or start animating to a stable position
  if (this.stabilize) {
    this._doStabilize();
  }
  this.start();
};

/**
 * Set options
 * @param {Object} options
 */
Graph.prototype.setOptions = function (options) {
  if (options) {
    // retrieve parameter values
    if (options.width != undefined)           {this.width = options.width;}
    if (options.height != undefined)          {this.height = options.height;}
    if (options.stabilize != undefined)       {this.stabilize = options.stabilize;}
    if (options.selectable != undefined)      {this.selectable = options.selectable;}

    // TODO: work out these options and document them
    if (options.edges) {
      for (var prop in options.edges) {
        if (options.edges.hasOwnProperty(prop)) {
          this.constants.edges[prop] = options.edges[prop];
        }
      }

      if (options.edges.length != undefined &&
          options.nodes && options.nodes.distance == undefined) {
        this.constants.edges.length   = options.edges.length;
        this.constants.nodes.distance = options.edges.length * 1.25;
      }

      if (!options.edges.fontColor) {
        this.constants.edges.fontColor = options.edges.color;
      }

      // Added to support dashed lines
      // David Jordan
      // 2012-08-08
      if (options.edges.dash) {
        if (options.edges.dash.length != undefined) {
          this.constants.edges.dash.length = options.edges.dash.length;
        }
        if (options.edges.dash.gap != undefined) {
          this.constants.edges.dash.gap = options.edges.dash.gap;
        }
        if (options.edges.dash.altLength != undefined) {
          this.constants.edges.dash.altLength = options.edges.dash.altLength;
        }
      }
    }

    if (options.nodes) {
      for (prop in options.nodes) {
        if (options.nodes.hasOwnProperty(prop)) {
          this.constants.nodes[prop] = options.nodes[prop];
        }
      }

      if (options.nodes.color) {
        this.constants.nodes.color = Node.parseColor(options.nodes.color);
      }

      /*
       if (options.nodes.widthMin) this.constants.nodes.radiusMin = options.nodes.widthMin;
       if (options.nodes.widthMax) this.constants.nodes.radiusMax = options.nodes.widthMax;
       */
    }

    if (options.groups) {
      for (var groupname in options.groups) {
        if (options.groups.hasOwnProperty(groupname)) {
          var group = options.groups[groupname];
          this.groups.add(groupname, group);
        }
      }
    }
  }

  this.setSize(this.width, this.height);
  this._setTranslation(this.frame.clientWidth / 2, this.frame.clientHeight / 2);
  this._setScale(1);
};

/**
 * fire an event
 * @param {String} event   The name of an event, for example 'select'
 * @param {Object} params  Optional object with event parameters
 * @private
 */
Graph.prototype._trigger = function (event, params) {
  events.trigger(this, event, params);
};


/**
 * Create the main frame for the Graph.
 * This function is executed once when a Graph object is created. The frame
 * contains a canvas, and this canvas contains all objects like the axis and
 * nodes.
 * @private
 */
Graph.prototype._create = function () {
  // remove all elements from the container element.
  while (this.containerElement.hasChildNodes()) {
    this.containerElement.removeChild(this.containerElement.firstChild);
  }

  this.frame = document.createElement('div');
  this.frame.className = 'graph-frame';
  this.frame.style.position = 'relative';
  this.frame.style.overflow = 'hidden';

  // create the graph canvas (HTML canvas element)
  this.frame.canvas = document.createElement( 'canvas' );
  this.frame.canvas.style.position = 'relative';
  this.frame.appendChild(this.frame.canvas);
  if (!this.frame.canvas.getContext) {
    var noCanvas = document.createElement( 'DIV' );
    noCanvas.style.color = 'red';
    noCanvas.style.fontWeight =  'bold' ;
    noCanvas.style.padding =  '10px';
    noCanvas.innerHTML =  'Error: your browser does not support HTML canvas';
    this.frame.canvas.appendChild(noCanvas);
  }

  var me = this;
  this.drag = {};
  this.pinch = {};
  this.hammer = Hammer(this.frame.canvas, {
    prevent_default: true
  });
  this.hammer.on('tap',       me._onTap.bind(me) );
  this.hammer.on('hold',      me._onHold.bind(me) );
  this.hammer.on('pinch',     me._onPinch.bind(me) );
  this.hammer.on('touch',     me._onTouch.bind(me) );
  this.hammer.on('dragstart', me._onDragStart.bind(me) );
  this.hammer.on('drag',      me._onDrag.bind(me) );
  this.hammer.on('dragend',   me._onDragEnd.bind(me) );
  this.hammer.on('mousewheel',me._onMouseWheel.bind(me) );
  this.hammer.on('DOMMouseScroll',me._onMouseWheel.bind(me) ); // for FF
  this.hammer.on('mousemove', me._onMouseMoveTitle.bind(me) );

  // add the frame to the container element
  this.containerElement.appendChild(this.frame);
};

/**
 *
 * @param {{x: Number, y: Number}} pointer
 * @return {Number | null} node
 * @private
 */
Graph.prototype._getNodeAt = function (pointer) {
  var x = this._canvasToX(pointer.x);
  var y = this._canvasToY(pointer.y);

  var obj = {
    left:   x,
    top:    y,
    right:  x,
    bottom: y
  };

  // if there are overlapping nodes, select the last one, this is the
  // one which is drawn on top of the others
  var overlappingNodes = this._getNodesOverlappingWith(obj);
  return (overlappingNodes.length > 0) ?
      overlappingNodes[overlappingNodes.length - 1] : null;
};

/**
 * Get the pointer location from a touch location
 * @param {{pageX: Number, pageY: Number}} touch
 * @return {{x: Number, y: Number}} pointer
 * @private
 */
Graph.prototype._getPointer = function (touch) {
  return {
    x: touch.pageX - vis.util.getAbsoluteLeft(this.frame.canvas),
    y: touch.pageY - vis.util.getAbsoluteTop(this.frame.canvas)
  };
};

/**
 * On start of a touch gesture, store the pointer
 * @param event
 * @private
 */
Graph.prototype._onTouch = function (event) {
  this.drag.pointer = this._getPointer(event.gesture.touches[0]);
  this.drag.pinched = false;
  this.pinch.scale = this._getScale();
};

/**
 * handle drag start event
 * @private
 */
Graph.prototype._onDragStart = function () {
  var drag = this.drag;

  drag.selection = [];
  drag.translation = this._getTranslation();
  drag.nodeId = this._getNodeAt(drag.pointer);
  // note: drag.pointer is set in _onTouch to get the initial touch location

  var node = this.nodes[drag.nodeId];
  if (node) {
    // select the clicked node if not yet selected
    if (!node.isSelected()) {
      this._selectNodes([drag.nodeId]);
    }

    // create an array with the selected nodes and their original location and status
    var me = this;
    this.selection.forEach(function (id) {
      var node = me.nodes[id];
      if (node) {
        var s = {
          id: id,
          node: node,

          // store original x, y, xFixed and yFixed, make the node temporarily Fixed
          x: node.x,
          y: node.y,
          xFixed: node.xFixed,
          yFixed: node.yFixed
        };

        node.xFixed = true;
        node.yFixed = true;

        drag.selection.push(s);
      }
    });

  }
};

/**
 * handle drag event
 * @private
 */
Graph.prototype._onDrag = function (event) {
  if (this.drag.pinched) {
    return;
  }

  var pointer = this._getPointer(event.gesture.touches[0]);

  var me = this,
      drag = this.drag,
      selection = drag.selection;
  if (selection && selection.length) {
    // calculate delta's and new location
    var deltaX = pointer.x - drag.pointer.x,
        deltaY = pointer.y - drag.pointer.y;

    // update position of all selected nodes
    selection.forEach(function (s) {
      var node = s.node;

      if (!s.xFixed) {
        node.x = me._canvasToX(me._xToCanvas(s.x) + deltaX);
      }

      if (!s.yFixed) {
        node.y = me._canvasToY(me._yToCanvas(s.y) + deltaY);
      }
    });

    // start animation if not yet running
    if (!this.moving) {
      this.moving = true;
      this.start();
    }
  }
  else {
    // move the graph
    var diffX = pointer.x - this.drag.pointer.x;
    var diffY = pointer.y - this.drag.pointer.y;

    this._setTranslation(
        this.drag.translation.x + diffX,
        this.drag.translation.y + diffY);
    this._redraw();

    this.moved = true;
  }
};

/**
 * handle drag start event
 * @private
 */
Graph.prototype._onDragEnd = function () {
  var selection = this.drag.selection;
  if (selection) {
    selection.forEach(function (s) {
      // restore original xFixed and yFixed
      s.node.xFixed = s.xFixed;
      s.node.yFixed = s.yFixed;
    });
  }
};

/**
 * handle tap/click event: select/unselect a node
 * @private
 */
Graph.prototype._onTap = function (event) {
  var pointer = this._getPointer(event.gesture.touches[0]);

  var nodeId = this._getNodeAt(pointer);
  var node = this.nodes[nodeId];
  if (node) {
    // select this node
    this._selectNodes([nodeId]);

    if (!this.moving) {
      this._redraw();
    }
  }
  else {
    // remove selection
    this._unselectNodes();
    this._redraw();
  }
};

/**
 * handle long tap event: multi select nodes
 * @private
 */
Graph.prototype._onHold = function (event) {
  var pointer = this._getPointer(event.gesture.touches[0]);
  var nodeId = this._getNodeAt(pointer);
  var node = this.nodes[nodeId];
  if (node) {
    if (!node.isSelected()) {
      // select this node, keep previous selection
      var append = true;
      this._selectNodes([nodeId], append);
    }
    else {
      this._unselectNodes([nodeId]);
    }

    if (!this.moving) {
      this._redraw();
    }
  }
  else {
    // Do nothing
  }
};

/**
 * Handle pinch event
 * @param event
 * @private
 */
Graph.prototype._onPinch = function (event) {
  var pointer = this._getPointer(event.gesture.center);

  this.drag.pinched = true;
  if (!('scale' in this.pinch)) {
    this.pinch.scale = 1;
  }

  // TODO: enable moving while pinching?
  var scale = this.pinch.scale * event.gesture.scale;
  this._zoom(scale, pointer)
};

/**
 * Zoom the graph in or out
 * @param {Number} scale a number around 1, and between 0.01 and 10
 * @param {{x: Number, y: Number}} pointer
 * @return {Number} appliedScale    scale is limited within the boundaries
 * @private
 */
Graph.prototype._zoom = function(scale, pointer) {
  var scaleOld = this._getScale();
  if (scale < 0.01) {
    scale = 0.01;
  }
  if (scale > 10) {
    scale = 10;
  }

  var translation = this._getTranslation();
  var scaleFrac = scale / scaleOld;
  var tx = (1 - scaleFrac) * pointer.x + translation.x * scaleFrac;
  var ty = (1 - scaleFrac) * pointer.y + translation.y * scaleFrac;

  this._setScale(scale);
  this._setTranslation(tx, ty);
  this._redraw();

  return scale;
};

/**
 * Event handler for mouse wheel event, used to zoom the timeline
 * See http://adomas.org/javascript-mouse-wheel/
 *     https://github.com/EightMedia/hammer.js/issues/256
 * @param {MouseEvent}  event
 * @private
 */
Graph.prototype._onMouseWheel = function(event) {
  // retrieve delta
  var delta = 0;
  if (event.wheelDelta) { /* IE/Opera. */
    delta = event.wheelDelta/120;
  } else if (event.detail) { /* Mozilla case. */
    // In Mozilla, sign of delta is different than in IE.
    // Also, delta is multiple of 3.
    delta = -event.detail/3;
  }

  // If delta is nonzero, handle it.
  // Basically, delta is now positive if wheel was scrolled up,
  // and negative, if wheel was scrolled down.
  if (delta) {
    if (!('mouswheelScale' in this.pinch)) {
      this.pinch.mouswheelScale = 1;
    }

    // calculate the new scale
    var scale = this.pinch.mouswheelScale;
    var zoom = delta / 10;
    if (delta < 0) {
      zoom = zoom / (1 - zoom);
    }
    scale *= (1 + zoom);

    // calculate the pointer location
    var gesture = Hammer.event.collectEventData(this, 'scroll', event);
    var pointer = this._getPointer(gesture.center);

    // apply the new scale
    scale = this._zoom(scale, pointer);

    // store the new, applied scale
    this.pinch.mouswheelScale = scale;
  }

  // Prevent default actions caused by mouse wheel.
  event.preventDefault();
};


/**
 * Mouse move handler for checking whether the title moves over a node with a title.
 * @param  {Event} event
 * @private
 */
Graph.prototype._onMouseMoveTitle = function (event) {
  var gesture = Hammer.event.collectEventData(this, 'mousemove', event);
  var pointer = this._getPointer(gesture.center);

  // check if the previously selected node is still selected
  if (this.popupNode) {
    this._checkHidePopup(pointer);
  }

  // start a timeout that will check if the mouse is positioned above
  // an element
  var me = this;
  var checkShow = function() {
    me._checkShowPopup(pointer);
  };
  if (this.popupTimer) {
    clearInterval(this.popupTimer); // stop any running timer
  }
  if (!this.leftButtonDown) {
    this.popupTimer = setTimeout(checkShow, 300);
  }
};

/**
 * Check if there is an element on the given position in the graph
 * (a node or edge). If so, and if this element has a title,
 * show a popup window with its title.
 *
 * @param {{x:Number, y:Number}} pointer
 * @private
 */
Graph.prototype._checkShowPopup = function (pointer) {
  var obj = {
    left:   this._canvasToX(pointer.x),
    top:    this._canvasToY(pointer.y),
    right:  this._canvasToX(pointer.x),
    bottom: this._canvasToY(pointer.y)
  };

  var id;
  var lastPopupNode = this.popupNode;

  if (this.popupNode == undefined) {
    // search the nodes for overlap, select the top one in case of multiple nodes
    var nodes = this.nodes;
    for (id in nodes) {
      if (nodes.hasOwnProperty(id)) {
        var node = nodes[id];
        if (node.getTitle() != undefined && node.isOverlappingWith(obj)) {
          this.popupNode = node;
          break;
        }
      }
    }
  }

  if (this.popupNode == undefined) {
    // search the edges for overlap
    var edges = this.edges;
    for (id in edges) {
      if (edges.hasOwnProperty(id)) {
        var edge = edges[id];
        if (edge.connected && (edge.getTitle() != undefined) &&
            edge.isOverlappingWith(obj)) {
          this.popupNode = edge;
          break;
        }
      }
    }
  }

  if (this.popupNode) {
    // show popup message window
    if (this.popupNode != lastPopupNode) {
      var me = this;
      if (!me.popup) {
        me.popup = new Popup(me.frame);
      }

      // adjust a small offset such that the mouse cursor is located in the
      // bottom left location of the popup, and you can easily move over the
      // popup area
      me.popup.setPosition(pointer.x - 3, pointer.y - 3);
      me.popup.setText(me.popupNode.getTitle());
      me.popup.show();
    }
  }
  else {
    if (this.popup) {
      this.popup.hide();
    }
  }
};

/**
 * Check if the popup must be hided, which is the case when the mouse is no
 * longer hovering on the object
 * @param {{x:Number, y:Number}} pointer
 * @private
 */
Graph.prototype._checkHidePopup = function (pointer) {
  if (!this.popupNode || !this._getNodeAt(pointer) ) {
    this.popupNode = undefined;
    if (this.popup) {
      this.popup.hide();
    }
  }
};

/**
 * Unselect selected nodes. If no selection array is provided, all nodes
 * are unselected
 * @param {Object[]} selection     Array with selection objects, each selection
 *                                 object has a parameter row. Optional
 * @param {Boolean} triggerSelect  If true (default), the select event
 *                                 is triggered when nodes are unselected
 * @return {Boolean} changed       True if the selection is changed
 * @private
 */
Graph.prototype._unselectNodes = function(selection, triggerSelect) {
  var changed = false;
  var i, iMax, id;

  if (selection) {
    // remove provided selections
    for (i = 0, iMax = selection.length; i < iMax; i++) {
      id = selection[i];
      this.nodes[id].unselect();

      var j = 0;
      while (j < this.selection.length) {
        if (this.selection[j] == id) {
          this.selection.splice(j, 1);
          changed = true;
        }
        else {
          j++;
        }
      }
    }
  }
  else if (this.selection && this.selection.length) {
    // remove all selections
    for (i = 0, iMax = this.selection.length; i < iMax; i++) {
      id = this.selection[i];
      this.nodes[id].unselect();
      changed = true;
    }
    this.selection = [];
  }

  if (changed && (triggerSelect == true || triggerSelect == undefined)) {
    // fire the select event
    this._trigger('select');
  }

  return changed;
};

/**
 * select all nodes on given location x, y
 * @param {Array} selection   an array with node ids
 * @param {boolean} append    If true, the new selection will be appended to the
 *                            current selection (except for duplicate entries)
 * @return {Boolean} changed  True if the selection is changed
 * @private
 */
Graph.prototype._selectNodes = function(selection, append) {
  var changed = false;
  var i, iMax;

  // TODO: the selectNodes method is a little messy, rework this

  // check if the current selection equals the desired selection
  var selectionAlreadyThere = true;
  if (selection.length != this.selection.length) {
    selectionAlreadyThere = false;
  }
  else {
    for (i = 0, iMax = Math.min(selection.length, this.selection.length); i < iMax; i++) {
      if (selection[i] != this.selection[i]) {
        selectionAlreadyThere = false;
        break;
      }
    }
  }
  if (selectionAlreadyThere) {
    return changed;
  }

  if (append == undefined || append == false) {
    // first deselect any selected node
    var triggerSelect = false;
    changed = this._unselectNodes(undefined, triggerSelect);
  }

  for (i = 0, iMax = selection.length; i < iMax; i++) {
    // add each of the new selections, but only when they are not duplicate
    var id = selection[i];
    var isDuplicate = (this.selection.indexOf(id) != -1);
    if (!isDuplicate) {
      this.nodes[id].select();
      this.selection.push(id);
      changed = true;
    }
  }

  if (changed) {
    // fire the select event
    this._trigger('select');
  }

  return changed;
};

/**
 * retrieve all nodes overlapping with given object
 * @param {Object} obj  An object with parameters left, top, right, bottom
 * @return {Number[]}   An array with id's of the overlapping nodes
 * @private
 */
Graph.prototype._getNodesOverlappingWith = function (obj) {
  var nodes = this.nodes,
      overlappingNodes = [];

  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      if (nodes[id].isOverlappingWith(obj)) {
        overlappingNodes.push(id);
      }
    }
  }

  return overlappingNodes;
};

/**
 * retrieve the currently selected nodes
 * @return {Number[] | String[]} selection    An array with the ids of the
 *                                            selected nodes.
 */
Graph.prototype.getSelection = function() {
  return this.selection.concat([]);
};

/**
 * select zero or more nodes
 * @param {Number[] | String[]} selection     An array with the ids of the
 *                                            selected nodes.
 */
Graph.prototype.setSelection = function(selection) {
  var i, iMax, id;

  if (!selection || (selection.length == undefined))
    throw 'Selection must be an array with ids';

  // first unselect any selected node
  for (i = 0, iMax = this.selection.length; i < iMax; i++) {
    id = this.selection[i];
    this.nodes[id].unselect();
  }

  this.selection = [];

  for (i = 0, iMax = selection.length; i < iMax; i++) {
    id = selection[i];

    var node = this.nodes[id];
    if (!node) {
      throw new RangeError('Node with id "' + id + '" not found');
    }
    node.select();
    this.selection.push(id);
  }

  this.redraw();
};

/**
 * Validate the selection: remove ids of nodes which no longer exist
 * @private
 */
Graph.prototype._updateSelection = function () {
  var i = 0;
  while (i < this.selection.length) {
    var id = this.selection[i];
    if (!this.nodes[id]) {
      this.selection.splice(i, 1);
    }
    else {
      i++;
    }
  }
};

/**
 * Temporary method to test calculating a hub value for the nodes
 * @param {number} level        Maximum number edges between two nodes in order
 *                              to call them connected. Optional, 1 by default
 * @return {Number[]} connectioncount array with the connection count
 *                                    for each node
 * @private
 */
Graph.prototype._getConnectionCount = function(level) {
  if (level == undefined) {
    level = 1;
  }

  // get the nodes connected to given nodes
  function getConnectedNodes(nodes) {
    var connectedNodes = [];

    for (var j = 0, jMax = nodes.length; j < jMax; j++) {
      var node = nodes[j];

      // find all nodes connected to this node
      var edges = node.edges;
      for (var i = 0, iMax = edges.length; i < iMax; i++) {
        var edge = edges[i];
        var other = null;

        // check if connected
        if (edge.from == node)
          other = edge.to;
        else if (edge.to == node)
          other = edge.from;

        // check if the other node is not already in the list with nodes
        var k, kMax;
        if (other) {
          for (k = 0, kMax = nodes.length; k < kMax; k++) {
            if (nodes[k] == other) {
              other = null;
              break;
            }
          }
        }
        if (other) {
          for (k = 0, kMax = connectedNodes.length; k < kMax; k++) {
            if (connectedNodes[k] == other) {
              other = null;
              break;
            }
          }
        }

        if (other)
          connectedNodes.push(other);
      }
    }

    return connectedNodes;
  }

  var connections = [];
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      var c = [nodes[id]];
      for (var l = 0; l < level; l++) {
        c = c.concat(getConnectedNodes(c));
      }
      connections.push(c);
    }
  }

  var hubs = [];
  for (var i = 0, len = connections.length; i < len; i++) {
    hubs.push(connections[i].length);
  }

  return hubs;
};


/**
 * Set a new size for the graph
 * @param {string} width   Width in pixels or percentage (for example '800px'
 *                         or '50%')
 * @param {string} height  Height in pixels or percentage  (for example '400px'
 *                         or '30%')
 */
Graph.prototype.setSize = function(width, height) {
  this.frame.style.width = width;
  this.frame.style.height = height;

  this.frame.canvas.style.width = '100%';
  this.frame.canvas.style.height = '100%';

  this.frame.canvas.width = this.frame.canvas.clientWidth;
  this.frame.canvas.height = this.frame.canvas.clientHeight;
};

/**
 * Set a data set with nodes for the graph
 * @param {Array | DataSet | DataView} nodes         The data containing the nodes.
 * @private
 */
Graph.prototype._setNodes = function(nodes) {
  var oldNodesData = this.nodesData;

  if (nodes instanceof DataSet || nodes instanceof DataView) {
    this.nodesData = nodes;
  }
  else if (nodes instanceof Array) {
    this.nodesData = new DataSet();
    this.nodesData.add(nodes);
  }
  else if (!nodes) {
    this.nodesData = new DataSet();
  }
  else {
    throw new TypeError('Array or DataSet expected');
  }

  if (oldNodesData) {
    // unsubscribe from old dataset
    util.forEach(this.nodesListeners, function (callback, event) {
      oldNodesData.unsubscribe(event, callback);
    });
  }

  // remove drawn nodes
  this.nodes = {};

  if (this.nodesData) {
    // subscribe to new dataset
    var me = this;
    util.forEach(this.nodesListeners, function (callback, event) {
      me.nodesData.subscribe(event, callback);
    });

    // draw all new nodes
    var ids = this.nodesData.getIds();
    this._addNodes(ids);
  }

  this._updateSelection();
};

/**
 * Add nodes
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._addNodes = function(ids) {
  var id;
  for (var i = 0, len = ids.length; i < len; i++) {
    id = ids[i];
    var data = this.nodesData.get(id);
    var node = new Node(data, this.images, this.groups, this.constants);
    this.nodes[id] = node; // note: this may replace an existing node

    if (!node.isFixed()) {
      // TODO: position new nodes in a smarter way!
      var radius = this.constants.edges.length * 2;
      var count = ids.length;
      var angle = 2 * Math.PI * (i / count);
      node.x = radius * Math.cos(angle);
      node.y = radius * Math.sin(angle);

      // note: no not use node.isMoving() here, as that gives the current
      // velocity of the node, which is zero after creation of the node.
      this.moving = true;
    }
  }

  this._reconnectEdges();
  this._updateValueRange(this.nodes);
};

/**
 * Update existing nodes, or create them when not yet existing
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._updateNodes = function(ids) {
  var nodes = this.nodes,
      nodesData = this.nodesData;
  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    var node = nodes[id];
    var data = nodesData.get(id);
    if (node) {
      // update node
      node.setProperties(data, this.constants);
    }
    else {
      // create node
      node = new Node(properties, this.images, this.groups, this.constants);
      nodes[id] = node;

      if (!node.isFixed()) {
        this.moving = true;
      }
    }
  }

  this._reconnectEdges();
  this._updateValueRange(nodes);
};

/**
 * Remove existing nodes. If nodes do not exist, the method will just ignore it.
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._removeNodes = function(ids) {
  var nodes = this.nodes;
  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    delete nodes[id];
  }

  this._reconnectEdges();
  this._updateSelection();
  this._updateValueRange(nodes);
};

/**
 * Load edges by reading the data table
 * @param {Array | DataSet | DataView} edges    The data containing the edges.
 * @private
 * @private
 */
Graph.prototype._setEdges = function(edges) {
  var oldEdgesData = this.edgesData;

  if (edges instanceof DataSet || edges instanceof DataView) {
    this.edgesData = edges;
  }
  else if (edges instanceof Array) {
    this.edgesData = new DataSet();
    this.edgesData.add(edges);
  }
  else if (!edges) {
    this.edgesData = new DataSet();
  }
  else {
    throw new TypeError('Array or DataSet expected');
  }

  if (oldEdgesData) {
    // unsubscribe from old dataset
    util.forEach(this.edgesListeners, function (callback, event) {
      oldEdgesData.unsubscribe(event, callback);
    });
  }

  // remove drawn edges
  this.edges = {};

  if (this.edgesData) {
    // subscribe to new dataset
    var me = this;
    util.forEach(this.edgesListeners, function (callback, event) {
      me.edgesData.subscribe(event, callback);
    });

    // draw all new nodes
    var ids = this.edgesData.getIds();
    this._addEdges(ids);
  }

  this._reconnectEdges();
};

/**
 * Add edges
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._addEdges = function (ids) {
  var edges = this.edges,
      edgesData = this.edgesData;
  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];

    var oldEdge = edges[id];
    if (oldEdge) {
      oldEdge.disconnect();
    }

    var data = edgesData.get(id);
    edges[id] = new Edge(data, this, this.constants);
  }

  this.moving = true;
  this._updateValueRange(edges);
};

/**
 * Update existing edges, or create them when not yet existing
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._updateEdges = function (ids) {
  var edges = this.edges,
      edgesData = this.edgesData;
  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];

    var data = edgesData.get(id);
    var edge = edges[id];
    if (edge) {
      // update edge
      edge.disconnect();
      edge.setProperties(data, this.constants);
      edge.connect();
    }
    else {
      // create edge
      edge = new Edge(data, this, this.constants);
      this.edges[id] = edge;
    }
  }

  this.moving = true;
  this._updateValueRange(edges);
};

/**
 * Remove existing edges. Non existing ids will be ignored
 * @param {Number[] | String[]} ids
 * @private
 */
Graph.prototype._removeEdges = function (ids) {
  var edges = this.edges;
  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    var edge = edges[id];
    if (edge) {
      edge.disconnect();
      delete edges[id];
    }
  }

  this.moving = true;
  this._updateValueRange(edges);
};

/**
 * Reconnect all edges
 * @private
 */
Graph.prototype._reconnectEdges = function() {
  var id,
      nodes = this.nodes,
      edges = this.edges;
  for (id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      nodes[id].edges = [];
    }
  }

  for (id in edges) {
    if (edges.hasOwnProperty(id)) {
      var edge = edges[id];
      edge.from = null;
      edge.to = null;
      edge.connect();
    }
  }
};

/**
 * Update the values of all object in the given array according to the current
 * value range of the objects in the array.
 * @param {Object} obj    An object containing a set of Edges or Nodes
 *                        The objects must have a method getValue() and
 *                        setValueRange(min, max).
 * @private
 */
Graph.prototype._updateValueRange = function(obj) {
  var id;

  // determine the range of the objects
  var valueMin = undefined;
  var valueMax = undefined;
  for (id in obj) {
    if (obj.hasOwnProperty(id)) {
      var value = obj[id].getValue();
      if (value !== undefined) {
        valueMin = (valueMin === undefined) ? value : Math.min(value, valueMin);
        valueMax = (valueMax === undefined) ? value : Math.max(value, valueMax);
      }
    }
  }

  // adjust the range of all objects
  if (valueMin !== undefined && valueMax !== undefined) {
    for (id in obj) {
      if (obj.hasOwnProperty(id)) {
        obj[id].setValueRange(valueMin, valueMax);
      }
    }
  }
};

/**
 * Redraw the graph with the current data
 * chart will be resized too.
 */
Graph.prototype.redraw = function() {
  this.setSize(this.width, this.height);

  this._redraw();
};

/**
 * Redraw the graph with the current data
 * @private
 */
Graph.prototype._redraw = function() {
  var ctx = this.frame.canvas.getContext('2d');

  // clear the canvas
  var w = this.frame.canvas.width;
  var h = this.frame.canvas.height;
  ctx.clearRect(0, 0, w, h);

  // set scaling and translation
  ctx.save();
  ctx.translate(this.translation.x, this.translation.y);
  ctx.scale(this.scale, this.scale);

  this._drawEdges(ctx);
  this._drawNodes(ctx);

  // restore original scaling and translation
  ctx.restore();
};

/**
 * Set the translation of the graph
 * @param {Number} offsetX    Horizontal offset
 * @param {Number} offsetY    Vertical offset
 * @private
 */
Graph.prototype._setTranslation = function(offsetX, offsetY) {
  if (this.translation === undefined) {
    this.translation = {
      x: 0,
      y: 0
    };
  }

  if (offsetX !== undefined) {
    this.translation.x = offsetX;
  }
  if (offsetY !== undefined) {
    this.translation.y = offsetY;
  }
};

/**
 * Get the translation of the graph
 * @return {Object} translation    An object with parameters x and y, both a number
 * @private
 */
Graph.prototype._getTranslation = function() {
  return {
    x: this.translation.x,
    y: this.translation.y
  };
};

/**
 * Scale the graph
 * @param {Number} scale   Scaling factor 1.0 is unscaled
 * @private
 */
Graph.prototype._setScale = function(scale) {
  this.scale = scale;
};
/**
 * Get the current scale of  the graph
 * @return {Number} scale   Scaling factor 1.0 is unscaled
 * @private
 */
Graph.prototype._getScale = function() {
  return this.scale;
};

/**
 * Convert a horizontal point on the HTML canvas to the x-value of the model
 * @param {number} x
 * @returns {number}
 * @private
 */
Graph.prototype._canvasToX = function(x) {
  return (x - this.translation.x) / this.scale;
};

/**
 * Convert an x-value in the model to a horizontal point on the HTML canvas
 * @param {number} x
 * @returns {number}
 * @private
 */
Graph.prototype._xToCanvas = function(x) {
  return x * this.scale + this.translation.x;
};

/**
 * Convert a vertical point on the HTML canvas to the y-value of the model
 * @param {number} y
 * @returns {number}
 * @private
 */
Graph.prototype._canvasToY = function(y) {
  return (y - this.translation.y) / this.scale;
};

/**
 * Convert an y-value in the model to a vertical point on the HTML canvas
 * @param {number} y
 * @returns {number}
 * @private
 */
Graph.prototype._yToCanvas = function(y) {
  return y * this.scale + this.translation.y ;
};

/**
 * Redraw all nodes
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext('2d');
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Graph.prototype._drawNodes = function(ctx) {
  // first draw the unselected nodes
  var nodes = this.nodes;
  var selected = [];
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      if (nodes[id].isSelected()) {
        selected.push(id);
      }
      else {
        nodes[id].draw(ctx);
      }
    }
  }

  // draw the selected nodes on top
  for (var s = 0, sMax = selected.length; s < sMax; s++) {
    nodes[selected[s]].draw(ctx);
  }
};

/**
 * Redraw all edges
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext('2d');
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Graph.prototype._drawEdges = function(ctx) {
  var edges = this.edges;
  for (var id in edges) {
    if (edges.hasOwnProperty(id)) {
      var edge = edges[id];
      if (edge.connected) {
        edges[id].draw(ctx);
      }
    }
  }
};

/**
 * Find a stable position for all nodes
 * @private
 */
Graph.prototype._doStabilize = function() {
  var start = new Date();

  // find stable position
  var count = 0;
  var vmin = this.constants.minVelocity;
  var stable = false;
  while (!stable && count < this.constants.maxIterations) {
    this._calculateForces();
    this._discreteStepNodes();
    stable = !this._isMoving(vmin);
    count++;
  }

  var end = new Date();

  // console.log('Stabilized in ' + (end-start) + ' ms, ' + count + ' iterations' ); // TODO: cleanup
};

/**
 * Calculate the external forces acting on the nodes
 * Forces are caused by: edges, repulsing forces between nodes, gravity
 * @private
 */
Graph.prototype._calculateForces = function() {
  // create a local edge to the nodes and edges, that is faster
  var id, dx, dy, angle, distance, fx, fy,
      repulsingForce, springForce, length, edgeLength,
      nodes = this.nodes,
      edges = this.edges;

  // gravity, add a small constant force to pull the nodes towards the center of
  // the graph
  // Also, the forces are reset to zero in this loop by using _setForce instead
  // of _addForce
  var gravity = 0.01,
      gx = this.frame.canvas.clientWidth / 2,
      gy = this.frame.canvas.clientHeight / 2;
  for (id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      var node = nodes[id];
      dx = gx - node.x;
      dy = gy - node.y;
      angle = Math.atan2(dy, dx);
      fx = Math.cos(angle) * gravity;
      fy = Math.sin(angle) * gravity;

      node._setForce(fx, fy);
    }
  }

  // repulsing forces between nodes
  var minimumDistance = this.constants.nodes.distance,
      steepness = 10; // higher value gives steeper slope of the force around the given minimumDistance

  for (var id1 in nodes) {
    if (nodes.hasOwnProperty(id1)) {
      var node1 = nodes[id1];
      for (var id2 in nodes) {
        if (nodes.hasOwnProperty(id2)) {
          var node2 = nodes[id2];
          // calculate normally distributed force
          dx = node2.x - node1.x;
          dy = node2.y - node1.y;
          distance = Math.sqrt(dx * dx + dy * dy);
          angle = Math.atan2(dy, dx);

          // TODO: correct factor for repulsing force
          //repulsingForce = 2 * Math.exp(-5 * (distance * distance) / (dmin * dmin) ); // TODO: customize the repulsing force
          //repulsingForce = Math.exp(-1 * (distance * distance) / (dmin * dmin) ); // TODO: customize the repulsing force
          repulsingForce = 1 / (1 + Math.exp((distance / minimumDistance - 1) * steepness)); // TODO: customize the repulsing force
          fx = Math.cos(angle) * repulsingForce;
          fy = Math.sin(angle) * repulsingForce;

          node1._addForce(-fx, -fy);
          node2._addForce(fx, fy);
        }
      }
    }
  }

  /* TODO: re-implement repulsion of edges
   for (var n = 0; n < nodes.length; n++) {
   for (var l = 0; l < edges.length; l++) {
   var lx = edges[l].from.x+(edges[l].to.x - edges[l].from.x)/2,
   ly = edges[l].from.y+(edges[l].to.y - edges[l].from.y)/2,

   // calculate normally distributed force
   dx = nodes[n].x - lx,
   dy = nodes[n].y - ly,
   distance = Math.sqrt(dx * dx + dy * dy),
   angle = Math.atan2(dy, dx),


   // TODO: correct factor for repulsing force
   //var repulsingforce = 2 * Math.exp(-5 * (distance * distance) / (dmin * dmin) ); // TODO: customize the repulsing force
   //repulsingforce = Math.exp(-1 * (distance * distance) / (dmin * dmin) ), // TODO: customize the repulsing force
   repulsingforce = 1 / (1 + Math.exp((distance / (minimumDistance / 2) - 1) * steepness)), // TODO: customize the repulsing force
   fx = Math.cos(angle) * repulsingforce,
   fy = Math.sin(angle) * repulsingforce;
   nodes[n]._addForce(fx, fy);
   edges[l].from._addForce(-fx/2,-fy/2);
   edges[l].to._addForce(-fx/2,-fy/2);
   }
   }
   */

  // forces caused by the edges, modelled as springs
  for (id in edges) {
    if (edges.hasOwnProperty(id)) {
      var edge = edges[id];
      if (edge.connected) {
        dx = (edge.to.x - edge.from.x);
        dy = (edge.to.y - edge.from.y);
        //edgeLength = (edge.from.width + edge.from.height + edge.to.width + edge.to.height)/2 || edge.length; // TODO: dmin
        //edgeLength = (edge.from.width + edge.to.width)/2 || edge.length; // TODO: dmin
        //edgeLength = 20 + ((edge.from.width + edge.to.width) || 0) / 2;
        edgeLength = edge.length;
        length =  Math.sqrt(dx * dx + dy * dy);
        angle = Math.atan2(dy, dx);

        springForce = edge.stiffness * (edgeLength - length);

        fx = Math.cos(angle) * springForce;
        fy = Math.sin(angle) * springForce;

        edge.from._addForce(-fx, -fy);
        edge.to._addForce(fx, fy);
      }
    }
  }

  /* TODO: re-implement repulsion of edges
   // repulsing forces between edges
   var minimumDistance = this.constants.edges.distance,
   steepness = 10; // higher value gives steeper slope of the force around the given minimumDistance
   for (var l = 0; l < edges.length; l++) {
   //Keep distance from other edge centers
   for (var l2 = l + 1; l2 < this.edges.length; l2++) {
   //var dmin = (nodes[n].width + nodes[n].height + nodes[n2].width + nodes[n2].height) / 1 || minimumDistance, // TODO: dmin
   //var dmin = (nodes[n].width + nodes[n2].width)/2  || minimumDistance, // TODO: dmin
   //dmin = 40 + ((nodes[n].width/2 + nodes[n2].width/2) || 0),
   var lx = edges[l].from.x+(edges[l].to.x - edges[l].from.x)/2,
   ly = edges[l].from.y+(edges[l].to.y - edges[l].from.y)/2,
   l2x = edges[l2].from.x+(edges[l2].to.x - edges[l2].from.x)/2,
   l2y = edges[l2].from.y+(edges[l2].to.y - edges[l2].from.y)/2,

   // calculate normally distributed force
   dx = l2x - lx,
   dy = l2y - ly,
   distance = Math.sqrt(dx * dx + dy * dy),
   angle = Math.atan2(dy, dx),


   // TODO: correct factor for repulsing force
   //var repulsingforce = 2 * Math.exp(-5 * (distance * distance) / (dmin * dmin) ); // TODO: customize the repulsing force
   //repulsingforce = Math.exp(-1 * (distance * distance) / (dmin * dmin) ), // TODO: customize the repulsing force
   repulsingforce = 1 / (1 + Math.exp((distance / minimumDistance - 1) * steepness)), // TODO: customize the repulsing force
   fx = Math.cos(angle) * repulsingforce,
   fy = Math.sin(angle) * repulsingforce;

   edges[l].from._addForce(-fx, -fy);
   edges[l].to._addForce(-fx, -fy);
   edges[l2].from._addForce(fx, fy);
   edges[l2].to._addForce(fx, fy);
   }
   }
   */
};


/**
 * Check if any of the nodes is still moving
 * @param {number} vmin   the minimum velocity considered as 'moving'
 * @return {boolean}      true if moving, false if non of the nodes is moving
 * @private
 */
Graph.prototype._isMoving = function(vmin) {
  // TODO: ismoving does not work well: should check the kinetic energy, not its velocity
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id) && nodes[id].isMoving(vmin)) {
      return true;
    }
  }
  return false;
};


/**
 * Perform one discrete step for all nodes
 * @private
 */
Graph.prototype._discreteStepNodes = function() {
  var interval = this.refreshRate / 1000.0; // in seconds
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      nodes[id].discreteStep(interval);
    }
  }
};

/**
 * Start animating nodes and edges
 */
Graph.prototype.start = function() {
  if (this.moving) {
    this._calculateForces();
    this._discreteStepNodes();

    var vmin = this.constants.minVelocity;
    this.moving = this._isMoving(vmin);
  }

  if (this.moving) {
    // start animation. only start timer if it is not already running
    if (!this.timer) {
      var graph = this;
      this.timer = window.setTimeout(function () {
        graph.timer = undefined;
        graph.start();
        graph._redraw();
      }, this.refreshRate);
    }
  }
  else {
    this._redraw();
  }
};

/**
 * Stop animating nodes and edges.
 */
Graph.prototype.stop = function () {
  if (this.timer) {
    window.clearInterval(this.timer);
    this.timer = undefined;
  }
};

/**
 * vis.js module exports
 */
var vis = {
  util: util,
  events: events,

  Controller: Controller,
  DataSet: DataSet,
  DataView: DataView,
  Range: Range,
  Stack: Stack,
  TimeStep: TimeStep,
  EventBus: EventBus,

  components: {
    items: {
      Item: Item,
      ItemBox: ItemBox,
      ItemPoint: ItemPoint,
      ItemRange: ItemRange
    },

    Component: Component,
    Panel: Panel,
    RootPanel: RootPanel,
    ItemSet: ItemSet,
    TimeAxis: TimeAxis
  },

  graph: {
    Node: Node,
    Edge: Edge,
    Popup: Popup,
    Groups: Groups,
    Images: Images
  },

  Timeline: Timeline,
  Graph: Graph
};

/**
 * CommonJS module exports
 */
if (typeof exports !== 'undefined') {
  exports = vis;
}
if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
  module.exports = vis;
}

/**
 * AMD module exports
 */
if (typeof(define) === 'function') {
  define(function () {
    return vis;
  });
}

/**
 * Window exports
 */
if (typeof window !== 'undefined') {
  // attach the module to the window, load as a regular javascript file
  window['vis'] = vis;
}

// inject css
util.loadCss("/* vis.js stylesheet */\n.vis.timeline {\n}\n\n\n.vis.timeline.rootpanel {\n  position: relative;\n  overflow: hidden;\n\n  border: 1px solid #bfbfbf;\n  -moz-box-sizing: border-box;\n  box-sizing: border-box;\n}\n\n.vis.timeline .panel {\n  position: absolute;\n  overflow: hidden;\n}\n\n\n.vis.timeline .groupset {\n  position: absolute;\n  padding: 0;\n  margin: 0;\n}\n\n.vis.timeline .labels {\n  position: absolute;\n  top: 0;\n  left: 0;\n  width: 100%;\n  height: 100%;\n\n  padding: 0;\n  margin: 0;\n\n  border-right: 1px solid #bfbfbf;\n  box-sizing: border-box;\n  -moz-box-sizing: border-box;\n}\n\n.vis.timeline .labels .label-set {\n  position: absolute;\n  top: 0;\n  left: 0;\n  width: 100%;\n  height: 100%;\n\n  overflow: hidden;\n\n  border-top: none;\n  border-bottom: 1px solid #bfbfbf;\n}\n\n.vis.timeline .labels .label-set .label {\n  position: absolute;\n  left: 0;\n  top: 0;\n  width: 100%;\n  color: #4d4d4d;\n}\n\n.vis.timeline.top .labels .label-set .label,\n.vis.timeline.top .groupset .itemset-axis {\n  border-top: 1px solid #bfbfbf;\n  border-bottom: none;\n}\n\n.vis.timeline.bottom .labels .label-set .label,\n.vis.timeline.bottom .groupset .itemset-axis {\n  border-top: none;\n  border-bottom: 1px solid #bfbfbf;\n}\n\n.vis.timeline .labels .label-set .label .inner {\n  display: inline-block;\n  padding: 5px;\n}\n\n\n.vis.timeline .itemset {\n  position: absolute;\n  padding: 0;\n  margin: 0;\n  overflow: hidden;\n}\n\n.vis.timeline .background {\n}\n\n.vis.timeline .foreground {\n}\n\n.vis.timeline .itemset-axis {\n  position: absolute;\n}\n\n\n.vis.timeline .item {\n  position: absolute;\n  color: #1A1A1A;\n  border-color: #97B0F8;\n  background-color: #D5DDF6;\n  display: inline-block;\n}\n\n.vis.timeline .item.selected {\n  border-color: #FFC200;\n  background-color: #FFF785;\n  z-index: 999;\n}\n\n.vis.timeline .item.cluster {\n  /* TODO: use another color or pattern? */\n  background: #97B0F8 url('img/cluster_bg.png');\n  color: white;\n}\n.vis.timeline .item.cluster.point {\n  border-color: #D5DDF6;\n}\n\n.vis.timeline .item.box {\n  text-align: center;\n  border-style: solid;\n  border-width: 1px;\n  border-radius: 5px;\n  -moz-border-radius: 5px; /* For Firefox 3.6 and older */\n}\n\n.vis.timeline .item.point {\n  background: none;\n}\n\n.vis.timeline .dot {\n  border: 5px solid #97B0F8;\n  position: absolute;\n  border-radius: 5px;\n  -moz-border-radius: 5px;  /* For Firefox 3.6 and older */\n}\n\n.vis.timeline .item.range {\n  overflow: hidden;\n  border-style: solid;\n  border-width: 1px;\n  border-radius: 2px;\n  -moz-border-radius: 2px;  /* For Firefox 3.6 and older */\n}\n\n.vis.timeline .item.rangeoverflow {\n  border-style: solid;\n  border-width: 1px;\n  border-radius: 2px;\n  -moz-border-radius: 2px;  /* For Firefox 3.6 and older */\n}\n\n.vis.timeline .item.range .drag-left, .vis.timeline .item.rangeoverflow .drag-left {\n  cursor: w-resize;\n  z-index: 1000;\n}\n\n.vis.timeline .item.range .drag-right, .vis.timeline .item.rangeoverflow .drag-right {\n  cursor: e-resize;\n  z-index: 1000;\n}\n\n.vis.timeline .item.range .content, .vis.timeline .item.rangeoverflow .content {\n  position: relative;\n  display: inline-block;\n}\n\n.vis.timeline .item.line {\n  position: absolute;\n  width: 0;\n  border-left-width: 1px;\n  border-left-style: solid;\n}\n\n.vis.timeline .item .content {\n  margin: 5px;\n  white-space: nowrap;\n  overflow: hidden;\n}\n\n.vis.timeline .axis {\n  position: relative;\n}\n\n.vis.timeline .axis .text {\n  position: absolute;\n  color: #4d4d4d;\n  padding: 3px;\n  white-space: nowrap;\n}\n\n.vis.timeline .axis .text.measure {\n  position: absolute;\n  padding-left: 0;\n  padding-right: 0;\n  margin-left: 0;\n  margin-right: 0;\n  visibility: hidden;\n}\n\n.vis.timeline .axis .grid.vertical {\n  position: absolute;\n  width: 0;\n  border-right: 1px solid;\n}\n\n.vis.timeline .axis .grid.horizontal {\n  position: absolute;\n  left: 0;\n  width: 100%;\n  height: 0;\n  border-bottom: 1px solid;\n}\n\n.vis.timeline .axis .grid.minor {\n  border-color: 

},{"hammerjs":1,"moment":2}]},{},[3])
(3)
});
;