// utility functions

// first check if moment.js is already loaded in the browser window, if so,
// use this instance. Else, load via commonjs.
var Hammer = require('./module/hammer');
var moment = require('./module/moment');

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

/**
 * Test whether given object is a string
 * @param {*} object
 * @return {Boolean} isString
 */
exports.isString = function(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
 */
exports.isDate = function(object) {
  if (object instanceof Date) {
    return true;
  }
  else if (exports.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
 */
exports.isDataTable = function(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
 */
exports.randomUUID = function() {
  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
 */
exports.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)) {
        a[prop] = other[prop];
      }
    }
  }

  return a;
};

/**
 * Extend object a with selected properties of object b or a series of objects
 * Only properties with defined values are copied
 * @param {Array.<String>} props
 * @param {Object} a
 * @param {... Object} b
 * @return {Object} a
 */
exports.selectiveExtend = function (props, a, b) {
  if (!Array.isArray(props)) {
    throw new Error('Array with property names expected as first argument');
  }

  for (var i = 2; i < arguments.length; i++) {
    var other = arguments[i];

    for (var p = 0; p < props.length; p++) {
      var prop = props[p];
      if (other.hasOwnProperty(prop)) {
        a[prop] = other[prop];
      }
    }
  }
  return a;
};

/**
 * Extend object a with selected properties of object b or a series of objects
 * Only properties with defined values are copied
 * @param {Array.<String>} props
 * @param {Object} a
 * @param {... Object} b
 * @return {Object} a
 */
exports.selectiveDeepExtend = function (props, a, b) {
  // TODO: add support for Arrays to deepExtend
  if (Array.isArray(b)) {
    throw new TypeError('Arrays are not supported by deepExtend');
  }
  for (var i = 2; i < arguments.length; i++) {
    var other = arguments[i];
    for (var p = 0; p < props.length; p++) {
      var prop = props[p];
      if (other.hasOwnProperty(prop)) {
        if (b[prop] && b[prop].constructor === Object) {
          if (a[prop] === undefined) {
            a[prop] = {};
          }
          if (a[prop].constructor === Object) {
            exports.deepExtend(a[prop], b[prop]);
          }
          else {
            a[prop] = b[prop];
          }
        } else if (Array.isArray(b[prop])) {
          throw new TypeError('Arrays are not supported by deepExtend');
        } else {
          a[prop] = b[prop];
        }

      }
    }
  }
  return a;
};

/**
 * Deep extend an object a with the properties of object b
 * @param {Object} a
 * @param {Object} b
 * @returns {Object}
 */
exports.deepExtend = function(a, b) {
  // TODO: add support for Arrays to deepExtend
  if (Array.isArray(b)) {
    throw new TypeError('Arrays are not supported by deepExtend');
  }

  for (var prop in b) {
    if (b.hasOwnProperty(prop)) {
      if (b[prop] && b[prop].constructor === Object) {
        if (a[prop] === undefined) {
          a[prop] = {};
        }
        if (a[prop].constructor === Object) {
          exports.deepExtend(a[prop], b[prop]);
        }
        else {
          a[prop] = b[prop];
        }
      } else if (Array.isArray(b[prop])) {
        throw new TypeError('Arrays are not supported by deepExtend');
      } else {
        a[prop] = b[prop];
      }
    }
  }
  return a;
};

/**
 * Test whether all elements in two arrays are equal.
 * @param {Array} a
 * @param {Array} b
 * @return {boolean} Returns true if both arrays have the same length and same
 *                   elements.
 */
exports.equalArray = function (a, b) {
  if (a.length != b.length) return false;

  for (var i = 0, len = a.length; i < len; i++) {
    if (a[i] != b[i]) return false;
  }

  return true;
};

/**
 * 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
 */
exports.convert = function(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 (exports.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 (exports.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 ' + exports.getType(object) +
                ' to type Date');
      }

    case 'Moment':
      if (exports.isNumber(object)) {
        return moment(object);
      }
      if (object instanceof Date) {
        return moment(object.valueOf());
      }
      else if (moment.isMoment(object)) {
        return moment(object);
      }
      if (exports.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 ' + exports.getType(object) +
                ' to type Date');
      }

    case 'ISODate':
      if (exports.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 (exports.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 ' + exports.getType(object) +
                ' to type ISODate');
      }

    case 'ASPDate':
      if (exports.isNumber(object)) {
        return '/Date(' + object + ')/';
      }
      else if (object instanceof Date) {
        return '/Date(' + object.valueOf() + ')/';
      }
      else if (exports.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 ' + exports.getType(object) +
                ' to type ASPDate');
      }

    default:
      throw new Error('Unknown 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 exports.getType([]) returns 'Array'
 * @param {*} object
 * @return {String} type
 */
exports.getType = function(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.
 */
exports.getAbsoluteLeft = function(elem) {
  return elem.getBoundingClientRect().left + window.pageXOffset;
};

/**
 * 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.
 */
exports.getAbsoluteTop = function(elem) {
  return elem.getBoundingClientRect().top + window.pageYOffset;
};

/**
 * add a className to the given elements style
 * @param {Element} elem
 * @param {String} className
 */
exports.addClassName = function(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
 */
exports.removeClassName = function(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)
 */
exports.forEach = function(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);
      }
    }
  }
};

/**
 * Convert an object into an array: all objects properties are put into the
 * array. The resulting array is unordered.
 * @param {Object} object
 * @param {Array} array
 */
exports.toArray = function(object) {
  var array = [];

  for (var prop in object) {
    if (object.hasOwnProperty(prop)) array.push(object[prop]);
  }

  return array;
}

/**
 * Update a property in an object
 * @param {Object} object
 * @param {String} key
 * @param {*} value
 * @return {Boolean} changed
 */
exports.updateProperty = function(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]
 */
exports.addEventListener = function(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]
 */
exports.removeEventListener = function(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);
  }
};

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

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

/**
 * Get HTML element which is the target of the event
 * @param {Event} event
 * @return {Element} target element
 */
exports.getTarget = function(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;
};

/**
 * Fake a hammer.js gesture. Event can be a ScrollEvent or MouseMoveEvent
 * @param {Element} element
 * @param {Event} event
 */
exports.fakeGesture = function(element, event) {
  var eventType = null;

  // for hammer.js 1.0.5
  var gesture = Hammer.event.collectEventData(this, eventType, event);

  // for hammer.js 1.0.6
  //var touches = Hammer.event.getTouchList(event, eventType);
  // var gesture = Hammer.event.collectEventData(this, eventType, touches, event);

  // on IE in standards mode, no touches are recognized by hammer.js,
  // resulting in NaN values for center.pageX and center.pageY
  if (isNaN(gesture.center.pageX)) {
    gesture.center.pageX = event.pageX;
  }
  if (isNaN(gesture.center.pageY)) {
    gesture.center.pageY = event.pageY;
  }

  return gesture;
};

exports.option = {};

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

  if (exports.isString(value)) {
    return value;
  }
  else if (exports.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
 */
exports.option.asElement = function (value, defaultValue) {
  if (typeof value == 'function') {
    value = value();
  }

  return value || defaultValue || null;
};



exports.GiveDec = function(Hex) {
  var Value;

  if (Hex == "A")
    Value = 10;
  else if (Hex == "B")
    Value = 11;
  else if (Hex == "C")
    Value = 12;
  else if (Hex == "D")
    Value = 13;
  else if (Hex == "E")
    Value = 14;
  else if (Hex == "F")
    Value = 15;
  else
    Value = eval(Hex);

  return Value;
};

exports.GiveHex = function(Dec) {
  var Value;

  if(Dec == 10)
    Value = "A";
  else if (Dec == 11)
    Value = "B";
  else if (Dec == 12)
    Value = "C";
  else if (Dec == 13)
    Value = "D";
  else if (Dec == 14)
    Value = "E";
  else if (Dec == 15)
    Value = "F";
  else
    Value = "" + Dec;

  return Value;
};

/**
 * Parse a color property into an object with border, background, and
 * highlight colors
 * @param {Object | String} color
 * @return {Object} colorObject
 */
exports.parseColor = function(color) {
  var c;
  if (exports.isString(color)) {
    if (exports.isValidHex(color)) {
      var hsv = exports.hexToHSV(color);
      var lighterColorHSV = {h:hsv.h,s:hsv.s * 0.45,v:Math.min(1,hsv.v * 1.05)};
      var darkerColorHSV  = {h:hsv.h,s:Math.min(1,hsv.v * 1.25),v:hsv.v*0.6};
      var darkerColorHex  = exports.HSVToHex(darkerColorHSV.h ,darkerColorHSV.h ,darkerColorHSV.v);
      var lighterColorHex = exports.HSVToHex(lighterColorHSV.h,lighterColorHSV.s,lighterColorHSV.v);

      c = {
        background: color,
        border:darkerColorHex,
        highlight: {
          background:lighterColorHex,
          border:darkerColorHex
        },
        hover: {
          background:lighterColorHex,
          border:darkerColorHex
        }
      };
    }
    else {
      c = {
        background:color,
        border:color,
        highlight: {
          background:color,
          border:color
        },
        hover: {
          background:color,
          border:color
        }
      };
    }
  }
  else {
    c = {};
    c.background = color.background || 'white';
    c.border = color.border || c.background;

    if (exports.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;
    }

    if (exports.isString(color.hover)) {
      c.hover = {
        border: color.hover,
        background: color.hover
      }
    }
    else {
      c.hover = {};
      c.hover.background = color.hover && color.hover.background || c.background;
      c.hover.border = color.hover && color.hover.border || c.border;
    }
  }

  return c;
};

/**
 * http://www.yellowpipe.com/yis/tools/hex-to-rgb/color-converter.php
 *
 * @param {String} hex
 * @returns {{r: *, g: *, b: *}}
 */
exports.hexToRGB = function(hex) {
  hex = hex.replace("#","").toUpperCase();

  var a = exports.GiveDec(hex.substring(0, 1));
  var b = exports.GiveDec(hex.substring(1, 2));
  var c = exports.GiveDec(hex.substring(2, 3));
  var d = exports.GiveDec(hex.substring(3, 4));
  var e = exports.GiveDec(hex.substring(4, 5));
  var f = exports.GiveDec(hex.substring(5, 6));

  var r = (a * 16) + b;
  var g = (c * 16) + d;
  var b = (e * 16) + f;

  return {r:r,g:g,b:b};
};

exports.RGBToHex = function(red,green,blue) {
  var a = exports.GiveHex(Math.floor(red / 16));
  var b = exports.GiveHex(red % 16);
  var c = exports.GiveHex(Math.floor(green / 16));
  var d = exports.GiveHex(green % 16);
  var e = exports.GiveHex(Math.floor(blue / 16));
  var f = exports.GiveHex(blue % 16);

  var hex = a + b + c + d + e + f;
  return "#" + hex;
};


/**
 * http://www.javascripter.net/faq/rgb2hsv.htm
 *
 * @param red
 * @param green
 * @param blue
 * @returns {*}
 * @constructor
 */
exports.RGBToHSV = function(red,green,blue) {
  red=red/255; green=green/255; blue=blue/255;
  var minRGB = Math.min(red,Math.min(green,blue));
  var maxRGB = Math.max(red,Math.max(green,blue));

  // Black-gray-white
  if (minRGB == maxRGB) {
    return {h:0,s:0,v:minRGB};
  }

  // Colors other than black-gray-white:
  var d = (red==minRGB) ? green-blue : ((blue==minRGB) ? red-green : blue-red);
  var h = (red==minRGB) ? 3 : ((blue==minRGB) ? 1 : 5);
  var hue = 60*(h - d/(maxRGB - minRGB))/360;
  var saturation = (maxRGB - minRGB)/maxRGB;
  var value = maxRGB;
  return {h:hue,s:saturation,v:value};
};


/**
 * https://gist.github.com/mjijackson/5311256
 * @param hue
 * @param saturation
 * @param value
 * @returns {{r: number, g: number, b: number}}
 * @constructor
 */
exports.HSVToRGB = function(h, s, v) {
  var r, g, b;

  var i = Math.floor(h * 6);
  var f = h * 6 - i;
  var p = v * (1 - s);
  var q = v * (1 - f * s);
  var t = v * (1 - (1 - f) * s);

  switch (i % 6) {
    case 0: r = v, g = t, b = p; break;
    case 1: r = q, g = v, b = p; break;
    case 2: r = p, g = v, b = t; break;
    case 3: r = p, g = q, b = v; break;
    case 4: r = t, g = p, b = v; break;
    case 5: r = v, g = p, b = q; break;
  }

  return {r:Math.floor(r * 255), g:Math.floor(g * 255), b:Math.floor(b * 255) };
};

exports.HSVToHex = function(h, s, v) {
  var rgb = exports.HSVToRGB(h, s, v);
  return exports.RGBToHex(rgb.r, rgb.g, rgb.b);
};

exports.hexToHSV = function(hex) {
  var rgb = exports.hexToRGB(hex);
  return exports.RGBToHSV(rgb.r, rgb.g, rgb.b);
};

exports.isValidHex = function(hex) {
  var isOk = /(^#[0-9A-F]{6}$)|(^#[0-9A-F]{3}$)/i.test(hex);
  return isOk;
};


/**
 * This recursively redirects the prototype of JSON objects to the referenceObject
 * This is used for default options.
 *
 * @param referenceObject
 * @returns {*}
 */
exports.selectiveBridgeObject = function(fields, referenceObject) {
  if (typeof referenceObject == "object") {
    var objectTo = Object.create(referenceObject);
    for (var i = 0; i < fields.length; i++) {
      if (referenceObject.hasOwnProperty(fields[i])) {
        if (typeof referenceObject[fields[i]] == "object") {
          objectTo[fields[i]] = exports.bridgeObject(referenceObject[fields[i]]);
        }
      }
    }
    return objectTo;
  }
  else {
    return null;
  }
};

/**
 * This recursively redirects the prototype of JSON objects to the referenceObject
 * This is used for default options.
 *
 * @param referenceObject
 * @returns {*}
 */
exports.bridgeObject = function(referenceObject) {
  if (typeof referenceObject == "object") {
    var objectTo = Object.create(referenceObject);
    for (var i in referenceObject) {
      if (referenceObject.hasOwnProperty(i)) {
        if (typeof referenceObject[i] == "object") {
          objectTo[i] = exports.bridgeObject(referenceObject[i]);
        }
      }
    }
    return objectTo;
  }
  else {
    return null;
  }
};


/**
 * this is used to set the options of subobjects in the options object. A requirement of these subobjects
 * is that they have an 'enabled' element which is optional for the user but mandatory for the program.
 *
 * @param [object] mergeTarget | this is either this.options or the options used for the groups.
 * @param [object] options     | options
 * @param [String] option      | this is the option key in the options argument
 * @private
 */
exports.mergeOptions = function (mergeTarget, options, option) {
  if (options[option] !== undefined) {
    if (typeof options[option] == 'boolean') {
      mergeTarget[option].enabled = options[option];
    }
    else {
      mergeTarget[option].enabled = true;
      for (prop in options[option]) {
        if (options[option].hasOwnProperty(prop)) {
          mergeTarget[option][prop] = options[option][prop];
        }
      }
    }
  }
}


/**
 * this is used to set the options of subobjects in the options object. A requirement of these subobjects
 * is that they have an 'enabled' element which is optional for the user but mandatory for the program.
 *
 * @param [object] mergeTarget | this is either this.options or the options used for the groups.
 * @param [object] options     | options
 * @param [String] option      | this is the option key in the options argument
 * @private
 */
exports.mergeOptions = function (mergeTarget, options, option) {
  if (options[option] !== undefined) {
    if (typeof options[option] == 'boolean') {
      mergeTarget[option].enabled = options[option];
    }
    else {
      mergeTarget[option].enabled = true;
      for (prop in options[option]) {
        if (options[option].hasOwnProperty(prop)) {
          mergeTarget[option][prop] = options[option][prop];
        }
      }
    }
  }
}




/**
 * This function does a binary search for a visible item. The user can select either the this.orderedItems.byStart or .byEnd
 * arrays. This is done by giving a boolean value true if you want to use the byEnd.
 * This is done to be able to select the correct if statement (we do not want to check if an item is visible, we want to check
 * if the time we selected (start or end) is within the current range).
 *
 * The trick is that every interval has to either enter the screen at the initial load or by dragging. The case of the ItemRange that is
 * before and after the current range is handled by simply checking if it was in view before and if it is again. For all the rest,
 * either the start OR end time has to be in the range.
 *
 * @param {Item[]} orderedItems  Items ordered by start
 * @param {{start: number, end: number}} range
 * @param {String} field
 * @param {String} field2
 * @returns {number}
 * @private
 */
exports.binarySearch = function(orderedItems, range, field, field2) {
  var array = orderedItems;

  var maxIterations = 10000;
  var iteration = 0;
  var found = false;
  var low = 0;
  var high = array.length;
  var newLow = low;
  var newHigh = high;
  var guess = Math.floor(0.5*(high+low));
  var value;

  if (high == 0) {
    guess = -1;
  }
  else if (high == 1) {
    if (array[guess].isVisible(range)) {
      guess =  0;
    }
    else {
      guess = -1;
    }
  }
  else {
    high -= 1;

    while (found == false && iteration < maxIterations) {
      value = field2 === undefined ? array[guess][field] : array[guess][field][field2];

      if (array[guess].isVisible(range)) {
        found = true;
      }
      else {
        if (value < range.start) { // it is too small --> increase low
          newLow = Math.floor(0.5*(high+low));
        }
        else {  // it is too big --> decrease high
          newHigh = Math.floor(0.5*(high+low));
        }
        // not in list;
        if (low == newLow && high == newHigh) {
          guess = -1;
          found = true;
        }
        else {
          high = newHigh; low = newLow;
          guess = Math.floor(0.5*(high+low));
        }
      }
      iteration++;
    }
    if (iteration >= maxIterations) {
      console.log("BinarySearch too many iterations. Aborting.");
    }
  }
  return guess;
};

/**
 * This function does a binary search for a visible item. The user can select either the this.orderedItems.byStart or .byEnd
 * arrays. This is done by giving a boolean value true if you want to use the byEnd.
 * This is done to be able to select the correct if statement (we do not want to check if an item is visible, we want to check
 * if the time we selected (start or end) is within the current range).
 *
 * The trick is that every interval has to either enter the screen at the initial load or by dragging. The case of the ItemRange that is
 * before and after the current range is handled by simply checking if it was in view before and if it is again. For all the rest,
 * either the start OR end time has to be in the range.
 *
 * @param {Array} orderedItems
 * @param {{start: number, end: number}} target
 * @param {String} field
 * @param {String} sidePreference   'before' or 'after'
 * @returns {number}
 * @private
 */
exports.binarySearchGeneric = function(orderedItems, target, field, sidePreference) {
  var maxIterations = 10000;
  var iteration = 0;
  var array = orderedItems;
  var found = false;
  var low = 0;
  var high = array.length;
  var newLow = low;
  var newHigh = high;
  var guess = Math.floor(0.5*(high+low));
  var newGuess;
  var prevValue, value, nextValue;

  if (high == 0) {guess = -1;}
  else if (high == 1) {
    value = array[guess][field];
    if (value == target) {
      guess =  0;
    }
    else {
      guess = -1;
    }
  }
  else {
    high -= 1;
    while (found == false && iteration < maxIterations) {
      prevValue = array[Math.max(0,guess - 1)][field];
      value = array[guess][field];
      nextValue = array[Math.min(array.length-1,guess + 1)][field];

      if (value == target || prevValue < target && value > target || value < target && nextValue > target) {
        found = true;
        if (value != target) {
          if (sidePreference == 'before') {
            if (prevValue < target && value > target) {
              guess = Math.max(0,guess - 1);
            }
          }
          else {
            if (value < target && nextValue > target) {
              guess = Math.min(array.length-1,guess + 1);
            }
          }
        }
      }
      else {
        if (value < target) { // it is too small --> increase low
          newLow = Math.floor(0.5*(high+low));
        }
        else {  // it is too big --> decrease high
          newHigh = Math.floor(0.5*(high+low));
        }
        newGuess = Math.floor(0.5*(high+low));
        // not in list;
        if (low == newLow && high == newHigh) {
          guess = -1;
          found = true;
        }
        else {
          high = newHigh; low = newLow;
          guess = Math.floor(0.5*(high+low));
        }
      }
      iteration++;
    }
    if (iteration >= maxIterations) {
      console.log("BinarySearch too many iterations. Aborting.");
    }
  }
  return guess;
};