var Emitter = require('emitter-component');
var Hammer = require('../module/hammer');
var keycharm = require('keycharm');
var util = require('../util');
var hammerUtil = require('../hammerUtil');
var DataSet = require('../DataSet');
var DataView = require('../DataView');
var dotparser = require('./dotparser');
var gephiParser = require('./gephiParser');
var Groups = require('./Groups');
var Images = require('./Images');
var Node = require('./Node');
var Edge = require('./Edge');
var Popup = require('./Popup');
var MixinLoader = require('./mixins/MixinLoader');
var Activator = require('../shared/Activator');
var locales = require('./locales');

// Load custom shapes into CanvasRenderingContext2D
require('./shapes');

/**
 * @constructor Network
 * Create a network visualization, displaying nodes and edges.
 *
 * @param {Element} container   The DOM element in which the Network will
 *                                  be created. Normally a div element.
 * @param {Object} data         An object containing parameters
 *                              {Array} nodes
 *                              {Array} edges
 * @param {Object} options      Options
 */
function Network (container, data, options) {
  if (!(this instanceof Network)) {
    throw new SyntaxError('Constructor must be called with the new operator');
  }

  this._determineBrowserMethod();
  this._initializeMixinLoaders();

  // create variables and set default values
  this.containerElement = container;

  // render and calculation settings
  this.renderRefreshRate = 60;                         // hz (fps)
  this.renderTimestep = 1000 / this.renderRefreshRate; // ms -- saves calculation later on
  this.renderTime = 0;                                 // measured time it takes to render a frame
  this.physicsTime = 0;                                // measured time it takes to render a frame
  this.runDoubleSpeed = false;
  this.physicsDiscreteStepsize = 0.50;                 // discrete stepsize of the simulation

  this.initializing = true;

  this.triggerFunctions = {add:null,edit:null,editEdge:null,connect:null,del:null};

  var customScalingFunction = function (min,max,total,value) {
    if (max == min) {
      return 0.5;
    }
    else {
      var scale = 1 / (max - min);
      return Math.max(0,(value - min)*scale);
    }
  };
  // set constant values
  this.defaultOptions = {
    nodes: {
      customScalingFunction: customScalingFunction,
      mass: 1,
      radiusMin: 10,
      radiusMax: 30,
      radius: 10,
      shape: 'ellipse',
      image: undefined,
      widthMin: 16, // px
      widthMax: 64, // px
      fontColor: 'black',
      fontSize: 14, // px
      fontFace: 'verdana',
      fontFill: undefined,
      fontStrokeWidth: 0, // px
      fontStrokeColor: '#ffffff',
      fontDrawThreshold: 3,
      scaleFontWithValue: false,
      fontSizeMin: 14,
      fontSizeMax: 30,
      fontSizeMaxVisible: 30,
      level: -1,
      color: {
          border: '#2B7CE9',
          background: '#97C2FC',
        highlight: {
          border: '#2B7CE9',
          background: '#D2E5FF'
        },
        hover: {
          border: '#2B7CE9',
          background: '#D2E5FF'
        }
      },
      group: undefined,
      borderWidth: 1,
      borderWidthSelected: undefined
    },
    edges: {
      customScalingFunction: customScalingFunction,
      widthMin: 1, //
      widthMax: 15,//
      width: 1,
      widthSelectionMultiplier: 2,
      hoverWidth: 1.5,
      style: 'line',
      color: {
        color:'#848484',
        highlight:'#848484',
        hover: '#848484'
      },
      opacity:1.0,
      fontColor: '#343434',
      fontSize: 14, // px
      fontFace: 'arial',
      fontFill: 'white',
      fontStrokeWidth: 0, // px
      fontStrokeColor: 'white',
      labelAlignment:'horizontal',
      arrowScaleFactor: 1,
      dash: {
        length: 10,
        gap: 5,
        altLength: undefined
      },
      inheritColor: "from", // to, from, false, true (== from)
      useGradients: false // release in 4.0
    },
    configurePhysics:false,
    physics: {
      barnesHut: {
        enabled: true,
        thetaInverted: 1 / 0.5, // inverted to save time during calculation
        gravitationalConstant: -2000,
        centralGravity: 0.3,
        springLength: 95,
        springConstant: 0.04,
        damping: 0.09
      },
      repulsion: {
        centralGravity: 0.0,
        springLength: 200,
        springConstant: 0.05,
        nodeDistance: 100,
        damping: 0.09
      },
      hierarchicalRepulsion: {
        enabled: false,
        centralGravity: 0.0,
        springLength: 100,
        springConstant: 0.01,
        nodeDistance: 150,
        damping: 0.09
      },
      damping: null,
      centralGravity: null,
      springLength: null,
      springConstant: null
    },
    clustering: {                   // Per Node in Cluster = PNiC
      enabled: false,               // (Boolean)             | global on/off switch for clustering.
      initialMaxNodes: 100,         // (# nodes)             | if the initial amount of nodes is larger than this, we cluster until the total number is less than this threshold.
      clusterThreshold:500,         // (# nodes)             | during calculate forces, we check if the total number of nodes is larger than this. If it is, cluster until reduced to reduceToNodes
      reduceToNodes:300,            // (# nodes)             | during calculate forces, we check if the total number of nodes is larger than clusterThreshold. If it is, cluster until reduced to this
      chainThreshold: 0.4,          // (% of all drawn nodes)| maximum percentage of allowed chainnodes (long strings of connected nodes) within all nodes. (lower means less chains).
      clusterEdgeThreshold: 20,     // (px)                  | edge length threshold. if smaller, this node is clustered.
      sectorThreshold: 100,         // (# nodes in cluster)  | cluster size threshold. If larger, expanding in own sector.
      screenSizeThreshold: 0.2,     // (% of canvas)         | relative size threshold. If the width or height of a clusternode takes up this much of the screen, decluster node.
      fontSizeMultiplier: 4.0,      // (px PNiC)             | how much the cluster font size grows per node in cluster (in px).
      maxFontSize: 1000,
      forceAmplification: 0.1,      // (multiplier PNiC)     | factor of increase fo the repulsion force of a cluster (per node in cluster).
      distanceAmplification: 0.1,   // (multiplier PNiC)     | factor how much the repulsion distance of a cluster increases (per node in cluster).
      edgeGrowth: 20,               // (px PNiC)             | amount of clusterSize connected to the edge is multiplied with this and added to edgeLength.
      nodeScaling: {width:  1,      // (px PNiC)             | growth of the width  per node in cluster.
                    height: 1,      // (px PNiC)             | growth of the height per node in cluster.
                    radius: 1},     // (px PNiC)             | growth of the radius per node in cluster.
      maxNodeSizeIncrements: 600,   // (# increments)        | max growth of the width  per node in cluster.
      activeAreaBoxSize: 80,        // (px)                  | box area around the curser where clusters are popped open.
      clusterLevelDifference: 2,    // used for normalization of the cluster levels
      clusterByZoom: true           // enable clustering through zooming in and out
    },
    navigation: {
      enabled: false
    },
    keyboard: {
      enabled: false,
      speed: {x: 10, y: 10, zoom: 0.02},
      bindToWindow: true
    },
    dataManipulation: {
      enabled: false,
      initiallyVisible: false
    },
    hierarchicalLayout: {
      enabled:false,
      levelSeparation: 150,
      nodeSpacing: 100,
      direction: "UD",   // UD, DU, LR, RL
      layout: "hubsize" // hubsize, directed
    },
    freezeForStabilization: false,
    smoothCurves: {
      enabled: true,
      dynamic: true,
      type: "continuous",
      roundness: 0.5
    },
    maxVelocity:  50,
    minVelocity:  0.1,   // px/s
    stabilize: true,  // stabilize before displaying the network
    stabilizationIterations: 1000,  // maximum number of iteration to stabilize
    zoomExtentOnStabilize: true,
    locale: 'en',
    locales: locales,
    tooltip: {
      delay: 300,
      fontColor: 'black',
      fontSize: 14, // px
      fontFace: 'verdana',
      color: {
        border: '#666',
        background: '#FFFFC6'
      }
    },
    dragNetwork: true,
    dragNodes: true,
    zoomable: true,
    hover: false,
    hideEdgesOnDrag: false,
    hideNodesOnDrag: false,
    width : '100%',
    height : '100%',
    selectable: true,
    useDefaultGroups: true
  };
  this.constants = util.extend({}, this.defaultOptions);
  this.pixelRatio = 1;
  
  
  this.hoverObj = {nodes:{},edges:{}};
  this.controlNodesActive = false;
  this.navigationHammers = [];
  this.manipulationHammers = [];

  // animation properties
  this.animationSpeed = 1/this.renderRefreshRate;
  this.animationEasingFunction = "easeInOutQuint";
  this.animating = false;
  this.easingTime = 0;
  this.sourceScale = 0;
  this.targetScale = 0;
  this.sourceTranslation = 0;
  this.targetTranslation = 0;
  this.lockedOnNodeId = null;
  this.lockedOnNodeOffset = null;
  this.touchTime = 0;
  this.redrawRequested = false;

  // Node variables
  var network = this;
  this.groups = new Groups(); // object with groups
  this.images = new Images(); // object with images
  this.images.setOnloadCallback(function (status) {
    network._requestRedraw();
  });

  // keyboard navigation variables
  this.xIncrement = 0;
  this.yIncrement = 0;
  this.zoomIncrement = 0;

  // loading all the mixins:
  // load the force calculation functions, grouped under the physics system.
  this._loadPhysicsSystem();
  // create a frame and canvas
  this._create();
  // load the sector system.    (mandatory, fully integrated with Network)
  this._loadSectorSystem();
  // load the cluster system.   (mandatory, even when not using the cluster system, there are function calls to it)
  this._loadClusterSystem();
  // load the selection system. (mandatory, required by Network)
  this._loadSelectionSystem();
  // load the selection system. (mandatory, required by Network)
  this._loadHierarchySystem();


  // apply options
  this._setTranslation(this.frame.clientWidth / 2, this.frame.clientHeight / 2);
  this._setScale(1);
  this.setOptions(options);

  // other vars
  this.freezeSimulationEnabled = false;// freeze the simulation
  this.cachedFunctions = {};
  this.startedStabilization = false;
  this.stabilized = false;
  this.stabilizationIterations = null;
  this.draggingNodes = false;

  // containers for nodes and edges
  this.calculationNodes = {};
  this.calculationNodeIndices = [];
  this.nodeIndices = [];        // array with all the indices of the nodes. Used to speed up forces calculation
  this.nodes = {};              // object with Node objects
  this.edges = {};              // object with Edge objects

  // position and scale variables and objects
  this.canvasTopLeft     = {"x": 0,"y": 0};   // coordinates of the top left of the canvas.     they will be set during _redraw.
  this.canvasBottomRight = {"x": 0,"y": 0};   // coordinates of the bottom right of the canvas. they will be set during _redraw
  this.pointerPosition = {"x": 0,"y": 0};   // coordinates of the bottom right of the canvas. they will be set during _redraw
  this.areaCenter = {};               // object with x and y elements used for determining the center of the zoom action
  this.scale = 1;                     // defining the global scale variable in the constructor
  this.previousScale = this.scale;    // this is used to check if the zoom operation is zooming in or out

  // datasets or dataviews
  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
  this.nodesListeners = {
    'add': function (event, params) {
      network._addNodes(params.items);
      network.start();
    },
    'update': function (event, params) {
      network._updateNodes(params.items);
      network.start();
    },
    'remove': function (event, params) {
      network._removeNodes(params.items);
      network.start();
    }
  };
  this.edgesListeners = {
    'add': function (event, params) {
      network._addEdges(params.items);
      network.start();
    },
    'update': function (event, params) {
      network._updateEdges(params.items);
      network.start();
    },
    'remove': function (event, params) {
      network._removeEdges(params.items);
      network.start();
    }
  };

  // properties for the animation
  this.moving = true;
  this.timer = undefined; // Scheduling function. Is definded in this.start();

  // load data (the disable start variable will be the same as the enabled clustering)
  this.setData(data,this.constants.clustering.enabled || this.constants.hierarchicalLayout.enabled);

  // hierarchical layout
  this.initializing = false;
  if (this.constants.hierarchicalLayout.enabled == true) {
    this._setupHierarchicalLayout();
  }
  else {
    // zoom so all data will fit on the screen, if clustering is enabled, we do not want start to be called here.
    if (this.constants.stabilize == false) {
      this.zoomExtent({duration:0}, true, this.constants.clustering.enabled);
    }
  }

  // if clustering is disabled, the simulation will have started in the setData function
  if (this.constants.clustering.enabled) {
    this.startWithClustering();
  }
}

// Extend Network with an Emitter mixin
Emitter(Network.prototype);

/**
 * Determine if the browser requires a setTimeout or a requestAnimationFrame. This was required because
 * some implementations (safari and IE9) did not support requestAnimationFrame
 * @private
 */
Network.prototype._determineBrowserMethod = function() {
  var browserType = navigator.userAgent.toLowerCase();
  this.requiresTimeout = false;
  if (browserType.indexOf('msie 9.0') != -1) { // IE 9
    this.requiresTimeout = true;
  }
  else if (browserType.indexOf('safari') != -1) {  // safari
    if (browserType.indexOf('chrome') <= -1) {
      this.requiresTimeout = true;
    }
  }
}


/**
 * Get the script path where the vis.js library is located
 *
 * @returns {string | null} path   Path or null when not found. Path does not
 *                                 end with a slash.
 * @private
 */
Network.prototype._getScriptPath = function() {
  var scripts = document.getElementsByTagName( 'script' );

  // find script named vis.js or vis.min.js
  for (var i = 0; i < scripts.length; i++) {
    var src = scripts[i].src;
    var match = src && /\/?vis(.min)?\.js$/.exec(src);
    if (match) {
      // return path without the script name
      return src.substring(0, src.length - match[0].length);
    }
  }

  return null;
};


/**
 * Find the center position of the network
 * @private
 */
Network.prototype._getRange = function(specificNodes) {
  var minY = 1e9, maxY = -1e9, minX = 1e9, maxX = -1e9, node;
  if (specificNodes.length > 0) {
    for (var i = 0; i < specificNodes.length; i++) {
      node = this.nodes[specificNodes[i]];
      if (minX > (node.boundingBox.left)) {
        minX = node.boundingBox.left;
      }
      if (maxX < (node.boundingBox.right)) {
        maxX = node.boundingBox.right;
      }
      if (minY > (node.boundingBox.bottom)) {
        minY = node.boundingBox.top;
      } // top is negative, bottom is positive
      if (maxY < (node.boundingBox.top)) {
        maxY = node.boundingBox.bottom;
      } // top is negative, bottom is positive
    }
  }
  else {
    for (var nodeId in this.nodes) {
      if (this.nodes.hasOwnProperty(nodeId)) {
        node = this.nodes[nodeId];
        if (minX > (node.boundingBox.left)) {
          minX = node.boundingBox.left;
        }
        if (maxX < (node.boundingBox.right)) {
          maxX = node.boundingBox.right;
        }
        if (minY > (node.boundingBox.bottom)) {
          minY = node.boundingBox.top;
        } // top is negative, bottom is positive
        if (maxY < (node.boundingBox.top)) {
          maxY = node.boundingBox.bottom;
        } // top is negative, bottom is positive
      }
    }
  }

  if (minX == 1e9 && maxX == -1e9 && minY == 1e9 && maxY == -1e9) {
    minY = 0, maxY = 0, minX = 0, maxX = 0;
  }
  return {minX: minX, maxX: maxX, minY: minY, maxY: maxY};
};


/**
 * @param {object} range = {minX: minX, maxX: maxX, minY: minY, maxY: maxY};
 * @returns {{x: number, y: number}}
 * @private
 */
Network.prototype._findCenter = function(range) {
  return {x: (0.5 * (range.maxX + range.minX)),
          y: (0.5 * (range.maxY + range.minY))};
};


/**
 * This function zooms out to fit all data on screen based on amount of nodes
 *
 * @param {Boolean} [initialZoom]  | zoom based on fitted formula or range, true = fitted, default = false;
 * @param {Boolean} [disableStart] | If true, start is not called.
 */
Network.prototype.zoomExtent = function(options, initialZoom, disableStart) {
  this._redraw(true);

  if (initialZoom      === undefined) {initialZoom = false;}
  if (disableStart     === undefined) {disableStart = false;}
  if (options === undefined) {options = {nodes:[]};}
  if (options.nodes === undefined) {
    options.nodes = [];
  }

  var range;
  var zoomLevel;

  if (initialZoom == true) {
    // check if more than half of the nodes have a predefined position. If so, we use the range, not the approximation.
    var positionDefined = 0;
    for (var nodeId in this.nodes) {
      if (this.nodes.hasOwnProperty(nodeId)) {
        var node = this.nodes[nodeId];
        if (node.predefinedPosition == true) {
          positionDefined += 1;
        }
      }
    }
    if (positionDefined > 0.5 * this.nodeIndices.length) {
      this.zoomExtent(options,false,disableStart);
      return;
    }

    range = this._getRange(options.nodes);

    var numberOfNodes = this.nodeIndices.length;
    if (this.constants.smoothCurves == true) {
      if (this.constants.clustering.enabled == true &&
        numberOfNodes >= this.constants.clustering.initialMaxNodes) {
        zoomLevel = 49.07548 / (numberOfNodes + 142.05338) + 9.1444e-04; // this is obtained from fitting a dataset from 5 points with scale levels that looked good.
      }
      else {
        zoomLevel = 12.662 / (numberOfNodes + 7.4147) + 0.0964822; // this is obtained from fitting a dataset from 5 points with scale levels that looked good.
      }
    }
    else {
      if (this.constants.clustering.enabled == true &&
          numberOfNodes >= this.constants.clustering.initialMaxNodes) {
        zoomLevel = 77.5271985 / (numberOfNodes + 187.266146) + 4.76710517e-05; // this is obtained from fitting a dataset from 5 points with scale levels that looked good.
      }
      else {
        zoomLevel = 30.5062972 / (numberOfNodes + 19.93597763) + 0.08413486; // this is obtained from fitting a dataset from 5 points with scale levels that looked good.
      }
    }

    // correct for larger canvasses.
    var factor = Math.min(this.frame.canvas.clientWidth / 600, this.frame.canvas.clientHeight / 600);
    zoomLevel *= factor;
  }
  else {
    range = this._getRange(options.nodes);
    var xDistance = Math.abs(range.maxX - range.minX) * 1.1;
    var yDistance = Math.abs(range.maxY - range.minY) * 1.1;

    var xZoomLevel = this.frame.canvas.clientWidth  / xDistance;
    var yZoomLevel = this.frame.canvas.clientHeight / yDistance;
    zoomLevel = (xZoomLevel <= yZoomLevel) ? xZoomLevel : yZoomLevel;
  }

  if (zoomLevel > 1.0) {
    zoomLevel = 1.0;
  }


  var center = this._findCenter(range);
  if (disableStart == false) {
    var options = {position: center, scale: zoomLevel, animation: options};
    this.moveTo(options);
    this.moving = true;
    this.start();
  }
  else {
    center.x *= zoomLevel;
    center.y *= zoomLevel;
    center.x -= 0.5 * this.frame.canvas.clientWidth;
    center.y -= 0.5 * this.frame.canvas.clientHeight;
    this._setScale(zoomLevel);
    this._setTranslation(-center.x,-center.y);
  }
};


/**
 * Update the this.nodeIndices with the most recent node index list
 * @private
 */
Network.prototype._updateNodeIndexList = function() {
  this._clearNodeIndexList();
  for (var idx in this.nodes) {
    if (this.nodes.hasOwnProperty(idx)) {
      this.nodeIndices.push(idx);
    }
  }
};


/**
 * 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
 *                                   {String} [gephi] String containing data in gephi JSON format
 *                                   {Options} [options] Object with options
 * @param {Boolean} [disableStart]   | optional: disable the calling of the start function.
 */
Network.prototype.setData = function(data, disableStart) {
  if (disableStart === undefined) {
    disableStart = false;
  }

  // unselect all to ensure no selections from old data are carried over.
  this._unselectAll(true);

  // we set initializing to true to ensure that the hierarchical layout is not performed until both nodes and edges are added.
  this.initializing = true;

  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.');
  }

  // clean up in case there is anyone in an active mode of the manipulation. This is the same option as bound to the escape button.
  if (this.constants.dataManipulation.enabled == true) {
    this._createManipulatorBar();
  }

  // set options
  this.setOptions(data && data.options);
  // set all data
  if (data && data.dot) {
    // parse DOT file
    if(data && data.dot) {
      var dotData = dotparser.DOTToGraph(data.dot);
      this.setData(dotData);
      return;
    }
  }
  else if (data && data.gephi) {
    // parse DOT file
    if(data && data.gephi) {
      var gephiData = gephiParser.parseGephi(data.gephi);
      this.setData(gephiData);
      return;
    }
  }
  else {
    this._setNodes(data && data.nodes);
    this._setEdges(data && data.edges);
  }
  this._putDataInSector();
  if (disableStart == false) {
    if (this.constants.hierarchicalLayout.enabled == true) {
      this._resetLevels();
      this._setupHierarchicalLayout();
    }
    else {
      // find a stable position or start animating to a stable position
      if (this.constants.stabilize == true) {
        this._stabilize();
      }
    }
    this.start();
  }
  this.initializing = false;
};

/**
 * Set options
 * @param {Object} options
 */
Network.prototype.setOptions = function (options) {
  if (options) {
    var prop;
    var fields = ['nodes','edges','smoothCurves','hierarchicalLayout','clustering','navigation',
      'keyboard','dataManipulation','onAdd','onEdit','onEditEdge','onConnect','onDelete','clickToUse'
    ];
    // extend all but the values in fields
    util.selectiveNotDeepExtend(fields,this.constants, options);
    util.selectiveNotDeepExtend(['color'],this.constants.nodes, options.nodes);
    util.selectiveNotDeepExtend(['color','length'],this.constants.edges, options.edges);

    this.groups.useDefaultGroups = this.constants.useDefaultGroups;
    if (options.physics) {
      util.mergeOptions(this.constants.physics, options.physics,'barnesHut');
      util.mergeOptions(this.constants.physics, options.physics,'repulsion');

      if (options.physics.hierarchicalRepulsion) {
        this.constants.hierarchicalLayout.enabled = true;
        this.constants.physics.hierarchicalRepulsion.enabled = true;
        this.constants.physics.barnesHut.enabled = false;
        for (prop in options.physics.hierarchicalRepulsion) {
          if (options.physics.hierarchicalRepulsion.hasOwnProperty(prop)) {
            this.constants.physics.hierarchicalRepulsion[prop] = options.physics.hierarchicalRepulsion[prop];
          }
        }
      }
    }

    if (options.onAdd) {this.triggerFunctions.add = options.onAdd;}
    if (options.onEdit) {this.triggerFunctions.edit = options.onEdit;}
    if (options.onEditEdge) {this.triggerFunctions.editEdge = options.onEditEdge;}
    if (options.onConnect) {this.triggerFunctions.connect = options.onConnect;}
    if (options.onDelete) {this.triggerFunctions.del = options.onDelete;}

    util.mergeOptions(this.constants, options,'smoothCurves');
    util.mergeOptions(this.constants, options,'hierarchicalLayout');
    util.mergeOptions(this.constants, options,'clustering');
    util.mergeOptions(this.constants, options,'navigation');
    util.mergeOptions(this.constants, options,'keyboard');
    util.mergeOptions(this.constants, options,'dataManipulation');


    if (options.dataManipulation) {
      this.editMode = this.constants.dataManipulation.initiallyVisible;
    }


    // TODO: work out these options and document them
    if (options.edges) {
      if (options.edges.color !== undefined) {
        if (util.isString(options.edges.color)) {
          this.constants.edges.color = {};
          this.constants.edges.color.color = options.edges.color;
          this.constants.edges.color.highlight = options.edges.color;
          this.constants.edges.color.hover = options.edges.color;
        }
        else {
          if (options.edges.color.color !== undefined)     {this.constants.edges.color.color = options.edges.color.color;}
          if (options.edges.color.highlight !== undefined) {this.constants.edges.color.highlight = options.edges.color.highlight;}
          if (options.edges.color.hover !== undefined)     {this.constants.edges.color.hover = options.edges.color.hover;}
        }
        this.constants.edges.inheritColor = false;
      }

      if (!options.edges.fontColor) {
        if (options.edges.color !== undefined) {
          if (util.isString(options.edges.color))           {this.constants.edges.fontColor = options.edges.color;}
          else if (options.edges.color.color !== undefined) {this.constants.edges.fontColor = options.edges.color.color;}
        }
      }
    }

    if (options.nodes) {
      if (options.nodes.color) {
        var newColorObj = util.parseColor(options.nodes.color);
        this.constants.nodes.color.background = newColorObj.background;
        this.constants.nodes.color.border = newColorObj.border;
        this.constants.nodes.color.highlight.background = newColorObj.highlight.background;
        this.constants.nodes.color.highlight.border = newColorObj.highlight.border;
        this.constants.nodes.color.hover.background = newColorObj.hover.background;
        this.constants.nodes.color.hover.border = newColorObj.hover.border;
      }
    }
    if (options.groups) {
      for (var groupname in options.groups) {
        if (options.groups.hasOwnProperty(groupname)) {
          var group = options.groups[groupname];
          this.groups.add(groupname, group);
        }
      }
    }

    if (options.tooltip) {
      for (prop in options.tooltip) {
        if (options.tooltip.hasOwnProperty(prop)) {
          this.constants.tooltip[prop] = options.tooltip[prop];
        }
      }
      if (options.tooltip.color) {
        this.constants.tooltip.color = util.parseColor(options.tooltip.color);
      }
    }

    if ('clickToUse' in options) {
      if (options.clickToUse) {
        if (!this.activator) {
          this.activator = new Activator(this.frame);
          this.activator.on('change', this._createKeyBinds.bind(this));
        }
      }
      else {
        if (this.activator) {
          this.activator.destroy();
          delete this.activator;
        }
      }
    }

    if (options.labels) {
      throw new Error('Option "labels" is deprecated. Use options "locale" and "locales" instead.');
    }


    // (Re)loading the mixins that can be enabled or disabled in the options.
    // load the force calculation functions, grouped under the physics system.
    this._loadPhysicsSystem();
    // load the navigation system.
    this._loadNavigationControls();
    // load the data manipulation system
    this._loadManipulationSystem();
    // configure the smooth curves
    this._configureSmoothCurves();

    // bind hammer
    this._bindHammer();

    // bind keys. If disabled, this will not do anything;
    this._createKeyBinds();

    this._markAllEdgesAsDirty();
    this.setSize(this.constants.width, this.constants.height);
    this.moving = true;
    if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
      this._resetLevels();
      this._setupHierarchicalLayout();
    }
    this.start();
  }
};



/**
 * Create the main frame for the Network.
 * This function is executed once when a Network object is created. The frame
 * contains a canvas, and this canvas contains all objects like the axis and
 * nodes.
 * @private
 */
Network.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 = 'vis network-frame';
  this.frame.style.position = 'relative';
  this.frame.style.overflow = 'hidden';
  this.frame.tabIndex = 900;


//////////////////////////////////////////////////////////////////

  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);
  }
  else {
    var ctx = this.frame.canvas.getContext("2d");
    this.pixelRatio = (window.devicePixelRatio || 1) / (ctx.webkitBackingStorePixelRatio ||
              ctx.mozBackingStorePixelRatio ||
              ctx.msBackingStorePixelRatio ||
              ctx.oBackingStorePixelRatio ||
              ctx.backingStorePixelRatio || 1);

    //this.pixelRatio = Math.max(1,this.pixelRatio); // this is to account for browser zooming out. The pixel ratio is ment to switch between 1 and 2 for HD screens.
    this.frame.canvas.getContext("2d").setTransform(this.pixelRatio, 0, 0, this.pixelRatio, 0, 0);
  }

  this._bindHammer();
};


/**
 * This function binds hammer, it can be repeated over and over due to the uniqueness check.
 * @private
 */
Network.prototype._bindHammer = function() {
  var me = this;
  if (this.hammer !== undefined) {
    this.hammer.dispose();
  }
  this.drag = {};
  this.pinch = {};
  this.hammer = Hammer(this.frame.canvas, {
    prevent_default: true
  });
  this.hammer.on('tap',       me._onTap.bind(me) );
  this.hammer.on('doubletap', me._onDoubleTap.bind(me) );
  this.hammer.on('hold',      me._onHold.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) );

  if (this.constants.zoomable == true) {
    this.hammer.on('mousewheel',      me._onMouseWheel.bind(me));
    this.hammer.on('DOMMouseScroll',  me._onMouseWheel.bind(me)); // for FF
    this.hammer.on('pinch',           me._onPinch.bind(me) );
  }

  this.hammer.on('mousemove', me._onMouseMoveTitle.bind(me) );

  this.hammerFrame = Hammer(this.frame, {
    prevent_default: true
  });
  this.hammerFrame.on('release', me._onRelease.bind(me) );

  // add the frame to the container element
  this.containerElement.appendChild(this.frame);
}

/**
 * Binding the keys for keyboard navigation. These functions are defined in the NavigationMixin
 * @private
 */
Network.prototype._createKeyBinds = function() {
  var me = this;
  if (this.keycharm !== undefined) {
    this.keycharm.destroy();
  }

  if (this.constants.keyboard.bindToWindow == true) {
    this.keycharm = keycharm({container: window, preventDefault: false});
  }
  else {
    this.keycharm = keycharm({container: this.frame, preventDefault: false});
  }

  this.keycharm.reset();

  if (this.constants.keyboard.enabled && this.isActive()) {
    this.keycharm.bind("up",   this._moveUp.bind(me)   , "keydown");
    this.keycharm.bind("up",   this._yStopMoving.bind(me), "keyup");
    this.keycharm.bind("down", this._moveDown.bind(me) , "keydown");
    this.keycharm.bind("down", this._yStopMoving.bind(me), "keyup");
    this.keycharm.bind("left", this._moveLeft.bind(me) , "keydown");
    this.keycharm.bind("left", this._xStopMoving.bind(me), "keyup");
    this.keycharm.bind("right",this._moveRight.bind(me), "keydown");
    this.keycharm.bind("right",this._xStopMoving.bind(me), "keyup");
    this.keycharm.bind("=",    this._zoomIn.bind(me),    "keydown");
    this.keycharm.bind("=",    this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("num+", this._zoomIn.bind(me),    "keydown");
    this.keycharm.bind("num+", this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("num-", this._zoomOut.bind(me),   "keydown");
    this.keycharm.bind("num-", this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("-",    this._zoomOut.bind(me),   "keydown");
    this.keycharm.bind("-",    this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("[",    this._zoomIn.bind(me),    "keydown");
    this.keycharm.bind("[",    this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("]",    this._zoomOut.bind(me),   "keydown");
    this.keycharm.bind("]",    this._stopZoom.bind(me),    "keyup");
    this.keycharm.bind("pageup",this._zoomIn.bind(me),   "keydown");
    this.keycharm.bind("pageup",this._stopZoom.bind(me),   "keyup");
    this.keycharm.bind("pagedown",this._zoomOut.bind(me),"keydown");
    this.keycharm.bind("pagedown",this._stopZoom.bind(me), "keyup");
  }

  if (this.constants.dataManipulation.enabled == true) {
    this.keycharm.bind("esc",this._createManipulatorBar.bind(me));
    this.keycharm.bind("delete",this._deleteSelected.bind(me));
  }
};

/**
 * Cleans up all bindings of the network, removing it fully from the memory IF the variable is set to null after calling this function.
 * var network = new vis.Network(..);
 * network.destroy();
 * network = null;
 */
Network.prototype.destroy = function() {
  this.start = function () {};
  this.redraw = function () {};
  this.timer = false;

  // cleanup physicsConfiguration if it exists
  this._cleanupPhysicsConfiguration();

  // remove keybindings
  this.keycharm.reset();

  // clear hammer bindings
  this.hammer.dispose();

  // clear events
  this.off();

  this._recursiveDOMDelete(this.containerElement);
}

Network.prototype._recursiveDOMDelete = function(DOMobject) {
  while (DOMobject.hasChildNodes() == true) {
    this._recursiveDOMDelete(DOMobject.firstChild);
    DOMobject.removeChild(DOMobject.firstChild);
  }
}

/**
 * Get the pointer location from a touch location
 * @param {{pageX: Number, pageY: Number}} touch
 * @return {{x: Number, y: Number}} pointer
 * @private
 */
Network.prototype._getPointer = function (touch) {
  return {
    x: touch.pageX - util.getAbsoluteLeft(this.frame.canvas),
    y: touch.pageY - util.getAbsoluteTop(this.frame.canvas)
  };
};

/**
 * On start of a touch gesture, store the pointer
 * @param event
 * @private
 */
Network.prototype._onTouch = function (event) {
  if (new Date().valueOf() - this.touchTime > 100) {
    this.drag.pointer = this._getPointer(event.gesture.center);
    this.drag.pinched = false;
    this.pinch.scale = this._getScale();

    // to avoid double fireing of this event because we have two hammer instances. (on canvas and on frame)
    this.touchTime = new Date().valueOf();

    this._handleTouch(this.drag.pointer);
  }
};

/**
 * handle drag start event
 * @private
 */
Network.prototype._onDragStart = function (event) {
  this._handleDragStart(event);
};


/**
 * This function is called by _onDragStart.
 * It is separated out because we can then overload it for the datamanipulation system.
 *
 * @private
 */
Network.prototype._handleDragStart = function(event) {
  // in case the touch event was triggered on an external div, do the initial touch now.
  if (this.drag.pointer === undefined) {
    this._onTouch(event);
  }

  var node = this._getNodeAt(this.drag.pointer);
  // note: drag.pointer is set in _onTouch to get the initial touch location

  this.drag.dragging = true;
  this.drag.selection = [];
  this.drag.translation = this._getTranslation();
  this.drag.nodeId = null;
  this.draggingNodes = false;

  if (node != null && this.constants.dragNodes == true) {
    this.draggingNodes = true;
    this.drag.nodeId = node.id;
    // select the clicked node if not yet selected
    if (!node.isSelected()) {
      this._selectObject(node,false);
    }

    this.emit("dragStart",{nodeIds:this.getSelection().nodes});

    // create an array with the selected nodes and their original location and status
    for (var objectId in this.selectionObj.nodes) {
      if (this.selectionObj.nodes.hasOwnProperty(objectId)) {
        var object = this.selectionObj.nodes[objectId];
        var s = {
          id: object.id,
          node: object,

          // store original x, y, xFixed and yFixed, make the node temporarily Fixed
          x: object.x,
          y: object.y,
          xFixed: object.xFixed,
          yFixed: object.yFixed
        };

        object.xFixed = true;
        object.yFixed = true;

        this.drag.selection.push(s);
      }
    }
  }
};


/**
 * handle drag event
 * @private
 */
Network.prototype._onDrag = function (event) {
  this._handleOnDrag(event)
};


/**
 * This function is called by _onDrag.
 * It is separated out because we can then overload it for the datamanipulation system.
 *
 * @private
 */
Network.prototype._handleOnDrag = function(event) {
  if (this.drag.pinched) {
    return;
  }

  // remove the focus on node if it is focussed on by the focusOnNode
  this.releaseNode();

  var pointer = this._getPointer(event.gesture.center);
  var me = this;
  var drag = this.drag;
  var selection = drag.selection;
  if (selection && selection.length && this.constants.dragNodes == true) {
    // calculate delta's and new location
    var deltaX = pointer.x - drag.pointer.x;
    var 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._XconvertDOMtoCanvas(me._XconvertCanvasToDOM(s.x) + deltaX);
      }

      if (!s.yFixed) {
        node.y = me._YconvertDOMtoCanvas(me._YconvertCanvasToDOM(s.y) + deltaY);
      }
    });


    // start _animationStep if not yet running
    if (!this.moving) {
      this.moving = true;
      this.start();
    }
  }
  else {
    // move the network
    if (this.constants.dragNetwork == true) {
      // if the drag was not started properly because the click started outside the network div, start it now.
      if (this.drag.pointer === undefined) {
        this._handleDragStart(event);
        return;
      }
      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();
    }
  }
};

/**
 * handle drag start event
 * @private
 */
Network.prototype._onDragEnd = function (event) {
  this._handleDragEnd(event);
};


Network.prototype._handleDragEnd = function(event) {
  this.drag.dragging = false;
  var selection = this.drag.selection;
  if (selection && selection.length) {
    selection.forEach(function (s) {
      // restore original xFixed and yFixed
      s.node.xFixed = s.xFixed;
      s.node.yFixed = s.yFixed;
    });
    this.moving = true;
    this.start();
  }
  else {
    this._redraw();
  }
  if (this.draggingNodes == false) {
    this.emit("dragEnd",{nodeIds:[]});
  }
  else {
    this.emit("dragEnd",{nodeIds:this.getSelection().nodes});
  }

}
/**
 * handle tap/click event: select/unselect a node
 * @private
 */
Network.prototype._onTap = function (event) {
  var pointer = this._getPointer(event.gesture.center);
  this.pointerPosition = pointer;
  this._handleTap(pointer);

};


/**
 * handle doubletap event
 * @private
 */
Network.prototype._onDoubleTap = function (event) {
  var pointer = this._getPointer(event.gesture.center);
  this._handleDoubleTap(pointer);
};


/**
 * handle long tap event: multi select nodes
 * @private
 */
Network.prototype._onHold = function (event) {
  var pointer = this._getPointer(event.gesture.center);
  this.pointerPosition = pointer;
  this._handleOnHold(pointer);
};

/**
 * handle the release of the screen
 *
 * @private
 */
Network.prototype._onRelease = function (event) {
  var pointer = this._getPointer(event.gesture.center);
  this._handleOnRelease(pointer);
};

/**
 * Handle pinch event
 * @param event
 * @private
 */
Network.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: enabled moving while pinching?
  var scale = this.pinch.scale * event.gesture.scale;
  this._zoom(scale, pointer)
};

/**
 * Zoom the network in or out
 * @param {Number} scale a number around 1, and between 0.01 and 10
 * @param {{x: Number, y: Number}} pointer    Position on screen
 * @return {Number} appliedScale    scale is limited within the boundaries
 * @private
 */
Network.prototype._zoom = function(scale, pointer) {
  if (this.constants.zoomable == true) {
    var scaleOld = this._getScale();
    if (scale < 0.00001) {
      scale = 0.00001;
    }
    if (scale > 10) {
      scale = 10;
    }

    var preScaleDragPointer = null;
    if (this.drag !== undefined) {
      if (this.drag.dragging == true) {
        preScaleDragPointer = this.DOMtoCanvas(this.drag.pointer);
      }
    }
  // + this.frame.canvas.clientHeight / 2
    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.areaCenter = {"x" : this._XconvertDOMtoCanvas(pointer.x),
                       "y" : this._YconvertDOMtoCanvas(pointer.y)};

    this._setScale(scale);
    this._setTranslation(tx, ty);
    this.updateClustersDefault();

    if (preScaleDragPointer != null) {
      var postScaleDragPointer = this.canvasToDOM(preScaleDragPointer);
      this.drag.pointer.x = postScaleDragPointer.x;
      this.drag.pointer.y = postScaleDragPointer.y;
    }

    this._redraw();

    if (scaleOld < scale) {
      this.emit("zoom", {direction:"+"});
    }
    else {
      this.emit("zoom", {direction:"-"});
    }

    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
 */
Network.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) {

    // calculate the new scale
    var scale = this._getScale();
    var zoom = delta / 10;
    if (delta < 0) {
      zoom = zoom / (1 - zoom);
    }
    scale *= (1 + zoom);

    // calculate the pointer location
    var gesture = hammerUtil.fakeGesture(this, event);
    var pointer = this._getPointer(gesture.center);

    // apply the new scale
    this._zoom(scale, pointer);
  }

  // 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
 */
Network.prototype._onMouseMoveTitle = function (event) {
  var gesture = hammerUtil.fakeGesture(this, event);
  var pointer = this._getPointer(gesture.center);
  var popupVisible = false;

  // check if the previously selected node is still selected
  if (this.popup !== undefined) {
    if (this.popup.hidden === false) {
      this._checkHidePopup(pointer);
    }

    // if the popup was not hidden above
    if (this.popup.hidden === false) {
      popupVisible = true;
      this.popup.setPosition(pointer.x + 3,pointer.y - 5)
      this.popup.show();
    }
  }

  // if we bind the keyboard to the div, we have to highlight it to use it. This highlights it on mouse over
  if (this.constants.keyboard.bindToWindow == false && this.constants.keyboard.enabled == true) {
    this.frame.focus();
  }

  // start a timeout that will check if the mouse is positioned above an element
  if (popupVisible === false) {
    var me = this;
    var checkShow = function () {
      me._checkShowPopup(pointer);
    };
    if (this.popupTimer) {
      clearInterval(this.popupTimer); // stop any running calculationTimer
    }
    if (!this.drag.dragging) {
      this.popupTimer = setTimeout(checkShow, this.constants.tooltip.delay);
    }
  }

  /**
   * Adding hover highlights
   */
  if (this.constants.hover == true) {
    // removing all hover highlights
    for (var edgeId in this.hoverObj.edges) {
      if (this.hoverObj.edges.hasOwnProperty(edgeId)) {
        this.hoverObj.edges[edgeId].hover = false;
        delete this.hoverObj.edges[edgeId];
      }
    }

    // adding hover highlights
    var obj = this._getNodeAt(pointer);
    if (obj == null) {
      obj = this._getEdgeAt(pointer);
    }
    if (obj != null) {
      this._hoverObject(obj);
    }

    // removing all node hover highlights except for the selected one.
    for (var nodeId in this.hoverObj.nodes) {
      if (this.hoverObj.nodes.hasOwnProperty(nodeId)) {
        if (obj instanceof Node && obj.id != nodeId || obj instanceof Edge || obj == null) {
          this._blurObject(this.hoverObj.nodes[nodeId]);
          delete this.hoverObj.nodes[nodeId];
        }
      }
    }
    this.redraw();
  }
};

/**
 * Check if there is an element on the given position in the network
 * (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
 */
Network.prototype._checkShowPopup = function (pointer) {
  var obj = {
    left:   this._XconvertDOMtoCanvas(pointer.x),
    top:    this._YconvertDOMtoCanvas(pointer.y),
    right:  this._XconvertDOMtoCanvas(pointer.x),
    bottom: this._YconvertDOMtoCanvas(pointer.y)
  };

  var id;
  var previousPopupObjId = this.popupObj === undefined ? undefined : this.popupObj.id;
  var nodeUnderCursor = false;
  var popupType = "node";

  if (this.popupObj == undefined) {
    // search the nodes for overlap, select the top one in case of multiple nodes
    var nodes = this.nodes;
    var overlappingNodes = [];
    for (id in nodes) {
      if (nodes.hasOwnProperty(id)) {
        var node = nodes[id];
        if (node.isOverlappingWith(obj)) {
          if (node.getTitle() !== undefined) {
            overlappingNodes.push(id);
          }
        }
      }
    }

    if (overlappingNodes.length > 0) {
      // if there are overlapping nodes, select the last one, this is the
      // one which is drawn on top of the others
      this.popupObj = this.nodes[overlappingNodes[overlappingNodes.length - 1]];
      // if you hover over a node, the title of the edge is not supposed to be shown.
      nodeUnderCursor = true;
    }
  }

  if (this.popupObj === undefined && nodeUnderCursor == false) {
    // search the edges for overlap
    var edges = this.edges;
    var overlappingEdges = [];
    for (id in edges) {
      if (edges.hasOwnProperty(id)) {
        var edge = edges[id];
        if (edge.connected && (edge.getTitle() !== undefined) &&
            edge.isOverlappingWith(obj)) {
          overlappingEdges.push(id);
        }
      }
    }

    if (overlappingEdges.length > 0) {
      this.popupObj = this.edges[overlappingEdges[overlappingEdges.length - 1]];
      popupType = "edge";
    }
  }

  if (this.popupObj) {
    // show popup message window
    if (this.popupObj.id != previousPopupObjId) {
      if (this.popup === undefined) {
        this.popup = new Popup(this.frame, this.constants.tooltip);
      }

      this.popup.popupTargetType = popupType;
      this.popup.popupTargetId = this.popupObj.id;

      // 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
      this.popup.setPosition(pointer.x + 3, pointer.y - 5);
      this.popup.setText(this.popupObj.getTitle());
      this.popup.show();
    }
  }
  else {
    if (this.popup) {
      this.popup.hide();
    }
  }
};


/**
 * Check if the popup must be hidden, which is the case when the mouse is no
 * longer hovering on the object
 * @param {{x:Number, y:Number}} pointer
 * @private
 */
Network.prototype._checkHidePopup = function (pointer) {
  var pointerObj = {
    left:   this._XconvertDOMtoCanvas(pointer.x),
    top:    this._YconvertDOMtoCanvas(pointer.y),
    right:  this._XconvertDOMtoCanvas(pointer.x),
    bottom: this._YconvertDOMtoCanvas(pointer.y)
  };

  var stillOnObj = false;
  if (this.popup.popupTargetType == 'node') {
    stillOnObj = this.nodes[this.popup.popupTargetId].isOverlappingWith(pointerObj);
    if (stillOnObj === true) {
      var overNode = this._getNodeAt(pointer);
      stillOnObj = overNode.id == this.popup.popupTargetId;
    }
  }
  else {
    if (this._getNodeAt(pointer) === null) {
      stillOnObj = this.edges[this.popup.popupTargetId].isOverlappingWith(pointerObj);
    }
  }


  if (stillOnObj === false) {
    this.popupObj = undefined;
    this.popup.hide();
  }
};


/**
 * Set a new size for the network
 * @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%')
 */
Network.prototype.setSize = function(width, height) {
  var emitEvent = false;
  var oldWidth = this.frame.canvas.width;
  var oldHeight = this.frame.canvas.height;
  if (width != this.constants.width || height != this.constants.height || this.frame.style.width != width || this.frame.style.height != 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.pixelRatio;
    this.frame.canvas.height = this.frame.canvas.clientHeight * this.pixelRatio;

    this.constants.width = width;
    this.constants.height = height;

    emitEvent = true;
  }
  else {
    // this would adapt the width of the canvas to the width from 100% if and only if
    // there is a change.

    if (this.frame.canvas.width != this.frame.canvas.clientWidth * this.pixelRatio) {
      this.frame.canvas.width = this.frame.canvas.clientWidth * this.pixelRatio;
      emitEvent = true;
    }
    if (this.frame.canvas.height != this.frame.canvas.clientHeight * this.pixelRatio) {
      this.frame.canvas.height = this.frame.canvas.clientHeight * this.pixelRatio;
      emitEvent = true;
    }
  }

  if (emitEvent == true) {
    this.emit('resize', {width:this.frame.canvas.width * this.pixelRatio,height:this.frame.canvas.height * this.pixelRatio, oldWidth: oldWidth * this.pixelRatio, oldHeight: oldHeight * this.pixelRatio});
  }
};

/**
 * Set a data set with nodes for the network
 * @param {Array | DataSet | DataView} nodes         The data containing the nodes.
 * @private
 */
Network.prototype._setNodes = function(nodes) {
  var oldNodesData = this.nodesData;

  if (nodes instanceof DataSet || nodes instanceof DataView) {
    this.nodesData = nodes;
  }
  else if (Array.isArray(nodes)) {
    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.off(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.on(event, callback);
    });

    // draw all new nodes
    var ids = this.nodesData.getIds();
    this._addNodes(ids);
  }
  this._updateSelection();
};

/**
 * Add nodes
 * @param {Number[] | String[]} ids
 * @private
 */
Network.prototype._addNodes = function(ids) {
  var id;
  var fieldId = this.nodesData._fieldId || null;
  for (var i = 0, len = ids.length; i < len; i++) {
    id = ids[i];
    var data = this.nodesData.get(id);
    if (fieldId) {
      data.id = data[fieldId];
    }

    var node = new Node(data, this.images, this.groups, this.constants);
    this.nodes[id] = node; // note: this may replace an existing node
    if ((node.xFixed == false || node.yFixed == false) && (node.x === null || node.y === null)) {
      var radius = 10 * 0.1*ids.length + 10;
      var angle = 2 * Math.PI * Math.random();
      if (node.xFixed == false) {node.x = radius * Math.cos(angle);}
      if (node.yFixed == false) {node.y = radius * Math.sin(angle);}
    }
    this.moving = true;
  }

  this._updateNodeIndexList();
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
  this._updateCalculationNodes();
  this._reconnectEdges();
  this._updateValueRange(this.nodes);
  this.updateLabels();
};

/**
 * Update existing nodes, or create them when not yet existing
 * @param {Number[] | String[]} ids
 * @private
 */
Network.prototype._updateNodes = function(ids) {
  var nodesData = this.nodesData.get(ids);
  var nodes = this.nodes;

  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    var node = nodes[id];
    var data = nodesData[i];
    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;
    }
  }
  this.moving = true;
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
  this._updateNodeIndexList();
  this._updateValueRange(nodes);
  this._markAllEdgesAsDirty();
};


Network.prototype._markAllEdgesAsDirty = function() {
  for (var edgeId in this.edges) {
    this.edges[edgeId].colorDirty = true;
  }
}

/**
 * Remove existing nodes. If nodes do not exist, the method will just ignore it.
 * @param {Number[] | String[]} ids
 * @private
 */
Network.prototype._removeNodes = function(ids) {
  var nodes = this.nodes;

  // remove from selection
  for (var i = 0, len = ids.length; i < len; i++) {
    if (this.selectionObj.nodes[ids[i]] !== undefined) {
      this.nodes[ids[i]].unselect();
      this._removeFromSelection(this.nodes[ids[i]]);
    }
  }

  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    delete nodes[id];
  }



  this._updateNodeIndexList();
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
  this._updateCalculationNodes();
  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
 */
Network.prototype._setEdges = function(edges) {
  var oldEdgesData = this.edgesData;

  if (edges instanceof DataSet || edges instanceof DataView) {
    this.edgesData = edges;
  }
  else if (Array.isArray(edges)) {
    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.off(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.on(event, callback);
    });

    // draw all new nodes
    var ids = this.edgesData.getIds();
    this._addEdges(ids);
  }

  this._reconnectEdges();
};

/**
 * Add edges
 * @param {Number[] | String[]} ids
 * @private
 */
Network.prototype._addEdges = function (ids) {
  var edges = this.edges;
  var edgesData = this.edgesData;
  var fieldId = this.edgesData._fieldId;

  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, {"showInternalIds" : true});
    if (fieldId) {
      data.id = data[fieldId];
    }
    edges[id] = new Edge(data, this, this.constants);
  }
  this.moving = true;
  this._updateValueRange(edges);
  this._createBezierNodes();
  this._updateCalculationNodes();
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
};

/**
 * Update existing edges, or create them when not yet existing
 * @param {Number[] | String[]} ids
 * @private
 */
Network.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._createBezierNodes();
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
  this.moving = true;
  this._updateValueRange(edges);
};

/**
 * Remove existing edges. Non existing ids will be ignored
 * @param {Number[] | String[]} ids
 * @private
 */
Network.prototype._removeEdges = function (ids) {
  var edges = this.edges;

  // remove from selection
  for (var i = 0, len = ids.length; i < len; i++) {
    if (this.selectionObj.edges[ids[i]] !== undefined) {
      edges[ids[i]].unselect();
      this._removeFromSelection(edges[ids[i]]);
    }
  }

  for (var i = 0, len = ids.length; i < len; i++) {
    var id = ids[i];
    var edge = edges[id];
    if (edge) {
      if (edge.via != null) {
        delete this.sectors['support']['nodes'][edge.via.id];
      }
      edge.disconnect();
      delete edges[id];
    }
  }

  this.moving = true;
  this._updateValueRange(edges);
  if (this.constants.hierarchicalLayout.enabled == true && this.initializing == false) {
    this._resetLevels();
    this._setupHierarchicalLayout();
  }
  this._updateCalculationNodes();
};

/**
 * Reconnect all edges
 * @private
 */
Network.prototype._reconnectEdges = function() {
  var id,
      nodes = this.nodes,
      edges = this.edges;
  for (id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      nodes[id].edges = [];
      nodes[id].dynamicEdges = [];
    }
  }

  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
 */
Network.prototype._updateValueRange = function(obj) {
  var id;

  // determine the range of the objects
  var valueMin = undefined;
  var valueMax = undefined;
  var valueTotal = 0;
  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);
        valueTotal += value;
      }
    }
  }

  // adjust the range of all objects
  if (valueMin !== undefined && valueMax !== undefined) {
    for (id in obj) {
      if (obj.hasOwnProperty(id)) {
        obj[id].setValueRange(valueMin, valueMax, valueTotal);
      }
    }
  }
};

/**
 * Redraw the network with the current data
 * chart will be resized too.
 */
Network.prototype.redraw = function() {
  this.setSize(this.constants.width, this.constants.height);
  this._redraw();
};

/**
 * Redraw the network with the current data
 * @param hidden | used to get the first estimate of the node sizes. only the nodes are drawn after which they are quickly drawn over.
 * @private
 */
Network.prototype._requestRedraw = function(hidden) {
  if (this.redrawRequested !== true) {
    this.redrawRequested = true;
    if (this.requiresTimeout === true) {
      window.setTimeout(this._redraw.bind(this, hidden),0);
    }
    else {
      window.requestAnimationFrame(this._redraw.bind(this, hidden, true));
    }
  }
};

Network.prototype._redraw = function(hidden, requested) {
  if (hidden === undefined) {
    hidden = false;
  }
  this.redrawRequested = false;
  var ctx = this.frame.canvas.getContext('2d');

  ctx.setTransform(this.pixelRatio, 0, 0, this.pixelRatio, 0, 0);

  // clear the canvas
  var w = this.frame.canvas.clientWidth;
  var h = this.frame.canvas.clientHeight;
  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.canvasTopLeft = {
    "x": this._XconvertDOMtoCanvas(0),
    "y": this._YconvertDOMtoCanvas(0)
  };
  this.canvasBottomRight = {
    "x": this._XconvertDOMtoCanvas(this.frame.canvas.clientWidth),
    "y": this._YconvertDOMtoCanvas(this.frame.canvas.clientHeight)
  };

  if (hidden === false) {
    this._doInAllSectors("_drawAllSectorNodes", ctx);
    if (this.drag.dragging == false || this.drag.dragging === undefined || this.constants.hideEdgesOnDrag == false) {
      this._doInAllSectors("_drawEdges", ctx);
    }
  }

  if (this.drag.dragging == false || this.drag.dragging === undefined || this.constants.hideNodesOnDrag == false) {
    this._doInAllSectors("_drawNodes",ctx,false);
  }

  if (hidden === false) {
    if (this.controlNodesActive == true) {
      this._doInAllSectors("_drawControlNodes", ctx);
    }
  }

//  this._doInSupportSector("_drawNodes",ctx,true);
//  this._drawTree(ctx,"#F00F0F");

  // restore original scaling and translation
  ctx.restore();

  if (hidden === true) {
    ctx.clearRect(0, 0, w, h);
  }
}

/**
 * Set the translation of the network
 * @param {Number} offsetX    Horizontal offset
 * @param {Number} offsetY    Vertical offset
 * @private
 */
Network.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;
  }

  this.emit('viewChanged');
};

/**
 * Get the translation of the network
 * @return {Object} translation    An object with parameters x and y, both a number
 * @private
 */
Network.prototype._getTranslation = function() {
  return {
    x: this.translation.x,
    y: this.translation.y
  };
};

/**
 * Scale the network
 * @param {Number} scale   Scaling factor 1.0 is unscaled
 * @private
 */
Network.prototype._setScale = function(scale) {
  this.scale = scale;
};

/**
 * Get the current scale of  the network
 * @return {Number} scale   Scaling factor 1.0 is unscaled
 * @private
 */
Network.prototype._getScale = function() {
  return this.scale;
};

/**
 * Convert the X coordinate in DOM-space (coordinate point in browser relative to the container div) to
 * the X coordinate in canvas-space (the simulation sandbox, which the camera looks upon)
 * @param {number} x
 * @returns {number}
 * @private
 */
Network.prototype._XconvertDOMtoCanvas = function(x) {
  return (x - this.translation.x) / this.scale;
};

/**
 * Convert the X coordinate in canvas-space (the simulation sandbox, which the camera looks upon) to
 * the X coordinate in DOM-space (coordinate point in browser relative to the container div)
 * @param {number} x
 * @returns {number}
 * @private
 */
Network.prototype._XconvertCanvasToDOM = function(x) {
  return x * this.scale + this.translation.x;
};

/**
 * Convert the Y coordinate in DOM-space (coordinate point in browser relative to the container div) to
 * the Y coordinate in canvas-space (the simulation sandbox, which the camera looks upon)
 * @param {number} y
 * @returns {number}
 * @private
 */
Network.prototype._YconvertDOMtoCanvas = function(y) {
  return (y - this.translation.y) / this.scale;
};

/**
 * Convert the Y coordinate in canvas-space (the simulation sandbox, which the camera looks upon) to
 * the Y coordinate in DOM-space (coordinate point in browser relative to the container div)
 * @param {number} y
 * @returns {number}
 * @private
 */
Network.prototype._YconvertCanvasToDOM = function(y) {
  return y * this.scale + this.translation.y ;
};


/**
 *
 * @param {object} pos   = {x: number, y: number}
 * @returns {{x: number, y: number}}
 * @constructor
 */
Network.prototype.canvasToDOM = function (pos) {
  return {x: this._XconvertCanvasToDOM(pos.x), y: this._YconvertCanvasToDOM(pos.y)};
};

/**
 *
 * @param {object} pos   = {x: number, y: number}
 * @returns {{x: number, y: number}}
 * @constructor
 */
Network.prototype.DOMtoCanvas = function (pos) {
  return {x: this._XconvertDOMtoCanvas(pos.x), y: this._YconvertDOMtoCanvas(pos.y)};
};

/**
 * Redraw all nodes
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext('2d');
 * @param {CanvasRenderingContext2D}   ctx
 * @param {Boolean} [alwaysShow]
 * @private
 */
Network.prototype._drawNodes = function(ctx,alwaysShow) {
  if (alwaysShow === undefined) {
    alwaysShow = false;
  }

  // first draw the unselected nodes
  var nodes = this.nodes;
  var selected = [];

  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      nodes[id].setScaleAndPos(this.scale,this.canvasTopLeft,this.canvasBottomRight);
      if (nodes[id].isSelected()) {
        selected.push(id);
      }
      else {
        if (nodes[id].inArea() || alwaysShow) {
          nodes[id].draw(ctx);
        }
      }
    }
  }

  // draw the selected nodes on top
  for (var s = 0, sMax = selected.length; s < sMax; s++) {
    if (nodes[selected[s]].inArea() || alwaysShow) {
      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
 */
Network.prototype._drawEdges = function(ctx) {
  var edges = this.edges;
  for (var id in edges) {
    if (edges.hasOwnProperty(id)) {
      var edge = edges[id];
      edge.setScale(this.scale);
      if (edge.connected) {
        edges[id].draw(ctx);
      }
    }
  }
};

/**
 * Redraw all edges
 * The 2d context of a HTML canvas can be retrieved by canvas.getContext('2d');
 * @param {CanvasRenderingContext2D}   ctx
 * @private
 */
Network.prototype._drawControlNodes = function(ctx) {
  var edges = this.edges;
  for (var id in edges) {
    if (edges.hasOwnProperty(id)) {
      edges[id]._drawControlNodes(ctx);
    }
  }
};

/**
 * Find a stable position for all nodes
 * @private
 */
Network.prototype._stabilize = function() {
  if (this.constants.freezeForStabilization == true) {
    this._freezeDefinedNodes();
  }

  // find stable position
  var count = 0;
  while (this.moving && count < this.constants.stabilizationIterations) {
    this._physicsTick();
    count++;
  }


  if (this.constants.zoomExtentOnStabilize == true) {
    this.zoomExtent({duration:0}, false, true);
  }

  if (this.constants.freezeForStabilization == true) {
    this._restoreFrozenNodes();
  }

  this.emit("stabilizationIterationsDone");
};

/**
 * When initializing and stabilizing, we can freeze nodes with a predefined position. This greatly speeds up stabilization
 * because only the supportnodes for the smoothCurves have to settle.
 *
 * @private
 */
Network.prototype._freezeDefinedNodes = function() {
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      if (nodes[id].x != null && nodes[id].y != null) {
        nodes[id].fixedData.x = nodes[id].xFixed;
        nodes[id].fixedData.y = nodes[id].yFixed;
        nodes[id].xFixed = true;
        nodes[id].yFixed = true;
      }
    }
  }
};

/**
 * Unfreezes the nodes that have been frozen by _freezeDefinedNodes.
 *
 * @private
 */
Network.prototype._restoreFrozenNodes = function() {
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes.hasOwnProperty(id)) {
      if (nodes[id].fixedData.x != null) {
        nodes[id].xFixed = nodes[id].fixedData.x;
        nodes[id].yFixed = nodes[id].fixedData.y;
      }
    }
  }
};


/**
 * 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
 */
Network.prototype._isMoving = function(vmin) {
  var nodes = this.nodes;
  for (var id in nodes) {
    if (nodes[id] !== undefined) {
      if (nodes[id].isMoving(vmin) == true) {
        return true;
      }
    }
  }
  return false;
};


/**
 * /**
 * Perform one discrete step for all nodes
 *
 * @private
 */
Network.prototype._discreteStepNodes = function() {
  var interval = this.physicsDiscreteStepsize;
  var nodes = this.nodes;
  var nodeId;
  var nodesPresent = false;

  if (this.constants.maxVelocity > 0) {
    for (nodeId in nodes) {
      if (nodes.hasOwnProperty(nodeId)) {
        nodes[nodeId].discreteStepLimited(interval, this.constants.maxVelocity);
        nodesPresent = true;
      }
    }
  }
  else {
    for (nodeId in nodes) {
      if (nodes.hasOwnProperty(nodeId)) {
        nodes[nodeId].discreteStep(interval);
        nodesPresent = true;
      }
    }
  }

  if (nodesPresent == true) {
    var vminCorrected = this.constants.minVelocity / Math.max(this.scale,0.05);
    if (vminCorrected > 0.5*this.constants.maxVelocity) {
      return true;
    }
    else {
      return this._isMoving(vminCorrected);
    }
  }
  return false;
};


Network.prototype._revertPhysicsState = function() {
  var nodes = this.nodes;
  for (var nodeId in nodes) {
    if (nodes.hasOwnProperty(nodeId)) {
      nodes[nodeId].revertPosition();
    }
  }
}

Network.prototype._revertPhysicsTick = function() {
  this._doInAllActiveSectors("_revertPhysicsState");
  if (this.constants.smoothCurves.enabled == true && this.constants.smoothCurves.dynamic == true) {
    this._doInSupportSector("_revertPhysicsState");
  }
}

/**
 * A single simulation step (or "tick") in the physics simulation
 *
 * @private
 */
Network.prototype._physicsTick = function() {
  if (!this.freezeSimulationEnabled) {
    if (this.moving == true) {
      var mainMovingStatus = false;
      var supportMovingStatus = false;

      this._doInAllActiveSectors("_initializeForceCalculation");
      var mainMoving = this._doInAllActiveSectors("_discreteStepNodes");
      if (this.constants.smoothCurves.enabled == true && this.constants.smoothCurves.dynamic == true) {
        supportMovingStatus = this._doInSupportSector("_discreteStepNodes");
      }

      // gather movement data from all sectors, if one moves, we are NOT stabilzied
      for (var i = 0; i < mainMoving.length; i++) {
        mainMovingStatus = mainMoving[i] || mainMovingStatus;
      }

      // determine if the network has stabilzied
      this.moving = mainMovingStatus || supportMovingStatus;
      if (this.moving == false) {
        this._revertPhysicsTick();
      }
      else {
        // this is here to ensure that there is no start event when the network is already stable.
        if (this.startedStabilization == false) {
          this.emit("startStabilization");
          this.startedStabilization = true;
        }
      }

      this.stabilizationIterations++;
    }
  }
};


/**
 * This function runs one step of the animation. It calls an x amount of physics ticks and one render tick.
 * It reschedules itself at the beginning of the function
 *
 * @private
 */
Network.prototype._animationStep = function() {
  // reset the timer so a new scheduled animation step can be set
  this.timer = undefined;

  if (this.requiresTimeout == true) {
    // this schedules a new animation step
    this.start();
  }

  // handle the keyboad movement
  this._handleNavigation();

  // check if the physics have settled
  if (this.moving == true) {
    var startTime = Date.now();
    this._physicsTick();
    var physicsTime = Date.now() - startTime;

    // run double speed if it is a little graph
    if ((this.renderTimestep - this.renderTime > 2 * physicsTime || this.runDoubleSpeed == true) && this.moving == true) {
      this._physicsTick();

      // this makes sure there is no jitter. The decision is taken once to run it at double speed.
      if (this.renderTime != 0) {
        this.runDoubleSpeed = true
      }
    }
  }

  var renderStartTime = Date.now();
  this._redraw();
  this.renderTime = Date.now() - renderStartTime;

  if (this.requiresTimeout == false) {
    // this schedules a new animation step
    this.start();
  }
};

if (typeof window !== 'undefined') {
  window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame ||
                                 window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
}

/**
 * Schedule a animation step with the refreshrate interval.
 */
Network.prototype.start = function() {
  if (this.freezeSimulationEnabled == true) {
    this.moving = false;
  }
  if (this.moving == true || this.xIncrement != 0 || this.yIncrement != 0 || this.zoomIncrement != 0 || this.animating == true) {
    if (!this.timer) {
      if (this.requiresTimeout == true) {
        this.timer = window.setTimeout(this._animationStep.bind(this), this.renderTimestep); // wait this.renderTimeStep milliseconds and perform the animation step function
      }
      else {
        this.timer = window.requestAnimationFrame(this._animationStep.bind(this)); // wait this.renderTimeStep milliseconds and perform the animation step function
      }
    }
  }
  else {
    this._requestRedraw();
    // this check is to ensure that the network does not emit these events if it was already stabilized and setOptions is called (setting moving to true and calling start())
    if (this.stabilizationIterations > 1) {
      // trigger the "stabilized" event.
      // The event is triggered on the next tick, to prevent the case that
      // it is fired while initializing the Network, in which case you would not
      // be able to catch it
      var me = this;
      var params = {
        iterations: me.stabilizationIterations
      };
      this.stabilizationIterations = 0;
      this.startedStabilization = false;
      setTimeout(function () {
        me.emit("stabilized", params);
      }, 0);
    }
    else {
      this.stabilizationIterations = 0;
    }
  }
};


/**
 * Move the network according to the keyboard presses.
 *
 * @private
 */
Network.prototype._handleNavigation = function() {
  if (this.xIncrement != 0 || this.yIncrement != 0) {
    var translation = this._getTranslation();
    this._setTranslation(translation.x+this.xIncrement, translation.y+this.yIncrement);
  }
  if (this.zoomIncrement != 0) {
    var center = {
      x: this.frame.canvas.clientWidth / 2,
      y: this.frame.canvas.clientHeight / 2
    };
    this._zoom(this.scale*(1 + this.zoomIncrement), center);
  }
};


/**
 *  Freeze the _animationStep
 */
Network.prototype.freezeSimulation = function(freeze) {
  if (freeze == true) {
    this.freezeSimulationEnabled = true;
    this.moving = false;
  }
  else {
    this.freezeSimulationEnabled = false;
    this.moving = true;
    this.start();
  }
};


/**
 * This function cleans the support nodes if they are not needed and adds them when they are.
 *
 * @param {boolean} [disableStart]
 * @private
 */
Network.prototype._configureSmoothCurves = function(disableStart) {
  if (disableStart === undefined) {
    disableStart = true;
  }
  if (this.constants.smoothCurves.enabled == true && this.constants.smoothCurves.dynamic == true) {
    this._createBezierNodes();
    // cleanup unused support nodes
    for (var nodeId in this.sectors['support']['nodes']) {
      if (this.sectors['support']['nodes'].hasOwnProperty(nodeId)) {
        if (this.edges[this.sectors['support']['nodes'][nodeId].parentEdgeId] === undefined) {
          delete this.sectors['support']['nodes'][nodeId];
        }
      }
    }
  }
  else {
    // delete the support nodes
    this.sectors['support']['nodes'] = {};
    for (var edgeId in this.edges) {
      if (this.edges.hasOwnProperty(edgeId)) {
        this.edges[edgeId].via = null;
      }
    }
  }


  this._updateCalculationNodes();
  if (!disableStart) {
    this.moving = true;
    this.start();
  }
};


/**
 * Bezier curves require an anchor point to calculate the smooth flow. These points are nodes. These nodes are invisible but
 * are used for the force calculation.
 *
 * @private
 */
Network.prototype._createBezierNodes = function() {
  if (this.constants.smoothCurves.enabled == true && this.constants.smoothCurves.dynamic == true) {
    for (var edgeId in this.edges) {
      if (this.edges.hasOwnProperty(edgeId)) {
        var edge = this.edges[edgeId];
        if (edge.via == null) {
          var nodeId = "edgeId:".concat(edge.id);
          this.sectors['support']['nodes'][nodeId] = new Node(
                  {id:nodeId,
                    mass:1,
                    shape:'circle',
                    image:"",
                    internalMultiplier:1
                  },{},{},this.constants);
          edge.via = this.sectors['support']['nodes'][nodeId];
          edge.via.parentEdgeId = edge.id;
          edge.positionBezierNode();
        }
      }
    }
  }
};

/**
 * load the functions that load the mixins into the prototype.
 *
 * @private
 */
Network.prototype._initializeMixinLoaders = function () {
  for (var mixin in MixinLoader) {
    if (MixinLoader.hasOwnProperty(mixin)) {
      Network.prototype[mixin] = MixinLoader[mixin];
    }
  }
};

/**
 * Load the XY positions of the nodes into the dataset.
 */
Network.prototype.storePosition = function() {
  console.log("storePosition is depricated: use .storePositions() from now on.")
  this.storePositions();
};

/**
 * Load the XY positions of the nodes into the dataset.
 */
Network.prototype.storePositions = function() {
  var dataArray = [];
  for (var nodeId in this.nodes) {
    if (this.nodes.hasOwnProperty(nodeId)) {
      var node = this.nodes[nodeId];
      var allowedToMoveX = !this.nodes.xFixed;
      var allowedToMoveY = !this.nodes.yFixed;
      if (this.nodesData._data[nodeId].x != Math.round(node.x) || this.nodesData._data[nodeId].y != Math.round(node.y)) {
        dataArray.push({id:nodeId,x:Math.round(node.x),y:Math.round(node.y),allowedToMoveX:allowedToMoveX,allowedToMoveY:allowedToMoveY});
      }
    }
  }
  this.nodesData.update(dataArray);
};

/**
 * Return the positions of the nodes.
 */
Network.prototype.getPositions = function(ids) {
  var dataArray = {};
  if (ids !== undefined) {
    if (Array.isArray(ids) == true) {
      for (var i = 0; i < ids.length; i++) {
        if (this.nodes[ids[i]] !== undefined) {
          var node = this.nodes[ids[i]];
          dataArray[ids[i]] = {x: Math.round(node.x), y: Math.round(node.y)};
        }
      }
    }
    else {
      if (this.nodes[ids] !== undefined) {
        var node = this.nodes[ids];
        dataArray[ids] = {x: Math.round(node.x), y: Math.round(node.y)};
      }
    }
  }
  else {
    for (var nodeId in this.nodes) {
      if (this.nodes.hasOwnProperty(nodeId)) {
        var node = this.nodes[nodeId];
        dataArray[nodeId] = {x: Math.round(node.x), y: Math.round(node.y)};
      }
    }
  }
  return dataArray;
};



/**
 * Center a node in view.
 *
 * @param {Number} nodeId
 * @param {Number} [options]
 */
Network.prototype.focusOnNode = function (nodeId, options) {
  if (this.nodes.hasOwnProperty(nodeId)) {
    if (options === undefined) {
      options = {};
    }
    var nodePosition = {x: this.nodes[nodeId].x, y: this.nodes[nodeId].y};
    options.position = nodePosition;
    options.lockedOnNode = nodeId;

    this.moveTo(options)
  }
  else {
    console.log("This nodeId cannot be found.");
  }
};

/**
 *
 * @param {Object} options  |  options.offset   = {x:Number, y:Number}   // offset from the center in DOM pixels
 *                          |  options.scale    = Number                 // scale to move to
 *                          |  options.position = {x:Number, y:Number}   // position to move to
 *                          |  options.animation = {duration:Number, easingFunction:String} || Boolean   // position to move to
 */
Network.prototype.moveTo = function (options) {
  if (options === undefined) {
    options = {};
    return;
  }
  if (options.offset    === undefined)           {options.offset    = {x: 0, y: 0};          }
  if (options.offset.x  === undefined)           {options.offset.x  = 0;                     }
  if (options.offset.y  === undefined)           {options.offset.y  = 0;                     }
  if (options.scale     === undefined)           {options.scale     = this._getScale();      }
  if (options.position  === undefined)           {options.position  = this._getTranslation();}
  if (options.animation === undefined)           {options.animation = {duration:0};          }
  if (options.animation === false    )           {options.animation = {duration:0};          }
  if (options.animation === true     )           {options.animation = {};                    }
  if (options.animation.duration === undefined)  {options.animation.duration = 1000;         }  // default duration
  if (options.animation.easingFunction === undefined)  {options.animation.easingFunction = "easeInOutQuad";  } // default easing function

  this.animateView(options);
};

/**
 *
 * @param {Object} options  |  options.offset   = {x:Number, y:Number}   // offset from the center in DOM pixels
 *                          |  options.time     = Number                 // animation time in milliseconds
 *                          |  options.scale    = Number                 // scale to animate to
 *                          |  options.position = {x:Number, y:Number}   // position to animate to
 *                          |  options.easingFunction = String           // linear, easeInQuad, easeOutQuad, easeInOutQuad,
 *                                                                       // easeInCubic, easeOutCubic, easeInOutCubic,
 *                                                                       // easeInQuart, easeOutQuart, easeInOutQuart,
 *                                                                       // easeInQuint, easeOutQuint, easeInOutQuint
 */
Network.prototype.animateView = function (options) {
  if (options === undefined) {
    options = {};
    return;
  }

  // release if something focussed on the node
  this.releaseNode();
  if (options.locked == true) {
    this.lockedOnNodeId = options.lockedOnNode;
    this.lockedOnNodeOffset = options.offset;
  }

  // forcefully complete the old animation if it was still running
  if (this.easingTime != 0) {
    this._transitionRedraw(1); // by setting easingtime to 1, we finish the animation.
  }

  this.sourceScale = this._getScale();
  this.sourceTranslation = this._getTranslation();
  this.targetScale = options.scale;

  // set the scale so the viewCenter is based on the correct zoom level. This is overridden in the transitionRedraw
  // but at least then we'll have the target transition
  this._setScale(this.targetScale);
  var viewCenter = this.DOMtoCanvas({x: 0.5 * this.frame.canvas.clientWidth, y: 0.5 * this.frame.canvas.clientHeight});
  var distanceFromCenter = { // offset from view, distance view has to change by these x and y to center the node
    x: viewCenter.x - options.position.x,
    y: viewCenter.y - options.position.y
  };
  this.targetTranslation = {
    x: this.sourceTranslation.x + distanceFromCenter.x * this.targetScale + options.offset.x,
    y: this.sourceTranslation.y + distanceFromCenter.y * this.targetScale + options.offset.y
  };

  // if the time is set to 0, don't do an animation
  if (options.animation.duration == 0) {
    if (this.lockedOnNodeId != null) {
      this._classicRedraw = this._redraw;
      this._redraw = this._lockedRedraw;
    }
    else {
      this._setScale(this.targetScale);
      this._setTranslation(this.targetTranslation.x, this.targetTranslation.y);
      this._redraw();
    }
  }
  else {
    this.animating = true;
    this.animationSpeed = 1 / (this.renderRefreshRate * options.animation.duration * 0.001) || 1 / this.renderRefreshRate;
    this.animationEasingFunction = options.animation.easingFunction;
    this._classicRedraw = this._redraw;
    this._redraw = this._transitionRedraw;
    this._redraw();
    this.start();
  }
};

/**
 * used to animate smoothly by hijacking the redraw function.
 * @private
 */
Network.prototype._lockedRedraw = function () {
  var nodePosition = {x: this.nodes[this.lockedOnNodeId].x, y: this.nodes[this.lockedOnNodeId].y};
  var viewCenter = this.DOMtoCanvas({x: 0.5 * this.frame.canvas.clientWidth, y: 0.5 * this.frame.canvas.clientHeight});
  var distanceFromCenter = { // offset from view, distance view has to change by these x and y to center the node
    x: viewCenter.x - nodePosition.x,
    y: viewCenter.y - nodePosition.y
  };
  var sourceTranslation = this._getTranslation();
  var targetTranslation = {
    x: sourceTranslation.x + distanceFromCenter.x * this.scale + this.lockedOnNodeOffset.x,
    y: sourceTranslation.y + distanceFromCenter.y * this.scale + this.lockedOnNodeOffset.y
  };

  this._setTranslation(targetTranslation.x,targetTranslation.y);
  this._classicRedraw();
}

Network.prototype.releaseNode = function () {
  if (this.lockedOnNodeId != null) {
    this._redraw = this._classicRedraw;
    this.lockedOnNodeId = null;
    this.lockedOnNodeOffset = null;
  }
}

/**
 *
 * @param easingTime
 * @private
 */
Network.prototype._transitionRedraw = function (easingTime) {
  this.easingTime = easingTime || this.easingTime + this.animationSpeed;
  this.easingTime += this.animationSpeed;

  var progress = util.easingFunctions[this.animationEasingFunction](this.easingTime);

  this._setScale(this.sourceScale + (this.targetScale - this.sourceScale) * progress);
  this._setTranslation(
    this.sourceTranslation.x + (this.targetTranslation.x - this.sourceTranslation.x) * progress,
    this.sourceTranslation.y + (this.targetTranslation.y - this.sourceTranslation.y) * progress
  );

  this._classicRedraw();

  // cleanup
  if (this.easingTime >= 1.0) {
    this.animating = false;
    this.easingTime = 0;
    if (this.lockedOnNodeId != null) {
      this._redraw = this._lockedRedraw;
    }
    else {
      this._redraw = this._classicRedraw;
    }
    this.emit("animationFinished");
  }
};

Network.prototype._classicRedraw = function () {
  // placeholder function to be overloaded by animations;
};

/**
 * Returns true when the Network is active.
 * @returns {boolean}
 */
Network.prototype.isActive = function () {
  return !this.activator || this.activator.active;
};


/**
 * Sets the scale
 * @returns {Number}
 */
Network.prototype.setScale = function () {
  return this._setScale();
};


/**
 * Returns the scale
 * @returns {Number}
 */
Network.prototype.getScale = function () {
  return this._getScale();
};


/**
 * Returns the scale
 * @returns {Number}
 */
Network.prototype.getCenterCoordinates = function () {
  return this.DOMtoCanvas({x: 0.5 * this.frame.canvas.clientWidth, y: 0.5 * this.frame.canvas.clientHeight});
};


Network.prototype.getBoundingBox = function(nodeId) {
  if (this.nodes[nodeId] !== undefined) {
    return this.nodes[nodeId].boundingBox;
  }
}

Network.prototype.getConnectedNodes = function(nodeId) {
  var nodeList = [];
  if (this.nodes[nodeId] !== undefined) {
    var node = this.nodes[nodeId];
    var nodeObj = {nodeId : true}; // used to quickly check if node already exists
    for (var i = 0; i < node.edges.length; i++) {
      var edge = node.edges[i];
      if (edge.toId == nodeId) {
        if (nodeObj[edge.fromId] === undefined) {
          nodeList.push(edge.fromId);
          nodeObj[edge.fromId] = true;
        }
      }
      else if (edge.fromId == nodeId) {
        if (nodeObj[edge.toId] === undefined) {
          nodeList.push(edge.toId)
          nodeObj[edge.toId] = true;
        }
      }
    }
  }
  return nodeList;
}


Network.prototype.getEdgesFromNode = function(nodeId) {
  var edgesList = [];
  if (this.nodes[nodeId] !== undefined) {
    var node = this.nodes[nodeId];
    for (var i = 0; i < node.edges.length; i++) {
      edgesList.push(node.edges[i].id);
    }
  }
  return edgesList;
}

Network.prototype.generateColorObject = function(color) {
  return util.parseColor(color);

}

module.exports = Network;