(function(global) {

  'use strict';

  var fabric = global.fabric || (global.fabric = { }),
      min = fabric.util.array.min,
      max = fabric.util.array.max;

  if (fabric.Group) {
    return;
  }

  /**
   * Group class
   * @class fabric.Group
   * @extends fabric.Object
   * @mixes fabric.Collection
   * @tutorial {@link http://fabricjs.com/fabric-intro-part-3#groups}
   * @see {@link fabric.Group#initialize} for constructor definition
   */
  fabric.Group = fabric.util.createClass(fabric.Object, fabric.Collection, /** @lends fabric.Group.prototype */ {

    /**
     * Type of an object
     * @type String
     * @default
     */
    type: 'group',

    /**
     * Width of stroke
     * @type Number
     * @default
     */
    strokeWidth: 0,

    /**
     * Indicates if click, mouseover, mouseout events & hoverCursor should also check for subtargets
     * @type Boolean
     * @default
     */
    subTargetCheck: false,

    /**
     * Groups are container, do not render anything on theyr own, ence no cache properties
     * @type Array
     * @default
     */
    cacheProperties: [],

    /**
     * setOnGroup is a method used for TextBox that is no more used since 2.0.0 The behavior is still
     * available setting this boolean to true.
     * @type Boolean
     * @since 2.0.0
     * @default
     */
    useSetOnGroup: false,

    /**
     * Constructor
     * @param {Object} objects Group objects
     * @param {Object} [options] Options object
     * @param {Boolean} [isAlreadyGrouped] if true, objects have been grouped already.
     * @return {Object} thisArg
     */
    initialize: function(objects, options, isAlreadyGrouped) {
      options = options || {};
      this._objects = [];
      // if objects enclosed in a group have been grouped already,
      // we cannot change properties of objects.
      // Thus we need to set options to group without objects,
      isAlreadyGrouped && this.callSuper('initialize', options);
      this._objects = objects || [];
      for (var i = this._objects.length; i--; ) {
        this._objects[i].group = this;
      }

      if (!isAlreadyGrouped) {
        var center = options && options.centerPoint;
        // we want to set origins before calculating the bounding box.
        // so that the topleft can be set with that in mind.
        // if specific top and left are passed, are overwritten later
        // with the callSuper('initialize', options)
        if (options.originX !== undefined) {
          this.originX = options.originX;
        }
        if (options.originY !== undefined) {
          this.originY = options.originY;
        }
        // if coming from svg i do not want to calc bounds.
        // i assume width and height are passed along options
        center || this._calcBounds();
        this._updateObjectsCoords(center);
        delete options.centerPoint;
        this.callSuper('initialize', options);
      }
      else {
        this._updateObjectsACoords();
      }

      this.setCoords();
    },

    /**
     * @private
     */
    _updateObjectsACoords: function() {
      var skipControls = true;
      for (var i = this._objects.length; i--; ){
        this._objects[i].setCoords(skipControls);
      }
    },

    /**
     * @private
     * @param {Boolean} [skipCoordsChange] if true, coordinates of objects enclosed in a group do not change
     */
    _updateObjectsCoords: function(center) {
      var center = center || this.getCenterPoint();
      for (var i = this._objects.length; i--; ){
        this._updateObjectCoords(this._objects[i], center);
      }
    },

    /**
     * @private
     * @param {Object} object
     * @param {fabric.Point} center, current center of group.
     */
    _updateObjectCoords: function(object, center) {
      var objectLeft = object.left,
          objectTop = object.top,
          skipControls = true;

      object.set({
        left: objectLeft - center.x,
        top: objectTop - center.y
      });
      object.group = this;
      object.setCoords(skipControls);
    },

    /**
     * Returns string represenation of a group
     * @return {String}
     */
    toString: function() {
      return '#<fabric.Group: (' + this.complexity() + ')>';
    },

    /**
     * Adds an object to a group; Then recalculates group's dimension, position.
     * @param {Object} object
     * @return {fabric.Group} thisArg
     * @chainable
     */
    addWithUpdate: function(object) {
      this._restoreObjectsState();
      fabric.util.resetObjectTransform(this);
      if (object) {
        this._objects.push(object);
        object.group = this;
        object._set('canvas', this.canvas);
      }
      this._calcBounds();
      this._updateObjectsCoords();
      this.setCoords();
      this.dirty = true;
      return this;
    },

    /**
     * Removes an object from a group; Then recalculates group's dimension, position.
     * @param {Object} object
     * @return {fabric.Group} thisArg
     * @chainable
     */
    removeWithUpdate: function(object) {
      this._restoreObjectsState();
      fabric.util.resetObjectTransform(this);

      this.remove(object);
      this._calcBounds();
      this._updateObjectsCoords();
      this.setCoords();
      this.dirty = true;
      return this;
    },

    /**
     * @private
     */
    _onObjectAdded: function(object) {
      this.dirty = true;
      object.group = this;
      object._set('canvas', this.canvas);
    },

    /**
     * @private
     */
    _onObjectRemoved: function(object) {
      this.dirty = true;
      delete object.group;
    },

    /**
     * @private
     */
    _set: function(key, value) {
      var i = this._objects.length;
      if (this.useSetOnGroup) {
        while (i--) {
          this._objects[i].setOnGroup(key, value);
        }
      }
      if (key === 'canvas') {
        while (i--) {
          this._objects[i]._set(key, value);
        }
      }
      fabric.Object.prototype._set.call(this, key, value);
    },

    /**
     * Returns object representation of an instance
     * @param {Array} [propertiesToInclude] Any properties that you might want to additionally include in the output
     * @return {Object} object representation of an instance
     */
    toObject: function(propertiesToInclude) {
      var _includeDefaultValues = this.includeDefaultValues;
      var objsToObject = this._objects.map(function(obj) {
        var originalDefaults = obj.includeDefaultValues;
        obj.includeDefaultValues = _includeDefaultValues;
        var _obj = obj.toObject(propertiesToInclude);
        obj.includeDefaultValues = originalDefaults;
        return _obj;
      });
      var obj = fabric.Object.prototype.toObject.call(this, propertiesToInclude);
      obj.objects = objsToObject;
      return obj;
    },

    /**
     * Returns object representation of an instance, in dataless mode.
     * @param {Array} [propertiesToInclude] Any properties that you might want to additionally include in the output
     * @return {Object} object representation of an instance
     */
    toDatalessObject: function(propertiesToInclude) {
      var objsToObject, sourcePath = this.sourcePath;
      if (sourcePath) {
        objsToObject = sourcePath;
      }
      else {
        var _includeDefaultValues = this.includeDefaultValues;
        objsToObject = this._objects.map(function(obj) {
          var originalDefaults = obj.includeDefaultValues;
          obj.includeDefaultValues = _includeDefaultValues;
          var _obj = obj.toDatalessObject(propertiesToInclude);
          obj.includeDefaultValues = originalDefaults;
          return _obj;
        });
      }
      var obj = fabric.Object.prototype.toDatalessObject.call(this, propertiesToInclude);
      obj.objects = objsToObject;
      return obj;
    },

    /**
     * Renders instance on a given context
     * @param {CanvasRenderingContext2D} ctx context to render instance on
     */
    render: function(ctx) {
      this._transformDone = true;
      this.callSuper('render', ctx);
      this._transformDone = false;
    },

    /**
     * Decide if the object should cache or not. Create its own cache level
     * needsItsOwnCache should be used when the object drawing method requires
     * a cache step. None of the fabric classes requires it.
     * Generally you do not cache objects in groups because the group is already cached.
     * @return {Boolean}
     */
    shouldCache: function() {
      var ownCache = fabric.Object.prototype.shouldCache.call(this);
      if (ownCache) {
        for (var i = 0, len = this._objects.length; i < len; i++) {
          if (this._objects[i].willDrawShadow()) {
            this.ownCaching = false;
            return false;
          }
        }
      }
      return ownCache;
    },

    /**
     * Check if this object or a child object will cast a shadow
     * @return {Boolean}
     */
    willDrawShadow: function() {
      if (fabric.Object.prototype.willDrawShadow.call(this)) {
        return true;
      }
      for (var i = 0, len = this._objects.length; i < len; i++) {
        if (this._objects[i].willDrawShadow()) {
          return true;
        }
      }
      return false;
    },

    /**
     * Check if this group or its parent group are caching, recursively up
     * @return {Boolean}
     */
    isOnACache: function() {
      return this.ownCaching || (this.group && this.group.isOnACache());
    },

    /**
     * Execute the drawing operation for an object on a specified context
     * @param {CanvasRenderingContext2D} ctx Context to render on
     */
    drawObject: function(ctx) {
      for (var i = 0, len = this._objects.length; i < len; i++) {
        this._objects[i].render(ctx);
      }
      this._drawClipPath(ctx);
    },

    /**
     * Check if cache is dirty
     */
    isCacheDirty: function(skipCanvas) {
      if (this.callSuper('isCacheDirty', skipCanvas)) {
        return true;
      }
      if (!this.statefullCache) {
        return false;
      }
      for (var i = 0, len = this._objects.length; i < len; i++) {
        if (this._objects[i].isCacheDirty(true)) {
          if (this._cacheCanvas) {
            // if this group has not a cache canvas there is nothing to clean
            var x = this.cacheWidth / this.zoomX, y = this.cacheHeight / this.zoomY;
            this._cacheContext.clearRect(-x / 2, -y / 2, x, y);
          }
          return true;
        }
      }
      return false;
    },

    /**
     * Retores original state of each of group objects (original state is that which was before group was created).
     * @private
     * @return {fabric.Group} thisArg
     * @chainable
     */
    _restoreObjectsState: function() {
      this._objects.forEach(this._restoreObjectState, this);
      return this;
    },

    /**
     * Realises the transform from this group onto the supplied object
     * i.e. it tells you what would happen if the supplied object was in
     * the group, and then the group was destroyed. It mutates the supplied
     * object.
     * @param {fabric.Object} object
     * @return {fabric.Object} transformedObject
     */
    realizeTransform: function(object) {
      var matrix = object.calcTransformMatrix(),
          options = fabric.util.qrDecompose(matrix),
          center = new fabric.Point(options.translateX, options.translateY);
      object.flipX = false;
      object.flipY = false;
      object.set('scaleX', options.scaleX);
      object.set('scaleY', options.scaleY);
      object.skewX = options.skewX;
      object.skewY = options.skewY;
      object.angle = options.angle;
      object.setPositionByOrigin(center, 'center', 'center');
      return object;
    },

    /**
     * Restores original state of a specified object in group
     * @private
     * @param {fabric.Object} object
     * @return {fabric.Group} thisArg
     */
    _restoreObjectState: function(object) {
      this.realizeTransform(object);
      delete object.group;
      object.setCoords();
      return this;
    },

    /**
     * Destroys a group (restoring state of its objects)
     * @return {fabric.Group} thisArg
     * @chainable
     */
    destroy: function() {
      // when group is destroyed objects needs to get a repaint to be eventually
      // displayed on canvas.
      this._objects.forEach(function(object) {
        object.set('dirty', true);
      });
      return this._restoreObjectsState();
    },

    /**
     * make a group an active selection, remove the group from canvas
     * the group has to be on canvas for this to work.
     * @return {fabric.ActiveSelection} thisArg
     * @chainable
     */
    toActiveSelection: function() {
      if (!this.canvas) {
        return;
      }
      var objects = this._objects, canvas = this.canvas;
      this._objects = [];
      var options = this.toObject();
      delete options.objects;
      var activeSelection = new fabric.ActiveSelection([]);
      activeSelection.set(options);
      activeSelection.type = 'activeSelection';
      canvas.remove(this);
      objects.forEach(function(object) {
        object.group = activeSelection;
        object.dirty = true;
        canvas.add(object);
      });
      activeSelection.canvas = canvas;
      activeSelection._objects = objects;
      canvas._activeObject = activeSelection;
      activeSelection.setCoords();
      return activeSelection;
    },

    /**
     * Destroys a group (restoring state of its objects)
     * @return {fabric.Group} thisArg
     * @chainable
     */
    ungroupOnCanvas: function() {
      return this._restoreObjectsState();
    },

    /**
     * Sets coordinates of all objects inside group
     * @return {fabric.Group} thisArg
     * @chainable
     */
    setObjectsCoords: function() {
      var skipControls = true;
      this.forEachObject(function(object) {
        object.setCoords(skipControls);
      });
      return this;
    },

    /**
     * @private
     */
    _calcBounds: function(onlyWidthHeight) {
      var aX = [],
          aY = [],
          o, prop,
          props = ['tr', 'br', 'bl', 'tl'],
          i = 0, iLen = this._objects.length,
          j, jLen = props.length;

      for ( ; i < iLen; ++i) {
        o = this._objects[i];
        o.aCoords = o.calcACoords();
        for (j = 0; j < jLen; j++) {
          prop = props[j];
          aX.push(o.aCoords[prop].x);
          aY.push(o.aCoords[prop].y);
        }
      }

      this._getBounds(aX, aY, onlyWidthHeight);
    },

    /**
     * @private
     */
    _getBounds: function(aX, aY, onlyWidthHeight) {
      var minXY = new fabric.Point(min(aX), min(aY)),
          maxXY = new fabric.Point(max(aX), max(aY)),
          top = minXY.y || 0, left = minXY.x || 0,
          width = (maxXY.x - minXY.x) || 0,
          height = (maxXY.y - minXY.y) || 0;
      this.width = width;
      this.height = height;
      if (!onlyWidthHeight) {
        // the bounding box always finds the topleft most corner.
        // whatever is the group origin, we set up here the left/top position.
        this.setPositionByOrigin({ x: left, y: top }, 'left', 'top');
      }
    },

    /* _TO_SVG_START_ */
    /**
     * Returns svg representation of an instance
     * @param {Function} [reviver] Method for further parsing of svg representation.
     * @return {String} svg representation of an instance
     */
    _toSVG: function(reviver) {
      var svgString = ['<g ', 'COMMON_PARTS', ' >\n'];

      for (var i = 0, len = this._objects.length; i < len; i++) {
        svgString.push('\t\t', this._objects[i].toSVG(reviver));
      }
      svgString.push('</g>\n');
      return svgString;
    },

    /**
     * Returns styles-string for svg-export, specific version for group
     * @return {String}
     */
    getSvgStyles: function() {
      var opacity = typeof this.opacity !== 'undefined' && this.opacity !== 1 ?
            'opacity: ' + this.opacity + ';' : '',
          visibility = this.visible ? '' : ' visibility: hidden;';
      return [
        opacity,
        this.getSvgFilter(),
        visibility
      ].join('');
    },

    /**
     * Returns svg clipPath representation of an instance
     * @param {Function} [reviver] Method for further parsing of svg representation.
     * @return {String} svg representation of an instance
     */
    toClipPathSVG: function(reviver) {
      var svgString = [];

      for (var i = 0, len = this._objects.length; i < len; i++) {
        svgString.push('\t', this._objects[i].toClipPathSVG(reviver));
      }

      return this._createBaseClipPathSVGMarkup(svgString, { reviver: reviver });
    },
    /* _TO_SVG_END_ */
  });

  /**
   * Returns {@link fabric.Group} instance from an object representation
   * @static
   * @memberOf fabric.Group
   * @param {Object} object Object to create a group from
   * @param {Function} [callback] Callback to invoke when an group instance is created
   */
  fabric.Group.fromObject = function(object, callback) {
    var objects = object.objects,
        options = fabric.util.object.clone(object, true);
    delete options.objects;
    if (typeof objects === 'string') {
      // it has to be an url or something went wrong.
      fabric.loadSVGFromURL(objects, function (elements) {
        var group = fabric.util.groupSVGElements(elements, object, objects);
        group.set(options);
        callback && callback(group);
      });
      return;
    }
    fabric.util.enlivenObjects(objects, function(enlivenedObjects) {
      fabric.util.enlivenObjects([object.clipPath], function(enlivedClipPath) {
        var options = fabric.util.object.clone(object, true);
        options.clipPath = enlivedClipPath[0];
        delete options.objects;
        callback && callback(new fabric.Group(enlivenedObjects, options, true));
      });
    });
  };

})(typeof exports !== 'undefined' ? exports : this);