(function() {
    // constants
    var HASH = '#',
        BEFORE_DRAW ='beforeDraw',
        DRAW = 'draw',

        /*
         * 2 - 3 - 4
         * |       |
         * 1 - 0   5
         *         |
         * 8 - 7 - 6     
         */
        INTERSECTION_OFFSETS = [
            {x:  0, y:  0}, // 0
            {x: -1, y:  0}, // 1
            {x: -1, y: -1}, // 2
            {x:  0, y: -1}, // 3
            {x:  1, y: -1}, // 4
            {x:  1, y:  0}, // 5
            {x:  1, y:  1}, // 6
            {x:  0, y:  1}, // 7
            {x: -1, y:  1}  // 8
        ],
        INTERSECTION_OFFSETS_LEN = INTERSECTION_OFFSETS.length;


    Kinetic.Util.addMethods(Kinetic.Layer, {
        ___init: function(config) {
            this.nodeType = 'Layer';
            this.canvas = new Kinetic.SceneCanvas();
            this.hitCanvas = new Kinetic.HitCanvas();
            // call super constructor
            Kinetic.Container.call(this, config);
        },
        _validateAdd: function(child) {
            var type = child.getType();
            if (type !== 'Group' && type !== 'Shape') {
                Kinetic.Util.error('You may only add groups and shapes to a layer.');
            }
        },
        /**
         * get visible intersection shape. This is the preferred
         * method for determining if a point intersects a shape or not
         * @method
         * @memberof Kinetic.Layer.prototype
         * @param {Object} pos
         * @param {Number} pos.x
         * @param {Number} pos.y
         * @returns {Kinetic.Shape}
         */
        getIntersection: function(pos) {
            var obj, i, intersectionOffset, shape;

            if(this.isVisible()) {
                for (i=0; i<INTERSECTION_OFFSETS_LEN; i++) {
                    intersectionOffset = INTERSECTION_OFFSETS[i];
                    obj = this._getIntersection({
                        x: pos.x + intersectionOffset.x,
                        y: pos.y + intersectionOffset.y
                    });
                    shape = obj.shape;
                    if (shape) {
                        return shape;
                    }
                    else if (!obj.antialiased) {
                        return null;
                    }
                }
            }
            else {
                return null;
            }
        },
        _getIntersection: function(pos) {
            var p = this.hitCanvas.context._context.getImageData(pos.x, pos.y, 1, 1).data,
                p3 = p[3],
                colorKey, shape;

            // fully opaque pixel
            if(p3 === 255) {
                colorKey = Kinetic.Util._rgbToHex(p[0], p[1], p[2]);
                shape = Kinetic.shapes[HASH + colorKey];
                return {
                    shape: shape
                };
            }
            // antialiased pixel
            else if(p3 > 0) {
                return {
                    antialiased: true
                };
            }
            // empty pixel
            else {
                return {};
            }
        },
        drawScene: function(canvas) {
            canvas = canvas || this.getCanvas();

            this._fire(BEFORE_DRAW, {
                node: this
            });

            if(this.getClearBeforeDraw()) {
                canvas.getContext().clear();
            }
            
            Kinetic.Container.prototype.drawScene.call(this, canvas);

            this._fire(DRAW, {
                node: this
            });

            return this;
        },
        drawHit: function() {
            var layer = this.getLayer();

            if(layer && layer.getClearBeforeDraw()) {
                layer.getHitCanvas().getContext().clear();
            }

            Kinetic.Container.prototype.drawHit.call(this);
            return this;
        },
        /**
         * get layer canvas
         * @method
         * @memberof Kinetic.Node.prototype
         */
        getCanvas: function() {
            return this.canvas;
        },
        /**
         * get layer hit canvas
         * @method
         * @memberof Kinetic.Node.prototype
         */
        getHitCanvas: function() {
            return this.hitCanvas;
        },
        /**
         * get layer canvas context
         * @method
         * @memberof Kinetic.Node.prototype
         */
        getContext: function() {
            return this.getCanvas().getContext();
        },
        /**
         * clear scene and hit canvas contexts tied to the layer
         * @method
         * @memberof Kinetic.Node.prototype
         * @param {Object} [bounds]
         * @param {Number} [bounds.x]
         * @param {Number} [bounds.y]
         * @param {Number} [bounds.width]
         * @param {Number} [bounds.height]
         * @example
         * layer.clear();<br>
         * layer.clear(0, 0, 100, 100);
         */
        clear: function(bounds) {
            var context = this.getContext(),
                hitContext = this.getHitCanvas().getContext();

            context.clear(bounds);
            hitContext.clear(bounds);
            return this;
        },
        // extend Node.prototype.setVisible
        setVisible: function(visible) {
            Kinetic.Node.prototype.setVisible.call(this, visible);
            if(visible) {
                this.getCanvas()._canvas.style.display = 'block';
                this.hitCanvas._canvas.style.display = 'block';
            }
            else {
                this.getCanvas()._canvas.style.display = 'none';
                this.hitCanvas._canvas.style.display = 'none';
            }
            return this;
        },
        // extend Node.prototype.setZIndex
        setZIndex: function(index) {
            Kinetic.Node.prototype.setZIndex.call(this, index);
            var stage = this.getStage();
            if(stage) {
                stage.content.removeChild(this.getCanvas()._canvas);

                if(index < stage.getChildren().length - 1) {
                    stage.content.insertBefore(this.getCanvas()._canvas, stage.getChildren()[index + 1].getCanvas()._canvas);
                }
                else {
                    stage.content.appendChild(this.getCanvas()._canvas);
                }
            }
            return this;
        },
        // extend Node.prototype.moveToTop
        moveToTop: function() {
            Kinetic.Node.prototype.moveToTop.call(this);
            var stage = this.getStage();
            if(stage) {
                stage.content.removeChild(this.getCanvas()._canvas);
                stage.content.appendChild(this.getCanvas()._canvas);
            }
        },
        // extend Node.prototype.moveUp
        moveUp: function() {
            if(Kinetic.Node.prototype.moveUp.call(this)) {
                var stage = this.getStage();
                if(stage) {
                    stage.content.removeChild(this.getCanvas()._canvas);

                    if(this.index < stage.getChildren().length - 1) {
                        stage.content.insertBefore(this.getCanvas()._canvas, stage.getChildren()[this.index + 1].getCanvas()._canvas);
                    }
                    else {
                        stage.content.appendChild(this.getCanvas()._canvas);
                    }
                }
            }
        },
        // extend Node.prototype.moveDown
        moveDown: function() {
            if(Kinetic.Node.prototype.moveDown.call(this)) {
                var stage = this.getStage();
                if(stage) {
                    var children = stage.getChildren();
                    stage.content.removeChild(this.getCanvas()._canvas);
                    stage.content.insertBefore(this.getCanvas()._canvas, children[this.index + 1].getCanvas()._canvas);
                }
            }
        },
        // extend Node.prototype.moveToBottom
        moveToBottom: function() {
            if(Kinetic.Node.prototype.moveToBottom.call(this)) {
                var stage = this.getStage();
                if(stage) {
                    var children = stage.getChildren();
                    stage.content.removeChild(this.getCanvas()._canvas);
                    stage.content.insertBefore(this.getCanvas()._canvas, children[1].getCanvas()._canvas);
                }
            }
        },
        getLayer: function() {
            return this;
        },
        remove: function() {
            var stage = this.getStage(), 
                canvas = this.getCanvas(), 
                _canvas = canvas._canvas;

            Kinetic.Node.prototype.remove.call(this);

            if(stage && _canvas && Kinetic.Util._isInDocument(_canvas)) {
                stage.content.removeChild(_canvas);
            }
            return this;
        },
        getStage: function() {
            return this.parent;
        }
    });
    Kinetic.Util.extend(Kinetic.Layer, Kinetic.Container);

    // add getters and setters
    Kinetic.Factory.addGetterSetter(Kinetic.Layer, 'clearBeforeDraw', function() {
        return true;
    });

    /**
     * set flag which determines if the layer is cleared or not
     *  before drawing
     * @name setClearBeforeDraw
     * @method
     * @memberof Kinetic.Node.prototype
     * @param {Boolean} clearBeforeDraw
     */

    /**
     * get flag which determines if the layer is cleared or not
     *  before drawing
     * @name getClearBeforeDraw
     * @method
     * @memberof Kinetic.Node.prototype
     */
})();