var ImagePreloader = (function(){

    var proxyImage = (function(){
        var canvas = createTag('canvas');
        canvas.width = 1;
        canvas.height = 1;
        var ctx = canvas.getContext('2d');
        ctx.fillStyle = 'rgba(0,0,0,0)';
        ctx.fillRect(0, 0, 1, 1);
        return canvas;
    }())

    function imageLoaded(){
        this.pendingImages -= 1;
        if(this.pendingImages === 0){
            if(this.imagesLoadedCb) {
                this.imagesLoadedCb(null);
            }
        }
    }

    function getAssetsPath(assetData, assetsPath, original_path) {
        var path = '';
        if (assetData.e) {
            path = assetData.p;
        } else if(assetsPath) {
            var imagePath = assetData.p;
            if (imagePath.indexOf('images/') !== -1) {
                imagePath = imagePath.split('/')[1];
            }
            path = assetsPath + imagePath;
        } else {
            path = original_path;
            path += assetData.u ? assetData.u : '';
            path += assetData.p;
        }
        return path;
    }

    function createImageData(assetData) {
        var path = getAssetsPath(assetData, this.assetsPath, this.path);
        var img = createTag('img');
        img.crossOrigin = 'anonymous';
        img.addEventListener('load', this._imageLoaded.bind(this), false);
        img.addEventListener('error', function() {
            ob.img = proxyImage;
            this._imageLoaded();
        }.bind(this), false);
        img.src = path;
        var ob = {
            img: img,
            assetData: assetData
        }
        return ob;
    }

    function loadAssets(assets, cb){
        this.imagesLoadedCb = cb;
        var i, len = assets.length;
        for (i = 0; i < len; i += 1) {
            if(!assets[i].layers){
                this.totalImages += 1;
                this.images.push(this._createImageData(assets[i]));
            }
        }
    }

    function setPath(path){
        this.path = path || '';
    }

    function setAssetsPath(path){
        this.assetsPath = path || '';
    }

    function getImage(assetData) {
        var i = 0, len = this.images.length;
        while (i < len) {
            if (this.images[i].assetData === assetData) {
                return this.images[i].img;
            }
            i += 1;
        }
    }

    function destroy() {
        this.imagesLoadedCb = null;
        this.images.length = 0;
    }

    function loaded() {
        return this.totalImages === this.loadedAssets;
    }

    return function ImagePreloader(){
        this.loadAssets = loadAssets;
        this.setAssetsPath = setAssetsPath;
        this.setPath = setPath;
        this.loaded = loaded;
        this.destroy = destroy;
        this.getImage = getImage;
        this._createImageData = createImageData;
        this._imageLoaded = imageLoaded;
        this.assetsPath = '';
        this.path = '';
        this.totalImages = 0;
        this.loadedAssets = 0;
        this.imagesLoadedCb = null;
        this.images = [];
    };
}());