/* global createTag, createNS, isSafari */
/* exported ImagePreloader */

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.loadedAssets += 1;
    if (this.loadedAssets === this.totalImages) {
      if (this.imagesLoadedCb) {
        this.imagesLoadedCb(null);
      }
    }
  }

  function getAssetsPath(assetData, assetsPath, originalPath) {
    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 = originalPath;
      path += assetData.u ? assetData.u : '';
      path += assetData.p;
    }
    return path;
  }

  function testImageLoaded(img) {
    var _count = 0;
    var intervalId = setInterval(function () {
      var box = img.getBBox();
      if (box.width || _count > 500) {
        this._imageLoaded();
        clearInterval(intervalId);
      }
      _count += 1;
    }.bind(this), 50);
  }

  function createImageData(assetData) {
    var path = getAssetsPath(assetData, this.assetsPath, this.path);
    var img = createNS('image');
    if (isSafari) {
      this.testImageLoaded(img);
    } else {
      img.addEventListener('load', this._imageLoaded, false);
    }
    img.addEventListener('error', function () {
      ob.img = proxyImage;
      this._imageLoaded();
    }.bind(this), false);
    img.setAttributeNS('http://www.w3.org/1999/xlink', 'href', path);
    if (this._elementHelper.append) {
      this._elementHelper.append(img);
    } else {
      this._elementHelper.appendChild(img);
    }
    var ob = {
      img: img,
      assetData: assetData,
    };
    return ob;
  }

  function createImgData(assetData) {
    var path = getAssetsPath(assetData, this.assetsPath, this.path);
    var img = createTag('img');
    img.crossOrigin = 'anonymous';
    img.addEventListener('load', this._imageLoaded, 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;
    var 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;
    var len = this.images.length;
    while (i < len) {
      if (this.images[i].assetData === assetData) {
        return this.images[i].img;
      }
      i += 1;
    }
    return null;
  }

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

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

  function setCacheType(type, elementHelper) {
    if (type === 'svg') {
      this._elementHelper = elementHelper;
      this._createImageData = this.createImageData.bind(this);
    } else {
      this._createImageData = this.createImgData.bind(this);
    }
  }

  function ImagePreloaderFactory() {
    this._imageLoaded = imageLoaded.bind(this);
    this.testImageLoaded = testImageLoaded.bind(this);
    this.assetsPath = '';
    this.path = '';
    this.totalImages = 0;
    this.loadedAssets = 0;
    this.imagesLoadedCb = null;
    this.images = [];
  }

  ImagePreloaderFactory.prototype = {
    loadAssets: loadAssets,
    setAssetsPath: setAssetsPath,
    setPath: setPath,
    loaded: loaded,
    destroy: destroy,
    getImage: getImage,
    createImgData: createImgData,
    createImageData: createImageData,
    imageLoaded: imageLoaded,
    setCacheType: setCacheType,
  };

  return ImagePreloaderFactory;
}());