/**
 * The image factory takes care that we only make requests for Image URLs which we have not already started downloading
 * @param graphics GameLib.D3.Graphics
 * @param baseUrl
 * @returns {Function}
 * @constructor
 */
GameLib.D3.ImageFactory = function (
    graphics,
    baseUrl
) {

    graphics.isNotThreeThrow();

    var promiseList = {};

    return function(imagePath, progressCallback) {

        if (!imagePath) {
            console.log('Attempted to download bad URL : ' + imagePath);
            throw new Error('Bad URL : ' + imagePath);
        }

        if (promiseList[imagePath]) {
            return promiseList[imagePath];
        }

        var defer = Q.defer();

        promiseList[imagePath] = defer.promise;

        GameLib.D3.ImageFactory.LoadImage(graphics, baseUrl + imagePath, defer, progressCallback);

        return promiseList[imagePath];
    }
};

/**
 * Loads an image and resolves the defered promise once it succeeded (or failed)
 * @param graphics
 * @param url
 * @param defer
 * @param progressCallback
 * @constructor
 */
GameLib.D3.ImageFactory.LoadImage = function (
    graphics,
    url,
    defer,
    progressCallback
) {

    var loader = new graphics.instance.ImageLoader();

    loader.crossOrigin = '';

    loader.load(
        url + '?ts=' + Date.now(),
        function (image) {
            defer.resolve(image);
        },
        function onProgress(xhr) {
            if (progressCallback) {
                progressCallback((xhr.loaded / xhr.total * 100));
            }
        },
        function onError() {
            defer.reject('Failed to download image : ' + url);
        }
    );
};