/**
 * Image resizing library
 * To resize an image before uploading it
 */
window.ImageResize = (function () {

    'use strict';

    // Polyfill
    if (!HTMLCanvasElement.prototype.toBlob) {
        Object.defineProperty(HTMLCanvasElement.prototype, 'toBlob', {
            value: function (callback, type, quality) {

                var binStr = atob( this.toDataURL(type, quality).split(',')[1] ),
                    len = binStr.length,
                    arr = new Uint8Array(len);

                for (var i=0; i<len; i++ ) {
                    arr[i] = binStr.charCodeAt(i);
                }

                callback( new Blob( [arr], {type: type || 'image/png'} ) );
            }
        });
    };

    function ImageResize() {
        //
    }

    ImageResize.prototype = {

        init: function(outputQuality) {
            this.outputQuality = (outputQuality === 'undefined' ? 0.8 : outputQuality);
        },

        photo: function(file, maxSize, outputType, callback) {

            var _this = this;

            var reader = new FileReader();
            reader.onload = function (readerEvent) {
                _this.resize(readerEvent.target.result, maxSize, outputType, callback);
            }
            reader.readAsDataURL(file);

        },

        resize: function(dataURL, maxSize, outputType, callback) {

            var _this = this;

            var image = new Image();
            image.onload = function (imageEvent) {

                // Resize image
                var canvas = document.createElement('canvas'),
                    width = image.width,
                    height = image.height;
                if (width > height) {
                    if (width > maxSize) {
                        height *= maxSize / width;
                        width = maxSize;
                    }
                } else {
                    if (height > maxSize) {
                        width *= maxSize / height;
                        height = maxSize;
                    }
                }
                canvas.width = width;
                canvas.height = height;
                canvas.getContext('2d').drawImage(image, 0, 0, width, height);

                _this.output(canvas, outputType, callback);

            }
            image.src = dataURL;

        },

        output: function(canvas, outputType, callback) {

            switch (outputType) {

                case 'file':
                    canvas.toBlob(function (blob) {
                        callback(blob);
                    }, 'image/jpeg', 0.8);
                    break;

                case 'dataURL':
                    callback(canvas.toDataURL('image/jpeg', 0.8));
                    break;

            }

        }

    };

    return ImageResize;

}());