var splitUpload =  (function(){
	/**
	 * 分割上传其中一块
     * @param  {[type]} file        [文件Flie对象]
	 * @param  {[type]} totalSize   [总大小]
	 * @param  {[type]} eachSize    [每次大小]
     * @param  {[type]} SucCallback [成功回调]
     *         回调参数
     *         		@param thunkTo [已上传大小]       
     *         		@param totalSize [总大小]        
     * @param  {[type]} ErrCallback [失败回调]
     *         回调参数
     *         		@param res [ajax回调的response]       
	 * @param  {[type]} count       [上传的次数] 
	 * @param  {[type]} counts       [上传的总次数]
     * @param  {[string]} uploadLink  [上传链接]  默认
	 */
    function loop(file, totalSize, eachSize, SucCallback, ErrCallback, count, counts, uploadLink){
    	var thunkFrom = count *	eachSize;// 切割起始端
    	var thunkTo = (count + 1) * eachSize > totalSize ? totalSize : (count + 1) * eachSize;// 切割末端

		fd = new FormData();
		fd.append('theFile', file.slice(thunkFrom, thunkTo)); // 分好段的文件
		fd.append('fileName', file.name); // 文件名
		fd.append('totalSize', totalSize); // 大小
		fd.append('isFirstChunk', count === 0); // 是否第一次上传
		fd.append('isLastChunk', count === counts - 1); // 是否最后一次上传

		var xhr = new XMLHttpRequest();

		xhr.open("post", uploadLink, true);

		xhr.onreadystatechange = function () {
          	if(xhr.readyState==4 && xhr.status==200){
	          	var rs = JSON.parse(xhr.responseText);
	          	if(rs.status == 200){
	          		SucCallback(thunkTo, totalSize)
	          		// isLastChunk
	          		if(count === counts - 1){
	          			return;
	          		}
	          		// 继续上传
					loop(file, totalSize, eachSize, SucCallback, ErrCallback, ++count, counts, uploadLink)
	          	}else{
          			ErrCallback(rs)
	          	}
			}
		};
		xhr.send(fd);
    }
    /**
     * 分割上传
     * @param  {[type]} file        [文件Flie对象]
     * @param  {[function]} SucCallback [成功回调]
     * @param  {[function]} ErrCallback [失败回调]
     * @param  {[string]} uploadLink  [上传链接] default 
     */
	return function(file, SucCallback, ErrCallback, uploadLink) {
		uploadLink = uploadLink || '/upload';
        var totalSize = file.size; // 总大小
        var eachSize = 1024 * 1000; // 每次上传大小  这里是100kb
        var counts = Math.ceil(totalSize / eachSize); // 上传的总次数

		loop(file, totalSize, eachSize, SucCallback, ErrCallback, 0, counts, uploadLink)
	//test
	/*size > 1024
            ? size / 1024 > 1024
	            ? size / (1024 * 1024) > 1024
		            ? (size / (1024 * 1024 * 1024)).toFixed(2) + 'GB'
		            : (size / (1024 * 1024)).toFixed(2) + 'MB'
	            : (size / 1024).toFixed(2) + 'KB'
            : (size).toFixed(2) + 'B';*/
})();