import { Component } from "./component";

import SparkMD5 from 'spark-md5';

export interface IAsset {
    assetType?: string;
    fetch?: Function;
}


/**
 * @description :  Asset 可以考虑放在资源管理器中
 * @param        {*}
 * @return       {*}
 * @example     : 
 */
export abstract class Asset extends Component implements IAsset {
    //文件的类型
    assetType?: string;
    // 如果是文本 , 文本的内容
    content?: any;
    //链接
    url: string = "";
    createTime: number = Date.now();
    // md5 hash码 用来快速判断文件是否相同
    hash: string = "";

    constructor() {
        super();
    }

    save() {

    }


    imageMD5(file: any): Promise<string> {
        var blobSlice = File.prototype.slice || (File as any).prototype.mozSlice || (File as any).prototype.webkitSlice;
        const chunkSize = 2097152; // read in chunks of 2MB
        const chunks = Math.ceil(file.size / chunkSize);
        let currentChunk = 0;
        const spark = new SparkMD5.ArrayBuffer();
        let log: string = "";

        const deferred = Promise;
        function frOnload(e: any): Promise<string> | void {
            spark.append(e.target.result); // append array buffer
            currentChunk++;
            if (currentChunk < chunks)
                return loadNext();
            else {
                deferred.resolve(spark.end());
            }
        };
        function frOnerror() {
            deferred.reject('文件出错');
        };

        function loadNext() {
            var fileReader = new FileReader();
            fileReader.onload = frOnload;
            fileReader.onerror = frOnerror;
            var start = currentChunk * chunkSize,
                end = ((start + chunkSize) >= file.size) ? file.size : start + chunkSize;
            fileReader.readAsArrayBuffer(blobSlice.call(file, start, end));
        }

        loadNext();
        return Promise.resolve("as")/* .promise */;
    }

}