/**
 * 文件下载器（框架 §8.3 / §9）。封装 @kit.NetworkKit http 流式请求 requestInStream。
 *
 * 边收边写盘（不全量入内存，支持大 zip），经回调汇报百分比进度。
 * http 流式请求为**原生异步、不阻塞 UI 线程**——故无需 TaskPool 即满足"下载不阻塞 UI"。
 * 进度回调在 UI 线程触发（http 回调即在调用线程），调用方可直接更新 UI。
 */
import { http } from '@kit.NetworkKit';
import { fileIo as fs } from '@kit.CoreFileKit';
import { FileSystem } from '../fs/FileSystem';
import { Logger } from 'common';

/** 下载进度回调：percent 为 0~100 整数（总长未知时回 -1）。 */
export type ProgressCallback = (percent: number) => void;

export class Downloader {
  private static readonly log: Logger = Logger.tag('Downloader');

  /** 下载 url 到 savePath（覆盖旧文件），可选进度回调。失败抛出。 */
  static async download(url: string, savePath: string, onProgress?: ProgressCallback): Promise<void> {
    FileSystem.ensureDir(FileSystem.dirOf(savePath));
    FileSystem.rmrf(savePath);
    const file: fs.File = fs.openSync(savePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE | fs.OpenMode.TRUNC);
    let offset: number = 0;
    const req: http.HttpRequest = http.createHttp();

    req.on('dataReceive', (chunk: ArrayBuffer) => {
      fs.writeSync(file.fd, chunk, { offset });
      offset += chunk.byteLength;
    });
    if (onProgress !== undefined) {
      req.on('dataReceiveProgress', (info: http.DataReceiveProgressInfo) => {
        const pct: number = info.totalSize > 0
          ? Math.floor(info.receiveSize * 100 / info.totalSize) : -1;
        onProgress(pct);
      });
    }

    try {
      const code: number = await req.requestInStream(url, {
        method: http.RequestMethod.GET,
        usingCache: false,
        connectTimeout: 15000,
        readTimeout: 300000,
      });
      if (code < 200 || code >= 300) {
        throw new Error(`download http ${code}`);
      }
      Downloader.log.i(`download ${url} -> ${savePath} (${offset} bytes)`);
    } finally {
      req.off('dataReceive');
      if (onProgress !== undefined) {
        req.off('dataReceiveProgress');
      }
      req.destroy();
      fs.closeSync(file);
    }
  }
}