fis_lib_vid/lib/async_vid/shell/reader.dart

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';

import 'package:fis_common/extensions/date.dart';
import 'package:fis_common/index.dart';
import 'package:fis_common/web/shell_api_hepler.dart';
import 'package:vid/us/vid_us_data_http_reader.dart';

import '../reader.dart';

class AsyncShellVidDataReader extends AsyncVidDataReaderBase {
  final int minChunkSize;
  int _imageCount = 0;
  bool _isBreak = false;
  bool _isStop = false;
  int _skipFrameIndex = 0;
  Completer<void> _completer = Completer<void>();

  late final String id =
      DateTime.now().format('MMddHHmmssSSS') + hashCode.toString();

  AsyncShellVidDataReader(
    String url, {
    DownloadCallback? downloadCallback,
    this.minChunkSize = 65536,
  }) : super(url, downloadCallback: downloadCallback);

  @override
  void close() {
    _isStop = true;
    cancelFetchVid();
  }

  @override
  void startDownload() async {
    final size = await getFileSize();
    // 获取到size即开始下载
    if (size == null) {
      setError(true, 'Get file size fail.');
    } else if (isVrd) {
      _imageCount = size;
      fetchFrames(0, size, isNeedReload: true);
    }
  }

  @override
  Future<void> skipToFrame(int index) async {
    if (_skipFrameIndex == index || index == 0) {
      return;
    }
    //停用上个不断获取帧的请求
    if (!_completer.isCompleted) {
      _isStop = true;
      _completer.complete();
    }
    _skipFrameIndex = index;
    print(
        "_skipFrameIndex change:$_skipFrameIndex _completer:${_completer.isCompleted}");
    await Future.delayed(const Duration(milliseconds: 2000));
    _isStop = false;
    print("fetchFrames : $_skipFrameIndex $_imageCount");
    //从跳帧的位置开始不断获取数据
    fetchFrames(_skipFrameIndex, _imageCount, isNeedReload: true);
  }

  void cancelFetchVid() {
    ShellApiHelper.call('cancelFetchVid', id);
  }

  /// 接收分片数据
  void receiveChunk(Uint8List chunk) {
    appendChunk(chunk);
    final progress = downloadedSize / totalSize;
    print('updateProgress : $progress');
    updateProgress(progress);
  }

  //注意：此处VRD返回的是总帧数，非VRD返回的是数据大小
  Future<int?> getFileSize() async {
    final result = await ShellApiHelper.call(
      (isVrd) ? 'dynamicFetchVidAsync' : 'fetchVid',
      {
        'Id': id,
        'Url': url,
        'MinChunkSize': minChunkSize,
      },
    );
    if (result != null) {
      if (isVrd) {
        _imageCount = result!;
      }
      initChunk(result);
    }
    await fetchFrames(0, 1, isNeedReload: true);
    print("getFileSize result:$result");
    return result;
  }

  @override
  Future<void> fetchFrames(int startIndex, int size,
      {bool isNeedReload = false}) async {
    _completer = Completer<void>();
    int batchSize = 5; // 每次获取的帧数

    try {
      for (int start = startIndex; start < size; start += batchSize) {
        if (_isStop) {
          break;
        }
        int end = start + batchSize;
        if (end > size) {
          end = size; // 确保最后一次获取不会超出范围
        }
        print("batchFetchFrames: start:$start end:$end");
        bool result = await batchFetchFrames(
          start,
          end,
          isNeedReload: isNeedReload,
        );
        if (_isStop) {
          break;
        }
        if (result == false) {
          continue;
        }
      }
    } finally {
      _completer.complete();
    }
    return _completer.future;
  }

  Future<bool> batchFetchFrames(
    int start,
    int end, {
    bool isNeedReload = false,
  }) async {
    print("batchFetchFrames : $start $end");
    final result = await ShellApiHelper.call(
      'batchFetchFrames',
      {
        'Id': id,
        'Url': url,
        'Start': start,
        'End': end,
      },
    );
    if (_isStop) {
      return false;
    }
    if (result.toString().isEmpty) {
      print("batchFetchFrames result is empty");
      _isBreak = true;
      if (isNeedReload) {
        await Future.delayed(const Duration(milliseconds: 1000));
        return await batchFetchFrames(start, end, isNeedReload: isNeedReload);
      }
      return false;
    }
    List<String> base64Frames = result.toString().split("&");
    int index = start;
    for (var f in base64Frames) {
      var frame = base64Decode(f);
      appendFrame(frame, index);
      print("appendFrame ${frame.length} index: $index");
      //非空，且之前没有中断，则允许更新进度
      if (frame.isNotEmpty) {
        if (!_isBreak) {
          if (_isStop) {
            return false;
          }
          updateProgress(index / _imageCount);
        }
      } else {
        //如果遇到获取不到帧，则中断更新进度
        print('updateProgress isBreak true');
        _isBreak = true;
      }
      index++;
    }
    //base64Decode
    print("batchFetchFrames result:${base64Frames.length}");
    return true;
  }
}