fis_lib_vid/lib/data_channel/channel.dart

import 'dart:async';

import 'package:fis_common/event/event_type.dart';
import 'package:fis_vid/async_vid/vid_data.dart';
import 'package:flutter/foundation.dart';
import 'package:vid/us/vid_us_data_http_reader.dart';
import 'package:vid/us/vid_us_image.dart';
import 'package:vid/us/vid_us_image_data.dart';
import 'package:vid/us/vid_us_probe.dart';

import 'channel_stub.dart'
    if (dart.library.html) 'channel_web.dart'
    if (dart.library.io) 'channel_io.dart';

import 'progress_info.dart';

abstract class VidDataChannel {
  @protected
  late final AsyncVidImageDataBase? source;

  final String url;

  VidDataChannel(this.url);

  factory VidDataChannel.create(String url) {
    return VidDataChannelImpl(url);
  }

  /// 下载进度变更事件
  final downloadProgressChanged = FEventHandler<VidDownloadProgressInfo>();

  bool _initialized = false;

  /// 是否初始化完成
  bool get initialized => _initialized;

  /// 开始加载数据
  ///
  /// [timeout] 超时时间，单位ms, 默认5s
  Future<bool> load([int timeout = 5 * 1000]) async {
    if (_initialized) return true;

    try {
      final completer = Completer<bool>();
      final timer = Timer(
        Duration(milliseconds: timeout),
        () {
          if (!completer.isCompleted) {
            completer.complete(_initialized);
          }
          if (!_initialized) {
            source?.close();
          }
        },
      );
      _innerLoad(timeout).then((value) {
        _initialized = true;
        if (timer.isActive) {
          timer.cancel();
        }
        completer.complete(true);
      });
      return completer.future;
    } catch (e) {
      return false;
    }
  }

  /// 分发下载进度回调
  @protected
  void onDownloadCallback(double progress, DownloadErrorException? error) {
    final info = VidDownloadProgressInfo(progress, error: error);
    downloadProgressChanged.emit(this, info);
  }

  Future<bool> _innerLoad(int timeout) async {
    try {
      source = await buildSource();
      source!.setReadHeaderTimeout(timeout + 50); // 50ms buffer 4 timer
      await source!.initialize();
      return true;
    } catch (e) {
      return false;
    }
  }

  VidUsProbe get probe => source!.probe;
  int get imageCount => source!.imageCount;
  VidUsImageFormat get imageFormat => source!.imageFormat;
  Uint8List get extendedData => source!.extendedData;

  /// 获取指定帧
  ///
  /// [index] 帧索引
  ///
  /// [timeout] 超时时间ms
  Future<VidUsImage> getImage(int index, [int timeout = 500]) async {
    source!.setReadImageTimeout(timeout);
    return source!.getImage(index);
  }

  /// 关闭通道
  void close() {
    _initialized = false;
    try {
      source?.close();
    } catch (e) {}
  }

  @protected
  Future<AsyncVidImageDataBase> buildSource();
}