freezer/lib/api/deezer_audio_source.dart

import 'dart:async';
import 'dart:io';
import 'dart:isolate';

import 'package:freezer/api/deezer.dart';
import 'package:freezer/api/deezer_audio.dart';
import 'package:freezer/api/definitions.dart';
import 'package:freezer/settings.dart';
import 'package:just_audio/just_audio.dart';
import 'package:http/http.dart' as http;
import 'package:logging/logging.dart';

typedef _IsolateMessage = (
  Stream<List<int>> source,
  int start,
  String trackId,
  SendPort sendPort
);

// Maybe better implementation of Blowfish CBC instead of random-ass, unpublished library from github?
// This class can be considered a rewrite in Dart of the Java backend (from the StreamServer.deezer() function and also from the Deezer class)
class DeezerAudioSource extends StreamAudioSource {
  static final _logger = Logger("DeezerAudioSource");

  late AudioQuality Function() _getQuality;
  late String _trackId;
  late String _md5origin;
  late String _mediaVersion;
  final String trackToken;
  final int trackTokenExpiration;
  final StreamInfoCallback? onStreamObtained;

  // some cache
  final DeezerAudio _deezerAudio;
  int? _cachedSourceLength;
  String? _cachedContentType;
  Uri? _downloadUrl;

  DeezerAudioSource({
    required AudioQuality Function() getQuality,
    required String trackId,
    required String md5origin,
    required String mediaVersion,
    required this.trackToken,
    required this.trackTokenExpiration,
    this.onStreamObtained,
  }) : _deezerAudio = DeezerAudio(
          deezerAPI: deezerAPI,
          md5origin: md5origin,
          quality: getQuality.call(),
          trackId: trackId,
          mediaVersion: mediaVersion,
        ) {
    _getQuality = getQuality;
    _trackId = trackId;
    _md5origin = md5origin;
    _mediaVersion = mediaVersion;
  }

  AudioQuality? get quality => _deezerAudio.quality;
  String get trackId => _trackId;
  String get md5origin => _md5origin;
  String get mediaVersion => _mediaVersion;

  @override
  Future<StreamAudioResponse> request([int? start, int? end]) async {
    start ??= 0;

    if (_cachedSourceLength != null) {
      if (start == _cachedSourceLength) {
        return StreamAudioResponse(
            sourceLength: _cachedSourceLength,
            contentLength: 0,
            offset: start,
            stream: const Stream<List<int>>.empty(),
            contentType: _cachedContentType!);
      }
    }

    _logger.fine("authorizing...");
    if (!await deezerAPI.authorize()) {
      _logger.severe("authorization failed! cannot continue!");
      throw Exception("Authorization failed!");
    }

    // determine quality to use
    final newQuality = _getQuality.call();

    if (_downloadUrl != null && quality != newQuality) {
      // update currentUrl to get tracks with new quality
      _downloadUrl = null;
    }

    _deezerAudio.quality = newQuality;

    if (_downloadUrl == null) {
      final gottenUrl =
          await _deezerAudio.getUrl(trackToken, trackTokenExpiration);
      if (gottenUrl != null) {
        _downloadUrl = gottenUrl;
      } else {
        _logger.warning('falling back to old url generation!');

        // OLD URL GENERATION
        try {
          _downloadUrl = await _deezerAudio.fallback();
        } on QualityException {
          rethrow;
        }
      }
    }

    _logger.fine("Downloading track from ${_downloadUrl!.toString()}");
    final int deezerStart = start - (start % 2048);
    final req = http.Request('GET', _downloadUrl!)
      ..headers.addAll({
        'User-Agent': DeezerAPI.userAgent,
        'Accept-Language': '*',
        'Accept': '*/*',
        if (deezerStart > 0)
          "Range": "bytes=$deezerStart-${end == null ? '' : end.toString()}"
      });

    final res = await req.send();
    final rc = res.statusCode;
    _logger
        .finest("request sent! rc: $rc, content-length: ${res.contentLength}");
    onStreamObtained?.call(StreamQualityInfo(
      format: quality == AudioQuality.FLAC ? Format.FLAC : Format.MP3,
      source: Source.stream,
      size: start + res.contentLength!,
      quality: quality,
    ));
    if (rc != HttpStatus.ok && rc != HttpStatus.partialContent) {
      throw Exception(await res.stream.bytesToString());
    }

    int dropBytes = start % DeezerAudio.chunkSize;
    _logger.finest(
        "deezerStart: $deezerStart (actual start: $start), end: $end, dropBytes: $dropBytes");
    final stream = DeezerAudio.decryptionStream(res.stream,
        start: start, trackId: trackId);

    final cl = res.contentLength! - dropBytes;

    if (end == null) {
      _cachedSourceLength = cl + start;
    }

    return StreamAudioResponse(
        sourceLength: _cachedSourceLength,
        contentLength: cl,
        offset: start,
        stream: stream,
        contentType: _cachedContentType =
            quality == AudioQuality.FLAC ? "audio/flac" : "audio/mpeg");
  }
}