freezer/lib/api/deezer_audio.dart

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

import 'package:crypto/crypto.dart';
import 'package:dart_blowfish/dart_blowfish.dart';
import 'package:encrypt/encrypt.dart';
import 'package:freezer/api/deezer.dart';
import 'package:freezer/api/definitions.dart';
import 'package:freezer/settings.dart';
import 'package:logging/logging.dart';
import 'package:http/http.dart' as http;

class DeezerAudio {
  static const chunkSize = 2048;

  final DeezerAPI deezerAPI;
  AudioQuality quality;
  String trackId;

  DeezerAudio({
    required this.deezerAPI,
    required this.quality,
    required this.trackId,
  });

  static final _logger = Logger('DeezerAudio');

  Future<({Uri uri, String md5origin, String mediaVersion})> fallback(
      {required String md5origin, required String mediaVersion}) async {
    final res = await fallbackUrl(
        md5origin: md5origin,
        preferredQuality: quality,
        trackId: trackId,
        mediaVersion: mediaVersion);
    quality = res.quality;
    trackId = res.trackId;
    return (
      uri: res.uri,
      md5origin: res.md5origin,
      mediaVersion: res.mediaVersion
    );
  }

  Future<
      ({
        String md5origin,
        String trackId,
        String mediaVersion,
        AudioQuality quality,
        Uri uri
      })> fallbackUrl({
    required String md5origin,
    required AudioQuality preferredQuality,
    required String trackId,
    required String mediaVersion,
  }) async {
    _logger.finer("called _fallbackUrl()");

    try {
      final rec = await qualityFallback(
          md5origin, preferredQuality, trackId, mediaVersion);
      return (
        md5origin: md5origin,
        trackId: trackId,
        mediaVersion: mediaVersion,
        quality: rec.$1,
        uri: rec.$2
      );
    } on QualityException {
      _logger.warning("quality fallback failed! trying trackId fallback");
    }

    Map? privateJson;
    try {
      // TRACK ID FALLBACK
      final data = await deezerAPI
          .callApi("deezer.pageTrack", params: {"sng_id": trackId});
      privateJson = data["results"]["DATA"];
      if (privateJson!.containsKey("FALLBACK")) {
        String fallbackId = privateJson["FALLBACK"]["SNG_ID"];
        if (fallbackId != trackId) {
          final newPrivate =
              await deezerAPI.callApi("song.getListData", params: {
            "sng_ids": [fallbackId]
          });
          final Map trackData = newPrivate["results"]["data"][0];
          trackId = trackData["SNG_ID"];
          md5origin = trackData["MD5_ORIGIN"];
          mediaVersion = trackData["MEDIA_VERSION"];
          return await fallbackUrl(
            md5origin: md5origin,
            preferredQuality: preferredQuality,
            trackId: trackId,
            mediaVersion: mediaVersion,
          );
        }
      }
    } catch (e, st) {
      _logger.warning("ID fallback failed! Trying ISRC fallback!", e, st);
    }

    try {
      final data =
          await deezerAPI.callPublicApi("track/isrc:${privateJson!["ISRC"]!}");
      final newId = data["id"] as int;
      if (newId == int.parse(trackId)) throw Exception();

      final newPrivate = await deezerAPI.callApi("song.getListData", params: {
        "sng_ids": [newId]
      });
      final trackData = newPrivate["results"]["data"][0] as Map;
      trackId = trackData["SNG_ID"];
      md5origin = trackData["MD5_ORIGIN"];
      mediaVersion = trackData["MEDIA_VERSION"];
      return await fallbackUrl(
        md5origin: md5origin,
        preferredQuality: preferredQuality,
        trackId: trackId,
        mediaVersion: mediaVersion,
      );
    } catch (e, st) {
      _logger.severe("ISRC Fallback failed, track unavailable!", e, st);
    }

    throw Exception(
        "Every known method of fallback failed, track unavailable!");
  }

  Future<(AudioQuality, Uri)> qualityFallback(String md5origin,
      AudioQuality currentQuality, String trackId, String mediaVersion) async {
    // only use url generation with MP3_128
    currentQuality = AudioQuality.MP3_128;
    final genUri =
        _generateTrackUri(md5origin, currentQuality, trackId, mediaVersion);

    final req = await http.head(genUri, headers: {
      'User-Agent': DeezerAPI.userAgent,
      'Accept-Language': '*',
      'Accept': '*/*'
    });
    int rc = req.statusCode;
    if (rc > 400) {
      _logger.warning(
          "quality fallback, response code: $rc, current quality: $currentQuality");
      switch (currentQuality) {
        case AudioQuality.FLAC:
          currentQuality = AudioQuality.MP3_320;
          break;
        case AudioQuality.MP3_320:
          currentQuality = AudioQuality.MP3_128;
          break;
        case AudioQuality.MP3_128:
        default:
          throw QualityException("No quality to fallback to!");
      }

      return await qualityFallback(
          md5origin, currentQuality, trackId, mediaVersion);
    }

    return (currentQuality, genUri);
  }

  Uri _generateTrackUri(String md5origin, AudioQuality quality, String trackId,
      String mediaVersion) {
    int magic = 164;
    // step 1
    final step1 = <int>[
      ...md5origin.codeUnits,
      magic,
      ...quality.toDeezerQualityInt().toString().codeUnits,
      magic,
      ...trackId.codeUnits,
      magic,
      ...mediaVersion.codeUnits,
    ];

    // get md5 hash of step1
    final md5hex = md5.convert(step1).toString().toLowerCase();

    // step2
    final step2 = <int>[
      ...md5hex.codeUnits,
      magic,
      ...step1,
      magic,
    ];

    // pad step2 with dots to get correct length
    while (step2.length % 16 > 0) {
      // step2.addAll(('.' * (step2.length % 16)).codeUnits);
      step2.add(46);
    }

    // encrypt with AES ECB
    final k = Uint8List.fromList('jo6aey6haid2Teih'.codeUnits);
    final encrypter = Encrypter(AES(Key(k), mode: AESMode.ecb, padding: null));
    final String step3 = encrypter
        .encryptBytes(step2, iv: IV(Uint8List(8)))
        .base16
        .toLowerCase();

    final uri =
        Uri.https('e-cdns-proxy-${md5origin[0]}.dzcdn.net', '/mobile/1/$step3');
    return uri;
  }

  static List<int> getKey(String id) {
    final secret = utf8.encode('g4el58wc0zvf9na1');
    final idmd5 =
        utf8.encode(md5.convert(utf8.encode(id)).toString().toLowerCase());
    final buffer = <int>[];
    for (int i = 0; i < 16; i++) {
      final s0 = idmd5[i];
      final s1 = idmd5[i + 16];
      final s2 = secret[i];
      buffer.add(s0 ^ s1 ^ s2);
    }
    return buffer;
  }

  static List<int> decryptChunk(List<int> key, List<int> data) {
    final Uint8List iv =
        Uint8List.fromList(const [00, 01, 02, 03, 04, 05, 06, 07]);
    final bf = Blowfish(
        key: Uint8List.fromList(key), mode: Mode.cbc, padding: Padding.none)
      ..setIv(iv);
    Uint8List decrypted = bf.decode(data, returnType: Type.uInt8Array);
    return decrypted;
  }

  static Stream<List<int>> decryptionStream(Stream<List<int>> source,
      {required int start, required String trackId}) async* {
    var dropBytes = start % 2048;
    final deezerStart = start - dropBytes;
    int counter = deezerStart ~/ chunkSize;
    final buffer = List<int>.empty(growable: true);
    final key = getKey(trackId);

    await for (var bytes in source) {
      buffer.addAll(bytes);

      int i;
      for (i = 0; i < buffer.length; i += chunkSize) {
        if (buffer.length <= i + chunkSize) {
          break;
        }

        bytes = buffer.sublist(i, i + chunkSize);

        if ((counter % 3) == 0) {
          bytes = decryptChunk(key, bytes);
        }

        if (dropBytes > 0) {
          bytes = bytes.sublist(dropBytes);
          dropBytes = 0;
        }

        counter++;
        yield bytes;
      }

      if (i < buffer.length) {
        buffer.removeRange(0, i);
      } else {
        buffer.clear();
      }
    }

    // add remaining items in buffer

    if (buffer.isNotEmpty) {
      if (dropBytes > 0) {
        yield buffer.sublist(dropBytes);
        return;
      }

      yield buffer;
    }
  }

  static bool isTokenExpired(int trackTokenExpiration) =>
      DateTime.now().millisecondsSinceEpoch ~/ 1000 > trackTokenExpiration;

  Future<Uri?> getUrl(String trackToken, int expiration) =>
      getTrackUrl(deezerAPI, trackId, trackToken, expiration, quality: quality);

  static Future<Uri?> getTrackUrl(
    DeezerAPI deezerAPI,
    String trackId,
    String trackToken,
    int expiration, {
    required AudioQuality quality,
  }) async {
    final String actualTrackToken;
    if (isTokenExpired(expiration)) {
      // get new token via pipe API
      final newTrack = await deezerAPI.track(trackId);
      actualTrackToken = newTrack.trackToken!;
    } else {
      actualTrackToken = trackToken;
    }

    final res = await deezerAPI.getTrackUrl(
        actualTrackToken, quality.toDeezerQualityString());
    if (res.error != null) {
      _logger.warning('Error while getting track url: ${res.error!}');
      return null;
    }
    if (res.sources == null) {
      _logger.warning('Error while getting track url: No sources!');
      return null;
    }

    return Uri.parse(res.sources![0].url);
  }
}