@Override
  public synchronized void download(
      List<MusicDirectory.Entry> songs, boolean save, boolean autoplay, boolean playNext) {
    shufflePlay = false;
    int offset = 1;

    if (songs.isEmpty()) {
      return;
    }

    if (save) {
      for (MusicDirectory.Entry song : songs) {
        DownloadFile downloadFile = forSong(song);
        downloadFile.pin();
        if (!downloadFile.isWorkDone() && !downloadList.contains(downloadFile)) {
          downloadList.add(downloadFile);
        }
      }
    } else if (playNext) {
      if (autoplay && getCurrentPlayingIndex() >= 0) {
        offset = 0;
      }
      for (MusicDirectory.Entry song : songs) {
        DownloadFile downloadFile = new DownloadFile(this, song);
        downloadList.add(getCurrentPlayingIndex() + offset, downloadFile);
        offset++;
      }

    } else {
      for (MusicDirectory.Entry song : songs) {
        DownloadFile downloadFile = new DownloadFile(this, song);
        downloadList.add(downloadFile);
      }
    }

    revision++;
    updateJukeboxPlaylist();

    if (autoplay) {
      play(0);
    } else {
      if (currentPlaying == null) {
        currentPlaying = downloadList.get(0);
      }
      checkDownloads();
    }
    lifecycleSupport.serializeDownloadQueue();
  }
  protected synchronized void checkDownloads() {

    if (!Util.isExternalStoragePresent() || !lifecycleSupport.isExternalStorageAvailable()) {
      return;
    }

    if (shufflePlay) {
      checkShufflePlay();
    }

    if (jukeboxEnabled || !Util.isNetworkConnected(this)) {
      return;
    }

    if (downloadList.isEmpty()) {
      return;
    }

    // Need to download current playing?
    if (currentPlaying != null
        && currentPlaying != currentDownloading
        && !currentPlaying.isCompleteFileAvailable()) {

      // Cancel current download, if necessary.
      if (currentDownloading != null) {
        currentDownloading.cancelDownload();
      }

      currentDownloading = currentPlaying;
      currentDownloading.download();
      cleanupCandidates.add(currentDownloading);
    }

    // Find a suitable target for download.
    else if (currentDownloading == null
        || currentDownloading.isWorkDone()
        || currentDownloading.isFailed()) {

      int n = size();
      if (n == 0) {
        return;
      }

      int preloaded = 0;

      int start = currentPlaying == null ? 0 : getCurrentPlayingIndex();
      int i = start;
      do {
        DownloadFile downloadFile = downloadList.get(i);
        if (!downloadFile.isWorkDone()) {
          if (downloadFile.shouldSave() || preloaded < Util.getPreloadCount(this)) {
            currentDownloading = downloadFile;
            currentDownloading.download();
            cleanupCandidates.add(currentDownloading);
            break;
          }
        } else if (currentPlaying != downloadFile) {
          preloaded++;
        }

        i = (i + 1) % n;
      } while (i != start);
    }

    // Delete obsolete .partial and .complete files.
    cleanup();
  }