/**
     * Waits for completed requests. Once the first request has been taken, the method will wait
     * WAIT_TIMEOUT ms longer to collect more completed requests.
     *
     * @return Collected feeds or null if the method has been interrupted during the first waiting
     *     period.
     */
    private List<Feed> collectCompletedRequests() {
      List<Feed> results = new LinkedList<Feed>();
      DownloadRequester requester = DownloadRequester.getInstance();
      int tasks = 0;

      try {
        DownloadRequest request = completedRequests.take();
        parserService.submit(new FeedParserTask(request));
        tasks++;
      } catch (InterruptedException e) {
        return null;
      }

      tasks += pollCompletedDownloads();

      isCollectingRequests = true;

      if (requester.isDownloadingFeeds()) {
        // wait for completion of more downloads
        long startTime = System.currentTimeMillis();
        long currentTime = startTime;
        while (requester.isDownloadingFeeds() && (currentTime - startTime) < WAIT_TIMEOUT) {
          try {
            if (BuildConfig.DEBUG)
              Log.d(TAG, "Waiting for " + (startTime + WAIT_TIMEOUT - currentTime) + " ms");
            sleep(startTime + WAIT_TIMEOUT - currentTime);
          } catch (InterruptedException e) {
            if (BuildConfig.DEBUG) Log.d(TAG, "interrupted while waiting for more downloads");
            tasks += pollCompletedDownloads();
          } finally {
            currentTime = System.currentTimeMillis();
          }
        }

        tasks += pollCompletedDownloads();
      }

      isCollectingRequests = false;

      for (int i = 0; i < tasks; i++) {
        try {
          Feed f = parserService.take().get();
          if (f != null) {
            results.add(f);
          }
        } catch (InterruptedException e) {
          e.printStackTrace();

        } catch (ExecutionException e) {
          e.printStackTrace();
        }
      }

      return results;
    }
 private int pollCompletedDownloads() {
   int tasks = 0;
   for (int i = 0; i < completedRequests.size(); i++) {
     parserService.submit(new FeedParserTask(completedRequests.poll()));
     tasks++;
   }
   return tasks;
 }
        @Override
        public void run() {
          if (BuildConfig.DEBUG) Log.d(TAG, "downloadCompletionThread was started");
          while (!isInterrupted()) {
            try {
              Downloader downloader = downloadExecutor.take().get();
              if (BuildConfig.DEBUG) Log.d(TAG, "Received 'Download Complete' - message.");
              removeDownload(downloader);
              DownloadStatus status = downloader.getResult();
              boolean successful = status.isSuccessful();

              final int type = status.getFeedfileType();
              if (successful) {
                if (type == Feed.FEEDFILETYPE_FEED) {
                  handleCompletedFeedDownload(downloader.getDownloadRequest());
                } else if (type == FeedImage.FEEDFILETYPE_FEEDIMAGE) {
                  handleCompletedImageDownload(status, downloader.getDownloadRequest());
                } else if (type == FeedMedia.FEEDFILETYPE_FEEDMEDIA) {
                  handleCompletedFeedMediaDownload(status, downloader.getDownloadRequest());
                }
              } else {
                numberOfDownloads.decrementAndGet();
                if (!status.isCancelled()) {
                  if (status.getReason() == DownloadError.ERROR_UNAUTHORIZED) {
                    postAuthenticationNotification(downloader.getDownloadRequest());
                  } else if (status.getReason() == DownloadError.ERROR_HTTP_DATA_ERROR
                      && Integer.valueOf(status.getReasonDetailed())
                          == HttpStatus.SC_REQUESTED_RANGE_NOT_SATISFIABLE) {

                    Log.d(TAG, "Requested invalid range, restarting download from the beginning");
                    FileUtils.deleteQuietly(
                        new File(downloader.getDownloadRequest().getDestination()));
                    DownloadRequester.getInstance()
                        .download(DownloadService.this, downloader.getDownloadRequest());
                  } else {
                    Log.e(TAG, "Download failed");
                    saveDownloadStatus(status);
                    handleFailedDownload(status, downloader.getDownloadRequest());
                  }
                }
                sendDownloadHandledIntent();
                queryDownloadsAsync();
              }
            } catch (InterruptedException e) {
              if (BuildConfig.DEBUG) Log.d(TAG, "DownloadCompletionThread was interrupted");
            } catch (ExecutionException e) {
              e.printStackTrace();
              numberOfDownloads.decrementAndGet();
            }
          }
          if (BuildConfig.DEBUG) Log.d(TAG, "End of downloadCompletionThread");
        }
  private void onDownloadQueued(Intent intent) {
    if (AppConfig.DEBUG) Log.d(TAG, "Received enqueue request");
    DownloadRequest request = intent.getParcelableExtra(EXTRA_REQUEST);
    if (request == null) {
      throw new IllegalArgumentException("ACTION_ENQUEUE_DOWNLOAD intent needs request extra");
    }

    Downloader downloader = getDownloader(request);
    if (downloader != null) {
      numberOfDownloads.incrementAndGet();
      downloads.add(downloader);
      downloadExecutor.submit(downloader);
      sendBroadcast(new Intent(ACTION_DOWNLOADS_CONTENT_CHANGED));
    }

    queryDownloads();
  }
        @Override
        public void run() {
          if (AppConfig.DEBUG) Log.d(TAG, "downloadCompletionThread was started");
          while (!isInterrupted()) {
            try {
              Downloader downloader = downloadExecutor.take().get();
              if (AppConfig.DEBUG) Log.d(TAG, "Received 'Download Complete' - message.");
              removeDownload(downloader);
              DownloadStatus status = downloader.getResult();
              boolean successful = status.isSuccessful();

              final int type = status.getFeedfileType();
              if (successful) {
                if (type == Feed.FEEDFILETYPE_FEED) {
                  handleCompletedFeedDownload(downloader.getDownloadRequest());
                } else if (type == FeedImage.FEEDFILETYPE_FEEDIMAGE) {
                  handleCompletedImageDownload(status, downloader.getDownloadRequest());
                } else if (type == FeedMedia.FEEDFILETYPE_FEEDMEDIA) {
                  handleCompletedFeedMediaDownload(status, downloader.getDownloadRequest());
                }
              } else {
                numberOfDownloads.decrementAndGet();
                if (!successful && !status.isCancelled()) {
                  Log.e(TAG, "Download failed");
                  saveDownloadStatus(status);
                }
                sendDownloadHandledIntent();
                queryDownloadsAsync();
              }
            } catch (InterruptedException e) {
              if (AppConfig.DEBUG) Log.d(TAG, "DownloadCompletionThread was interrupted");
            } catch (ExecutionException e) {
              e.printStackTrace();
              numberOfDownloads.decrementAndGet();
            }
          }
          if (AppConfig.DEBUG) Log.d(TAG, "End of downloadCompletionThread");
        }