MediaInfoUpdater.java

/**
 * Copyright 2009 Marc Stogaitis and Mimi Sun
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.gmote.server.media;

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.Timer;
import java.util.TimerTask;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.blinkenlights.jid3.MP3File;
import org.gmote.common.TcpConnection;
import org.gmote.common.media.MediaMetaInfo;
import org.gmote.common.packet.AbstractPacket;
import org.gmote.common.packet.MediaInfoPacket;
import org.gmote.common.packet.MediaInfoReqPacket;

/**
 * Periodically polls information about the currently playing media and sends it
 * to the phone. This is needed for media players that do not allow us to
 * receive a callback when media changes (such as a playlist going to the next
 * song, or the user changing the song directly on the computer's user
 * interface.
 * 
 * @author Marc Stogaitis
 */

public class MediaInfoUpdater {
  private static final Logger LOGGER = Logger.getLogger(MediaInfoUpdater.class.getName());
  private static MediaInfoUpdater instance = null;
  private static final int MEDIA_INFO_UPDATE_DELAY = 5000;
  private byte[] lastGeneratedImageData = null;
  
  Timer pollingTimer = new Timer("MediaInfoTimer");

  MediaPlayerInterface mediaPlayer;
  TcpConnection con = null;

  // Private constructor to prevent instantiation.
  private MediaInfoUpdater() {

  }

  public static MediaInfoUpdater instance() {
    if (instance == null) {
      instance = new MediaInfoUpdater();
    }
    return instance;
  }

  public void setClientConnection(TcpConnection con) {
    this.con = con;
    changePollingState();
  }

  /**
   * Sends information about the currently playing media to the client.
   * 
   * @param mediaInfo
   */
  public synchronized void sendMediaUpdate(MediaMetaInfo mediaInfo) {
    if (mediaInfo == null || con == null) {
      return;
    } else {
      try {
        LOGGER.info("Sending media info update");
        con.sendPacket(new MediaInfoPacket(mediaInfo));
      } catch (IOException e) {
        LOGGER.log(Level.SEVERE, e.getMessage(), e);
        setClientConnection(null);
      }
    }
  }

  public synchronized void setPlayerToPoll(MediaPlayerInterface mediaPlayer) {
    this.mediaPlayer = mediaPlayer;
    changePollingState();
  }

  private boolean shouldPoll() {
    return mediaPlayer != null;
  }

  private boolean clientIsConnected() {
    return con != null;
  }

  private void changePollingState() {
    if (!clientIsConnected()) {
      pollingTimer.cancel();
    } else if (!shouldPoll()) {
      pollingTimer.cancel();
    } else {
      pollingTimer.cancel();
      pollingTimer = new Timer("MediaInfoTimer");
      pollingTimer.schedule(new UpdateTask(), MEDIA_INFO_UPDATE_DELAY, MEDIA_INFO_UPDATE_DELAY);
    }
  }

  class UpdateTask extends TimerTask {
    @Override
    public synchronized void run() {
      sendMediaUpdate(mediaPlayer.getNewMediaInfo());
    }
  }

  /**
   * Convenience function to generate information about media based only on a
   * file on the local disc. Most media players have access to more information
   * than this and will therefore implement their own algorithm.
   * @param forceImageUpdate 
   */
  public MediaMetaInfo generateMediaMetaInfo(String fileName, boolean forceImageUpdate) {
    MP3File mp3 = new MP3File(new File(fileName));
    MediaMetaInfo fileInfo = PlayerUtil.getSongMetaInfo(mp3);
    byte[] imageData = PlayerUtil.extractEmbeddedImageData(mp3);
    if (imageData == null) {
      // In windows, a folder.jpg file often contains the album art
      imageData = PlayerUtil.extractImageFromFolder(fileName);
    }
    
    boolean imageIsSame = lastGeneratedImageData != null && imageData != null && Arrays.equals(lastGeneratedImageData, imageData);
    if (imageIsSame && !forceImageUpdate) {
      fileInfo.setImageSameAsPrevious(true);
    } else {
      lastGeneratedImageData = imageData;
      fileInfo.setImage(imageData);
    }
    
    return fileInfo;
  }
  
  /**
   * Returns a packet with the latest media info.
   */
  public AbstractPacket handleMediaInfoReq(AbstractPacket packet) {
    MediaInfoReqPacket mediaInfoReq = (MediaInfoReqPacket) packet;
    if (new File(mediaInfoReq.getPathAndFileName()).exists()) {
      MediaMetaInfo fileInfo = generateMediaMetaInfo(mediaInfoReq.getPathAndFileName(), mediaInfoReq.isForceImageUpdate());
      if (fileInfo.getTitle() != null || fileInfo.getArtist() != null
          || fileInfo.getImage() != null) {
        return new MediaInfoPacket(fileInfo);
      }
    }
    return null;
  }
}