package org.daisy.pipeline.audio.impl;
   
   import java.io.File;
   import java.io.FileOutputStream;
   import java.io.InputStream;
   import java.util.Map;
   import java.util.Optional;
   
   import javax.sound.sampled.AudioFileFormat;
  import javax.sound.sampled.AudioInputStream;
  
  import javazoom.jl.converter.Converter;
  
  import com.google.common.io.ByteStreams;
  
  import org.daisy.pipeline.audio.AudioDecoder;
  import org.daisy.pipeline.audio.AudioDecoderService;
  import org.daisy.pipeline.audio.AudioFileTypes;
  
  import org.osgi.service.component.annotations.Component;
  
  /*
   * Note that it is in theory also possibly to support MP3 in SystemAudioDecoder, through the MP3SPI
   * library (com.googlecode.soundlibs:mp3spi). When this library is on the class path,
   * AudioSystem.getAudioInputStream() applied on an MP3 file will return an MPEG encoded audio
   * stream, which we could then convert to a PCM encoded audio stream. Unfortunately this conversion
   * does not work for some reason. The resulting PCM encoded stream contains all zeros. Another issue
   * is that when MP3SPI is on the class path, AudioSystem.getAudioInputStream() may incorrectly read
   * a WAV file as MPEGL1.
   */
  @Component(
  	name = "jlayer-mp3-decoder",
  	immediate = true,
  	service = { AudioDecoderService.class }
  )
  public class JLayerMP3Decoder implements AudioDecoderService {
  
  	@Override
  	public boolean supportsFileType(AudioFileFormat.Type fileType) {
  		return AudioFileTypes.MP3.equals(fileType);
  	}
  
  	@Override
  	public Optional<AudioDecoder> newDecoder(Map<String,String> params) {
  		if (instance == null)
  			instance = new AudioDecoder() {
  					@Override
  					public AudioInputStream decode(InputStream input) throws Throwable {
  						File tmpMp3 = File.createTempFile("mp3-to-wav-", ".mp3");
  						ByteStreams.copy(input, new FileOutputStream(tmpMp3));
  						try {
  							return decode(tmpMp3);
  						} finally {
  							tmpMp3.delete();
  						}
  					}
  					@Override
  					public AudioInputStream decode(File inputFile) throws Throwable {
  						File tmpWav = File.createTempFile("mp3-to-wav-", ".wav");
  						tmpWav.deleteOnExit();
  						new Converter().convert(inputFile.getAbsolutePath(), tmpWav.getAbsolutePath());
  						try {
  							return SystemAudioDecoder.getInstance().decode(tmpWav);
  						} finally {
  							tmpWav.delete();
  						}
  					}
  				};
  		return Optional.of(instance);
  	}
  
  	private static AudioDecoder instance = null;
  
  }