package org.daisy.pipeline.audio.impl;
   
   import java.io.BufferedInputStream;
   import java.io.InputStream;
   import java.util.Map;
   import java.util.Optional;
   
   import javax.sound.sampled.AudioFileFormat;
   import javax.sound.sampled.AudioInputStream;
  import javax.sound.sampled.AudioSystem;
  import javax.sound.sampled.UnsupportedAudioFileException;
  
  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;
  
  @Component(
  	name = "system-audio-decoder",
  	immediate = true,
  	service = { AudioDecoderService.class }
  )
  public class SystemAudioDecoder implements AudioDecoderService {
  
  	@Override
  	public boolean supportsFileType(AudioFileFormat.Type fileType) {
  		return AudioFileTypes.WAVE.equals(fileType);
  	}
  
  	@Override
  	public Optional<AudioDecoder> newDecoder(Map<String,String> params) {
  		return Optional.of(getInstance());
  	}
  
  	static AudioDecoder instance = null;
  
  	static AudioDecoder getInstance() {
  		if (instance == null)
  			instance = new AudioDecoder() {
  					@Override
  					public AudioInputStream decode(InputStream input) throws UnsupportedAudioFileException, Throwable {
  						/* Javadoc of AudioSystem.getAudioInputStream: The implementation of this
  						 * method may require multiple parsers to examine the stream to determine
  						 * whether they support it. These parsers must be able to mark the stream,
  						 * read enough data to determine whether they support the stream, and, if
  						 * not, reset the stream's read pointer to its original position. If the
  						 * input stream does not support these operation, this method may fail with
  						 * an IOException. */
  						if (!input.markSupported())
  							input = new BufferedInputStream(input);
  						return AudioSystem.getAudioInputStream(input);
  					}
  				};
  		return instance;
  	}
  }