/**
 * A class that encodes a Sound using an array of differences
 * between sound samples.  It is lossless only if every
 * difference is in the range [-128..127].
 * 
 * @author Eugene Wallingford
 * @date   November 7, 2006
 */

import java.io.*;

public class DiffSound
{
  //  ----- Instance variables ----------------------------------
  
  private int firstSample;
  private byte[] differences;
  
  //  ----- Constructors ----------------------------------------
  
  /**
   * Initialize the DiffSound using a given first sample
   * and array of differences between adjacent samples.
   * @param sample   the first sample in the sound [-32768..32767]
   * @param diffs    an array of differences between samples
   */
  public DiffSound( int sample, byte[] diffs )
  {
    firstSample = sample;
    differences = diffs;
  }
  
  //  ----- I/O methods -----------------------------------------
  
  /**
   * Display to standard output the difference values
   * between locations start and end, inclusive.
   * @param start   the location of the first value to display
   * @param end     the location of the last value to display
   */
  public void displayDifferences( int start, int end )
  {
    for (int i = start; i < end; i++ )
      System.out.println( differences[i] );
  }
  
  /**
   * Write compressed object to a file of the given name,
   * in the media path directory
   * @param filename   the short name of the file
   */
  public void write( String filename )
  {
    String fullname = FileChooser.getMediaPath( filename );
    
    try {
      BufferedWriter file = new BufferedWriter( new FileWriter(fullname) );
      
      file.write( ""+ firstSample );
      file.newLine();
      file.write( ""+ differences.length );
      file.newLine();
      
      for (int i = 0; i < differences.length; i++ )
      {
        file.write( ""+ differences[i] );
        file.newLine();
      }
      
      file.close();
    } catch (IOException e ) {
    }
  }
  
  //  ----- Other methods ---------------------------------------
  
  /**
   * Deompresses the receiver as a Sound, reconstructing the array
   * of samples from its array of _differences_ between  samples.
   * @return a Sound object
   */
  public Sound decompress()
  {
    Sound fullSound = new Sound( 1 + differences.length );
    int nextValue;
    
    fullSound.setSampleValueAt( 0, firstSample );
    int lastValue = firstSample;

    for (int i = 1; i < fullSound.getLength(); i++ )
    {
      nextValue = lastValue + differences[i-1];
      fullSound.setSampleValueAt( i, nextValue );
      
      lastValue = nextValue;
    }
    return fullSound;
  }
}