/**
 * JWave - Java implementation of wavelet transform algorithms
 *
 * Copyright 2010-2012 Christian Scheiblich
 *  
 * 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. 
 *
 * This file WaveletPacketTransform.java is part of JWave.
 *
 * @author Christian Scheiblich
 * date 23.02.2010 13:44:05
 * contact graetz@mailfish.de
 */
package math.jwave.transforms;

import math.jwave.exc.JWaveException;
import math.jwave.transforms.wavelets.Wavelet;

/**
 * Base class for the forward and reverse Wavelet Packet Transform (WPT) also
 * called Wavelet Packet Decomposition (WPD) using a specified Wavelet by
 * inheriting class.
 * 
 * @date 23.02.2010 13:44:05
 * @author Christian Scheiblich
 */
public class WaveletPacketTransform extends WaveletTransform {
  
  /**
   * Constructor receiving a Wavelet object.
   * 
   * @date 23.02.2010 13:44:05
   * @author Christian Scheiblich
   * @param wavelet
   *          object of type Wavelet; Haar02, Daub02, Coif06, ...
   * @throws JWaveException 
   */
  public WaveletPacketTransform( Wavelet wavelet ) {
    super( wavelet );
    
    try {
      checkConfig( );
    } catch( JWaveException e ) {
      e.printStackTrace( );
    }
    
  } // WaveletPacketTransform
  
  /**
   * Constructor receiving a Wavelet object.
   * 
   * @date 23.02.2010 13:44:05
   * @author Christian Scheiblich
   * @param wavelet
   *          object of type Wavelet; Haar02, Daub02, Coif06, ...
   * @param steps
   *          how many steps the algorithm should perform
   * @throws JWaveException 
   */
  public WaveletPacketTransform( Wavelet wavelet, int steps ) {
    
    super( wavelet, steps );
    
    try {
      checkConfig( );
    } catch( JWaveException e ) {
      e.printStackTrace( );
    }
    
  } // WaveletPacketTransform
  
  /**
   * Implementation of the 1-D forward wavelet packet transform for arrays of
   * dim N by filtering with the longest wavelet first and then always with both
   * sub bands -- low and high (approximation and details) -- by the next
   * smaller wavelet.
   * 
   * @date 23.02.2010 13:44:05
   * @author Christian Scheiblich
   * @see math.jwave.transforms.BasicTransform#forward(double[])
   */
  @Override
  public double[ ] forward( double[ ] arrTime ) {
    
    double[ ] arrHilb = new double[ arrTime.length ];
    for( int i = 0; i < arrTime.length; i++ )
      arrHilb[ i ] = arrTime[ i ];
    
    int level = 0;
    int k = arrTime.length;
    int h = arrTime.length;
    int minWaveLength = _wavelet.getWaveLength( );
    if( h >= minWaveLength ) {
      
      while( h >= minWaveLength && ( level < _steps || _steps == -1 ) ) {
        
        int g = k / h; // 1 -> 2 -> 4 -> 8 -> ...
        
        for( int p = 0; p < g; p++ ) {
          
          double[ ] iBuf = new double[ h ];
          
          for( int i = 0; i < h; i++ )
            iBuf[ i ] = arrHilb[ i + ( p * h ) ];
          
          double[ ] oBuf = _wavelet.forward( iBuf );
          
          for( int i = 0; i < h; i++ )
            arrHilb[ i + ( p * h ) ] = oBuf[ i ];
          
        } // packets
        
        h = h >> 1;
        
        level++;
        
      } // levels
      
    } // if
    
    return arrHilb;
  } // forward
  
  /**
   * Implementation of the 1-D reverse wavelet packet transform for arrays of
   * dim N by filtering with the smallest wavelet for all sub bands -- low and
   * high bands (approximation and details) -- and the by the next greater
   * wavelet combining two smaller and all other sub bands.
   * 
   * @date 23.02.2010 13:44:05
   * @author Christian Scheiblich
   * @see math.jwave.transforms.BasicTransform#reverse(double[])
   */
  @Override
  public double[ ] reverse( double[ ] arrHilb ) {
    
    double[ ] arrTime = new double[ arrHilb.length ];
    
    for( int i = 0; i < arrHilb.length; i++ )
      arrTime[ i ] = arrHilb[ i ];
    
    int level = 0;
    int minWaveLength = _wavelet.getWaveLength( );
    int k = arrTime.length;
    int h = minWaveLength;
    if( arrHilb.length >= minWaveLength ) {
      
      while( h <= arrTime.length && h >= minWaveLength && ( level < _steps || _steps == -1 ) ) {
        
        int g = k / h; // ... -> 8 -> 4 -> 2 -> 1
        
        for( int p = 0; p < g; p++ ) {
          
          double[ ] iBuf = new double[ h ];
          
          for( int i = 0; i < h; i++ )
            iBuf[ i ] = arrTime[ i + ( p * h ) ];
          
          double[ ] oBuf = _wavelet.reverse( iBuf );
          
          for( int i = 0; i < h; i++ )
            arrTime[ i + ( p * h ) ] = oBuf[ i ];
          
        } // packets
        
        h = h << 1;
        
        level++;
        
      } // levels
      
    } // if
    
    return arrTime;
  } // reverse
  
} // class