/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * 
 */
package org.openimaj.audio.filters;

import org.openimaj.audio.SampleChunk;
import org.openimaj.audio.processor.FixedSizeSampleAudioProcessor;
import org.openimaj.audio.samples.SampleBuffer;

/**
 *      A basic feed-forward comb filter.  A buffer is used to buffer the samples during the
 *      overlap of the sample chunks and it is initialised lazily, so the first
 *      time through the filter will take slightly longer. This filter extends the
 *      {@link FixedSizeSampleAudioProcessor} to ensure that the sample chunks are
 *      the same length as the required delay; this means that the buffer need only
 *      be copied in between each iteration. 
 *
 *      @author David Dupplaw (dpd@ecs.soton.ac.uk)
 *  @created 27 Apr 2012
 *      
 */
public class FeedForwardCombFilter extends FixedSizeSampleAudioProcessor
{
        /** The sample buffer that is used for dealing with the overlap sample chunks */
        private SampleBuffer buffer = null;
        
        /** The gain of the delayed signal */
        private double gain = 1d;
        
        /** The power of each frame of the output */
        private double outputPower = 0;
        
        /** The power of each frame of the input */
        private double inputPower = 0;
        
        /** The frequency being detected */
        private double frequency = 0;
        
        /**
         *      Constructor that takes the number of samples delay
         *      to apply to the signal.
         * 
         *      @param nSamplesDelay The number of delay samples
         *      @param gain The gain of the delayed signal
         */
        public FeedForwardCombFilter( final int nSamplesDelay, final double gain )
        {
                super( nSamplesDelay );
                this.gain = gain;
                this.frequency = -1;
        }
        
        /**
         *      Constructor that takes the frequency at which the comb filter
         *      will operate and the gain to apply to the delayed signal.
         * 
         *      @param frequency The frequency
         *      @param sampleRate The sample rate of the signal in Hz
         *      @param gain the gain of the delayed signal
         */
        public FeedForwardCombFilter( final double frequency, final double sampleRate, final double gain )
        {
                this( (int)(sampleRate/frequency), gain );
                this.frequency = frequency;
        }
        
        /**
         *      This returns the frequency that this comb filter is set to detect.
         *      This is only available if the frequency was used during construction.
         *  @return The frequency.
         */
        public double getFrequency()
        {
                return this.frequency;
        }

        /** 
         *      {@inheritDoc}
         *      @see org.openimaj.audio.processor.AudioProcessor#process(org.openimaj.audio.SampleChunk)
         */
        @Override
        public SampleChunk process( final SampleChunk sample ) throws Exception
        {
                // If we don't yet have a buffer, we must be at the start of
                // the stream, so we pass the first samples on unedited and store
                // them for the delayed signal.
                if( this.buffer == null )
                {
                        this.buffer = sample.getSampleBuffer();
                        return sample;
                }
                
                // Make a copy of the sample chunk and store it for later.
                this.buffer = sample.clone().getSampleBuffer();
                
                // We'll side-affect the incoming chunk here
                double p = 0;
                double ip = 0;
                final SampleBuffer b = sample.getSampleBuffer();
                for( int i = 0; i < b.size(); i++ )
                {
                        final float d = (float)(b.get(i) - this.gain*this.buffer.get(i));
                        p += d*d;
                        ip += b.get(i) * b.get(i);
                        b.set( i, d );
                }
                
                this.outputPower = p;
                this.inputPower = ip;
                
                // Return the incoming chunk, side-affected.
                return sample;
        }
        
        /**
         *      Returns the output power for the last processed frame.
         *      @return the output power for the last processed frame.
         */
        public double getOutputPower()
        {
                return this.outputPower;
        }
        
        /**
         *      Returns the input power for the last processed frame. 
         *  @return the input power for the last processed frame.
         */
        public double getInputPower()
        {
                return this.inputPower;
        }
        
        /**
         *      Returns the harmonicity power.
         *  @return the harmonicity power.
         */
        public double getHarmonicity()
        {
                return this.getOutputPower() / (this.getInputPower()*4);
        }
}