/**
 * 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.util;

import java.util.ArrayList;
import java.util.List;

import org.openimaj.audio.AudioStream;
import org.openimaj.audio.SampleChunk;

/**
 *      Provides a buffered audio source such that the audio can be reset
 *      and re-read as many times as needed without the need for redecoding.
 *      You should pass your audio stream through this method if you need
 *      to do certain complete-source calculations on the data (such as
 *      finding peak or means) prior to some other processing. Clearly,
 *      the limitation to how long an audio source you can store with this
 *      class is the memory of your machine, and remember that the audio
 *      samples are stored uncompressed, so they take up a lot of room! If
 *      you're planning on performing complete-source calculations on large
 *      audio data, it is recommended to stream the data multiple times.
 *
 *      @author David Dupplaw (dpd@ecs.soton.ac.uk)
 *  @created 4 Mar 2013
 *      @version $Author$, $Revision$, $Date$
 */
public class MemoryAudioSource extends AudioStream
{
        /** The original audio stream */
        private AudioStream stream = null;

        /** The buffered sample list */
        private final List<SampleChunk> buffer = new ArrayList<SampleChunk>();

        /** The current index in the buffer being read */
        private int currentIndex = -1;

        /** The number of milliseconds of data in the buffer */
        private long bufferLength = 0;

        /**
         *      Constructor that takes the audio stream to buffer.
         *      @param as The audio stream
         */
        public MemoryAudioSource( final AudioStream as )
        {
                this.stream = as;
        }

        /**
         *      {@inheritDoc}
         *      @see org.openimaj.audio.AudioStream#nextSampleChunk()
         */
        @Override
        public SampleChunk nextSampleChunk()
        {
                // See if we're reading from the buffer and if so, return
                // the current sample chunk in the buffer (and move to the next index)
                if( !this.buffer.isEmpty() && this.currentIndex < this.buffer.size() )
                        return this.buffer.get( this.currentIndex++ -1 );
                else
                {
                        // If we're outside of the buffer, we'll try to get the next
                        // sample chunk from the original stream...
                        final SampleChunk sc = this.stream.nextSampleChunk();

                        // If we get one, we'll add it to the buffer then return it...
                        if( sc != null )
                        {
                                this.buffer.add( sc );
                                this.currentIndex++;
                                this.bufferLength += (long)(sc.getNumberOfSamples()
                                                / sc.getFormat().getSampleRateKHz() );
                                return sc;
                        }
                        // Otherwise we're at the end of the buffer and the original
                        // stream, so we'll just return null (end of stream).
                        else
                                return null;
                }
        }

        /**
         *      {@inheritDoc}
         *      @see org.openimaj.audio.AudioStream#reset()
         */
        @Override
        public void reset()
        {
                this.currentIndex = 0;
        }

        /**
         *      For live streams, returns the length of the buffered audio,
         *      otherwise returns the length of the original stream.
         *
         *      @see org.openimaj.audio.AudioStream#getLength()
         */
        @Override
        public long getLength()
        {
                if( this.stream.getLength() == -1 )
                        return this.bufferLength;
                else    return this.stream.getLength();
        }
}