/*
 * 11/19/04  1.0 moved to LGPL.
 * 
 * 11/17/04	 Uncomplete frames discarded. E.B, javalayer@javazoom.net 
 *
 * 12/05/03	 ID3v2 tag returned. E.B, javalayer@javazoom.net 
 *
 * 12/12/99	 Based on Ibitstream. Exceptions thrown on errors,
 *			 Temporary removed seek functionality. mdm@techie.com
 *
 * 02/12/99 : Java Conversion by E.B , javalayer@javazoom.net
 *
 * 04/14/97 : Added function prototypes for new syncing and seeking
 * mechanisms. Also made this file portable. Changes made by Jeff Tsay
 *
 *  @(#) ibitstream.h 1.5, last edit: 6/15/94 16:55:34
 *  @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de)
 *  @(#) Berlin University of Technology
 *-----------------------------------------------------------------------
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *----------------------------------------------------------------------
 */

package javazoom.jl.decoder;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;


/**
 * The <code>Bistream</code> class is responsible for parsing
 * an MPEG audio bitstream.
 *
 * <b>REVIEW:</b> much of the parsing currently occurs in the
 * various decoders. This should be moved into this class and associated
 * inner classes.
 */
public final class Bitstream implements BitstreamErrors
{
	/**
	 * Synchronization control constant for the initial
	 * synchronization to the start of a frame.
	 */
	static byte		INITIAL_SYNC = 0;

	/**
	 * Synchronization control constant for non-initial frame
	 * synchronizations.
	 */
	static byte		STRICT_SYNC = 1;

	// max. 1730 bytes per frame: 144 * 384kbit/s / 32000 Hz + 2 Bytes CRC
	/**
	 * Maximum size of the frame buffer.
	 */
	private static final int	BUFFER_INT_SIZE = 433;

	/**
	 * The frame buffer that holds the data for the current frame.
	 */
	private final int[]		framebuffer = new int[BUFFER_INT_SIZE];

	/**
	 * Number of valid bytes in the frame buffer.
	 */
	private int				framesize;

	/**
	 * The bytes read from the stream.
	 */
	private byte[]			frame_bytes = new byte[BUFFER_INT_SIZE*4];

	/**
	 * Index into <code>framebuffer</code> where the next bits are
	 * retrieved.
	 */
	private int				wordpointer;

	/**
	 * Number (0-31, from MSB to LSB) of next bit for get_bits()
	 */
	private int				bitindex;

	/**
	 * The current specified syncword
	 */
	private int				syncword;
	
	/**
	 * Audio header position in stream.
	 */
	private int				header_pos = 0;

	/**
	 *
	 */
	private boolean			single_ch_mode;
  //private int 			current_frame_number;
  //private int				last_frame_number;

	private final int		bitmask[] = {0,	// dummy
	 0x00000001, 0x00000003, 0x00000007, 0x0000000F,
	 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,
	 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,
	 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF,
     0x0001FFFF };

	private final PushbackInputStream	source;

	private final Header			header = new Header();

	private final byte				syncbuf[] = new byte[4];

	private Crc16[]					crc = new Crc16[1];

	private byte[]					rawid3v2 = null;

	private boolean					firstframe = true;


	/**
	 * Construct a IBitstream that reads data from a
	 * given InputStream.
	 *
	 * @param in	The InputStream to read from.
	 */
	public Bitstream(InputStream in)
	{
		if (in==null) throw new NullPointerException("in");
		in = new BufferedInputStream(in);		
		loadID3v2(in);
		firstframe = true;
		//source = new PushbackInputStream(in, 1024);
		source = new PushbackInputStream(in, BUFFER_INT_SIZE*4);
		
		closeFrame();
		//current_frame_number = -1;
		//last_frame_number = -1;
	}

	/**
	 * Return position of the first audio header.
	 * @return size of ID3v2 tag frames.
	 */
	public int header_pos()
	{
		return header_pos;
	}
	
	/**
	 * Load ID3v2 frames.
	 * @param in MP3 InputStream.
	 * @author JavaZOOM
	 */
	private void loadID3v2(InputStream in)
	{		
		int size = -1;
		try
		{
			// Read ID3v2 header (10 bytes).
			in.mark(10);			
			size = readID3v2Header(in);
			header_pos = size;			
		}
		catch (IOException e)
		{}
		finally
		{
			try
			{
				// Unread ID3v2 header (10 bytes).
				in.reset();
			}
			catch (IOException e)
			{}
		}
		// Load ID3v2 tags.
		try
		{
			if (size > 0)
			{
				rawid3v2 = new byte[size];
				in.read(rawid3v2,0,rawid3v2.length);
			}			
		}
		catch (IOException e)
		{}
	}
	
	/**
	 * Parse ID3v2 tag header to find out size of ID3v2 frames. 
	 * @param in MP3 InputStream
	 * @return size of ID3v2 frames + header
	 * @throws IOException
	 * @author JavaZOOM
	 */
	private int readID3v2Header(InputStream in) throws IOException
	{		
		byte[] id3header = new byte[4];
		int size = -10;
		in.read(id3header,0,3);
		// Look for ID3v2
		if ( (id3header[0]=='I') && (id3header[1]=='D') && (id3header[2]=='3'))
		{
			in.read(id3header,0,3);
			int majorVersion = id3header[0];
			int revision = id3header[1];
			in.read(id3header,0,4);
			size = (int) (id3header[0] << 21) + (id3header[1] << 14) + (id3header[2] << 7) + (id3header[3]);
		}
		return (size+10);
	}
	
	/**
	 * Return raw ID3v2 frames + header.
	 * @return ID3v2 InputStream or null if ID3v2 frames are not available.
	 */
	public InputStream getRawID3v2()
	{
		if (rawid3v2 == null) return null;
		else
		{
			ByteArrayInputStream bain = new ByteArrayInputStream(rawid3v2);		
			return bain;
		}
	}

	/**
	 * Close the Bitstream.
	 * @throws BitstreamException
	 */
	public void close() throws BitstreamException
	{
		try
		{
			source.close();
		}
		catch (IOException ex)
		{
			throw newBitstreamException(STREAM_ERROR, ex);
		}
	}

	/**
	 * Reads and parses the next frame from the input source.
	 * @return the Header describing details of the frame read,
	 *	or null if the end of the stream has been reached.
	 */
	public Header readFrame() throws BitstreamException
	{
		Header result = null;
		try
		{
			result = readNextFrame();
			// E.B, Parse VBR (if any) first frame.
			if (firstframe == true)
			{
				result.parseVBR(frame_bytes);
				firstframe = false;
			}			
		}
		catch (BitstreamException ex)
		{
			if ((ex.getErrorCode()==INVALIDFRAME))
			{
				// Try to skip this frame.
				//System.out.println("INVALIDFRAME");
				try
				{
					closeFrame();
					result = readNextFrame();
				}
				catch (BitstreamException e)
				{
					if ((e.getErrorCode()!=STREAM_EOF))
					{
						// wrap original exception so stack trace is maintained.
						throw newBitstreamException(e.getErrorCode(), e);
					}
				}
			}
			else if ((ex.getErrorCode()!=STREAM_EOF))
			{
				// wrap original exception so stack trace is maintained.
				throw newBitstreamException(ex.getErrorCode(), ex);
			}
		}
		return result;
	}

	/**
	 * Read next MP3 frame.
	 * @return MP3 frame header.
	 * @throws BitstreamException
	 */
	private Header readNextFrame() throws BitstreamException
	{
		if (framesize == -1)
		{
			nextFrame();
		}
		return header;
	}


	/**
	 * Read next MP3 frame.
	 * @throws BitstreamException
	 */
	private void nextFrame() throws BitstreamException
	{
		// entire frame is read by the header class.
		header.read_header(this, crc);