/*
WAVInputStream - reads a WAV file.
see http://www.mediatel.lu/workshop/audio/fileformat for format spec.

Issues: 
Available method gives raw bytes of file, not actual bytes of audio.
default reads, plus skip just pass through - use readSample
*/
import java.io.*;

public class WAVInputStream extends java.io.FilterInputStream
{
	private static final int RIFFid = ('R' << 24) | ('I' << 16) + ('F' << 8) + 'F';
	private static final int WAVEid = ('W' << 24) | ('A' << 16) + ('V' << 8) + 'E';
	private static final int fmtid = ('f' << 24) | ('m' << 16) + ('t' << 8) + ' ';
	private static final int dataid = ('d' << 24) | ('a' << 16) + ('t' << 8) + 'a';

	private int numChannels;
	private int sampleDepth;
	private int sampleRate;
	private int numSamples;

	//for intel byte order. YAY!
	private short readShort() throws IOException
	{
		int a = in.read();
		int b = in.read();
		if(b == -1) throw(new EOFException());
		return (short)(a | (b << 8));
	}

	private int readInt() throws IOException
	{
		int a = in.read();
		int b = in.read();
		int c = in.read();
		int d = in.read();
		if(d == -1) throw(new EOFException());
		return a | (b << 8) | (c << 16) | (d << 24);
	}

	//this allows us to read binary data from the stream
	private DataInputStream DataIn;

	public int channels()
	{
		return numChannels;
	}

	public int depth()
	{
		return sampleDepth;
	}

	public int rate()
	{
		return sampleRate;
	}

	public int length()
	{
		return numSamples;
	}

	public WAVInputStream(InputStream _in) throws IOException, Exception
	{
		super(_in);
		DataIn = new DataInputStream(in);

		//read "RIFF"
		if(DataIn.readInt() != RIFFid)
			throw(new Exception("Not a valid RIFF file"));
		//read chunk size
		DataIn.readInt();
		//read "WAVE"
		if(DataIn.readInt() != WAVEid)
			throw(new Exception("Not a valid WAVE file"));
		//find the beg of the next audio chunk. This'll get the chunk with format info.
		SeekAudio();
	}

	public boolean marksupported()
	{
		return false;
	}

	public void readSample(byte b[], int start, int length) throws IOException
	{
		in.read(b, start * numChannels, length * numChannels);
	}

	public void readSample(short b[], int start, int length) throws IOException
	{
		for(int off = 0; off < length; off++)
			for(int channel = 0; channel < numChannels; channel++)
				b[channel + (start + off) * numChannels] = readShort();
	}

	public void readSample(int b[], int start, int length) throws IOException
	{
		for(int off = 0; off < length; off++)
			for(int channel = 0; channel < numChannels; channel++)
				b[b[channel + (start + off) * numChannels]] = readInt();
	}

	private void Readfmt(int size) throws IOException, Exception
	{
		//PCM format thingy
		if(readShort() != 1)
			throw(new Exception("Can only read PCM files"));
		numChannels = readShort();
		sampleRate = readInt();
		//bytes/sec, block alignment
		DataIn.readInt();
		DataIn.readShort();
		sampleDepth = readShort();
		if(sampleDepth != 8 && sampleDepth != 16 && sampleDepth != 32)
			throw(new Exception("Only 8, 16, or 32 bit samples are handled"));
		int read = 16;
		while(size > read)
		{
			read();
			read++;
		}
	}

	private void SeekAudio() throws IOException, Exception
	{
		while(true) //Since we're using datain, we will get an exception at eof., so this won't go forever.
		{
			int ChunkType = DataIn.readInt();
			int ckSize = readInt();
			switch(ChunkType)
			{
			case fmtid:
				Readfmt(ckSize);
				break;
			case dataid:
				numSamples = ckSize * 8 / numChannels / sampleDepth;
				return;
			default:
				if(in.skip(ckSize) != ckSize)
					throw(new Exception("Input didn't fully skip chunk"));
			}
		}
	}
}