package zero1hd.wavedecoder;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.InvalidParameterException;

public class WavDecoder {
	DataInputStream readStream;
	private int channels;
	private double sampleRate;
	private int dataSize;
	private int byteRate;
	
	public void setAudioFile(File file) throws InvalidParameterException {
		try {
			FileInputStream audioFile = new FileInputStream(file);
			readStream = new DataInputStream(audioFile);

			if (!readBytesToString(4).equals("RIFF")) {
				throw new InvalidParameterException("RIFF tag not found in header.");
			}
			dataSize = littleEndianIntBytes();

			if (!readBytesToString(4).equals("WAVE")) {
				throw new InvalidParameterException("WAVE format tag not found.");
			}
			
			if (!readBytesToString(4).equals("fmt ")) {
				throw new InvalidParameterException("fmt header not found.");
			}
			
			if (readStream.readByte() != 16) {
				throw new InvalidParameterException("Data not pcm?");
			}
			
			readStream.skipBytes(3);
			if (readStream.readByte() != 1) {
				throw new InvalidParameterException("Data not pcm?");
			}
			readStream.skipBytes(1);

			channels = readStream.readByte();
			readStream.skipBytes(1);

			sampleRate = littleEndianIntBytes();
			
			byteRate = littleEndianIntBytes();
			
			readStream.skipBytes(38);
			
			if (!readBytesToString(4).equals("data")) {
				throw new InvalidParameterException("initial data section tag not found");
			}
			readStream.skipBytes(4);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	private String readBytesToString(int bytesToRead) throws IOException {
		byte byteString[] = new byte[bytesToRead];
		readStream.read(byteString);
		return new String(byteString);
	}

	private int littleEndianIntBytes() throws IOException {
		int data = readStream.readInt();
		return Integer.reverseBytes(data);
	}
	
	private short readLittleEndianShort() throws IOException {
		short data = readStream.readShort();
		return Short.reverseBytes(data);
	}
	
	public int getChannels() {
		return channels;
	}
	
	public double getSampleRate() {
		return sampleRate;
	}
	
	public int getByteRate() {
		return byteRate;
	}
	
	public int getDataSize() {
		return dataSize;
	}
	
	public int readSamples(float[] samples) {
		int samplesRead = 0;
		
		for (int i = 0; i < samples.length; i++) {
			try {
				
				int currentSample = 0;
				for (int channel = 0; channel < channels; channel++) {
					currentSample += readLittleEndianShort();
				}
				currentSample /= channels*Short.MAX_VALUE+1;
				samples[i] = currentSample;
				samplesRead++;
			} catch (IOException e) {
				break;
			}
		}
		
		return samplesRead;
	}
	
}