import java.io.*;

public class Avs2YuvSession {
	
	//Path to Avs2YUV
	public static String AVS2YUV_PATH = ...;
	
	private Thread reader;
	private InputStream stderr;
	private OutputStreamWriter stdout;
	private Process proc;
	private Yuv4Mpeg2Stream video;
	
	public Avs2YuvSession(String scriptPath) throws IOException, Yuv4Mpeg2StreamException {
		
		//Start Avs2YUV
		proc = Runtime.getRuntime().exec(new String[] {AVS2YUV_PATH, "-slave", scriptPath, "-o", "-"});
		
		stderr = new BufferedInputStream(proc.getErrorStream());
		stdout = new OutputStreamWriter(proc.getOutputStream(), "US-ASCII");
		
		//Starts a thread that *should* print info from stderr, but never prints anything (see StderrReader class below)
		reader = new StderrReader();
		reader.start();
		
		//Wraps stdout from Avs2YUV in a YUV4MPEG stream parser
		video = new Yuv4Mpeg2Stream(new BufferedInputStream(proc.getInputStream()));
		
	}
	
	//Sends a frame number to Avs2YUV and puts the returned frame into the given buffer
	public synchronized void getFrame(int frame, I420Frame buffer) throws IOException, Yuv4Mpeg2StreamException {
		
		stdout.write(Integer.toString(frame));
		stdout.write('\n');
		stdout.flush();
		
		video.readFrame(buffer);
		
	}
	
	//Creates a buffer that can store a video frame
	public I420Frame createFrameBuffer() {
		return video.createFrameBuffer();
	}
	
	//Closes stdin and stdout
	public void close() {
		
		try { stdout.close(); } catch(Exception e) {}
		try { video.close(); } catch(Exception e) {}
		
	}
	
	//This class extends thread and just reads the stderr stream and prints its output
	private class StderrReader extends Thread {
		
		public void run() {
			
			try {
				
				//I should be getting the information from stderr printed out here, but no such luck
				
				int ch;
				
				for(;;) {
					
					//If end-of-stream was reached, clean things up and return
					if((ch = stderr.read()) < 0) {
						
						System.out.println("End of stream");
						try { stderr.close(); } catch(Exception e) {}
						return;
					
					}
					
					//Print the character read from stderr
					System.out.print((char) ch);
					
				}
				
			} catch(Exception e) {
				
				//If there was an exception reading stderr
				System.out.println("UH-OH!!! :P");
				try { stderr.close(); } catch(Exception ex) {}
				
			}
			
		}
		
	}

}