package edu.vt.marian.uip;

import java.io.*;
import java.net.*;
import java.util.*;

import edu.vt.marian.common.*;


//--------------------------------------------------------------------------------------------------------
//  Class name: packet_output_stream
//  Class description: kind of wrapper of DatagramPacket and the DatagramSocket, used
//			for udp communication
//  Author: Jianxin Zhao
//  Finished time: June 2, 1998
//  Known bugs: none
//  Platform: jdk1.1.5 under UNIX
//--------------------------------------------------------------------------------------------------------
public class packet_output_stream
{
	// used for debugging
	private Debug debug = null;

	// this is the address of the receiver
	private InetAddress address = null;
	private int port = -1;

	// this variable contains the data to be sented
	private StringBuffer sb = new StringBuffer();

	// this is the udp fragment size
	private final static int MAX_PACKET_SIZE = 8000;

	// this is the socket associated with the stream
	private DatagramSocket socket = null;


	// this constructor will create a packet_input_stream object
	public packet_output_stream(InetAddress address, int port, Debug debug)
	{
		this.debug = debug;

		this.address = address;
		this.port = port;

		// create the socket in the constructor
		try
		{
			socket = new DatagramSocket();
		}
		catch (Exception e)
		{
			debug.dumpTrace("class packet_output_stream, constructor, create socket error");
		}
	}


	// this constructor will create a packet_input_stream object 
	public packet_output_stream(String host_name, int port, Debug debug)
	{
		this.debug = debug;

		try
		{
			address = InetAddress.getByName(host_name);
			this.port = port;
		}
		catch (Exception e)
		{
			debug.dumpTrace("class packet_output_stream, constructor, error get ip address from the hostname");
		}

		// create the socket in the constructor
		try
		{
			socket = new DatagramSocket();
		}
		catch (Exception e)
		{
			debug.dumpTrace("class packet_output_stream, constructor, create socket error");
		}
	}


	// this method will write one line to the data of this object
	public void println(String data)
	{
		sb.append(data + "\n");
	}


	// the method will really send the data to the receiver
	public void flush()
	{
		try
		{
			// caculate the number of packets need to be sent
			int length = sb.length();
			int number_of_packets = length / MAX_PACKET_SIZE + 1;
			sb.insert(0, Integer.toString(number_of_packets) + "\n");
			String s = sb.toString();
//debug.dumpTrace("class packet_output_stream, method flush, data is ");
//debug.dumpTrace(s);
			// send the packets
			int i;
			for (i = 0; i < number_of_packets - 1; i++)
			{
				byte[] buffer = (s.substring(i * MAX_PACKET_SIZE, 
					(i + 1) * MAX_PACKET_SIZE)).getBytes();
				DatagramPacket dp = new DatagramPacket(buffer, buffer.length, address, port);
				socket.send(dp);
			}

			// don't forget the last one, there is the possibility
			// that this one will be a little longer than 8000 because
			// we added the packet number
			byte[] buffer = (s.substring(i * MAX_PACKET_SIZE)).getBytes();
			DatagramPacket dp = new DatagramPacket(buffer, buffer.length, address, port);
			socket.send(dp);
		}
		catch (Exception e)
		{
			debug.dumpTrace("class packet_output_stream, method flush, error create socket or send data");
		}
	}


	// this method will return the socket of this stream
	public DatagramSocket get_socket()
	{
		return socket;
	}


	// this method will return the local port number of this stream
	public void close()
	{
		socket.close();
	}
}