package arq;


import java.net.DatagramPacket;

import comm.MyFrame;
import comm.TxRx;

public class receiver {

	public static void main(String[] args) {

		if (args.length != 4) {
			System.out.println("Usage: receiver windowSize maxSeq localPort debug");
			System.exit(-1);
		}
		DatagramPacket packet;
		int nextFrame = 0;
		int maxSeq = Integer.parseInt(args[1]);
		int windowSize = Integer.parseInt(args[0]);
		int framesNotAnswered = 0;
		boolean sendControl;
		MyFrame frame;
		MyFrame control;
		TxRx txrx = new TxRx(Integer.parseInt(args[2]));
		boolean debug;
		if (Integer.parseInt(args[3]) == 0)
			debug = false;
		else
			debug = true;

		while (true){
			if (debug)
				System.out.println("Waiting for frame: " + nextFrame);
			//Waiting for a data packet
			packet = txrx.receive();
			//Packet received. Now, extract the frame
			frame = TxRx.getPacketFrame(packet);
			sendControl = true;
			if (debug)
				System.out.println("Received frame: " + frame.getSeq());
			if (frame.CRCOK() == true) {
				//Frame is OK.
				//Is the sequence correct?
				if (frame.getSeq() == nextFrame)  {
					if (!debug)
						System.out.print(frame.getContent());
					else
						System.out.println("Received frame: " + nextFrame);
					nextFrame = (nextFrame+1)%(maxSeq+1); //next frame mod maxSeq
					control = new MyFrame(1, nextFrame, ""); //RR with next frame
					if (framesNotAnswered < (windowSize-1)){
						if (Math.random() < 0.5) {
							framesNotAnswered++;
							sendControl = false;
						}
					}
				}
				else { //the sequence is not correct
					if (debug)
						System.out.println("Sequence not in order");
					control = new MyFrame(1, nextFrame, ""); //RR
				}
			}
			else { //the frame has errors
				if (debug)
					System.out.println("BAD CRC!!!");
				control = new MyFrame(2, nextFrame, ""); //REJ
			}
			if (sendControl) {
				if (debug)
					System.out.println("Sending: " + control);
				txrx.send(control, packet.getPort()); //sending a control frame
				framesNotAnswered = 0;
			}
		}
	}
}