/* $Id$ */
package org.noreply.fancydress.type3;

import org.noreply.fancydress.misc.Util;
import org.noreply.fancydress.type3.routing.*;
import org.noreply.fancydress.crypto.*;
import org.noreply.fancydress.status.*;
import java.util.*;

public class Packet {

	private byte[] packet;
	private RoutingForward thisRoute;

	public Packet(
		Path path,
		RoutingDestination address,
		byte[] payload)
	throws Mix3BadArgumentsChainTooLongException
	{
		ForwardLeg leg2 = new ForwardLeg(path.getSecondHalf(), address);
		if (!(leg2.getRoute() instanceof RoutingForward))
			throw new Error("Routing Type of second leg is not a forward type.");
		ForwardLeg leg1 = new ForwardLeg(path.getFirstHalf(), ((RoutingForward)leg2.getRoute()).asSwap());
		makePacket(leg1, leg2, payload);
	}

	public Packet(
		HalfPath path,
		SURB surb,
		byte[] payload)
	throws Mix3BadArgumentsChainTooLongException
	{
		ForwardLeg leg1 = new ForwardLeg(path, surb.getRoute());
		makePacket(leg1, surb, payload);
	}

	public static boolean isPacketVersionSupported(String s) {
		return s.equals(SingleLeg.MAJOR_VERSION + "." + SingleLeg.MINOR_VERSION);
	}

	private void makePacket(ForwardLeg leg1, SingleLeg leg2, byte[] p) {
		byte h1[] = leg1.asOctets();
		byte h2[] = leg2.asOctets();

		if (p.length != 28*1024)
			throw new IllegalArgumentException("Payload needs to be 28 kb long");

		// Phase 1
		if (leg2 instanceof SURB) {
			byte[] k = ((SURB) leg2).getEncryptionKey();
			p = CryptoPrimitives.sprpDecrypt(k, "PAYLOAD ENCRYPT", p);
		} else {
			byte[][] sk = ((ForwardLeg) leg2).getSharedKeys();
			for (int i=sk.length-1; i>=0; i--)
				p = CryptoPrimitives.sprpEncrypt(sk[i], "PAYLOAD ENCRYPT", p);
		}

		// Phase 2
		h2 = CryptoPrimitives.sprpEncrypt(CryptoPrimitives.hash(p), "HIDE HEADER", h2);
		p = CryptoPrimitives.sprpEncrypt(CryptoPrimitives.hash(h2), "HIDE PAYLOAD", p);

		byte[][] sk = leg1.getSharedKeys();
		for (int i=sk.length-1; i>=0; i--) {
			h2 = CryptoPrimitives.sprpEncrypt(sk[i], "HEADER ENCRYPT", h2);
			p = CryptoPrimitives.sprpEncrypt(sk[i], "PAYLOAD ENCRYPT", p);
		}

		packet = Util.concat(Util.concat(h1,h2),p);
		thisRoute = leg1.getRoute();

		if (packet.length != 32*1024)
			throw new Error("packet is not 32k bytes");
	}

	public RoutingForward getRoute() {
		return thisRoute;
	}

	public byte[] asOctets() {
		return packet;
	}
}