/*
 * NetChannel.java
 * Copyright (C) 2003
 * 
 * $Id: Netchan.java,v 1.2.2.1 2004-09-06 19:39:18 hzi Exp $
 */
/*
Copyright (C) 1997-2001 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
package jake2.qcommon;

import jake2.Defines;
import jake2.Globals;
import jake2.game.cvar_t;
import jake2.server.SV_MAIN;
import jake2.sys.NET;
import jake2.sys.Sys;

/**
 * Netchan
 */
public final class Netchan extends SV_MAIN {

	/*
	
	packet header
	-------------
	31	sequence
	1	does this message contains a reliable payload
	31	acknowledge sequence
	1	acknowledge receipt of even/odd message
	16	qport
	
	The remote connection never knows if it missed a reliable message, the
	local side detects that it has been dropped by seeing a sequence acknowledge
	higher thatn the last reliable sequence, but without the correct evon/odd
	bit for the reliable set.
	
	If the sender notices that a reliable message has been dropped, it will be
	retransmitted.  It will not be retransmitted again until a message after
	the retransmit has been acknowledged and the reliable still failed to get there.
	
	if the sequence number is -1, the packet should be handled without a netcon
	
	The reliable message can be added to at any time by doing
	MSG_Write* (&netchan.message, <data>).
	
	If the message buffer is overflowed, either by a single message, or by
	multiple frames worth piling up while the last reliable transmit goes
	unacknowledged, the netchan signals a fatal error.
	
	Reliable messages are always placed first in a packet, then the unreliable
	message is included if there is sufficient room.
	
	To the receiver, there is no distinction between the reliable and unreliable
	parts of the message, they are just processed out as a single larger message.
	
	Illogical packet sequence numbers cause the packet to be dropped, but do
	not kill the connection.  This, combined with the tight window of valid
	reliable acknowledgement numbers provides protection against malicious
	address spoofing.
	
	
	The qport field is a workaround for bad address translating routers that
	sometimes remap the client's source port on a packet during gameplay.
	
	If the base part of the net address matches and the qport matches, then the
	channel matches even if the IP port differs.  The IP port should be updated
	to the new value before sending out any replies.
	
	
	If there is no information that needs to be transfered on a given frame,
	such as during the connection stage while waiting for the client to load,
	then a packet only needs to be delivered if there is something in the
	unacknowledged reliable
	*/

	public static cvar_t showpackets;
	public static cvar_t showdrop;
	public static cvar_t qport;

	//public static netadr_t net_from = new netadr_t();
	public static sizebuf_t net_message = new sizebuf_t();
	public static byte net_message_buffer[] = new byte[Defines.MAX_MSGLEN];

	/*
	===============
	Netchan_Init
	
	===============
	*/
	//ok.
	public static void Netchan_Init() {
		long port;

		// pick a port value that should be nice and random
		port = Sys.Milliseconds() & 0xffff;

		showpackets = Cvar.Get("showpackets", "0", 0);
		showdrop = Cvar.Get("showdrop", "0", 0);
		qport = Cvar.Get("qport", "" + port, Defines.CVAR_NOSET);
	}

	/*
	===============
	Netchan_OutOfBand
	
	Sends an out-of-band datagram
	================
	*/
	//ok.
	public static void Netchan_OutOfBand(int net_socket, netadr_t adr, int length, byte data[]) {
		sizebuf_t send = new sizebuf_t();
		byte send_buf[] = new byte[Defines.MAX_MSGLEN];

		// write the packet header
		SZ.Init(send, send_buf, Defines.MAX_MSGLEN);

		MSG.WriteInt(send, -1); // -1 sequence means out of band
		SZ.Write(send, data, length);

		// send the datagram
		NET.SendPacket(net_socket, send.cursize, send.data, adr);
	}
	
	public static void OutOfBandPrint(int net_socket, netadr_t adr, String s) {
		Netchan_OutOfBand(net_socket, adr, s.length(), s.getBytes());
	}

	/*
	==============
	Netchan_Setup
	
	called to open a channel to a remote system
	==============
	*/
	public static void Setup(int sock, netchan_t chan, netadr_t adr, int qport) {
		//memset (chan, 0, sizeof(*chan));

		chan.clear();
		chan.sock = sock;
		chan.remote_address.set(adr);
		chan.qport = qport;
		chan.last_received = Globals.curtime;
		chan.incoming_sequence = 0;
		chan.outgoing_sequence = 1;

		SZ.Init(chan.message, chan.message_buf, chan.message_buf.length);
		chan.message.allowoverflow = true;
	}

	/*
	===============
	Netchan_CanReliable
	
	Returns true if the last reliable message has acked
	================
	*/
	public static boolean Netchan_CanReliable(netchan_t chan) {
		if (chan.reliable_length != 0)
			return false; // waiting for ack
		return true;
	}
	// das ist richtig !!!
	public static boolean Netchan_NeedReliable(netchan_t chan) {
		boolean send_reliable;

		// if the remote side dropped the last reliable message, resend it
		send_reliable = false;

		if (chan.incoming_acknowledged > chan.last_reliable_sequence && chan.incoming_reliable_acknowledged != chan.reliable_sequence)
			send_reliable = true;

		// if the reliable transmit buffer is empty, copy the current message out
		if (0 == chan.reliable_length && chan.message.cursize != 0) {
			send_reliable = true;
		}

		return send_reliable;
	}

	/*
	===============
	Netchan_Transmit
	
	tries to send an unreliable message to a connection, and handles the
	transmition / retransmition of the reliable messages.
	
	A 0 length will still generate a packet and deal with the reliable messages.
	================
	*/
	public static void Transmit(netchan_t chan, int length, byte data[]) {
		sizebuf_t send = new sizebuf_t();
		byte send_buf[] = new byte[MAX_MSGLEN];
		int send_reliable;
		int w1, w2;

		// check for message overflow
		if (chan.message.overflowed) {
			chan.fatal_error = true;
			Com.Printf(NET.AdrToString(chan.remote_address) + ":Outgoing message overflow\n");
			return;
		}

		send_reliable = Netchan_NeedReliable(chan) ? 1 : 0;

		if (chan.reliable_length == 0 && chan.message.cursize != 0) {
			System.arraycopy(chan.message_buf, 0, chan.reliable_buf, 0, chan.message.cursize);
			chan.reliable_length = chan.message.cursize;
			chan.message.cursize = 0;
			chan.reliable_sequence ^= 1;
		}

		// write the packet header
		SZ.Init(send, send_buf, send_buf.length);

		w1 = (chan.outgoing_sequence & ~(1 << 31)) | (send_reliable << 31);
		w2 = (chan.incoming_sequence & ~(1 << 31)) | (chan.incoming_reliable_sequence << 31);

		chan.outgoing_sequence++;
		chan.last_sent = (int) Globals.curtime;

		MSG.WriteInt(send, w1);
		MSG.WriteInt(send, w2);

		// send the qport if we are a client
		if (chan.sock == Defines.NS_CLIENT)
			MSG.WriteShort(send, (int) qport.value);

		// copy the reliable message to the packet first
		if (send_reliable != 0) {
			SZ.Write(send, chan.reliable_buf, chan.reliable_length);
			chan.last_reliable_sequence = chan.outgoing_sequence;
		}

		// add the unreliable part if space is available
		if (send.maxsize - send.cursize >= length)
			SZ.Write(send, data, length);
		else
			Com.Printf("Netchan_Transmit: dumped unreliable\n");

		// send the datagram
		NET.SendPacket(chan.sock, send.cursize, send.data, chan.remote_address);

		if (showpackets.value != 0) {
			if (send_reliable != 0)
				Com.Printf(//"send %4i : s=%i reliable=%i ack=%i rack=%i\n"
				"send "
					+ send.cursize
					+ " : s="
					+ (chan.outgoing_sequence - 1)
					+ " reliable="
					+ chan.reliable_sequence
					+ " ack="
					+ chan.incoming_sequence
					+ " rack="
					+ chan.incoming_reliable_sequence
					+ "\n");
			else
				Com.Printf(//"send %4i : s=%i ack=%i rack=%i\n"
				"send "
					+ send.cursize
					+ " : s="
					+ (chan.outgoing_sequence - 1)
					+ " ack="
					+ chan.incoming_sequence
					+ " rack="
					+ chan.incoming_reliable_sequence
					+ "\n");
		}
	}

	/*
	=================
	Netchan_Process
	
	called when the current net_message is from remote_address
	modifies net_message so that it points to the packet payload
	=================
	*/
	public static boolean Process(netchan_t chan, sizebuf_t msg) {
		int sequence, sequence_ack;
		int reliable_ack, reliable_message;
		int qport;

		// get sequence numbers		
		MSG.BeginReading(msg);
		sequence = MSG.ReadLong(msg);
		sequence_ack = MSG.ReadLong(msg);

		// read the qport if we are a server
		if (chan.sock == NS_SERVER)
			qport = MSG.ReadShort(msg);

		// achtung unsigned int
		reliable_message = sequence >>> 31;
		reliable_ack = sequence_ack >>> 31;

		sequence &= ~(1 << 31);
		sequence_ack &= ~(1 << 31);

		if (showpackets.value != 0) {
			if (reliable_message != 0)
				Com.Printf(//"recv %4i : s=%i reliable=%i ack=%i rack=%i\n"
				"recv "
					+ msg.cursize
					+ " : s="
					+ sequence
					+ " reliable="
					+ (chan.incoming_reliable_sequence ^ 1)
					+ " ack="
					+ sequence_ack
					+ " rack="
					+ reliable_ack
					+ "\n");
			else
				Com.Printf(//"recv %4i : s=%i ack=%i rack=%i\n"
				"recv " + msg.cursize + " : s=" + sequence + " ack=" + sequence_ack + " rack=" + reliable_ack + "\n");
		}

		//
		// discard stale or duplicated packets
		//
		if (sequence <= chan.incoming_sequence) {
			if (showdrop.value != 0)
				Com.Printf(
					NET.AdrToString(chan.remote_address)
						+ ":Out of order packet "
						+ sequence
						+ " at "
						+ chan.incoming_sequence
						+ "\n");
			return false;
		}

		//
		// dropped packets don't keep the message from being used
		//
		chan.dropped = sequence - (chan.incoming_sequence + 1);
		if (chan.dropped > 0) {
			if (showdrop.value != 0)
				Com.Printf(NET.AdrToString(chan.remote_address) + ":Dropped " + chan.dropped + " packets at " + sequence + "\n");
		}

		//
		// if the current outgoing reliable message has been acknowledged
		// clear the buffer to make way for the next
		//
		if (reliable_ack == chan.reliable_sequence)
			chan.reliable_length = 0; // it has been received

		//
		// if this message contains a reliable message, bump incoming_reliable_sequence 
		//
		chan.incoming_sequence = sequence;
		chan.incoming_acknowledged = sequence_ack;
		chan.incoming_reliable_acknowledged = reliable_ack;
		if (reliable_message != 0) {
			chan.incoming_reliable_sequence ^= 1;
		}

		//
		// the message can now be read from the current message pointer
		//
		chan.last_received = (int) Globals.curtime;

		return true;
	}

}