/*
	net_chan.c

	(description)

	Copyright (C) 1996-1997  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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

	$Id$
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifndef _WIN32
# include <unistd.h>
#else
# include <windows.h>
#endif
#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif

#include <time.h>
#include <stdarg.h>

#include "client.h"
#include "commdef.h"
#include "console.h"
#include "cvar.h"
#include "msg.h"
#include "net.h"

#define	PACKET_HEADER	8

/*

packet header
-------------
31	sequence
1	does this message contain 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 allways 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.


*/

int         net_drop;
cvar_t     *showpackets;
cvar_t     *showdrop;
cvar_t     *qport;
extern qboolean is_server;

/*
	Netchan_Init
*/
void
Netchan_Init (void)
{
	int         port;

	// pick a port value that should be nice and random
#ifdef _WIN32
	port = ((int) (timeGetTime () * 1000) * time (NULL)) & 0xffff;
#else
	port = ((int) (getpid () + getuid () * 1000) * time (NULL)) & 0xffff;
#endif

	Cvar_SetValue (qport, port);
}

void
Netchan_Init_Cvars (void)
{
	showpackets = Cvar_Get ("showpackets", "0", CVAR_NONE, "Show all network packets");
	showdrop = Cvar_Get ("showdrop", "0", CVAR_NONE, "Toggle the display of how many packets you are dropping");
        qport = Cvar_Get ("qport", "0", CVAR_NONE, "The internal port number for the game networking code."
        "Useful for clients who use multiple connections through one IP address (NAT/IP-MASQ) because default port is random.");
}

/*
	Netchan_OutOfBand

	Sends an out-of-band datagram
*/
void
Netchan_OutOfBand (netadr_t adr, int length, byte * data)
{
	sizebuf_t   send;
	byte        send_buf[MAX_MSGLEN + PACKET_HEADER];

// write the packet header
	send.data = send_buf;
	send.maxsize = sizeof (send_buf);
	send.cursize = 0;

	MSG_WriteLong (&send, -1);			// -1 sequence means out of band
	SZ_Write (&send, data, length);

// send the datagram
	// zoid, no input in demo playback mode
	if (!is_server) {
		if (!cls.demoplayback)
			NET_SendPacket (send.cursize, send.data, adr);
	} else
		NET_SendPacket (send.cursize, send.data, adr);

}

/*
	Netchan_OutOfBandPrint

	Sends a text message in an out-of-band datagram
*/
void
Netchan_OutOfBandPrint (netadr_t adr, char *format, ...)
{
	va_list     argptr;
	static char string[8192];			// ?? why static?

	va_start (argptr, format);
	vsnprintf (string, sizeof (string), format, argptr);
	va_end (argptr);


	Netchan_OutOfBand (adr, strlen (string), (byte *) string);
}


/*
	Netchan_Setup

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

	chan->remote_address = adr;
	chan->last_received = realtime;

	chan->message.data = chan->message_buf;
	chan->message.allowoverflow = true;
	chan->message.maxsize = sizeof (chan->message_buf);

	chan->qport = qport;

	chan->rate = 1.0 / 2500;
}


/*
	Netchan_CanPacket

	Returns true if the bandwidth choke isn't active
*/
#define	MAX_BACKUP	200
qboolean
Netchan_CanPacket (netchan_t *chan)
{
	if (chan->cleartime < realtime + MAX_BACKUP * chan->rate)
		return true;
	return false;
}


/*
	Netchan_CanReliable

	Returns true if the bandwidth choke isn't 
*/
qboolean
Netchan_CanReliable (netchan_t *chan)
{
	if (chan->reliable_length)
		return false;					// waiting for ack
	return Netchan_CanPacket (chan);
}

qboolean    ServerPaused (void);

/*
	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.
*/
void
Netchan_Transmit (netchan_t *chan, int length, byte * data)
{
	sizebuf_t   send;
	byte        send_buf[MAX_MSGLEN + PACKET_HEADER];
	qboolean    send_reliable;
	unsigned int w1, w2;
	int         i;

// check for message overflow
	if (chan->message.overflowed) {
		chan->fatal_error = true;
		Con_Printf ("%s:Outgoing message overflow\n",
					NET_AdrToString (chan->remote_address));
		return;
	}
// 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 (!chan->reliable_length && chan->message.cursize) {
		memcpy (chan->reliable_buf, chan->message_buf, chan->message.cursize);
		chan->reliable_length = chan->message.cursize;
		chan->message.cursize = 0;
		chan->reliable_sequence ^= 1;
		send_reliable = true;
	}
// write the packet header
	send.data = send_buf;
	send.maxsize = sizeof (send_buf);
	send.cursize = 0;

	w1 = chan->outgoing_sequence | (send_reliable << 31);
	w2 = chan->incoming_sequence | (chan->incoming_reliable_sequence << 31);

	chan->outgoing_sequence++;

	MSG_WriteLong (&send, w1);
	MSG_WriteLong (&send, w2);

	// send the qport if we are a client
	if (!is_server)
		MSG_WriteShort (&send, cls.qport);

// copy the reliable message to the packet first
	if (send_reliable) {
		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);

// send the datagram
	i = chan->outgoing_sequence & (MAX_LATENT - 1);
	chan->outgoing_size[i] = send.cursize;
	chan->outgoing_time[i] = realtime;

	// zoid, no input in demo playback mode
	if (!is_server) {
		if (!cls.demoplayback)
			NET_SendPacket (send.cursize, send.data, chan->remote_address);
	} else
		NET_SendPacket (send.cursize, send.data, chan->remote_address);

	if (chan->cleartime < realtime)
		chan->cleartime = realtime + send.cursize * chan->rate;
	else
		chan->cleartime += send.cursize * chan->rate;
	if (ServerPaused ())
		chan->cleartime = realtime;

	if (showpackets->int_val)
		Con_Printf ("--> s=%i(%i) a=%i(%i) %i\n", chan->outgoing_sequence,
					send_reliable, chan->incoming_sequence,
					chan->incoming_reliable_sequence, send.cursize);

}

/*
	Netchan_Process

	called when the current net_message is from remote_address
	modifies net_message so that it points to the packet payload
*/
qboolean
Netchan_Process (netchan_t *chan)
{
	unsigned int sequence, sequence_ack;
	unsigned int reliable_ack, reliable_message;
	int         qport;

	if (is_server) {
		if (!NET_CompareAdr (net_from, chan->remote_address))
			return false;
	} else {
		if (!cls.demoplayback &&
			!NET_CompareAdr (net_from, chan->remote_address)) return false;
	}

// get sequence numbers     
	MSG_BeginReading ();
	sequence = MSG_ReadLong ();
	sequence_ack = MSG_ReadLong ();

	// read the qport if we are a server
	if (is_server)
		qport = MSG_ReadShort ();

	reliable_message = sequence >> 31;
	reliable_ack = sequence_ack >> 31;

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

	if (showpackets->int_val)
		Con_Printf ("<-- s=%i(%i) a=%i(%i) %i\n", sequence, reliable_message,
					sequence_ack, reliable_ack, net_message.cursize);

// get a rate estimation
#if 0
	if (chan->outgoing_sequence - sequence_ack < MAX_LATENT) {
		int         i;
		double      time, rate;

		i = sequence_ack & (MAX_LATENT - 1);
		time = realtime - chan->outgoing_time[i];
		time -= 0.1;					// subtract 100 ms
		if (time <= 0) {				// gotta be a digital link for <100
										// ms ping
			if (chan->rate > 1.0 / 5000)
				chan->rate = 1.0 / 5000;
		} else {
			if (chan->outgoing_size[i] < 512) {	// only deal with small
												// messages
				rate = chan->outgoing_size[i] / time;
				if (rate > 5000)
					rate = 5000;
				rate = 1.0 / rate;
				if (chan->rate > rate)
					chan->rate = rate;
			}
		}
	}
#endif

//
// discard stale or duplicated packets
//
	if (sequence <= (unsigned int) chan->incoming_sequence) {
		if (showdrop->int_val)
			Con_Printf ("%s:Out of order packet %i at %i\n",
						NET_AdrToString (chan->remote_address), sequence,
						chan->incoming_sequence);
		return false;
	}
//
// dropped packets don't keep the message from being used
//
	net_drop = sequence - (chan->incoming_sequence + 1);
	if (net_drop > 0) {
		chan->drop_count += 1;

		if (showdrop->int_val)
			Con_Printf ("%s:Dropped %i packets at %i\n",
						NET_AdrToString (chan->remote_address),
						sequence - (chan->incoming_sequence + 1)
						, sequence);
	}
//
// if the current outgoing reliable message has been acknowledged
// clear the buffer to make way for the next
//
	if (reliable_ack == (unsigned int) 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)
		chan->incoming_reliable_sequence ^= 1;

//
// the message can now be read from the current message pointer
// update statistics counters
//
	chan->frame_latency = chan->frame_latency * OLD_AVG
		+ (chan->outgoing_sequence - sequence_ack) * (1.0 - OLD_AVG);
	chan->frame_rate = chan->frame_rate * OLD_AVG
		+ (realtime - chan->last_received) * (1.0 - OLD_AVG);
	chan->good_count += 1;

	chan->last_received = realtime;

	return true;
}