/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2009 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2008 Robin Burchell <robin+git@viroteck.net>
 *
 * This file is part of InspIRCd.  InspIRCd 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, version 2.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */


#include "inspircd.h"

#include "treesocket.h"
#include "treeserver.h"
#include "utils.h"
#include "commandbuilder.h"

/*
 * Yes, this function looks a little ugly.
 * However, in some circumstances we may not have a User, so we need to do things this way.
 * Returns 1 if colliding local client, 2 if colliding remote, 3 if colliding both.
 * Sends SAVEs as appropriate and forces nickchanges too.
 */
int SpanningTreeUtilities::DoCollision(User* u, TreeServer* server, time_t remotets, const std::string& remoteident, const std::string& remoteip, const std::string& remoteuid)
{
	// At this point we're sure that a collision happened, increment the counter regardless of who wins
	ServerInstance->stats.Collisions++;

	/*
	 * Under old protocol rules, we would have had to kill both clients.
	 * Really, this sucks.
	 * These days, we have UID. And, so what we do is, force nick change client(s)
	 * involved according to timestamp rules.
	 *
	 * RULES:
	 *  user@ip equal:
	 *   Force nick change on OLDER timestamped client
	 *  user@ip differ:
	 *   Force nick change on NEWER timestamped client
	 *  TS EQUAL:
	 *   FNC both.
	 *
	 * This stops abusive use of collisions, simplifies problems with loops, and so on.
	 *   -- w00t
	 */
	bool bChangeLocal = true;
	bool bChangeRemote = true;

	/* for brevity, don't use the User - use defines to avoid any copy */
	#define localts u->age
	#define localident u->ident
	#define localip u->GetIPString()

	/* mmk. let's do this again. */
	if (remotets == localts)
	{
		/* equal. fuck them both! do nada, let the handler at the bottom figure this out. */
	}
	else
	{
		/* fuck. now it gets complex. */

		/* first, let's see if ident@host matches. */
		bool SamePerson = (localident == remoteident)
				&& (localip == remoteip);

		/*
		 * if ident@ip is equal, and theirs is newer, or
		 * ident@ip differ, and ours is newer
		 */
		if((SamePerson && remotets < localts) ||
		   (!SamePerson && remotets > localts))
		{
			/* remote needs to change */
			bChangeLocal = false;
		}
		else
		{
			/* ours needs to change */
			bChangeRemote = false;
		}
	}

	/*
	 * Cheat a little here. Instead of a dedicated command to change UID,
	 * use SAVE and accept the losing client with its UID (as we know the SAVE will
	 * not fail under any circumstances -- UIDs are netwide exclusive).
	 *
	 * This means that each side of a collide will generate one extra NICK back to where
	 * they have just linked (and where it got the SAVE from), however, it will
	 * be dropped harmlessly as it will come in as :928AAAB NICK 928AAAB, and we already
	 * have 928AAAB's nick set to that.
	 *   -- w00t
	 */

	if (bChangeLocal)
	{
		/*
		 * Local-side nick needs to change. Just in case we are hub, and
		 * this "local" nick is actually behind us, send an SAVE out.
		 */
		CmdBuilder params("SAVE");
		params.push_back(u->uuid);
		params.push_back(ConvToStr(u->age));
		params.Broadcast();

		u->ChangeNick(u->uuid);

		if (!bChangeRemote)
			return 1;
	}
	if (bChangeRemote)
	{
		User *remote = ServerInstance->FindUUID(remoteuid);
		/*
		 * remote side needs to change. If this happens, we will modify
		 * the UID or halt the propagation of the nick change command,
		 * so other servers don't need to see the SAVE
		 */
		TreeSocket* sock = server->GetSocket();
		sock->WriteLine(":"+ServerInstance->Config->GetSID()+" SAVE "+remoteuid+" "+ ConvToStr(remotets));

		if (remote)
		{
			/* nick change collide. Force change their nick. */
			remote->ChangeNick(remoteuid);
		}

		if (!bChangeLocal)
			return 2;
	}

	return 3;
}