/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2019-2023 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2017 B00mX0r <b00mx0r@aureus.pw>
 *   Copyright (C) 2012-2014, 2016 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012, 2019 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2012, 2014 Shawn Smith <ShawnSmith0828@gmail.com>
 *   Copyright (C) 2009 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2008 Robin Burchell <robin+git@viroteck.net>
 *   Copyright (C) 2006 Craig Edwards <brain@inspircd.org>
 *
 * 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 "extension.h"
#include "numerichelper.h"

/** Handle channel mode +L
 */
class Redirect final
	: public ParamMode<Redirect, StringExtItem>
{
public:
	Redirect(Module* Creator)
		: ParamMode<Redirect, StringExtItem>(Creator, "redirect", 'L')
	{
		syntax = "<target>";
	}

	bool OnSet(User* source, Channel* channel, std::string& parameter) override
	{
		if (IS_LOCAL(source))
		{
			if (!ServerInstance->Channels.IsChannel(parameter))
			{
				source->WriteNumeric(Numerics::NoSuchChannel(parameter));
				return false;
			}
		}

		if (IS_LOCAL(source) && !source->IsOper())
		{
			auto* c = ServerInstance->Channels.Find(parameter);
			if (!c)
			{
				source->WriteNumeric(690, FMT::format("Target channel {} must exist to be set as a redirect.", parameter));
				return false;
			}
			else if (c->GetPrefixValue(source) < OP_VALUE)
			{
				source->WriteNumeric(690, FMT::format("You must be opped on {} to set it as a redirect.", parameter));
				return false;
			}
		}

		/*
		 * We used to do some checking for circular +L here, but there is no real need for this any more especially as we
		 * now catch +L looping in PreJoin. Remove it, since O(n) logic makes me sad, and we catch it anyway. :) -- w00t
		 */
		ext.Set(channel, parameter);
		return true;
	}

	void SerializeParam(Channel* chan, const std::string* str, std::string& out)
	{
		out += *str;
	}
};

class ModuleRedirect final
	: public Module
{
private:
	Redirect re;
	SimpleUserMode antiredirectmode;
	ChanModeReference limitmode;

public:
	ModuleRedirect()
		: Module(VF_VENDOR, "Allows users to be redirected to another channel when the user limit is reached.")
		, re(this)
		, antiredirectmode(this, "antiredirect", 'L')
		, limitmode(this, "limit")
	{
	}

	ModResult OnUserPreJoin(LocalUser* user, Channel* chan, const std::string& cname, std::string& privs, const std::string& keygiven, bool override) override
	{
		if (!override && chan)
		{
			if (chan->IsModeSet(re) && chan->IsModeSet(limitmode))
			{
				if (chan->GetUsers().size() >= ConvToNum<size_t>(chan->GetModeParameter(limitmode)))
				{
					const std::string& channel = *re.ext.Get(chan);

					/* sometimes broken services can make circular or chained +L, avoid this */
					auto* destchan = ServerInstance->Channels.Find(channel);
					if (destchan && destchan->IsModeSet(re))
					{
						user->WriteNumeric(470, cname, '*', "You may not join this channel. A redirect is set, but you may not be redirected as it is a circular loop.");
						return MOD_RES_DENY;
					}

					if (user->IsModeSet(antiredirectmode))
					{
						user->WriteNumeric(470, cname, channel, "Force redirection stopped.");
						return MOD_RES_DENY;
					}
					else
					{
						user->WriteNumeric(470, cname, channel, "You may not join this channel, so you are automatically being transferred to the redirected channel.");
						Channel::JoinUser(user, channel);
						return MOD_RES_DENY;
					}
				}
			}
		}
		return MOD_RES_PASSTHRU;
	}
};

MODULE_INIT(ModuleRedirect)