/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2013, 2017-2019, 2021 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2012-2014, 2016 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012, 2019 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2009 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2007-2008 Robin Burchell <robin+git@viroteck.net>
 *   Copyright (C) 2007 John Brooks <special@inspircd.org>
 *   Copyright (C) 2007 Dennis Friis <peavey@inspircd.org>
 *   Copyright (C) 2006, 2008 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 "duration.h"
#include "modules/ctctags.h"
#include "modules/exemption.h"
#include "numerichelper.h"

/** Holds flood settings and state for mode +f
 */
class floodsettings final
{
public:
	bool ban;
	unsigned int secs;
	unsigned int lines;
	time_t reset;
	insp::flat_map<User*, double> counters;

	floodsettings(bool a, unsigned int b, unsigned int c)
		: ban(a)
		, secs(b)
		, lines(c)
	{
		reset = ServerInstance->Time() + secs;
	}

	bool addmessage(User* who, double weight)
	{
		if (ServerInstance->Time() > reset)
		{
			counters.clear();
			reset = ServerInstance->Time() + secs;
		}

		counters[who] += weight;
		return (counters[who] >= this->lines);
	}

	void clear(User* who)
	{
		counters.erase(who);
	}
};

/** Handles channel mode +f
 */
class MsgFlood final
	: public ParamMode<MsgFlood, SimpleExtItem<floodsettings>>
{
public:
	MsgFlood(Module* Creator)
		: ParamMode<MsgFlood, SimpleExtItem<floodsettings>>(Creator, "flood", 'f')
	{
		syntax = "[*]<messages>:<seconds>";
	}

	bool OnSet(User* source, Channel* channel, std::string& parameter) override
	{
		std::string::size_type colon = parameter.find(':');
		if ((colon == std::string::npos) || (parameter.find('-') != std::string::npos))
		{
			source->WriteNumeric(Numerics::InvalidModeParameter(channel, this, parameter));
			return false;
		}

		/* Set up the flood parameters for this channel */
		bool ban = (parameter[0] == '*');
		unsigned int nlines = ConvToNum<unsigned int>(parameter.substr(ban ? 1 : 0, ban ? colon-1 : colon));
		unsigned int nsecs = ConvToNum<unsigned int>(parameter.substr(colon+1));

		if ((nlines<2) || (nsecs<1))
		{
			source->WriteNumeric(Numerics::InvalidModeParameter(channel, this, parameter));
			return false;
		}

		ext.SetFwd(channel, ban, nsecs, nlines);
		return true;
	}

	void SerializeParam(Channel* chan, const floodsettings* fs, std::string& out)
	{
		if (fs->ban)
			out.push_back('*');
		out.append(ConvToStr(fs->lines)).push_back(':');
		out.append(ConvToStr(fs->secs));
	}
};

class ModuleMsgFlood final
	: public Module
	, public CTCTags::EventListener
{
private:
	ChanModeReference banmode;
	CheckExemption::EventProvider exemptionprov;
	MsgFlood mf;
	double notice;
	double privmsg;
	double tagmsg;
	std::string kickmessage;

public:
	ModuleMsgFlood()
		: Module(VF_VENDOR, "Adds channel mode f (flood) which helps protect against spammers which mass-message channels.")
		, CTCTags::EventListener(this)
		, banmode(this, "ban")
		, exemptionprov(this)
		, mf(this)
	{
	}

	void ReadConfig(ConfigStatus&) override
	{
		const auto& tag = ServerInstance->Config->ConfValue("messageflood");
		notice = tag->getNum<float>("notice", 1.0);
		privmsg = tag->getNum<float>("privmsg", 1.0);
		tagmsg = tag->getNum<float>("tagmsg", 0.2);
		kickmessage = tag->getString("kickmessage", "Message flood (trigger is %lines% messages in %duration%)", 1);
	}

	ModResult HandleMessage(User* user, const MessageTarget& target, double weight)
	{
		if (target.type != MessageTarget::TYPE_CHANNEL)
			return MOD_RES_PASSTHRU;

		Channel* dest = target.Get<Channel>();
		if ((!IS_LOCAL(user)) || !dest->IsModeSet(mf))
			return MOD_RES_PASSTHRU;

		ModResult res = exemptionprov.Check(user, dest, "flood");
		if (res == MOD_RES_ALLOW)
			return MOD_RES_PASSTHRU;

		floodsettings* f = mf.ext.Get(dest);
		if (f)
		{
			if (f->addmessage(user, weight))
			{
				/* You're outttta here! */
				f->clear(user);
				if (f->ban)
				{
					Modes::ChangeList changelist;
					changelist.push_add(*banmode, "*!" + user->GetBanIdent() + "@" + user->GetDisplayedHost());
					ServerInstance->Modes.Process(ServerInstance->FakeClient, dest, nullptr, changelist);
				}

				const std::string kickmsg = Template::Replace(kickmessage, {
					{ "duration", Duration::ToString(f->secs) },
					{ "lines",    ConvToStr(f->lines)               },
					{ "seconds",  ConvToStr(f->secs)                },
				});
				dest->KickUser(ServerInstance->FakeClient, user, kickmsg);

				return MOD_RES_DENY;
			}
		}

		return MOD_RES_PASSTHRU;
	}

	ModResult OnUserPreMessage(User* user, const MessageTarget& target, MessageDetails& details) override
	{
		return HandleMessage(user, target, (details.type == MessageType::PRIVMSG ? privmsg : notice));
	}

	ModResult OnUserPreTagMessage(User* user, const MessageTarget& target, CTCTags::TagMessageDetails& details) override
	{
		return HandleMessage(user, target, tagmsg);
	}

	void Prioritize() override
	{
		// we want to be after all modules that might deny the message (e.g. m_muteban, m_noctcp, m_blockcolor, etc.)
		ServerInstance->Modules.SetPriority(this, I_OnUserPreMessage, PRIORITY_LAST);
	}
};

MODULE_INIT(ModuleMsgFlood)