/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2019 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2018 linuxdaemon <linuxdaemon.irc@gmail.com>
 *   Copyright (C) 2018 Dylan Frank <b00mx0r@aureus.pw>
 *   Copyright (C) 2017-2020 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2014-2015, 2018 Attila Molnar <attilamolnar@hush.com>
 *
 * 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 "core_channel.h"
#include "invite.h"
#include "listmode.h"

namespace
{
/** Hook that sends a MODE after a JOIN if the user in the JOIN has some modes prefix set.
 * This happens e.g. when modules such as operprefix explicitly set prefix modes on the joining
 * user, or when a member with prefix modes does a host cycle.
 */
class JoinHook : public ClientProtocol::EventHook
{
	ClientProtocol::Messages::Mode modemsg;
	Modes::ChangeList modechangelist;
	const User* joininguser;

 public:
	/** If true, MODE changes after JOIN will be sourced from the user, rather than the server
	 */
	bool modefromuser;

	JoinHook(Module* mod)
		: ClientProtocol::EventHook(mod, "JOIN")
	{
	}

	void OnEventInit(const ClientProtocol::Event& ev) CXX11_OVERRIDE
	{
		const ClientProtocol::Events::Join& join = static_cast<const ClientProtocol::Events::Join&>(ev);
		const Membership& memb = *join.GetMember();

		modechangelist.clear();
		for (std::string::const_iterator i = memb.modes.begin(); i != memb.modes.end(); ++i)
		{
			PrefixMode* const pm = ServerInstance->Modes.FindPrefixMode(*i);
			if (!pm)
				continue; // Shouldn't happen
			modechangelist.push_add(pm, memb.user->nick);
		}

		if (modechangelist.empty())
		{
			// Member got no modes on join
			joininguser = NULL;
			return;
		}

		joininguser = memb.user;

		// Prepare a mode protocol event that we can append to the message list in OnPreEventSend()
		modemsg.SetParams(memb.chan, NULL, modechangelist);
		if (modefromuser)
			modemsg.SetSource(join);
		else
			modemsg.SetSourceUser(ServerInstance->FakeClient);
	}

	ModResult OnPreEventSend(LocalUser* user, const ClientProtocol::Event& ev, ClientProtocol::MessageList& messagelist) CXX11_OVERRIDE
	{
		// If joininguser is NULL then they didn't get any modes on join, skip.
		// Also don't show their own modes to them, they get that in the NAMES list not via MODE.
		if ((joininguser) && (user != joininguser))
			messagelist.push_back(&modemsg);
		return MOD_RES_PASSTHRU;
	}
};

}

class CoreModChannel : public Module, public CheckExemption::EventListener
{
	Invite::APIImpl invapi;
	CommandInvite cmdinvite;
	CommandJoin cmdjoin;
	CommandKick cmdkick;
	CommandNames cmdnames;
	CommandTopic cmdtopic;
	Events::ModuleEventProvider evprov;
	JoinHook joinhook;

	ModeChannelBan banmode;
	SimpleChannelModeHandler inviteonlymode;
	ModeChannelKey keymode;
	ModeChannelLimit limitmode;
	SimpleChannelModeHandler moderatedmode;
	SimpleChannelModeHandler noextmsgmode;
	ModeChannelOp opmode;
	SimpleChannelModeHandler privatemode;
	SimpleChannelModeHandler secretmode;
	SimpleChannelModeHandler topiclockmode;
	ModeChannelVoice voicemode;

	insp::flat_map<std::string, char> exemptions;

	ModResult IsInvited(User* user, Channel* chan)
	{
		LocalUser* localuser = IS_LOCAL(user);
		if ((localuser) && (invapi.IsInvited(localuser, chan)))
			return MOD_RES_ALLOW;
		return MOD_RES_PASSTHRU;
	}

 public:
	CoreModChannel()
		: CheckExemption::EventListener(this, UINT_MAX)
		, invapi(this)
		, cmdinvite(this, invapi)
		, cmdjoin(this)
		, cmdkick(this)
		, cmdnames(this)
		, cmdtopic(this)
		, evprov(this, "event/channel")
		, joinhook(this)
		, banmode(this)
		, inviteonlymode(this, "inviteonly", 'i')
		, keymode(this)
		, limitmode(this)
		, moderatedmode(this, "moderated", 'm')
		, noextmsgmode(this, "noextmsg", 'n')
		, opmode(this)
		, privatemode(this, "private", 'p')
		, secretmode(this, "secret", 's')
		, topiclockmode(this, "topiclock", 't')
		, voicemode(this)
	{
	}

	void ReadConfig(ConfigStatus& status) CXX11_OVERRIDE
	{
		ConfigTag* optionstag = ServerInstance->Config->ConfValue("options");

		std::string current;
		irc::spacesepstream defaultstream(optionstag->getString("exemptchanops"));
		insp::flat_map<std::string, char> exempts;
		while (defaultstream.GetToken(current))
		{
			std::string::size_type pos = current.find(':');
			if (pos == std::string::npos || (pos + 2) > current.size())
				throw ModuleException("Invalid exemptchanops value '" + current + "' at " + optionstag->getTagLocation());

			const std::string restriction = current.substr(0, pos);
			const char prefix = current[pos + 1];

			ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Exempting prefix %c from %s", prefix, restriction.c_str());
			exempts[restriction] = prefix;
		}

		ConfigTag* securitytag = ServerInstance->Config->ConfValue("security");
		const std::string announceinvites = securitytag->getString("announceinvites", "dynamic", 1);
		Invite::AnnounceState newannouncestate;
		if (stdalgo::string::equalsci(announceinvites, "none"))
			newannouncestate = Invite::ANNOUNCE_NONE;
		else if (stdalgo::string::equalsci(announceinvites, "all"))
			newannouncestate = Invite::ANNOUNCE_ALL;
		else if (stdalgo::string::equalsci(announceinvites, "ops"))
			newannouncestate = Invite::ANNOUNCE_OPS;
		else if (stdalgo::string::equalsci(announceinvites, "dynamic"))
			newannouncestate = Invite::ANNOUNCE_DYNAMIC;
		else
			throw ModuleException(announceinvites + " is an invalid <security:announceinvites> value, at " + securitytag->getTagLocation());

		// Config is valid, apply it

		// Validates and applies <maxlist> tags, so do it first
		banmode.DoRehash();

		exemptions.swap(exempts);
		// In 2.0 we allowed limits of 0 to be set. This is non-standard behaviour
		// and will be removed in the next major release.
		limitmode.minlimit = optionstag->getBool("allowzerolimit", true) ? 0 : 1;;
		cmdinvite.announceinvites = newannouncestate;
		joinhook.modefromuser = optionstag->getBool("cyclehostsfromuser");

		Implementation events[] = { I_OnCheckKey, I_OnCheckLimit, I_OnCheckChannelBan };
		if (optionstag->getBool("invitebypassmodes", true))
			ServerInstance->Modules.Attach(events, this, sizeof(events)/sizeof(Implementation));
		else
		{
			for (unsigned int i = 0; i < sizeof(events)/sizeof(Implementation); i++)
				ServerInstance->Modules.Detach(events[i], this);
		}
	}

	void On005Numeric(std::map<std::string, std::string>& tokens) CXX11_OVERRIDE
	{
		tokens["KEYLEN"] = ConvToStr(ModeChannelKey::maxkeylen);

		insp::flat_map<int, std::string> limits;
		std::string vlist;
		const ModeParser::ListModeList& listmodes = ServerInstance->Modes->GetListModes();
		for (ModeParser::ListModeList::const_iterator iter = listmodes.begin(); iter != listmodes.end(); ++iter)
		{
			ListModeBase* lm = *iter;

			const unsigned int limit = lm->GetLowerLimit();
			limits[limit].push_back(lm->GetModeChar());

			if (lm->HasVariableLength())
				vlist.push_back(lm->GetModeChar());
		}

		std::string& buffer = tokens["MAXLIST"];
		for (insp::flat_map<int, std::string>::const_iterator iter = limits.begin(); iter != limits.end(); ++iter)
		{
			if (!buffer.empty())
				buffer.push_back(',');

			std::string modes(iter->second);
			std::sort(modes.begin(), modes.end());

			buffer.append(modes);
			buffer.push_back(':');
			buffer.append(ConvToStr(iter->first));
		}

		if (!vlist.empty())
		{
			tokens["VBANLIST"]; // deprecated
			tokens["VLIST"] = vlist;
		}
	}

	ModResult OnUserPreJoin(LocalUser* user, Channel* chan, const std::string&, std::string&, const std::string& keygiven) CXX11_OVERRIDE
	{
		if (!chan)
			return MOD_RES_PASSTHRU;

		// Check whether the channel key is correct.
		const std::string ckey = chan->GetModeParameter(&keymode);
		if (!ckey.empty())
		{
			ModResult MOD_RESULT;
			FIRST_MOD_RESULT(OnCheckKey, MOD_RESULT, (user, chan, keygiven));
			if (!MOD_RESULT.check(InspIRCd::TimingSafeCompare(ckey, keygiven)))
			{
				// If no key provided, or key is not the right one, and can't bypass +k (not invited or option not enabled)
				user->WriteNumeric(ERR_BADCHANNELKEY, chan->name, "Cannot join channel (incorrect channel key)");
				return MOD_RES_DENY;
			}
		}

		// Check whether the invite only mode is set.
		if (chan->IsModeSet(inviteonlymode))
		{
			ModResult MOD_RESULT;
			FIRST_MOD_RESULT(OnCheckInvite, MOD_RESULT, (user, chan));
			if (MOD_RESULT != MOD_RES_ALLOW)
			{
				user->WriteNumeric(ERR_INVITEONLYCHAN, chan->name, "Cannot join channel (invite only)");
				return MOD_RES_DENY;
			}
		}

		// Check whether the limit would be exceeded by this user joining.
		if (chan->IsModeSet(limitmode))
		{
			ModResult MOD_RESULT;
			FIRST_MOD_RESULT(OnCheckLimit, MOD_RESULT, (user, chan));
			if (!MOD_RESULT.check(chan->GetUserCounter() < static_cast<size_t>(limitmode.ext.get(chan))))
			{
				user->WriteNumeric(ERR_CHANNELISFULL, chan->name, "Cannot join channel (channel is full)");
				return MOD_RES_DENY;
			}
		}

		// Everything looks okay.
		return MOD_RES_PASSTHRU;
	}

	void OnPostJoin(Membership* memb) CXX11_OVERRIDE
	{
		Channel* const chan = memb->chan;
		LocalUser* const localuser = IS_LOCAL(memb->user);
		if (localuser)
		{
			// Remove existing invite, if any
			invapi.Remove(localuser, chan);

			if (chan->topic.length())
				Topic::ShowTopic(localuser, chan);

			// Show all members of the channel, including invisible (+i) users
			cmdnames.SendNames(localuser, chan, true);
		}
	}

	ModResult OnCheckKey(User* user, Channel* chan, const std::string& keygiven) CXX11_OVERRIDE
	{
		// Hook only runs when being invited bypasses +bkl
		return IsInvited(user, chan);
	}

	ModResult OnCheckChannelBan(User* user, Channel* chan) CXX11_OVERRIDE
	{
		// Hook only runs when being invited bypasses +bkl
		return IsInvited(user, chan);
	}

	ModResult OnCheckLimit(User* user, Channel* chan) CXX11_OVERRIDE
	{
		// Hook only runs when being invited bypasses +bkl
		return IsInvited(user, chan);
	}

	ModResult OnCheckInvite(User* user, Channel* chan) CXX11_OVERRIDE
	{
		// Hook always runs
		return IsInvited(user, chan);
	}

	void OnUserDisconnect(LocalUser* user) CXX11_OVERRIDE
	{
		invapi.RemoveAll(user);
	}

	void OnChannelDelete(Channel* chan) CXX11_OVERRIDE
	{
		// Make sure the channel won't appear in invite lists from now on, don't wait for cull to unset the ext
		invapi.RemoveAll(chan);
	}

	ModResult OnCheckExemption(User* user, Channel* chan, const std::string& restriction) CXX11_OVERRIDE
	{
		if (!exemptions.count(restriction))
			return MOD_RES_PASSTHRU;

		unsigned int mypfx = chan->GetPrefixValue(user);
		char minmode = exemptions[restriction];

		PrefixMode* mh = ServerInstance->Modes->FindPrefixMode(minmode);
		if (mh && mypfx >= mh->GetPrefixRank())
			return MOD_RES_ALLOW;
		if (mh || minmode == '*')
			return MOD_RES_DENY;
		return MOD_RES_PASSTHRU;
	}

	void Prioritize() CXX11_OVERRIDE
	{
		ServerInstance->Modules.SetPriority(this, I_OnPostJoin, PRIORITY_FIRST);
		ServerInstance->Modules.SetPriority(this, I_OnUserPreJoin, PRIORITY_LAST);
	}

	Version GetVersion() CXX11_OVERRIDE
	{
		return Version("Provides the INVITE, JOIN, KICK, NAMES, and TOPIC commands", VF_VENDOR|VF_CORE);
	}
};

MODULE_INIT(CoreModChannel)
