/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2016 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"

namespace
{
class Settings
{
	typedef insp::flat_map<std::string, unsigned int> RanksToSeeMap;
	RanksToSeeMap rankstosee;

 public:
	unsigned int GetRequiredRank(const ModeHandler& mh) const
	{
		RanksToSeeMap::const_iterator it = rankstosee.find(mh.name);
		if (it != rankstosee.end())
			return it->second;
		return 0;
	}

	void Load()
	{
		RanksToSeeMap newranks;

		ConfigTagList tags = ServerInstance->Config->ConfTags("hidemode");
		for (ConfigIter i = tags.first; i != tags.second; ++i)
		{
			ConfigTag* tag = i->second;
			const std::string modename = tag->getString("mode");
			if (modename.empty())
				throw ModuleException("<hidemode:mode> is empty at " + tag->getTagLocation());

			unsigned int rank = tag->getUInt("rank", 0);
			if (!rank)
				throw ModuleException("<hidemode:rank> must be greater than 0 at " + tag->getTagLocation());

			ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Hiding the %s mode from users below rank %u", modename.c_str(), rank);
			newranks.insert(std::make_pair(modename, rank));
		}
		rankstosee.swap(newranks);
	}
};

class ModeHook : public ClientProtocol::EventHook
{
	typedef insp::flat_map<unsigned int, const ClientProtocol::MessageList*> FilteredModeMap;

	std::vector<Modes::ChangeList> modechangelists;
	std::list<ClientProtocol::Messages::Mode> filteredmodelist;
	std::list<ClientProtocol::MessageList> filteredmsgplists;
	FilteredModeMap cache;

	static ModResult HandleResult(const ClientProtocol::MessageList* filteredmessagelist, ClientProtocol::MessageList& messagelist)
	{
		// Deny if member isn't allowed to see even a single mode change from this mode event
		if (!filteredmessagelist)
			return MOD_RES_DENY;

		// Member is allowed to see at least one mode change, replace list
		if (filteredmessagelist != &messagelist)
			messagelist = *filteredmessagelist;

		return MOD_RES_PASSTHRU;
	}

	Modes::ChangeList* FilterModeChangeList(const ClientProtocol::Events::Mode& mode, unsigned int rank)
	{
		Modes::ChangeList* modechangelist = NULL;
		for (Modes::ChangeList::List::const_iterator i = mode.GetChangeList().getlist().begin(); i != mode.GetChangeList().getlist().end(); ++i)
		{
			const Modes::Change& curr = *i;
			if (settings.GetRequiredRank(*curr.mh) <= rank)
			{
				 // No restriction on who can see this mode or there is one but the member's rank is sufficient
				if (modechangelist)
					modechangelist->push(curr);

				continue;
			}

			// Member cannot see the current mode change

			if (!modechangelist)
			{
				// Create new mode change list or reuse the last one if it's empty
				if ((modechangelists.empty()) || (!modechangelists.back().empty()))
					modechangelists.push_back(Modes::ChangeList());

				// Add all modes to it which we've accepted so far
				modechangelists.back().push(mode.GetChangeList().getlist().begin(), i);
				modechangelist = &modechangelists.back();
			}
		}
		return modechangelist;
	}

	void OnEventInit(const ClientProtocol::Event& ev) CXX11_OVERRIDE
	{
		cache.clear();
		filteredmsgplists.clear();
		filteredmodelist.clear();
		modechangelists.clear();

		// Ensure no reallocations will happen
		const size_t numprefixmodes = ServerInstance->Modes.GetPrefixModes().size();
		modechangelists.reserve(numprefixmodes);
	}

	ModResult OnPreEventSend(LocalUser* user, const ClientProtocol::Event& ev, ClientProtocol::MessageList& messagelist) CXX11_OVERRIDE
	{
		const ClientProtocol::Events::Mode& mode = static_cast<const ClientProtocol::Events::Mode&>(ev);
		Channel* const chan = mode.GetMessages().front().GetChanTarget();
		if (!chan)
			return MOD_RES_PASSTHRU;

		Membership* const memb = chan->GetUser(user);
		if (!memb)
			return MOD_RES_PASSTHRU;

		// Check cache first
		const FilteredModeMap::const_iterator it = cache.find(memb->getRank());
		if (it != cache.end())
			return HandleResult(it->second, messagelist);

		// Message for this rank isn't cached, generate it now
		const Modes::ChangeList* const filteredchangelist = FilterModeChangeList(mode, memb->getRank());

		// If no new change list was generated (above method returned NULL) it means the member and everyone else
		// with the same rank can see everything in the original change list.
		ClientProtocol::MessageList* finalmsgplist = &messagelist;
		if (filteredchangelist)
		{
			if (filteredchangelist->empty())
			{
				// This rank cannot see any mode changes in the original change list
				finalmsgplist = NULL;
			}
			else
			{
				// This rank can see some of the mode changes in the filtered mode change list.
				// Create and store a new protocol message from it.
				filteredmsgplists.push_back(ClientProtocol::MessageList());
				ClientProtocol::Events::Mode::BuildMessages(mode.GetMessages().front().GetSourceUser(), chan, NULL, *filteredchangelist, filteredmodelist, filteredmsgplists.back());
				finalmsgplist = &filteredmsgplists.back();
			}
		}

		// Cache the result in all cases so it can be reused for further members with the same rank
		cache.insert(std::make_pair(memb->getRank(), finalmsgplist));
		return HandleResult(finalmsgplist, messagelist);
	}

 public:
	Settings settings;

	ModeHook(Module* mod)
		: ClientProtocol::EventHook(mod, "MODE", 10)
	{
	}
};
}

class ModuleHideMode : public Module
{
 private:
	ModeHook modehook;

 public:
	ModuleHideMode()
		: modehook(this)
	{
	}

	void ReadConfig(ConfigStatus& status) CXX11_OVERRIDE
	{
		modehook.settings.Load();
	}

	Version GetVersion() CXX11_OVERRIDE
	{
		return Version("Provides support for hiding mode changes", VF_VENDOR);
	}
};

MODULE_INIT(ModuleHideMode)
