/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2021 Herman <GermanAizek@yandex.ru>
 *   Copyright (C) 2019 Matt Schatz <genius3000@g3k.solutions>
 *   Copyright (C) 2013, 2015, 2018-2023 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2012-2013 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012, 2014 Adam <Adam@anope.org>
 *   Copyright (C) 2012 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2012 ChrisTX <xpipe@hotmail.de>
 *   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 <filesystem>
#include <fstream>

#include "inspircd.h"
#include "xline.h"

class ModuleXLineDB final
	: public Module
	, public Timer
{
private:
	bool dirty;
	std::string xlinedbpath;
	unsigned long saveperiod;
	unsigned long maxbackoff;
	unsigned char backoff;

public:
	ModuleXLineDB()
		: Module(VF_VENDOR, "Allows X-lines to be saved and reloaded on restart.")
		, Timer(0, true)
	{
	}

	void init() override
	{
		/* Load the configuration
		 * Note:
		 *		This is on purpose not changed on a rehash. It would be non-trivial to change the database on-the-fly.
		 *		Imagine a scenario where the new file already exists. Merging the current XLines with the existing database is likely a bad idea
		 *		...and so is discarding all current in-memory XLines for the ones in the database.
		 */
		const auto& Conf = ServerInstance->Config->ConfValue("xlinedb");
		xlinedbpath = ServerInstance->Config->Paths.PrependData(Conf->getString("filename", "xline.db", 1));
		saveperiod = Conf->getDuration("saveperiod", 5);
		backoff = Conf->getNum<uint8_t>("backoff", 0);
		maxbackoff = Conf->getDuration("maxbackoff", saveperiod * 120, saveperiod);
		SetInterval(saveperiod);

		// Read xlines before attaching to events
		ReadDatabase();

		dirty = false;
	}

	/** Called whenever an xline is added by a local user.
	 * This method is triggered after the line is added.
	 * @param source The sender of the line or NULL for local server
	 * @param line The xline being added
	 */
	void OnAddLine(User* source, XLine* line) override
	{
		if (!line->from_config)
			dirty = true;
	}

	/** Called whenever an xline is deleted.
	 * This method is triggered after the line is deleted.
	 * @param source The user removing the line or NULL for local server
	 * @param line the line being deleted
	 */
	void OnDelLine(User* source, XLine* line) override
	{
		OnAddLine(source, line);
	}

	bool Tick() override
	{
		if (dirty)
		{
			if (WriteDatabase())
			{
				// If we were previously unable to write but now can then reset the time interval.
				if (GetInterval() != saveperiod)
					SetInterval(saveperiod, false);

				dirty = false;
			}
			else
			{
				// Back off a bit to avoid spamming opers.
				if (backoff > 1)
					SetInterval(std::min(GetInterval() * backoff, maxbackoff), false);
				ServerInstance->Logs.Debug(MODNAME, "Trying again in {} seconds", GetInterval());
			}
		}
		return true;
	}

	bool WriteDatabase()
	{
		/*
		 * We need to perform an atomic write so as not to fuck things up.
		 * So, let's write to a temporary file, flush it, then rename the file..
		 * Technically, that means that this can block, but I have *never* seen that.
		 *     -- w00t
		 */
		ServerInstance->Logs.Debug(MODNAME, "Opening temporary database");
		const std::string xlinenewdbpath = xlinedbpath + ".new." + ConvToStr(ServerInstance->Time());
		std::ofstream stream(xlinenewdbpath);
		if (!stream.is_open())
		{
			ServerInstance->Logs.Critical(MODNAME, "Cannot create database \"{}\"! {} ({})", xlinenewdbpath, strerror(errno), errno);
			ServerInstance->SNO.WriteToSnoMask('x', "database: cannot create new xline db \"{}\": {} ({})", xlinenewdbpath, strerror(errno), errno);
			return false;
		}

		ServerInstance->Logs.Debug(MODNAME, "Opened. Writing..");

		/*
		 * Now, much as I hate writing semi-unportable formats, additional
		 * xline types may not have a conf tag, so let's just write them.
		 * In addition, let's use a file version, so we can maintain some
		 * semblance of backwards compatibility for reading on startup..
		 *		-- w00t
		 */
		stream << "VERSION 1" << std::endl;

		// Now, let's write.
		for (const auto& xltype : ServerInstance->XLines->GetAllTypes())
		{
			XLineLookup* lookup = ServerInstance->XLines->GetAll(xltype);
			if (!lookup)
				continue; // Not possible as we just obtained the list from XLineManager

			for (const auto& [_, line] : *lookup)
			{
				if (line->from_config)
					continue;

				stream << "LINE " << line->type << " " << line->Displayable() << " "
					<< line->source << " " << line->set_time << " "
					<< line->duration << " :" << line->reason << std::endl;
			}
		}

		ServerInstance->Logs.Debug(MODNAME, "Finished writing XLines. Checking for error..");

		if (stream.fail())
		{
			ServerInstance->Logs.Critical(MODNAME, "Cannot write to new database \"{}\"! {} ({})", xlinenewdbpath, strerror(errno), errno);
			ServerInstance->SNO.WriteToSnoMask('x', "database: cannot write to new xline db \"{}\": {} ({})", xlinenewdbpath, strerror(errno), errno);
			return false;
		}
		stream.close();

#ifdef _WIN32
		remove(xlinedbpath.c_str());
#endif
		// Use rename to move temporary to new db - this is guaranteed not to fuck up, even in case of a crash.
		if (rename(xlinenewdbpath.c_str(), xlinedbpath.c_str()) < 0)
		{
			ServerInstance->Logs.Critical(MODNAME, "Cannot replace old database \"{}\" with new database \"{}\"! {} ({})", xlinedbpath, xlinenewdbpath, strerror(errno), errno);
			ServerInstance->SNO.WriteToSnoMask('x', "database: cannot replace old xline db \"{}\" with new db \"{}\": {} ({})", xlinedbpath, xlinenewdbpath, strerror(errno), errno);
			return false;
		}

		return true;
	}

	bool ReadDatabase()
	{
		// If the xline database doesn't exist then we don't need to load it.
		std::error_code ec;
		if (!std::filesystem::is_regular_file(xlinedbpath, ec))
			return true;

		std::ifstream stream(xlinedbpath);
		if (!stream.is_open())
		{
			ServerInstance->Logs.Critical(MODNAME, "Cannot read database \"{}\"! {} ({})", xlinedbpath, strerror(errno), errno);
			ServerInstance->SNO.WriteToSnoMask('x', "database: cannot read xline db \"{}\": {} ({})", xlinedbpath, strerror(errno), errno);
			return false;
		}

		std::string line;
		while (std::getline(stream, line))
		{
			// Inspired by the command parser. :)
			irc::tokenstream tokens(line);
			int items = 0;
			std::string command_p[7];
			std::string tmp;

			while (tokens.GetTrailing(tmp) && (items < 7))
			{
				command_p[items] = tmp;
				items++;
			}

			ServerInstance->Logs.Debug(MODNAME, "Processing {}", line);

			if (command_p[0] == "VERSION")
			{
				if (command_p[1] != "1")
				{
					stream.close();
					ServerInstance->Logs.Critical(MODNAME, "I got database version {} - I don't understand it", command_p[1]);
					ServerInstance->SNO.WriteToSnoMask('x', "database: I got a database version ({}) I don't understand", command_p[1]);
					return false;
				}
			}
			else if (command_p[0] == "LINE")
			{
				// Mercilessly stolen from spanningtree
				XLineFactory* xlf = ServerInstance->XLines->GetFactory(command_p[1]);

				if (!xlf)
				{
					ServerInstance->SNO.WriteToSnoMask('x', "database: Unknown line type ({}).", command_p[1]);
					continue;
				}

				XLine* xl = xlf->Generate(ServerInstance->Time(), ConvToNum<unsigned long>(command_p[5]), command_p[3], command_p[6], command_p[2]);
				xl->SetCreateTime(ConvToNum<time_t>(command_p[4]));

				if (ServerInstance->XLines->AddLine(xl, nullptr))
				{
					ServerInstance->SNO.WriteToSnoMask('x', "database: Added a line of type {}", command_p[1]);
				}
				else
					delete xl;
			}
		}
		stream.close();
		return true;
	}
};

MODULE_INIT(ModuleXLineDB)
