/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2019 Peter Powell <petpow@saberuk.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/>.
 */

/// $CompilerFlags: find_compiler_flags("libmaxminddb" "")
/// $LinkerFlags: find_linker_flags("libmaxminddb" "-lmaxminddb")

/// $PackageInfo: require_system("darwin") libmaxminddb pkg-config
/// $PackageInfo: require_system("debian" "9.0") libmaxminddb-dev pkg-config
/// $PackageInfo: require_system("ubuntu" "16.04") libmaxminddb-dev pkg-config

#ifdef _WIN32
# pragma comment(lib, "libmaxminddb.lib")
#endif

#include "inspircd.h"
#include "modules/geolocation.h"
#include <maxminddb.h>

class GeolocationExtItem : public LocalExtItem
{
 public:
	GeolocationExtItem(Module* parent)
		: LocalExtItem("geolocation", ExtensionItem::EXT_USER, parent)
	{
	}

	void free(Extensible* container, void* item) CXX11_OVERRIDE
	{
		Geolocation::Location* old = static_cast<Geolocation::Location*>(item);
		if (old)
			old->refcount_dec();
	}

	Geolocation::Location* get(const Extensible* item) const
	{
		return static_cast<Geolocation::Location*>(get_raw(item));
	}

	void set(Extensible* item, Geolocation::Location* value)
	{
		value->refcount_inc();
		free(item, set_raw(item, value));
	}

	void unset(Extensible* container)
	{
		free(container, unset_raw(container));
	}
};

typedef insp::flat_map<std::string, Geolocation::Location*> LocationMap;

class GeolocationAPIImpl : public Geolocation::APIBase
{
 public:
	GeolocationExtItem ext;
	LocationMap locations;
	MMDB_s mmdb;

	GeolocationAPIImpl(Module* parent)
		: Geolocation::APIBase(parent)
		, ext(parent)
	{
	}

	Geolocation::Location* GetLocation(User* user) CXX11_OVERRIDE
	{
		// If we have the location cached then use that instead.
		Geolocation::Location* location = ext.get(user);
		if (location)
			return location;

		// Attempt to locate this user.
		location = GetLocation(user->client_sa);
		if (!location)
			return NULL;

		// We found the user. Cache their location for future use.
		ext.set(user, location);
		return location;
	}

	Geolocation::Location* GetLocation(irc::sockets::sockaddrs& sa) CXX11_OVERRIDE
	{
		// Skip trying to look up a UNIX socket.
		if (sa.family() != AF_INET && sa.family() != AF_INET6)
			return NULL;

		// Attempt to look up the socket address.
		int result;
		MMDB_lookup_result_s lookup = MMDB_lookup_sockaddr(&mmdb, &sa.sa, &result);
		if (result != MMDB_SUCCESS || !lookup.found_entry)
			return NULL;

		// Attempt to retrieve the country code.
		MMDB_entry_data_s country_code;
		result = MMDB_get_value(&lookup.entry, &country_code, "country", "iso_code", NULL);
		if (result != MMDB_SUCCESS || !country_code.has_data || country_code.type != MMDB_DATA_TYPE_UTF8_STRING || country_code.data_size != 2)
			return NULL;

		// If the country has been seen before then use our cached Location object.
		const std::string code(country_code.utf8_string, country_code.data_size);
		LocationMap::iterator liter = locations.find(code);
		if (liter != locations.end())
			return liter->second;

		// Attempt to retrieve the country name.
		MMDB_entry_data_s country_name;
		result = MMDB_get_value(&lookup.entry, &country_name, "country", "names", "en", NULL);
		if (result != MMDB_SUCCESS || !country_name.has_data || country_name.type != MMDB_DATA_TYPE_UTF8_STRING)
			return NULL;

		// Create a Location object and cache it.
		const std::string cname(country_name.utf8_string, country_name.data_size);
		Geolocation::Location* location = new Geolocation::Location(code, cname);
		locations[code] = location;
		return location;
	}
};

class ModuleGeoMaxMind : public Module
{
 private:
	GeolocationAPIImpl geoapi;

 public:
	ModuleGeoMaxMind()
		: geoapi(this)
	{
		memset(&geoapi.mmdb, 0, sizeof(geoapi.mmdb));
	}

	~ModuleGeoMaxMind()
	{
		MMDB_close(&geoapi.mmdb);
	}

	Version GetVersion() CXX11_OVERRIDE
	{
		return Version("Provides Geolocation lookups using the libMaxMindDB library", VF_VENDOR);
	}

	void ReadConfig(ConfigStatus& status) CXX11_OVERRIDE
	{
		ConfigTag* tag = ServerInstance->Config->ConfValue("maxmind");
		const std::string file = ServerInstance->Config->Paths.PrependConfig(tag->getString("file", "GeoLite2-Country.mmdb"));

		// Try to read the new database.
		MMDB_s mmdb;
		int result = MMDB_open(file.c_str(), MMDB_MODE_MMAP, &mmdb);
		if (result != MMDB_SUCCESS)
			throw ModuleException(InspIRCd::Format("Unable to load the MaxMind database (%s): %s",
				file.c_str(), MMDB_strerror(result)));

		// Swap the new database with the old database.
		std::swap(mmdb, geoapi.mmdb);

		// Free the old database.
		MMDB_close(&mmdb);
	}

	void OnGarbageCollect() CXX11_OVERRIDE
	{
		for (LocationMap::iterator iter = geoapi.locations.begin(); iter != geoapi.locations.end(); )
		{	
			Geolocation::Location* location = iter->second;
			if (location->GetUseCount())
			{
				ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Preserving geolocation data for %s (%s) with use count %u... ",
					location->GetName().c_str(), location->GetCode().c_str(), location->GetUseCount());
				iter++;
			}
			else
			{
				ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Deleting unused geolocation data for %s (%s)",
					location->GetName().c_str(), location->GetCode().c_str());
				delete location;
				iter = geoapi.locations.erase(iter);
			}
		}
	}

	void OnSetUserIP(LocalUser* user) CXX11_OVERRIDE
	{
		// Unset the extension so that the location of this user is looked
		// up again next time it is requested.
		geoapi.ext.unset(user);
	}
};

MODULE_INIT(ModuleGeoMaxMind)