/*
 * nheko Copyright (C) 2017  Konstantinos Sideris <siderisk@auth.gr>
 *
 * This program 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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 <stdexcept>

#include <QDebug>
#include <QDir>
#include <QFile>
#include <QStandardPaths>

#include "Cache.h"
#include "MemberEventContent.h"

namespace events = matrix::events;

static const lmdb::val NEXT_BATCH_KEY("next_batch");
static const lmdb::val transactionID("transaction_id");

Cache::Cache(const QString &userId)
    : env_{nullptr}
    , stateDb_{0}
    , roomDb_{0}
    , isMounted_{false}
    , userId_{userId}
{
	auto statePath = QString("%1/%2/state")
				 .arg(QStandardPaths::writableLocation(QStandardPaths::CacheLocation))
				 .arg(QString::fromUtf8(userId_.toUtf8().toHex()));

	bool isInitial = !QFile::exists(statePath);

	env_ = lmdb::env::create();
	env_.set_mapsize(128UL * 1024UL * 1024UL); /* 128 MB */
	env_.set_max_dbs(1024UL);

	if (isInitial) {
		qDebug() << "[cache] First time initializing LMDB";

		if (!QDir().mkpath(statePath)) {
			throw std::runtime_error(("Unable to create state directory:" + statePath).toStdString().c_str());
		}
	}

	try {
		env_.open(statePath.toStdString().c_str());
	} catch (const lmdb::error &e) {
		if (e.code() != MDB_VERSION_MISMATCH && e.code() != MDB_INVALID) {
			throw std::runtime_error("LMDB initialization failed" + std::string(e.what()));
		}

		qWarning() << "Resetting cache due to LMDB version mismatch:" << e.what();

		QDir stateDir(statePath);

		for (const auto &file : stateDir.entryList(QDir::NoDotAndDotDot)) {
			if (!stateDir.remove(file))
				throw std::runtime_error(("Unable to delete file " + file).toStdString().c_str());
		}

		env_.open(statePath.toStdString().c_str());
	}

	auto txn = lmdb::txn::begin(env_);
	stateDb_ = lmdb::dbi::open(txn, "state", MDB_CREATE);
	roomDb_ = lmdb::dbi::open(txn, "rooms", MDB_CREATE);

	txn.commit();

	isMounted_ = true;
}

void Cache::insertRoomState(const QString &roomid, const RoomState &state)
{
	if (!isMounted_)
		return;

	auto txn = lmdb::txn::begin(env_);

	auto stateEvents = QJsonDocument(state.serialize()).toBinaryData();
	auto id = roomid.toUtf8();

	lmdb::dbi_put(
		txn,
		roomDb_,
		lmdb::val(id.data(), id.size()),
		lmdb::val(stateEvents.data(), stateEvents.size()));

	for (const auto &membership : state.memberships) {
		lmdb::dbi membersDb = lmdb::dbi::open(txn, roomid.toStdString().c_str(), MDB_CREATE);

		// The user_id this membership event relates to, is used
		// as the index on the membership database.
		auto key = membership.stateKey().toUtf8();
		auto memberEvent = QJsonDocument(membership.serialize()).toBinaryData();

		switch (membership.content().membershipState()) {
		// We add or update (e.g invite -> join) a new user to the membership list.
		case events::Membership::Invite:
		case events::Membership::Join: {
			lmdb::dbi_put(
				txn,
				membersDb,
				lmdb::val(key.data(), key.size()),
				lmdb::val(memberEvent.data(), memberEvent.size()));
			break;
		}
		// We remove the user from the membership list.
		case events::Membership::Leave:
		case events::Membership::Ban: {
			lmdb::dbi_del(
				txn,
				membersDb,
				lmdb::val(key.data(), key.size()),
				lmdb::val(memberEvent.data(), memberEvent.size()));
			break;
		}
		case events::Membership::Knock: {
			qWarning() << "Skipping knock membership" << roomid << key;
			break;
		}
		}
	}

	txn.commit();
}

QMap<QString, RoomState> Cache::states()
{
	QMap<QString, RoomState> states;

	auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
	auto cursor = lmdb::cursor::open(txn, roomDb_);

	std::string room;
	std::string stateData;

	// Retrieve all the room names.
	while (cursor.get(room, stateData, MDB_NEXT)) {
		auto roomid = QString::fromUtf8(room.data(), room.size());
		auto json = QJsonDocument::fromBinaryData(QByteArray(stateData.data(), stateData.size()));

		RoomState state;
		state.parse(json.object());

		auto memberDb = lmdb::dbi::open(txn, roomid.toStdString().c_str(), MDB_CREATE);
		QMap<QString, events::StateEvent<events::MemberEventContent>> members;

		auto memberCursor = lmdb::cursor::open(txn, memberDb);

		std::string memberId;
		std::string memberContent;

		while (memberCursor.get(memberId, memberContent, MDB_NEXT)) {
			auto userid = QString::fromUtf8(memberId.data(), memberId.size());
			auto data = QJsonDocument::fromBinaryData(QByteArray(memberContent.data(), memberContent.size()));

			try {
				events::StateEvent<events::MemberEventContent> member;
				member.deserialize(data.object());
				members.insert(userid, member);
			} catch (const DeserializationException &e) {
				qWarning() << e.what();
				qWarning() << "Fault while parsing member event" << data.object();
				continue;
			}
		}

		qDebug() << members.size() << "members for" << roomid;

		state.memberships = members;
		states.insert(roomid, state);
	}

	qDebug() << "Retrieved" << states.size() << "rooms";

	cursor.close();

	txn.commit();

	return states;
}

void Cache::setNextBatchToken(const QString &token)
{
	auto txn = lmdb::txn::begin(env_);
	auto value = token.toUtf8();

	lmdb::dbi_put(txn, stateDb_, NEXT_BATCH_KEY, lmdb::val(value.data(), value.size()));

	txn.commit();
}

bool Cache::isInitialized()
{
	auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
	lmdb::val token;

	bool res = lmdb::dbi_get(txn, stateDb_, NEXT_BATCH_KEY, token);

	txn.commit();

	return res;
}

QString Cache::nextBatchToken()
{
	auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
	lmdb::val token;

	lmdb::dbi_get(txn, stateDb_, NEXT_BATCH_KEY, token);

	txn.commit();

	return QString::fromUtf8(token.data<const char>());
}