Cache.cpp

/*
 * 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 <limits>
#include <stdexcept>

#include <QByteArray>
#include <QFile>
#include <QHash>
#include <QSettings>
#include <QStandardPaths>

#include <mtx/responses/common.hpp>
#include <variant.hpp>

#include "Cache.h"
#include "Utils.h"

//! Should be changed when a breaking change occurs in the cache format.
//! This will reset client's data.
static const std::string CURRENT_CACHE_FORMAT_VERSION("2018.06.10");
static const std::string SECRET("secret");

static const lmdb::val NEXT_BATCH_KEY("next_batch");
static const lmdb::val OLM_ACCOUNT_KEY("olm_account");
static const lmdb::val CACHE_FORMAT_VERSION_KEY("cache_format_version");

constexpr size_t MAX_RESTORED_MESSAGES = 30;

//! Cache databases and their format.
//!
//! Contains UI information for the joined rooms. (i.e name, topic, avatar url etc).
//! Format: room_id -> RoomInfo
constexpr auto ROOMS_DB("rooms");
constexpr auto INVITES_DB("invites");
//! Keeps already downloaded media for reuse.
//! Format: matrix_url -> binary data.
constexpr auto MEDIA_DB("media");
//! Information that  must be kept between sync requests.
constexpr auto SYNC_STATE_DB("sync_state");
//! Read receipts per room/event.
constexpr auto READ_RECEIPTS_DB("read_receipts");
constexpr auto NOTIFICATIONS_DB("sent_notifications");

//! Encryption related databases.

//! user_id -> list of devices
constexpr auto DEVICES_DB("devices");
//! device_id -> device keys
constexpr auto DEVICE_KEYS_DB("device_keys");
//! room_ids that have encryption enabled.
constexpr auto ENCRYPTED_ROOMS_DB("encrypted_rooms");

//! room_id -> pickled OlmInboundGroupSession
constexpr auto INBOUND_MEGOLM_SESSIONS_DB("inbound_megolm_sessions");
//! MegolmSessionIndex -> pickled OlmOutboundGroupSession
constexpr auto OUTBOUND_MEGOLM_SESSIONS_DB("outbound_megolm_sessions");

using CachedReceipts = std::multimap<uint64_t, std::string, std::greater<uint64_t>>;
using Receipts       = std::map<std::string, std::map<std::string, uint64_t>>;

namespace {
std::unique_ptr<Cache> instance_ = nullptr;
}

namespace cache {
void
init(const QString &user_id)
{
        qRegisterMetaType<SearchResult>();
        qRegisterMetaType<QVector<SearchResult>>();
        qRegisterMetaType<RoomMember>();
        qRegisterMetaType<RoomSearchResult>();
        qRegisterMetaType<RoomInfo>();
        qRegisterMetaType<QMap<QString, RoomInfo>>();
        qRegisterMetaType<std::map<QString, RoomInfo>>();
        qRegisterMetaType<std::map<QString, mtx::responses::Timeline>>();

        instance_ = std::make_unique<Cache>(user_id);
}

Cache *
client()
{
        return instance_.get();
}
} // namespace cache

Cache::Cache(const QString &userId, QObject *parent)
  : QObject{parent}
  , env_{nullptr}
  , syncStateDb_{0}
  , roomsDb_{0}
  , invitesDb_{0}
  , mediaDb_{0}
  , readReceiptsDb_{0}
  , notificationsDb_{0}
  , devicesDb_{0}
  , deviceKeysDb_{0}
  , inboundMegolmSessionDb_{0}
  , outboundMegolmSessionDb_{0}
  , localUserId_{userId}
{
        setup();
}

void
Cache::setup()
{
        nhlog::db()->debug("setting up cache");

        auto statePath = QString("%1/%2")
                           .arg(QStandardPaths::writableLocation(QStandardPaths::CacheLocation))
                           .arg(QString::fromUtf8(localUserId_.toUtf8().toHex()));

        cacheDirectory_ = QString("%1/%2")
                            .arg(QStandardPaths::writableLocation(QStandardPaths::CacheLocation))
                            .arg(QString::fromUtf8(localUserId_.toUtf8().toHex()));

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

        env_ = lmdb::env::create();
        env_.set_mapsize(256UL * 1024UL * 1024UL); /* 256 MB */
        env_.set_max_dbs(1024UL);

        if (isInitial) {
                nhlog::db()->info("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()));
                }

                nhlog::db()->warn("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_);
        syncStateDb_     = lmdb::dbi::open(txn, SYNC_STATE_DB, MDB_CREATE);
        roomsDb_         = lmdb::dbi::open(txn, ROOMS_DB, MDB_CREATE);
        invitesDb_       = lmdb::dbi::open(txn, INVITES_DB, MDB_CREATE);
        mediaDb_         = lmdb::dbi::open(txn, MEDIA_DB, MDB_CREATE);
        readReceiptsDb_  = lmdb::dbi::open(txn, READ_RECEIPTS_DB, MDB_CREATE);
        notificationsDb_ = lmdb::dbi::open(txn, NOTIFICATIONS_DB, MDB_CREATE);

        // Device management
        devicesDb_    = lmdb::dbi::open(txn, DEVICES_DB, MDB_CREATE);
        deviceKeysDb_ = lmdb::dbi::open(txn, DEVICE_KEYS_DB, MDB_CREATE);

        // Session management
        inboundMegolmSessionDb_  = lmdb::dbi::open(txn, INBOUND_MEGOLM_SESSIONS_DB, MDB_CREATE);
        outboundMegolmSessionDb_ = lmdb::dbi::open(txn, OUTBOUND_MEGOLM_SESSIONS_DB, MDB_CREATE);

        txn.commit();
}

void
Cache::setEncryptedRoom(lmdb::txn &txn, const std::string &room_id)
{
        nhlog::db()->info("mark room {} as encrypted", room_id);

        auto db = lmdb::dbi::open(txn, ENCRYPTED_ROOMS_DB, MDB_CREATE);
        lmdb::dbi_put(txn, db, lmdb::val(room_id), lmdb::val("0"));
}

bool
Cache::isRoomEncrypted(const std::string &room_id)
{
        lmdb::val unused;

        auto txn = lmdb::txn::begin(env_);
        auto db  = lmdb::dbi::open(txn, ENCRYPTED_ROOMS_DB, MDB_CREATE);
        auto res = lmdb::dbi_get(txn, db, lmdb::val(room_id), unused);
        txn.commit();

        return res;
}

//
// Device Management
//

//
// Session Management
//

void
Cache::saveInboundMegolmSession(const MegolmSessionIndex &index,
                                mtx::crypto::InboundGroupSessionPtr session)
{
        using namespace mtx::crypto;
        const auto key     = index.to_hash();
        const auto pickled = pickle<InboundSessionObject>(session.get(), SECRET);

        auto txn = lmdb::txn::begin(env_);
        lmdb::dbi_put(txn, inboundMegolmSessionDb_, lmdb::val(key), lmdb::val(pickled));
        txn.commit();

        {
                std::unique_lock<std::mutex> lock(session_storage.group_inbound_mtx);
                session_storage.group_inbound_sessions[key] = std::move(session);
        }
}

OlmInboundGroupSession *
Cache::getInboundMegolmSession(const MegolmSessionIndex &index)
{
        std::unique_lock<std::mutex> lock(session_storage.group_inbound_mtx);
        return session_storage.group_inbound_sessions[index.to_hash()].get();
}

bool
Cache::inboundMegolmSessionExists(const MegolmSessionIndex &index) noexcept
{
        std::unique_lock<std::mutex> lock(session_storage.group_inbound_mtx);
        return session_storage.group_inbound_sessions.find(index.to_hash()) !=
               session_storage.group_inbound_sessions.end();
}

void
Cache::updateOutboundMegolmSession(const std::string &room_id, int message_index)
{
        using namespace mtx::crypto;

        if (!outboundMegolmSessionExists(room_id))
                return;

        OutboundGroupSessionData data;
        OlmOutboundGroupSession *session;
        {
                std::unique_lock<std::mutex> lock(session_storage.group_outbound_mtx);
                data    = session_storage.group_outbound_session_data[room_id];
                session = session_storage.group_outbound_sessions[room_id].get();

                // Update with the current message.
                data.message_index                                   = message_index;
                session_storage.group_outbound_session_data[room_id] = data;
        }

        // Save the updated pickled data for the session.
        json j;
        j["data"]    = data;
        j["session"] = pickle<OutboundSessionObject>(session, SECRET);

        auto txn = lmdb::txn::begin(env_);
        lmdb::dbi_put(txn, outboundMegolmSessionDb_, lmdb::val(room_id), lmdb::val(j.dump()));
        txn.commit();
}

void
Cache::saveOutboundMegolmSession(const std::string &room_id,
                                 const OutboundGroupSessionData &data,
                                 mtx::crypto::OutboundGroupSessionPtr session)
{
        using namespace mtx::crypto;
        const auto pickled = pickle<OutboundSessionObject>(session.get(), SECRET);

        json j;
        j["data"]    = data;
        j["session"] = pickled;

        auto txn = lmdb::txn::begin(env_);
        lmdb::dbi_put(txn, outboundMegolmSessionDb_, lmdb::val(room_id), lmdb::val(j.dump()));
        txn.commit();

        {
                std::unique_lock<std::mutex> lock(session_storage.group_outbound_mtx);
                session_storage.group_outbound_session_data[room_id] = data;
                session_storage.group_outbound_sessions[room_id]     = std::move(session);
        }
}

bool
Cache::outboundMegolmSessionExists(const std::string &room_id) noexcept
{
        std::unique_lock<std::mutex> lock(session_storage.group_outbound_mtx);
        return (session_storage.group_outbound_sessions.find(room_id) !=
                session_storage.group_outbound_sessions.end()) &&
               (session_storage.group_outbound_session_data.find(room_id) !=
                session_storage.group_outbound_session_data.end());
}

OutboundGroupSessionDataRef
Cache::getOutboundMegolmSession(const std::string &room_id)
{
        std::unique_lock<std::mutex> lock(session_storage.group_outbound_mtx);
        return OutboundGroupSessionDataRef{session_storage.group_outbound_sessions[room_id].get(),
                                           session_storage.group_outbound_session_data[room_id]};
}

//
// OLM sessions.
//

void
Cache::saveOlmSession(const std::string &curve25519, mtx::crypto::OlmSessionPtr session)
{
        using namespace mtx::crypto;

        auto txn = lmdb::txn::begin(env_);
        auto db  = getOlmSessionsDb(txn, curve25519);

        const auto pickled    = pickle<SessionObject>(session.get(), SECRET);
        const auto session_id = mtx::crypto::session_id(session.get());

        lmdb::dbi_put(txn, db, lmdb::val(session_id), lmdb::val(pickled));

        txn.commit();
}

boost::optional<mtx::crypto::OlmSessionPtr>
Cache::getOlmSession(const std::string &curve25519, const std::string &session_id)
{
        using namespace mtx::crypto;

        auto txn = lmdb::txn::begin(env_);
        auto db  = getOlmSessionsDb(txn, curve25519);

        lmdb::val pickled;
        bool found = lmdb::dbi_get(txn, db, lmdb::val(session_id), pickled);

        txn.commit();

        if (found) {
                auto data = std::string(pickled.data(), pickled.size());
                return unpickle<SessionObject>(data, SECRET);
        }

        return boost::none;
}

std::vector<std::string>
Cache::getOlmSessions(const std::string &curve25519)
{
        using namespace mtx::crypto;

        auto txn = lmdb::txn::begin(env_);
        auto db  = getOlmSessionsDb(txn, curve25519);

        std::string session_id, unused;
        std::vector<std::string> res;

        auto cursor = lmdb::cursor::open(txn, db);
        while (cursor.get(session_id, unused, MDB_NEXT))
                res.emplace_back(session_id);
        cursor.close();

        txn.commit();

        return res;
}

void
Cache::saveOlmAccount(const std::string &data)
{
        auto txn = lmdb::txn::begin(env_);
        lmdb::dbi_put(txn, syncStateDb_, OLM_ACCOUNT_KEY, lmdb::val(data));
        txn.commit();
}

void
Cache::restoreSessions()
{
        using namespace mtx::crypto;

        auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
        std::string key, value;

        //
        // Inbound Megolm Sessions
        //
        {
                auto cursor = lmdb::cursor::open(txn, inboundMegolmSessionDb_);
                while (cursor.get(key, value, MDB_NEXT)) {
                        auto session = unpickle<InboundSessionObject>(value, SECRET);
                        session_storage.group_inbound_sessions[key] = std::move(session);
                }
                cursor.close();
        }

        //
        // Outbound Megolm Sessions
        //
        {
                auto cursor = lmdb::cursor::open(txn, outboundMegolmSessionDb_);
                while (cursor.get(key, value, MDB_NEXT)) {
                        json obj;

                        try {
                                obj = json::parse(value);

                                session_storage.group_outbound_session_data[key] =
                                  obj.at("data").get<OutboundGroupSessionData>();

                                auto session =
                                  unpickle<OutboundSessionObject>(obj.at("session"), SECRET);
                                session_storage.group_outbound_sessions[key] = std::move(session);
                        } catch (const nlohmann::json::exception &e) {
                                nhlog::db()->critical(
                                  "failed to parse outbound megolm session data: {}", e.what());
                        }
                }
                cursor.close();
        }

        txn.commit();

        nhlog::db()->info("sessions restored");
}

std::string
Cache::restoreOlmAccount()
{
        auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
        lmdb::val pickled;
        lmdb::dbi_get(txn, syncStateDb_, OLM_ACCOUNT_KEY, pickled);
        txn.commit();

        return std::string(pickled.data(), pickled.size());
}

//
// Media Management
//

void
Cache::saveImage(const std::string &url, const std::string &img_data)
{
        if (url.empty() || img_data.empty())
                return;

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

                lmdb::dbi_put(txn,
                              mediaDb_,
                              lmdb::val(url.data(), url.size()),
                              lmdb::val(img_data.data(), img_data.size()));

                txn.commit();
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("saveImage: {}", e.what());
        }
}

void
Cache::saveImage(const QString &url, const QByteArray &image)
{
        saveImage(url.toStdString(), std::string(image.constData(), image.length()));
}

QByteArray
Cache::image(lmdb::txn &txn, const std::string &url) const
{
        if (url.empty())
                return QByteArray();

        try {
                lmdb::val image;
                bool res = lmdb::dbi_get(txn, mediaDb_, lmdb::val(url), image);

                if (!res)
                        return QByteArray();

                return QByteArray(image.data(), image.size());
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("image: {}, {}", e.what(), url);
        }

        return QByteArray();
}

QByteArray
Cache::image(const QString &url) const
{
        if (url.isEmpty())
                return QByteArray();

        auto key = url.toUtf8();

        try {
                auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);

                lmdb::val image;

                bool res = lmdb::dbi_get(txn, mediaDb_, lmdb::val(key.data(), key.size()), image);

                txn.commit();

                if (!res)
                        return QByteArray();

                return QByteArray(image.data(), image.size());
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("image: {} {}", e.what(), url.toStdString());
        }

        return QByteArray();
}

void
Cache::removeInvite(lmdb::txn &txn, const std::string &room_id)
{
        lmdb::dbi_del(txn, invitesDb_, lmdb::val(room_id), nullptr);
        lmdb::dbi_drop(txn, getInviteStatesDb(txn, room_id), true);
        lmdb::dbi_drop(txn, getInviteMembersDb(txn, room_id), true);
}

void
Cache::removeInvite(const std::string &room_id)
{
        auto txn = lmdb::txn::begin(env_);
        removeInvite(txn, room_id);
        txn.commit();
}

void
Cache::removeRoom(lmdb::txn &txn, const std::string &roomid)
{
        lmdb::dbi_del(txn, roomsDb_, lmdb::val(roomid), nullptr);
        lmdb::dbi_drop(txn, getStatesDb(txn, roomid), true);
        lmdb::dbi_drop(txn, getMembersDb(txn, roomid), true);
}

void
Cache::removeRoom(const std::string &roomid)
{
        auto txn = lmdb::txn::begin(env_, nullptr, 0);
        lmdb::dbi_del(txn, roomsDb_, lmdb::val(roomid), nullptr);
        txn.commit();
}

void
Cache::setNextBatchToken(lmdb::txn &txn, const std::string &token)
{
        lmdb::dbi_put(txn, syncStateDb_, NEXT_BATCH_KEY, lmdb::val(token.data(), token.size()));
}

void
Cache::setNextBatchToken(lmdb::txn &txn, const QString &token)
{
        setNextBatchToken(txn, token.toStdString());
}

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

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

        txn.commit();

        return res;
}

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

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

        txn.commit();

        return std::string(token.data(), token.size());
}

void
Cache::deleteData()
{
        // TODO: We need to remove the env_ while not accepting new requests.
        if (!cacheDirectory_.isEmpty()) {
                QDir(cacheDirectory_).removeRecursively();
                nhlog::db()->info("deleted cache files from disk");
        }
}

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

        lmdb::val current_version;
        bool res = lmdb::dbi_get(txn, syncStateDb_, CACHE_FORMAT_VERSION_KEY, current_version);

        txn.commit();

        if (!res)
                return true;

        std::string stored_version(current_version.data(), current_version.size());

        if (stored_version != CURRENT_CACHE_FORMAT_VERSION) {
                nhlog::db()->warn("breaking changes in the cache format. stored: {}, current: {}",
                                  stored_version,
                                  CURRENT_CACHE_FORMAT_VERSION);
                return false;
        }

        return true;
}

void
Cache::setCurrentFormat()
{
        auto txn = lmdb::txn::begin(env_);

        lmdb::dbi_put(
          txn,
          syncStateDb_,
          CACHE_FORMAT_VERSION_KEY,
          lmdb::val(CURRENT_CACHE_FORMAT_VERSION.data(), CURRENT_CACHE_FORMAT_VERSION.size()));

        txn.commit();
}

std::vector<QString>
Cache::pendingReceiptsEvents(lmdb::txn &txn, const std::string &room_id)
{
        auto db = getPendingReceiptsDb(txn);

        std::string key, unused;
        std::vector<QString> pending;

        auto cursor = lmdb::cursor::open(txn, db);
        while (cursor.get(key, unused, MDB_NEXT)) {
                ReadReceiptKey receipt;
                try {
                        receipt = json::parse(key);
                } catch (const nlohmann::json::exception &e) {
                        nhlog::db()->warn("pendingReceiptsEvents: {}", e.what());
                        continue;
                }

                if (receipt.room_id == room_id)
                        pending.emplace_back(QString::fromStdString(receipt.event_id));
        }

        cursor.close();

        return pending;
}

void
Cache::removePendingReceipt(lmdb::txn &txn, const std::string &room_id, const std::string &event_id)
{
        auto db = getPendingReceiptsDb(txn);

        ReadReceiptKey receipt_key{event_id, room_id};
        auto key = json(receipt_key).dump();

        try {
                lmdb::dbi_del(txn, db, lmdb::val(key.data(), key.size()), nullptr);
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("removePendingReceipt: {}", e.what());
        }
}

void
Cache::addPendingReceipt(const QString &room_id, const QString &event_id)
{
        auto txn = lmdb::txn::begin(env_);
        auto db  = getPendingReceiptsDb(txn);

        ReadReceiptKey receipt_key{event_id.toStdString(), room_id.toStdString()};
        auto key = json(receipt_key).dump();
        std::string empty;

        try {
                lmdb::dbi_put(txn,
                              db,
                              lmdb::val(key.data(), key.size()),
                              lmdb::val(empty.data(), empty.size()));
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("addPendingReceipt: {}", e.what());
        }

        txn.commit();
}

CachedReceipts
Cache::readReceipts(const QString &event_id, const QString &room_id)
{
        CachedReceipts receipts;

        ReadReceiptKey receipt_key{event_id.toStdString(), room_id.toStdString()};
        nlohmann::json json_key = receipt_key;

        try {
                auto txn = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
                auto key = json_key.dump();

                lmdb::val value;

                bool res =
                  lmdb::dbi_get(txn, readReceiptsDb_, lmdb::val(key.data(), key.size()), value);

                txn.commit();

                if (res) {
                        auto json_response = json::parse(std::string(value.data(), value.size()));
                        auto values        = json_response.get<std::map<std::string, uint64_t>>();

                        for (const auto &v : values)
                                // timestamp, user_id
                                receipts.emplace(v.second, v.first);
                }

        } catch (const lmdb::error &e) {
                nhlog::db()->critical("readReceipts: {}", e.what());
        }

        return receipts;
}

std::vector<QString>
Cache::filterReadEvents(const QString &room_id,
                        const std::vector<QString> &event_ids,
                        const std::string &excluded_user)
{
        std::vector<QString> read_events;

        for (const auto &event : event_ids) {
                auto receipts = readReceipts(event, room_id);

                if (receipts.size() == 0)
                        continue;

                if (receipts.size() == 1) {
                        if (receipts.begin()->second == excluded_user)
                                continue;
                }

                read_events.emplace_back(event);
        }

        return read_events;
}

void
Cache::updateReadReceipt(lmdb::txn &txn, const std::string &room_id, const Receipts &receipts)
{
        for (const auto &receipt : receipts) {
                const auto event_id = receipt.first;
                auto event_receipts = receipt.second;

                ReadReceiptKey receipt_key{event_id, room_id};
                nlohmann::json json_key = receipt_key;

                try {
                        const auto key = json_key.dump();

                        lmdb::val prev_value;

                        bool exists = lmdb::dbi_get(
                          txn, readReceiptsDb_, lmdb::val(key.data(), key.size()), prev_value);

                        std::map<std::string, uint64_t> saved_receipts;

                        // If an entry for the event id already exists, we would
                        // merge the existing receipts with the new ones.
                        if (exists) {
                                auto json_value =
                                  json::parse(std::string(prev_value.data(), prev_value.size()));

                                // Retrieve the saved receipts.
                                saved_receipts = json_value.get<std::map<std::string, uint64_t>>();
                        }

                        // Append the new ones.
                        for (const auto &event_receipt : event_receipts)
                                saved_receipts.emplace(event_receipt.first, event_receipt.second);

                        // Save back the merged (or only the new) receipts.
                        nlohmann::json json_updated_value = saved_receipts;
                        std::string merged_receipts       = json_updated_value.dump();

                        lmdb::dbi_put(txn,
                                      readReceiptsDb_,
                                      lmdb::val(key.data(), key.size()),
                                      lmdb::val(merged_receipts.data(), merged_receipts.size()));

                } catch (const lmdb::error &e) {
                        nhlog::db()->critical("updateReadReceipts: {}", e.what());
                }
        }
}

void
Cache::notifyForReadReceipts(lmdb::txn &txn, const std::string &room_id)
{
        QSettings settings;
        auto local_user = settings.value("auth/user_id").toString();

        auto matches = filterReadEvents(QString::fromStdString(room_id),
                                        pendingReceiptsEvents(txn, room_id),
                                        local_user.toStdString());

        for (const auto &m : matches)
                removePendingReceipt(txn, room_id, m.toStdString());

        if (!matches.empty())
                emit newReadReceipts(QString::fromStdString(room_id), matches);
}

void
Cache::saveState(const mtx::responses::Sync &res)
{
        auto txn = lmdb::txn::begin(env_);

        setNextBatchToken(txn, res.next_batch);

        // Save joined rooms
        for (const auto &room : res.rooms.join) {
                auto statesdb  = getStatesDb(txn, room.first);
                auto membersdb = getMembersDb(txn, room.first);

                saveStateEvents(txn, statesdb, membersdb, room.first, room.second.state.events);
                saveStateEvents(txn, statesdb, membersdb, room.first, room.second.timeline.events);

                saveTimelineMessages(txn, room.first, room.second.timeline);

                RoomInfo updatedInfo;
                updatedInfo.name  = getRoomName(txn, statesdb, membersdb).toStdString();
                updatedInfo.topic = getRoomTopic(txn, statesdb).toStdString();
                updatedInfo.avatar_url =
                  getRoomAvatarUrl(txn, statesdb, membersdb, QString::fromStdString(room.first))
                    .toStdString();

                lmdb::dbi_put(
                  txn, roomsDb_, lmdb::val(room.first), lmdb::val(json(updatedInfo).dump()));

                updateReadReceipt(txn, room.first, room.second.ephemeral.receipts);

                // Clean up non-valid invites.
                removeInvite(txn, room.first);
        }

        saveInvites(txn, res.rooms.invite);

        removeLeftRooms(txn, res.rooms.leave);

        txn.commit();

        for (const auto &room : res.rooms.join) {
                auto tmpTxn = lmdb::txn::begin(env_);
                notifyForReadReceipts(tmpTxn, room.first);
                tmpTxn.commit();
        }
}

void
Cache::saveInvites(lmdb::txn &txn, const std::map<std::string, mtx::responses::InvitedRoom> &rooms)
{
        for (const auto &room : rooms) {
                auto statesdb  = getInviteStatesDb(txn, room.first);
                auto membersdb = getInviteMembersDb(txn, room.first);

                saveInvite(txn, statesdb, membersdb, room.second);

                RoomInfo updatedInfo;
                updatedInfo.name  = getInviteRoomName(txn, statesdb, membersdb).toStdString();
                updatedInfo.topic = getInviteRoomTopic(txn, statesdb).toStdString();
                updatedInfo.avatar_url =
                  getInviteRoomAvatarUrl(txn, statesdb, membersdb).toStdString();
                updatedInfo.is_invite = true;

                lmdb::dbi_put(
                  txn, invitesDb_, lmdb::val(room.first), lmdb::val(json(updatedInfo).dump()));
        }
}

void
Cache::saveInvite(lmdb::txn &txn,
                  lmdb::dbi &statesdb,
                  lmdb::dbi &membersdb,
                  const mtx::responses::InvitedRoom &room)
{
        using namespace mtx::events;
        using namespace mtx::events::state;

        for (const auto &e : room.invite_state) {
                if (mpark::holds_alternative<StrippedEvent<Member>>(e)) {
                        auto msg = mpark::get<StrippedEvent<Member>>(e);

                        auto display_name = msg.content.display_name.empty()
                                              ? msg.state_key
                                              : msg.content.display_name;

                        MemberInfo tmp{display_name, msg.content.avatar_url};

                        lmdb::dbi_put(
                          txn, membersdb, lmdb::val(msg.state_key), lmdb::val(json(tmp).dump()));
                } else {
                        mpark::visit(
                          [&txn, &statesdb](auto msg) {
                                  bool res = lmdb::dbi_put(txn,
                                                           statesdb,
                                                           lmdb::val(to_string(msg.type)),
                                                           lmdb::val(json(msg).dump()));

                                  if (!res)
                                          std::cout << "couldn't save data" << json(msg).dump()
                                                    << '\n';
                          },
                          e);
                }
        }
}

std::vector<std::string>
Cache::roomsWithStateUpdates(const mtx::responses::Sync &res)
{
        std::vector<std::string> rooms;
        for (const auto &room : res.rooms.join) {
                bool hasUpdates = false;
                for (const auto &s : room.second.state.events) {
                        if (containsStateUpdates(s)) {
                                hasUpdates = true;
                                break;
                        }
                }

                for (const auto &s : room.second.timeline.events) {
                        if (containsStateUpdates(s)) {
                                hasUpdates = true;
                                break;
                        }
                }

                if (hasUpdates)
                        rooms.emplace_back(room.first);
        }

        for (const auto &room : res.rooms.invite) {
                for (const auto &s : room.second.invite_state) {
                        if (containsStateUpdates(s)) {
                                rooms.emplace_back(room.first);
                                break;
                        }
                }
        }

        return rooms;
}

RoomInfo
Cache::singleRoomInfo(const std::string &room_id)
{
        auto txn      = lmdb::txn::begin(env_, nullptr, MDB_RDONLY);
        auto statesdb = getStatesDb(txn, room_id);

        lmdb::val data;

        // Check if the room is joined.
        if (lmdb::dbi_get(txn, roomsDb_, lmdb::val(room_id), data)) {
                try {
                        RoomInfo tmp     = json::parse(std::string(data.data(), data.size()));
                        tmp.member_count = getMembersDb(txn, room_id).size(txn);
                        tmp.join_rule    = getRoomJoinRule(txn, statesdb);
                        tmp.guest_access = getRoomGuestAccess(txn, statesdb);

                        txn.commit();

                        return tmp;