matrixion/src/timeline/EventStore.cpp

// SPDX-FileCopyrightText: 2021 Nheko Contributors
//
// SPDX-License-Identifier: GPL-3.0-or-later

#include "EventStore.h"

#include <QThread>
#include <QTimer>

#include <mtx/responses/common.hpp>

#include "Cache.h"
#include "Cache_p.h"
#include "ChatPage.h"
#include "EventAccessors.h"
#include "Logging.h"
#include "MatrixClient.h"
#include "Olm.h"
#include "Utils.h"

Q_DECLARE_METATYPE(Reaction)

QCache<EventStore::IdIndex, mtx::events::collections::TimelineEvents> EventStore::decryptedEvents_{
  1000};
QCache<EventStore::IdIndex, mtx::events::collections::TimelineEvents> EventStore::events_by_id_{
  1000};
QCache<EventStore::Index, mtx::events::collections::TimelineEvents> EventStore::events_{1000};

EventStore::EventStore(std::string room_id, QObject *)
  : room_id_(std::move(room_id))
{
        static auto reactionType = qRegisterMetaType<Reaction>();
        (void)reactionType;

        auto range = cache::client()->getTimelineRange(room_id_);

        if (range) {
                this->first = range->first;
                this->last  = range->last;
        }

        connect(
          this,
          &EventStore::eventFetched,
          this,
          [this](std::string id,
                 std::string relatedTo,
                 mtx::events::collections::TimelineEvents timeline) {
                  cache::client()->storeEvent(room_id_, id, {timeline});

                  if (!relatedTo.empty()) {
                          auto idx = idToIndex(relatedTo);
                          if (idx)
                                  emit dataChanged(*idx, *idx);
                  }
          },
          Qt::QueuedConnection);

        connect(
          this,
          &EventStore::oldMessagesRetrieved,
          this,
          [this](const mtx::responses::Messages &res) {
                  if (res.end.empty() || cache::client()->previousBatchToken(room_id_) == res.end) {
                          noMoreMessages = true;
                          emit fetchedMore();
                          return;
                  }

                  uint64_t newFirst = cache::client()->saveOldMessages(room_id_, res);
                  if (newFirst == first)
                          fetchMore();
                  else {
                          if (this->last != std::numeric_limits<uint64_t>::max()) {
                                  emit beginInsertRows(toExternalIdx(newFirst),
                                                       toExternalIdx(this->first - 1));
                                  this->first = newFirst;
                                  emit endInsertRows();
                                  emit fetchedMore();
                          } else {
                                  auto range = cache::client()->getTimelineRange(room_id_);

                                  if (range && range->last - range->first != 0) {
                                          emit beginInsertRows(0, int(range->last - range->first));
                                          this->first = range->first;
                                          this->last  = range->last;
                                          emit endInsertRows();
                                          emit fetchedMore();
                                  } else {
                                          fetchMore();
                                  }
                          }
                  }
          },
          Qt::QueuedConnection);

        connect(this, &EventStore::processPending, this, [this]() {
                if (!current_txn.empty()) {
                        nhlog::ui()->debug("Already processing {}", current_txn);
                        return;
                }

                auto event = cache::client()->firstPendingMessage(room_id_);

                if (!event) {
                        nhlog::ui()->debug("No event to send");
                        return;
                }

                std::visit(
                  [this](auto e) {
                          auto txn_id       = e.event_id;
                          this->current_txn = txn_id;

                          if (txn_id.empty() || txn_id[0] != 'm') {
                                  nhlog::ui()->debug("Invalid txn id '{}'", txn_id);
                                  cache::client()->removePendingStatus(room_id_, txn_id);
                                  return;
                          }

                          if constexpr (mtx::events::message_content_to_type<decltype(e.content)> !=
                                        mtx::events::EventType::Unsupported)
                                  http::client()->send_room_message(
                                    room_id_,
                                    txn_id,
                                    e.content,
                                    [this, txn_id, e](const mtx::responses::EventId &event_id,
                                                      mtx::http::RequestErr err) {
                                            if (err) {
                                                    const int status_code =
                                                      static_cast<int>(err->status_code);
                                                    nhlog::net()->warn(
                                                      "[{}] failed to send message: {} {}",
                                                      txn_id,
                                                      err->matrix_error.error,
                                                      status_code);
                                                    emit messageFailed(txn_id);
                                                    return;
                                            }

                                            emit messageSent(txn_id, event_id.event_id.to_string());
                                            if constexpr (std::is_same_v<
                                                            decltype(e.content),
                                                            mtx::events::msg::Encrypted>) {
                                                    auto event =
                                                      decryptEvent({room_id_, e.event_id}, e);
                                                    if (auto dec =
                                                          std::get_if<mtx::events::RoomEvent<
                                                            mtx::events::msg::
                                                              KeyVerificationRequest>>(event)) {
                                                            emit updateFlowEventId(
                                                              event_id.event_id.to_string());
                                                    }
                                            }
                                    });
                  },
                  event->data);
        });

        connect(
          this,
          &EventStore::messageFailed,
          this,
          [this](std::string txn_id) {
                  if (current_txn == txn_id) {
                          current_txn_error_count++;
                          if (current_txn_error_count > 10) {
                                  nhlog::ui()->debug("failing txn id '{}'", txn_id);
                                  cache::client()->removePendingStatus(room_id_, txn_id);
                                  current_txn_error_count = 0;
                          }
                  }
                  QTimer::singleShot(1000, this, [this]() {
                          nhlog::ui()->debug("timeout");
                          this->current_txn = "";
                          emit processPending();
                  });
          },
          Qt::QueuedConnection);

        connect(
          this,
          &EventStore::messageSent,
          this,
          [this](std::string txn_id, std::string event_id) {
                  nhlog::ui()->debug("sent {}", txn_id);

                  // Replace the event_id in pending edits/replies/redactions with the actual
                  // event_id of this event
                  for (auto related_event_id : cache::client()->relatedEvents(room_id_, txn_id)) {
                          if (cache::client()->getEvent(room_id_, related_event_id)) {
                                  auto related_event =
                                    cache::client()->getEvent(room_id_, related_event_id).value();
                                  auto relations = mtx::accessors::relations(related_event.data);

                                  for (mtx::common::Relation &rel : relations.relations) {
                                          if (rel.event_id == txn_id)
                                                  rel.event_id = event_id;
                                  }

                                  mtx::accessors::set_relations(related_event.data, relations);

                                  cache::client()->replaceEvent(
                                    room_id_, related_event_id, related_event);

                                  auto id = idToIndex(event_id);

                                  events_by_id_.remove({room_id_, related_event_id});
                                  events_.remove({room_id_, toInternalIdx(*id)});

                                  emit dataChanged(*id, *id);
                          }
                  }

                  http::client()->read_event(
                    room_id_, event_id, [this, event_id](mtx::http::RequestErr err) {
                            if (err) {
                                    nhlog::net()->warn(
                                      "failed to read_event ({}, {})", room_id_, event_id);
                            }
                    });

                  auto id = idToIndex(event_id);

                  if (id)
                          emit dataChanged(id.value(), id.value());

                  cache::client()->removePendingStatus(room_id_, txn_id);
                  this->current_txn             = "";
                  this->current_txn_error_count = 0;
                  emit processPending();
          },
          Qt::QueuedConnection);
}

void
EventStore::addPending(mtx::events::collections::TimelineEvents event)
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        cache::client()->savePendingMessage(this->room_id_, {event});
        mtx::responses::Timeline events;
        events.limited = false;
        events.events.emplace_back(event);
        handleSync(events);

        emit processPending();
}

void
EventStore::clearTimeline()
{
        emit beginResetModel();

        cache::client()->clearTimeline(room_id_);
        auto range = cache::client()->getTimelineRange(room_id_);
        if (range) {
                nhlog::db()->info("Range {} {}", range->last, range->first);
                this->last  = range->last;
                this->first = range->first;
        } else {
                this->first = std::numeric_limits<uint64_t>::max();
                this->last  = std::numeric_limits<uint64_t>::max();
        }
        nhlog::ui()->info("Range {} {}", this->last, this->first);

        decryptedEvents_.clear();
        events_.clear();

        emit endResetModel();
}

void
EventStore::receivedSessionKey(const std::string &session_id)
{
        if (!pending_key_requests.count(session_id))
                return;

        auto request = pending_key_requests.at(session_id);

        // Don't request keys again until Nheko is restarted (for now)
        pending_key_requests[session_id].events.clear();

        if (!request.events.empty())
                olm::send_key_request_for(request.events.front(), request.request_id, true);

        for (const auto &e : request.events) {
                auto idx = idToIndex(e.event_id);
                if (idx) {
                        decryptedEvents_.remove({room_id_, e.event_id});
                        events_by_id_.remove({room_id_, e.event_id});
                        events_.remove({room_id_, toInternalIdx(*idx)});
                        emit dataChanged(*idx, *idx);
                }
        }
}

void
EventStore::handleSync(const mtx::responses::Timeline &events)
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        auto range = cache::client()->getTimelineRange(room_id_);
        if (!range) {
                emit beginResetModel();
                this->first = std::numeric_limits<uint64_t>::max();
                this->last  = std::numeric_limits<uint64_t>::max();

                decryptedEvents_.clear();
                events_.clear();
                emit endResetModel();
                return;
        }

        if (events.limited) {
                emit beginResetModel();
                this->last  = range->last;
                this->first = range->first;

                decryptedEvents_.clear();
                events_.clear();
                emit endResetModel();
        } else if (range->last > this->last) {
                emit beginInsertRows(toExternalIdx(this->last + 1), toExternalIdx(range->last));
                this->last = range->last;
                emit endInsertRows();
        }

        for (const auto &event : events.events) {
                std::set<std::string> relates_to;
                if (auto redaction =
                      std::get_if<mtx::events::RedactionEvent<mtx::events::msg::Redaction>>(
                        &event)) {
                        // fixup reactions
                        auto redacted = events_by_id_.object({room_id_, redaction->redacts});
                        if (redacted) {
                                auto id = mtx::accessors::relations(*redacted);
                                if (id.annotates()) {
                                        auto idx = idToIndex(id.annotates()->event_id);
                                        if (idx) {
                                                events_by_id_.remove(
                                                  {room_id_, redaction->redacts});
                                                events_.remove({room_id_, toInternalIdx(*idx)});
                                                emit dataChanged(*idx, *idx);
                                        }
                                }
                        }

                        relates_to.insert(redaction->redacts);
                } else {
                        for (const auto &r : mtx::accessors::relations(event).relations)
                                relates_to.insert(r.event_id);
                }

                for (const auto &relates_to_id : relates_to) {
                        auto idx = cache::client()->getTimelineIndex(room_id_, relates_to_id);
                        if (idx) {
                                events_by_id_.remove({room_id_, relates_to_id});
                                decryptedEvents_.remove({room_id_, relates_to_id});
                                events_.remove({room_id_, *idx});
                                emit dataChanged(toExternalIdx(*idx), toExternalIdx(*idx));
                        }
                }

                if (auto txn_id = mtx::accessors::transaction_id(event); !txn_id.empty()) {
                        auto idx = cache::client()->getTimelineIndex(
                          room_id_, mtx::accessors::event_id(event));
                        if (idx) {
                                Index index{room_id_, *idx};
                                events_.remove(index);
                                emit dataChanged(toExternalIdx(*idx), toExternalIdx(*idx));
                        }
                }

                // decrypting and checking some encrypted messages
                if (auto encrypted =
                      std::get_if<mtx::events::EncryptedEvent<mtx::events::msg::Encrypted>>(
                        &event)) {
                        mtx::events::collections::TimelineEvents *d_event =
                          decryptEvent({room_id_, encrypted->event_id}, *encrypted);
                        if (std::visit(
                              [](auto e) { return (e.sender != utils::localUser().toStdString()); },
                              *d_event)) {
                                handle_room_verification(*d_event);
                        }
                }
        }
}

namespace {
template<class... Ts>
struct overloaded : Ts...
{
        using Ts::operator()...;
};
template<class... Ts>
overloaded(Ts...) -> overloaded<Ts...>;
}

void
EventStore::handle_room_verification(mtx::events::collections::TimelineEvents event)
{
        std::visit(
          overloaded{
            [this](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationRequest> &msg) {
                    nhlog::db()->debug("handle_room_verification: Request");
                    emit startDMVerification(msg);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationCancel> &msg) {
                    nhlog::db()->debug("handle_room_verification: Cancel");
                    ChatPage::instance()->receivedDeviceVerificationCancel(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationAccept> &msg) {
                    nhlog::db()->debug("handle_room_verification: Accept");
                    ChatPage::instance()->receivedDeviceVerificationAccept(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationKey> &msg) {
                    nhlog::db()->debug("handle_room_verification: Key");
                    ChatPage::instance()->receivedDeviceVerificationKey(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationMac> &msg) {
                    nhlog::db()->debug("handle_room_verification: Mac");
                    ChatPage::instance()->receivedDeviceVerificationMac(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationReady> &msg) {
                    nhlog::db()->debug("handle_room_verification: Ready");
                    ChatPage::instance()->receivedDeviceVerificationReady(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationDone> &msg) {
                    nhlog::db()->debug("handle_room_verification: Done");
                    ChatPage::instance()->receivedDeviceVerificationDone(msg.content);
            },
            [](const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationStart> &msg) {
                    nhlog::db()->debug("handle_room_verification: Start");
                    ChatPage::instance()->receivedDeviceVerificationStart(msg.content, msg.sender);
            },
            [](const auto &) {},
          },
          event);
}

std::vector<mtx::events::collections::TimelineEvents>
EventStore::edits(const std::string &event_id)
{
        auto event_ids = cache::client()->relatedEvents(room_id_, event_id);

        auto original_event = get(event_id, "", false, false);
        if (!original_event)
                return {};

        auto original_sender    = mtx::accessors::sender(*original_event);
        auto original_relations = mtx::accessors::relations(*original_event);

        std::vector<mtx::events::collections::TimelineEvents> edits;
        for (const auto &id : event_ids) {
                auto related_event = get(id, event_id, false, false);
                if (!related_event)
                        continue;

                auto related_ev = *related_event;

                auto edit_rel = mtx::accessors::relations(related_ev);
                if (edit_rel.replaces() == event_id &&
                    original_sender == mtx::accessors::sender(related_ev)) {
                        if (edit_rel.synthesized && original_relations.reply_to() &&
                            !edit_rel.reply_to()) {
                                edit_rel.relations.push_back(
                                  {mtx::common::RelationType::InReplyTo,
                                   original_relations.reply_to().value()});
                                mtx::accessors::set_relations(related_ev, std::move(edit_rel));
                        }
                        edits.push_back(std::move(related_ev));
                }
        }

        auto c = cache::client();
        std::sort(edits.begin(),
                  edits.end(),
                  [this, c](const mtx::events::collections::TimelineEvents &a,
                            const mtx::events::collections::TimelineEvents &b) {
                          return c->getArrivalIndex(this->room_id_, mtx::accessors::event_id(a)) <
                                 c->getArrivalIndex(this->room_id_, mtx::accessors::event_id(b));
                  });

        return edits;
}

QVariantList
EventStore::reactions(const std::string &event_id)
{
        auto event_ids = cache::client()->relatedEvents(room_id_, event_id);

        struct TempReaction
        {
                int count = 0;
                std::vector<std::string> users;
                std::string reactedBySelf;
        };
        std::map<std::string, TempReaction> aggregation;
        std::vector<Reaction> reactions;

        auto self = http::client()->user_id().to_string();
        for (const auto &id : event_ids) {
                auto related_event = get(id, event_id);
                if (!related_event)
                        continue;

                if (auto reaction = std::get_if<mtx::events::RoomEvent<mtx::events::msg::Reaction>>(
                      related_event);
                    reaction && reaction->content.relations.annotates() &&
                    reaction->content.relations.annotates()->key) {
                        auto key  = reaction->content.relations.annotates()->key.value();
                        auto &agg = aggregation[key];

                        if (agg.count == 0) {
                                Reaction temp{};
                                temp.key_ = QString::fromStdString(key);
                                reactions.push_back(temp);
                        }

                        agg.count++;
                        agg.users.push_back(cache::displayName(room_id_, reaction->sender));
                        if (reaction->sender == self)
                                agg.reactedBySelf = reaction->event_id;
                }
        }

        QVariantList temp;
        for (auto &reaction : reactions) {
                const auto &agg            = aggregation[reaction.key_.toStdString()];
                reaction.count_            = agg.count;
                reaction.selfReactedEvent_ = QString::fromStdString(agg.reactedBySelf);

                bool firstReaction = true;
                for (const auto &user : agg.users) {
                        if (firstReaction)
                                firstReaction = false;
                        else
                                reaction.users_ += ", ";

                        reaction.users_ += QString::fromStdString(user);
                }

                nhlog::db()->debug("key: {}, count: {}, users: {}",
                                   reaction.key_.toStdString(),
                                   reaction.count_,
                                   reaction.users_.toStdString());
                temp.append(QVariant::fromValue(reaction));
        }

        return temp;
}

mtx::events::collections::TimelineEvents *
EventStore::get(int idx, bool decrypt)
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        Index index{room_id_, toInternalIdx(idx)};
        if (index.idx > last || index.idx < first)
                return nullptr;

        auto event_ptr = events_.object(index);
        if (!event_ptr) {
                auto event_id = cache::client()->getTimelineEventId(room_id_, index.idx);
                if (!event_id)
                        return nullptr;

                std::optional<mtx::events::collections::TimelineEvent> event;
                auto edits_ = edits(*event_id);
                if (edits_.empty())
                        event = cache::client()->getEvent(room_id_, *event_id);
                else
                        event = {edits_.back()};

                if (!event)
                        return nullptr;
                else
                        event_ptr =
                          new mtx::events::collections::TimelineEvents(std::move(event->data));
                events_.insert(index, event_ptr);
        }

        if (decrypt)
                if (auto encrypted =
                      std::get_if<mtx::events::EncryptedEvent<mtx::events::msg::Encrypted>>(
                        event_ptr))
                        return decryptEvent({room_id_, encrypted->event_id}, *encrypted);

        return event_ptr;
}

std::optional<int>
EventStore::idToIndex(std::string_view id) const
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        auto idx = cache::client()->getTimelineIndex(room_id_, id);
        if (idx)
                return toExternalIdx(*idx);
        else
                return std::nullopt;
}
std::optional<std::string>
EventStore::indexToId(int idx) const
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        return cache::client()->getTimelineEventId(room_id_, toInternalIdx(idx));
}

mtx::events::collections::TimelineEvents *
EventStore::decryptEvent(const IdIndex &idx,
                         const mtx::events::EncryptedEvent<mtx::events::msg::Encrypted> &e)
{
        if (auto cachedEvent = decryptedEvents_.object(idx))
                return cachedEvent;

        MegolmSessionIndex index;
        index.room_id    = room_id_;
        index.session_id = e.content.session_id;
        index.sender_key = e.content.sender_key;

        auto asCacheEntry = [&idx](mtx::events::collections::TimelineEvents &&event) {
                auto event_ptr = new mtx::events::collections::TimelineEvents(std::move(event));
                decryptedEvents_.insert(idx, event_ptr);
                return event_ptr;
        };

        auto decryptionResult = olm::decryptEvent(index, e);

        mtx::events::RoomEvent<mtx::events::msg::Notice> dummy;
        dummy.origin_server_ts = e.origin_server_ts;
        dummy.event_id         = e.event_id;
        dummy.sender           = e.sender;

        if (decryptionResult.error) {
                switch (*decryptionResult.error) {
                case olm::DecryptionErrorCode::MissingSession:
                case olm::DecryptionErrorCode::MissingSessionIndex: {
                        if (decryptionResult.error == olm::DecryptionErrorCode::MissingSession)
                                dummy.content.body =
                                  tr("-- Encrypted Event (No keys found for decryption) --",
                                     "Placeholder, when the message was not decrypted yet or can't "
                                     "be "
                                     "decrypted.")
                                    .toStdString();
                        else
                                dummy.content.body =
                                  tr("-- Encrypted Event (Key not valid for this index) --",
                                     "Placeholder, when the message can't be decrypted with this "
                                     "key since it is not valid for this index ")
                                    .toStdString();
                        nhlog::crypto()->info("Could not find inbound megolm session ({}, {}, {})",
                                              index.room_id,
                                              index.session_id,
                                              e.sender);
                        // TODO: Check if this actually works and look in key backup
                        auto copy    = e;
                        copy.room_id = room_id_;
                        if (pending_key_requests.count(e.content.session_id)) {
                                pending_key_requests.at(e.content.session_id)
                                  .events.push_back(copy);
                        } else {
                                PendingKeyRequests request;
                                request.request_id =
                                  "key_request." + http::client()->generate_txn_id();
                                request.events.push_back(copy);
                                olm::send_key_request_for(copy, request.request_id);
                                pending_key_requests[e.content.session_id] = request;
                        }
                        break;
                }
                case olm::DecryptionErrorCode::DbError:
                        nhlog::db()->critical(
                          "failed to retrieve megolm session with index ({}, {}, {})",
                          index.room_id,
                          index.session_id,
                          index.sender_key,
                          decryptionResult.error_message.value_or(""));
                        dummy.content.body =
                          tr("-- Decryption Error (failed to retrieve megolm keys from db) --",
                             "Placeholder, when the message can't be decrypted, because the DB "
                             "access "
                             "failed.")
                            .toStdString();
                        break;
                case olm::DecryptionErrorCode::DecryptionFailed:
                        nhlog::crypto()->critical(
                          "failed to decrypt message with index ({}, {}, {}): {}",
                          index.room_id,
                          index.session_id,
                          index.sender_key,
                          decryptionResult.error_message.value_or(""));
                        dummy.content.body =
                          tr("-- Decryption Error (%1) --",
                             "Placeholder, when the message can't be decrypted. In this case, the "
                             "Olm "
                             "decrytion returned an error, which is passed as %1.")
                            .arg(
                              QString::fromStdString(decryptionResult.error_message.value_or("")))
                            .toStdString();
                        break;
                case olm::DecryptionErrorCode::ParsingFailed:
                        dummy.content.body =
                          tr("-- Encrypted Event (Unknown event type) --",
                             "Placeholder, when the message was decrypted, but we couldn't parse "
                             "it, because "
                             "Nheko/mtxclient don't support that event type yet.")
                            .toStdString();
                        break;
                case olm::DecryptionErrorCode::ReplayAttack:
                        nhlog::crypto()->critical(
                          "Reply attack while decryptiong event {} in room {} from {}!",
                          e.event_id,
                          room_id_,
                          index.sender_key);
                        dummy.content.body =
                          tr("-- Replay attack! This message index was reused! --").toStdString();
                        break;
                case olm::DecryptionErrorCode::UnknownFingerprint:
                        // TODO: don't fail, just show in UI.
                        nhlog::crypto()->critical("Message by unverified fingerprint {}",
                                                  index.sender_key);
                        dummy.content.body =
                          tr("-- Message by unverified device! --").toStdString();
                        break;
                }
                return asCacheEntry(std::move(dummy));
        }

        std::string msg_str;
        try {
                auto session = cache::client()->getInboundMegolmSession(index);
                auto res =
                  olm::client()->decrypt_group_message(session.get(), e.content.ciphertext);
                msg_str = std::string((char *)res.data.data(), res.data.size());
        } catch (const lmdb::error &e) {
                nhlog::db()->critical("failed to retrieve megolm session with index ({}, {}, {})",
                                      index.room_id,
                                      index.session_id,
                                      index.sender_key,
                                      e.what());
                dummy.content.body =
                  tr("-- Decryption Error (failed to retrieve megolm keys from db) --",
                     "Placeholder, when the message can't be decrypted, because the DB "
                     "access "
                     "failed.")
                    .toStdString();
                return asCacheEntry(std::move(dummy));
        } catch (const mtx::crypto::olm_exception &e) {
                nhlog::crypto()->critical("failed to decrypt message with index ({}, {}, {}): {}",
                                          index.room_id,
                                          index.session_id,
                                          index.sender_key,
                                          e.what());
                dummy.content.body =
                  tr("-- Decryption Error (%1) --",
                     "Placeholder, when the message can't be decrypted. In this case, the "
                     "Olm "
                     "decrytion returned an error, which is passed as %1.")
                    .arg(e.what())
                    .toStdString();
                return asCacheEntry(std::move(dummy));
        }

        // Add missing fields for the event.
        json body                = json::parse(msg_str);
        body["event_id"]         = e.event_id;
        body["sender"]           = e.sender;
        body["origin_server_ts"] = e.origin_server_ts;
        body["unsigned"]         = e.unsigned_data;

        // relations are unencrypted in content...
        mtx::common::add_relations(body["content"], e.content.relations);

        json event_array = json::array();
        event_array.push_back(body);

        std::vector<mtx::events::collections::TimelineEvents> temp_events;
        mtx::responses::utils::parse_timeline_events(event_array, temp_events);

        if (temp_events.size() == 1) {
                auto encInfo = mtx::accessors::file(temp_events[0]);

                if (encInfo)
                        emit newEncryptedImage(encInfo.value());

                return asCacheEntry(std::move(temp_events[0]));
        }

        auto encInfo = mtx::accessors::file(decryptionResult.event.value());
        if (encInfo)
                emit newEncryptedImage(encInfo.value());

        return asCacheEntry(std::move(decryptionResult.event.value()));
}

mtx::events::collections::TimelineEvents *
EventStore::get(std::string id, std::string_view related_to, bool decrypt, bool resolve_edits)
{
        if (this->thread() != QThread::currentThread())
                nhlog::db()->warn("{} called from a different thread!", __func__);

        if (id.empty())
                return nullptr;

        IdIndex index{room_id_, std::move(id)};
        if (resolve_edits) {
                auto edits_ = edits(index.id);
                if (!edits_.empty()) {
                        index.id = mtx::accessors::event_id(edits_.back());
                        auto event_ptr =
                          new mtx::events::collections::TimelineEvents(std::move(edits_.back()));
                        events_by_id_.insert(index, event_ptr);
                }
        }

        auto event_ptr = events_by_id_.object(index);
        if (!event_ptr) {
                auto event = cache::client()->getEvent(room_id_, index.id);
                if (!event) {
                        http::client()->get_event(
                          room_id_,
                          index.id,
                          [this, relatedTo = std::string(related_to), id = index.id](
                            const mtx::events::collections::TimelineEvents &timeline,
                            mtx::http::RequestErr err) {
                                  if (err) {
                                          nhlog::net()->error(
                                            "Failed to retrieve event with id {}, which was "
                                            "requested to show the replyTo for event {}",
                                            relatedTo,
                                            id);
                                          return;
                                  }
                                  emit eventFetched(id, relatedTo, timeline);
                          });
                        return nullptr;
                }
                event_ptr = new mtx::events::collections::TimelineEvents(std::move(event->data));
                events_by_id_.insert(index, event_ptr);
        }

        if (decrypt)
                if (auto encrypted =
                      std::get_if<mtx::events::EncryptedEvent<mtx::events::msg::Encrypted>>(
                        event_ptr))
                        return decryptEvent(index, *encrypted);

        return event_ptr;
}

void
EventStore::fetchMore()
{
        if (noMoreMessages)
                return;

        mtx::http::MessagesOpts opts;
        opts.room_id = room_id_;
        opts.from    = cache::client()->previousBatchToken(room_id_);

        nhlog::ui()->debug("Paginating room {}, token {}", opts.room_id, opts.from);

        http::client()->messages(
          opts, [this, opts](const mtx::responses::Messages &res, mtx::http::RequestErr err) {
                  if (cache::client()->previousBatchToken(room_id_) != opts.from) {
                          nhlog::net()->warn("Cache cleared while fetching more messages, dropping "
                                             "/messages response");
                          if (!opts.to.empty())
                                  emit fetchedMore();
                          return;
                  }
                  if (err) {
                          nhlog::net()->error("failed to call /messages ({}): {} - {} - {}",
                                              opts.room_id,
                                              mtx::errors::to_string(err->matrix_error.errcode),
                                              err->matrix_error.error,
                                              err->parse_error);
                          emit fetchedMore();
                          return;
                  }

                  emit oldMessagesRetrieved(std::move(res));
          });
}