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

#pragma once

#include <limits>
#include <string>

#include <QCache>
#include <QObject>
#include <QVariant>

#include <mtx/events/collections.hpp>
#include <mtx/responses/messages.hpp>
#include <mtx/responses/sync.hpp>

#include "Reaction.h"

class EventStore : public QObject
{
        Q_OBJECT

public:
        EventStore(std::string room_id, QObject *parent);

        // taken from QtPrivate::QHashCombine
        static uint hashCombine(uint hash, uint seed)
        {
                return seed ^ (hash + 0x9e3779b9 + (seed << 6) + (seed >> 2));
        };
        struct Index
        {
                std::string room;
                uint64_t idx;

                friend uint qHash(const Index &i, uint seed = 0) noexcept
                {
                        seed =
                          hashCombine(qHashBits(i.room.data(), (int)i.room.size(), seed), seed);
                        seed = hashCombine(qHash(i.idx, seed), seed);
                        return seed;
                }

                friend bool operator==(const Index &a, const Index &b) noexcept
                {
                        return a.idx == b.idx && a.room == b.room;
                }
        };
        struct IdIndex
        {
                std::string room, id;

                friend uint qHash(const IdIndex &i, uint seed = 0) noexcept
                {
                        seed =
                          hashCombine(qHashBits(i.room.data(), (int)i.room.size(), seed), seed);
                        seed = hashCombine(qHashBits(i.id.data(), (int)i.id.size(), seed), seed);
                        return seed;
                }

                friend bool operator==(const IdIndex &a, const IdIndex &b) noexcept
                {
                        return a.id == b.id && a.room == b.room;
                }
        };

        void fetchMore();
        void handleSync(const mtx::responses::Timeline &events);

        // optionally returns the event or nullptr and fetches it, after which it emits a
        // relatedFetched event
        mtx::events::collections::TimelineEvents *get(std::string id,
                                                      std::string_view related_to,
                                                      bool decrypt       = true,
                                                      bool resolve_edits = true);
        // always returns a proper event as long as the idx is valid
        mtx::events::collections::TimelineEvents *get(int idx, bool decrypt = true);

        QVariantList reactions(const std::string &event_id);

        int size() const
        {
                return (last != std::numeric_limits<uint64_t>::max() && last >= first)
                         ? static_cast<int>(last - first) + 1
                         : 0;
        }
        int toExternalIdx(uint64_t idx) const { return static_cast<int>(idx - first); }
        uint64_t toInternalIdx(int idx) const { return first + idx; }

        std::optional<int> idToIndex(std::string_view id) const;
        std::optional<std::string> indexToId(int idx) const;

signals:
        void beginInsertRows(int from, int to);
        void endInsertRows();
        void beginResetModel();
        void endResetModel();
        void dataChanged(int from, int to);
        void newEncryptedImage(mtx::crypto::EncryptedFile encryptionInfo);
        void eventFetched(std::string id,
                          std::string relatedTo,
                          mtx::events::collections::TimelineEvents timeline);
        void oldMessagesRetrieved(const mtx::responses::Messages &);
        void fetchedMore();

        void processPending();
        void messageSent(std::string txn_id, std::string event_id);
        void messageFailed(std::string txn_id);
        void startDMVerification(
          const mtx::events::RoomEvent<mtx::events::msg::KeyVerificationRequest> &msg);
        void updateFlowEventId(std::string event_id);

public slots:
        void addPending(mtx::events::collections::TimelineEvents event);
        void receivedSessionKey(const std::string &session_id);
        void clearTimeline();

private:
        std::vector<mtx::events::collections::TimelineEvents> edits(const std::string &event_id);
        mtx::events::collections::TimelineEvents *decryptEvent(
          const IdIndex &idx,
          const mtx::events::EncryptedEvent<mtx::events::msg::Encrypted> &e);
        void handle_room_verification(mtx::events::collections::TimelineEvents event);

        std::string room_id_;

        uint64_t first = std::numeric_limits<uint64_t>::max(),
                 last  = std::numeric_limits<uint64_t>::max();

        static QCache<IdIndex, mtx::events::collections::TimelineEvents> decryptedEvents_;
        static QCache<Index, mtx::events::collections::TimelineEvents> events_;
        static QCache<IdIndex, mtx::events::collections::TimelineEvents> events_by_id_;

        struct PendingKeyRequests
        {
                std::string request_id;
                std::vector<mtx::events::EncryptedEvent<mtx::events::msg::Encrypted>> events;
        };
        std::map<std::string, PendingKeyRequests> pending_key_requests;

        std::string current_txn;
        int current_txn_error_count = 0;
        bool noMoreMessages         = false;
};