// SPDX-FileCopyrightText: 2021 Nheko Contributors
// SPDX-FileCopyrightText: 2022 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"
#include "encryption/Olm.h"

class EventStore final : 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(const 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);
    std::vector<mtx::events::collections::TimelineEvents> edits(const std::string &event_id);
    olm::DecryptionErrorCode decryptionError(std::string id);
    void
    requestSession(const mtx::events::EncryptedEvent<mtx::events::msg::Encrypted> &ev, bool manual);

    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 pinsChanged();
    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();
    void enableKeyRequests(bool suppressKeyRequests_);

private:
    olm::DecryptionResult *
    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, olm::DecryptionResult> 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;
        qint64 requested_at;
    };
    std::map<std::string, PendingKeyRequests> pending_key_requests;

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