/*!
 *
 * Copyright (c) 2026 Diality Inc. - All Rights Reserved.
 * \copyright
 * THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
 * WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
 *
 * \file    MqttTcpTransport.h
 * \author  (original)  Stephen Quong
 * \date    (original)  30-Jul-2026
 *
 */
#pragma once

#include <QAbstractSocket>
#include <QByteArray>
#include <QHash>
#include <QObject>
#include <QTcpSocket>
#include <QTimer>

#include "MqttPacket.h"
#include "MqttTransport.h"

/*!
 * \brief   MqttTransport over a plain TCP socket.
 * \note    No TLS. This is the test transport; the production path is the AWS
 *          SDK transport, which mTLS is part of. Pointing this at AWS IoT Core
 *          will be refused at the TCP layer.
 * \note    Unlike the AWS transport, the callbacks fire on the Qt thread that owns
 *          the socket rather than a foreign event loop. That makes MqttPublisher's
 *          marshalling a same-thread queued call, so it exercises the ordering but
 *          not the cross-thread hazard.
 */
class MqttTcpTransport : public QObject, public MqttTransport
{
    Q_OBJECT

public:
    explicit MqttTcpTransport(QObject *parent = nullptr);
    ~MqttTcpTransport() override;

    bool open(const Config &config) override;
    void close() override;
    bool isConnected() const override;
    bool publish(const QString &topic, const QByteArray &payload, qint64 messageId) override;
    void setCallbacks(StateCallback onState, AckCallback onAck) override;
    void clearCallbacks() override;

private Q_SLOTS:
    void onSocketConnected();
    void onSocketDisconnected();
    void onReadyRead();
    void onKeepAliveTimer();

private:
    void handlePacket(const Mqtt::Packet &packet);
    void setSessionState(bool established);
    void failPending();
    quint16 nextPacketId();

    QTcpSocket _socket;
    QTimer _keepAliveTimer;
    Config _config;
    QByteArray _rxBuf;
    QHash<quint16, qint64> _pending;
    StateCallback _onState;
    AckCallback _onAck;
    quint16 _lastPacketId = 0;
    bool _sessionUp = false;
};