/*!
 *
 * 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    MqttClient.h
 * \author  (original)  Stephen Quong
 * \date    (original)  30-Jul-2026
 *
 */
#pragma once

#include <QByteArray>
#include <QHash>
#include <QObject>
#include <QSslConfiguration>
#include <QString>
#include <QtMqtt/QMqttClient>
#include <QtMqtt/QMqttMessageStatusProperties>

class QMqttClient;

/*!
 * \brief   Encrypted client MQTT connection to a broker for message sending and receiving.
 *          Lifecycle: init() -> open() -> close().
 */
class MqttClient : public QObject
{
    Q_OBJECT

public:
    /*!
     * \brief   Parameters for one MQTT session.
     */
    struct Config
    {
        QString endpoint;           // Broker FQDN or address; no scheme or trailing slash.
        quint16 port = 8883;        // Broker port; the session is always TLS.
        QString certPath;           // Client certificate for mTLS, PEM; optional.
        QString keyPath;            // Unencrypted private key matching certPath, PEM; required.
        QString caPath;             // CA bundle to verify the broker, PEM; optional, falls back
                                    // to the system CA set.
        QString clientId;           // Must equal the IoT Thing name; the device policy scopes iot:Connect to it.
        quint16 keepAliveSecs = 30; // MQTT keep-alive interval; PINGREQ is QMqttClient's job.
        bool cleanSession = true;   // No broker-side queue; durability is the device's job.
    };

    explicit MqttClient(QObject *parent = nullptr);
    ~MqttClient() override;

    bool init(const Config &config);
    bool open();
    void close();
    bool publish(const QString &topic, const QByteArray &payload, qint32 &msgId, quint8 qos=1);
    bool subscribe(const QString &topicFilter, quint8 qos=1);

Q_SIGNALS:
    /*!
     * \brief   Emitted when the state of the session changes (i.e. connect, disconnect)
     * \note    Subscriptions belong to the QMqttClient that gets destroyed on disconnect,
     *          so re-subscription is required on every new connection.
     * \note    Not emitted for a caller-initiated close()
     */
    void didStateChanged(QMqttClient::ClientState state);

    /*!
     * \brief   Emitted for status change of every sent message.
     */
    void didMessageStatusChanged(quint32 id, QMqtt::MessageStatus status,
        const QMqttMessageStatusProperties &properties);

    /*!
     * \brief   Emitted for every message the broker delivers to this client.
     * \details Covers all active subscriptions; the receiver demultiplexes by topic.
     */
    void didMessageReceived(const QByteArray &message, const QMqttTopicName &topic);

private Q_SLOTS:
    void onStateChanged();

private:
    QMqttClient *_client = nullptr;
    Config _config;
    QSslConfiguration _sslConfig;
};