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

#include <QByteArray>
#include <QString>

/*!
 * \brief   MQTT packet encoding and decoding.
 */
namespace Mqtt {

enum class PacketType : quint8
{
    Connect     = 1,
    ConnAck     = 2,
    Publish     = 3,
    PubAck      = 4,
    PingReq     = 12,
    PingResp    = 13,
    Disconnect  = 14,
};

enum class ConnAckCode : quint8
{
    Accepted             = 0,
    UnacceptableProtocol = 1,
    IdentifierRejected   = 2,
    ServerUnavailable    = 3,
    BadCredentials       = 4,
    NotAuthorized        = 5,
};

/// Outcome of one readPacket() call.
enum class ReadState
{
    Incomplete,   ///< Need more bytes; nothing was consumed.
    Complete,     ///< One packet was decoded and consumed.
    Error,        ///< Malformed; the caller should drop the connection.
};

/*!
 * \brief   One decoded MQTT packet.
 */
struct Packet
{
    PacketType type = PacketType::Disconnect;

    QString topic;
    quint16 packetId = 0;
    quint8 qos = 0;
    QByteArray payload;
    bool dup = false;
    bool retain = false;

    QString clientId;
    quint16 keepAliveSecs = 0;
    bool cleanSession = true;

    ConnAckCode returnCode = ConnAckCode::Accepted;
    bool sessionPresent = false;
};

QByteArray buildConnect(const QString &clientId, quint16 keepAliveSecs, bool cleanSession);
QByteArray buildConnAck(ConnAckCode code, bool sessionPresent = false);
QByteArray buildPublish(const QString &topic, const QByteArray &payload, quint8 qos, quint16 packetId);
QByteArray buildPubAck(quint16 packetId);
QByteArray buildPingReq();
QByteArray buildPingResp();
QByteArray buildDisconnect();

ReadState readPacket(QByteArray &bytes, Packet &packet);

QString typeName(PacketType type);

}   // namespace Mqtt