Function applyPublisherEndpoint

app/src/API/Handlers/MqttHandler.cpp:263–300

* @brief Applies endpoint + credential fields to the publisher; returns error on failure. */

 * @brief Applies endpoint + credential fields to the publisher; returns error on failure.
 */
[[nodiscard]] static std::optional<QString> applyPublisherEndpoint(MQTT::Publisher& p,
                                                                   const QJsonObject& params)
{
  if (params.contains(QStringLiteral("hostname"))) {
    const auto host = params.value(QStringLiteral("hostname")).toString();
    if (host.trimmed().isEmpty())
      return QStringLiteral("hostname must not be empty");

    p.setHostname(host);
  }

  if (params.contains(QStringLiteral("port"))) {
    const int port = params.value(QStringLiteral("port")).toInt(-1);
    if (!portIsValid(port))
      return QStringLiteral("port must be in [1, 65535] (got %1)").arg(port);

    p.setPort(static_cast<quint16>(port));
  }

  if (params.contains(QStringLiteral("clientId")))
    p.setClientId(params.value(QStringLiteral("clientId")).toString());

  if (params.contains(QStringLiteral("customClientId")))
    p.setCustomClientId(params.value(QStringLiteral("customClientId")).toBool());

  const bool hasUser = params.contains(QStringLiteral("username"));
  const bool hasPass = params.contains(QStringLiteral("password"));
  if (hasPass && !hasUser)
    return QStringLiteral("Setting 'password' requires 'username' in the same call");

  if (hasUser)
    p.setUsername(params.value(QStringLiteral("username")).toString());

  if (hasPass)
    p.setPassword(params.value(QStringLiteral("password")).toString());

  return std::nullopt;
}

/**
 * @brief Applies topic + mode + frequency fields to the publisher; returns error on failure.