const mqtt = require("mqtt");
const config = require("./config");
const logger = require("./logger");

function createMqttClient() {
  if (!config.mqtt || !config.mqtt.enabled) {
    logger.info("MQTT is disabled by config");
    return {
      client: null,
      publishDeviceData: () => {}
    };
  }

  // 兼容当前配置结构：url 为主机名，port 为端口
  const host = config.mqtt.url || "127.0.0.1";
  const port = config.mqtt.port || 1883;
  const brokerUrl = `mqtt://${host}:${port}`;

  const client = mqtt.connect(brokerUrl, {
    username: config.mqtt.username || undefined,
    password: config.mqtt.password || undefined,
    clientId: config.mqtt.clientId,
    reconnectPeriod: config.mqtt.reconnectPeriod
  });

  client.on("connect", () => {
    logger.info("MQTT connected", { url: brokerUrl });
  });

  client.on("reconnect", () => {
    logger.info("MQTT reconnecting");
  });

  client.on("error", (err) => {
    logger.error("MQTT error", err.message || err);
  });

  client.on("close", () => {
    logger.warn("MQTT connection closed");
  });

  function publishDeviceData(deviceNumber, data) {
    if (!client.connected) {
      logger.warn("MQTT not connected, skip publish");
      return;
    }
    // Topic 前缀优先取配置的 defaultTopicPrefix，否则退回 "dialysis"
    const prefix = config.mqtt.defaultTopicPrefix || config.mqtt.topicPrefix || "dialysis";
    const topic = `${prefix}/${deviceNumber}`;
    const payload = JSON.stringify({
      deviceId: data.deviceNumber,
      ts: Date.now(),
      ...data
    });
    // 记录发送到 MQTT 的物模型/数据内容，便于对比阿里云或下游收到的报文
    logger.info("MQTT publish", {
      topic,
      deviceNumber,
      ...data
    });
    client.publish(topic, payload, { qos: 0, retain: !!config.mqtt.retain }, (err) => {
      if (err) {
        logger.error("MQTT publish error", err.message || err);
      } else {
        logger.info("MQTT publish success", { topic, deviceNumber });
      }
    });
  }

  return { client, publishDeviceData };
}

module.exports = createMqttClient;