'use strict';
const mqtt = require('mqtt');

const PREFIX = process.env.MQTT_TOPIC_PREFIX || 'myprimal';

let client = null;

function connect() {
  return new Promise((resolve, reject) => {
    const url = process.env.MQTT_URL || 'mqtt://localhost:1883';
    const opts = {
      clientId:  `myprimal_${Math.random().toString(16).slice(2, 8)}`,
      clean:     true,
      reconnectPeriod: 5000,
    };
    if (process.env.MQTT_USERNAME) opts.username = process.env.MQTT_USERNAME;
    if (process.env.MQTT_PASSWORD) opts.password = process.env.MQTT_PASSWORD;

    client = mqtt.connect(url, opts);

    client.once('connect', () => {
      console.log(`[mqtt] Connected to ${url}`);
      resolve(client);
    });

    client.once('error', err => {
      console.error('[mqtt] Connection error:', err.message);
      reject(err);
    });

    client.on('error', err => console.error('[mqtt] Error:', err.message));

    client.on('reconnect', () => console.log('[mqtt] Reconnecting…'));
  });
}

function publish(topic, payload, opts = {}) {
  if (!client) return;
  const msg = typeof payload === 'string' ? payload : JSON.stringify(payload);
  client.publish(`${PREFIX}/${topic}`, msg, { retain: true, ...opts });
}

function subscribe(topic, handler) {
  if (!client) return;
  const full = `${PREFIX}/${topic}`;
  client.subscribe(full);
  client.on('message', (t, buf) => {
    if (t !== full) return;
    try {
      handler(JSON.parse(buf.toString()));
    } catch {
      handler(buf.toString());
    }
  });
}

function getPrefix() { return PREFIX; }

function getClient() { return client; }

module.exports = { connect, publish, subscribe, getPrefix, getClient };