let logger = require('./log')

logger.info('mqttHandler executed')


var mqtt = require('mqtt');

var client = undefined;
var topicCallbacks = {};


function start() {
    client = mqtt.connect('mqtt://172.16.2.16');

    client.on('error', (err) => {
        logger.error(`Error in mqttHandler: ${err}`)
    });
    client.on('connect', () => {
        client.publish('dispatcher_ng/status', 'dispatcher_ng running');
        client.subscribe('dispatcher_ng/cmd');
        Object.keys(topicCallbacks).forEach((topic) => {
            client.subscribe(topic);
            logger.info(`${topic} subscribed`);
        });
        logger.info('mqtt connection established');
    });
    client.on('message', (topic, payload) => {
        payload = payload.toString('UTF-8');
        logger.info(`message received on topic ${topic}: ${payload}`);
        if (topic in topicCallbacks) {
            topicCallbacks[topic].forEach((cb) => { cb(topic, payload) });
        }
    });
}

function send(topic, payload) {
    client.publish(topic, payload);
}

function register(topics, cb) {
    if (! (topics instanceof Array)) {
        topics = [ topics ];
    }    
    topics.forEach((topic) => {
        if (topic in topicCallbacks) {
            topicCallbacks[topic].push(cb);
            logger.info(`additional callback registered for ${topic}`);
        } else {
            topicCallbacks[topic] = [ cb ];
            logger.info(`first callback registered for ${topic}`);
        }
    })
}

module.exports = {
    start,
    send,
    register
};