node-log-mqtt/lib/index.js

A lightweight and efficient logger for Node.js applications that leverages MQTT for centralized log management. Ideal for distributed systems requiring traceability and log persistence, this package provides easy MQTT client integration and a simple inter

'use strict';

const { MQTTClient } = require('node-mqtt-client');

/**
 * Class representing a Logger that utilizes MQTT for logging messages.
 */
class Logger {
    static #MQTTClient = null;
    static #instance = null;
    static suffix = 'logs';

    /**
     * Create a Logger object. Private to prevent direct instantiation.
     * @throws {Error} If an attempt is made to create multiple instances.
     */
    constructor() {
        if (Logger.#instance instanceof Logger)
            throw new Error('Cannot create multiple instances of Logger.');
    }

    /**
     * Initialize the Logger with an MQTT client.
     * @param {MQTTClient} MQTTClient - The MQTT client to use for logging.
     * @returns {Logger} The singleton instance of the Logger.
     * @throws {Error} If the MQTTClient does not have a publish method.
     */
    static initialize(client) {
        if (false === (client instanceof MQTTClient))
            throw new Error('The client parameter must be an instance of MQTTClient.');
        if (this.#instance instanceof Logger) return this.#instance;
        if (typeof client.publish !== 'function')
            throw new Error('The instance of MQTTClient does not have a public method to publish messages.');

        this.#instance = new Logger();
        this.#MQTTClient = client;

        console.log('Logger initialized.');
        return this.#instance;
    }

    /**
     * Log a message using the MQTT client.
     * @param {string} message - The message to log.
     * @param {string} topic - The MQTT topic suffix to publish to (optional).
     */
    static log(message, topic = '') {
        if (false === (this.#instance instanceof Logger)) {
            console.error('Logger not initialized.');
            return;
        } else {
            const logMessage = `[${new Date().toISOString()}] ${message}`;
            if (topic && false === topic.startsWith(String.fromCharCode(47)))
                topic = String.fromCharCode(47) + topic;
            // Publish message to specific topic
            this.#MQTTClient.publish(this.suffix + topic, logMessage);
        }
    }
}

module.exports = {
    Logger,
    MQTTClient
};