@totallyinformation/node-red-contrib-events/nodes/event-in.js

Event broadcast and receive nodes for Node-RED.

/** Listens for an event based on a msg.topic and outputs a copy of the msg 
 *  Destructured to make for easier and more consistent logic.
 * 
 * Copyright (c) 2021 Julian Knight (Totally Information)
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict'

/** --- Type Defs ---
 * @typedef {import('../typedefs.js').runtimeRED} runtimeRED
 * @typedef {import('../typedefs.js').runtimeNodeConfig} runtimeNodeConfig
 * @typedef {import('../typedefs.js').runtimeNode} runtimeNode
 * typedef {import('../typedefs.js').myNode} myNode
 */

//#region ----- Module level variables ---- //

const tiEvents = require('@totallyinformation/ti-common-event-handler')

/** Main (module) variables - acts as a configuration object
 *  that can easily be passed around.
 */
const mod = {
    /** @type {runtimeRED} Reference to the master RED instance */
    RED: undefined,
    /** @type {string} Custom Node Name - has to match with html file and package.json `red` section */
    nodeName: 'event-in',
}

//#endregion ----- Module level variables ---- //

//#region ----- Module-level support functions ----- //

/** 2) This is run when an actual instance of our node is committed to a flow
 * @param {runtimeNodeConfig} config The Node-RED node instance config object
 */
function nodeInstance(config) {
    // As a module-level named function, it will inherit `mod` and other module-level variables

    // If you need it - which you will here - or just use mod.RED if you prefer:
    const RED = mod.RED

    // Create the node instance - `this` can only be referenced AFTER here
    RED.nodes.createNode(this, config) 

    // Transfer config items from the Editor panel to the runtime
    this.name = config.name
    this.topic = config.topic

    // Allow for and convert MQTT-style wildcards
    this.topic = this.topic.replace(/#/g, '**').replace(/\+/g, '*')

    // Add the unique prefix for these nodes (allows the event system to be reused in other nodes)
    const eventName = `node-red-contrib-events/${this.topic}`

    // Event handler
    const sender = (msg) => {
        this.send(msg)
    }

    // Create new listener for the given topic, record it so that it can be removed on close
    tiEvents.on(eventName, sender)

    /** Put things here if you need to do anything when a node instance is removed
     * Or if Node-RED is shutting down.
     * Note the use of an arrow function, ensures that the function keeps the
     * same `this` context and so has access to all of the node instance properties.
     */
    this.on('close', (removed, done) => { 
        // Remove this event listener
        tiEvents.removeListener(eventName, sender)

        done()
    })

    /** Properties of `this`
     * Methods: updateWires(wires), context(), on(event,callback), emit(event,...args), removeListener(name,listener), removeAllListeners(name), close(removed)
     *          send(msg), receive(msg), log(msg), warn(msg), error(logMessage,msg), debug(msg), trace(msg), metric(eventname, msg, metricValue), status(status)
     * Other: credentials, id, type, z, wires, x, y
     * + any props added manually from config, typically at least name and topic
     */
}

//#endregion ----- Module-level support functions ----- //

/** 1) Complete module definition for our Node. This is where things actually start.
 * @param {runtimeRED} RED The Node-RED runtime object
 */
function EventIn(RED) {
    // As a module-level named function, it will inherit `mod` and other module-level variables

    // Save a reference to the RED runtime for convenience
    mod.RED = RED

    // Register a new instance of the specified node type (2)
    RED.nodes.registerType(mod.nodeName, nodeInstance)
}

// Export the module definition (1), this is consumed by Node-RED on startup.
module.exports = EventIn

//EOF