✨ Add MQTT & Trigger Node (#1705)

* ✨ MQTT-Node

* ⚡ Small fix

* ⚡ Error when the publish method faile

* ⚡ Improvements

* ⚡ Improvements

* ⚡ Add Send Input Data parameter

* ⚡ Minor improvements

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>

packages/nodes-base/nodes/MQTT/Mqtt.node.ts

@@ -0,0 +1,171 @@
+import {
+	IExecuteFunctions,
+} from 'n8n-core';
+
+import {
+	IDataObject,
+	INodeExecutionData,
+	INodeType,
+	INodeTypeDescription,
+} from 'n8n-workflow';
+
+import * as mqtt from 'mqtt';
+
+import {
+	IClientOptions,
+} from 'mqtt';
+
+export class Mqtt implements INodeType {
+	description: INodeTypeDescription = {
+		displayName: 'MQTT',
+		name: 'mqtt',
+		icon: 'file:mqtt.svg',
+		group: ['input'],
+		version: 1,
+		description: 'Push messages to MQTT',
+		defaults: {
+			name: 'MQTT',
+			color: '#9b27af',
+		},
+		inputs: ['main'],
+		outputs: ['main'],
+		credentials: [
+			{
+				name: 'mqtt',
+				required: true,
+			},
+		],
+		properties: [
+			{
+				displayName: 'Topic',
+				name: 'topic',
+				type: 'string',
+				required: true,
+				default: '',
+				description: `The topic to publish to`,
+			},
+			{
+				displayName: 'Send Input Data',
+				name: 'sendInputData',
+				type: 'boolean',
+				default: true,
+				description: 'Send the the data the node receives as JSON.',
+			},
+			{
+				displayName: 'Message',
+				name: 'message',
+				type: 'string',
+				required: true,
+				displayOptions: {
+					show: {
+						sendInputData: [
+							false,
+						],
+					},
+				},
+				default: '',
+				description: 'The message to publish',
+			},
+			{
+				displayName: 'Options',
+				name: 'options',
+				type: 'collection',
+				placeholder: 'Add Option',
+				default: {},
+				options: [
+					{
+						displayName: 'QoS',
+						name: 'qos',
+						type: 'options',
+						options: [
+							{
+								name: 'Received at Most Once',
+								value: 0,
+							},
+							{
+								name: 'Received at Least Once',
+								value: 1,
+							},
+							{
+								name: 'Exactly Once',
+								value: 2,
+							},
+						],
+						default: 0,
+						description: 'QoS subscription level',
+					},
+					{
+						displayName: 'Retain',
+						name: 'retain',
+						type: 'boolean',
+						default: false,
+						description: `Normally if a publisher publishes a message to a topic, and no one is subscribed to<br>
+						that topic the message is simply discarded by the broker. However the publisher can tell the broker<br>
+						to keep the last message on that topic by setting the retain flag to true.`,
+					},
+				],
+			},
+		],
+	};
+
+	async execute(this: IExecuteFunctions): Promise<INodeExecutionData[][]> {
+		const items = this.getInputData();
+		const length = (items.length as unknown) as number;
+		const credentials = this.getCredentials('mqtt') as IDataObject;
+
+		const protocol = credentials.protocol as string || 'mqtt';
+		const host = credentials.host as string;
+		const brokerUrl = `${protocol}://${host}`;
+		const port = credentials.port as number || 1883;
+		const clientId = credentials.clientId as string || `mqttjs_${Math.random().toString(16).substr(2, 8)}`;
+		const clean = credentials.clean as boolean;
+
+		const clientOptions: IClientOptions = {
+			port,
+			clean,
+			clientId,
+		};
+
+		if (credentials.username && credentials.password) {
+			clientOptions.username = credentials.username as string;
+			clientOptions.password = credentials.password as string;
+		}
+
+		const client = mqtt.connect(brokerUrl, clientOptions);
+		const sendInputData = this.getNodeParameter('sendInputData', 0) as boolean;
+
+		// tslint:disable-next-line: no-any
+		const data = await new Promise((resolve, reject): any => {
+			client.on('connect', () => {
+				for (let i = 0; i < length; i++) {
+
+					let message;
+					const topic = (this.getNodeParameter('topic', i) as string);
+					const options = (this.getNodeParameter('options', i) as IDataObject);
+
+					try {
+						if (sendInputData === true) {
+							message = JSON.stringify(items[i].json);
+						} else {
+							message = this.getNodeParameter('message', i) as string;
+						}
+						client.publish(topic, message, options);
+					} catch (e) {
+						reject(e);
+					}
+				}
+				//wait for the in-flight messages to be acked.
+				//needed for messages with QoS 1 & 2
+				client.end(false, {}, () => {
+					resolve([items]);
+				});
+
+				client.on('error', (e: string | undefined) => {
+					reject(e);
+				});
+			});
+		});
+
+		return data as INodeExecutionData[][];
+	}
+}