first commit

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

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+import type { ISubscriptionMap } from 'mqtt';
+import type { QoS } from 'mqtt-packet';
+import type {
+	ITriggerFunctions,
+	IDataObject,
+	INodeType,
+	INodeTypeDescription,
+	ITriggerResponse,
+	IRun,
+} from 'n8n-workflow';
+import { NodeConnectionTypes, NodeOperationError } from 'n8n-workflow';
+
+import { createClient, type MqttCredential } from './GenericFunctions';
+
+interface Options {
+	jsonParseBody: boolean;
+	onlyMessage: boolean;
+	parallelProcessing: boolean;
+}
+
+export class MqttTrigger implements INodeType {
+	description: INodeTypeDescription = {
+		displayName: 'MQTT Trigger',
+		name: 'mqttTrigger',
+		icon: 'file:mqtt.svg',
+		group: ['trigger'],
+		version: 1,
+		description: 'Listens to MQTT events',
+		eventTriggerDescription: '',
+		defaults: {
+			name: 'MQTT Trigger',
+		},
+		triggerPanel: {
+			header: '',
+			executionsHelp: {
+				inactive:
+					"<b>While building your workflow</b>, click the 'execute step' button, then trigger an MQTT event. This will trigger an execution, which will show up in this editor.<br /> <br /><b>Once you're happy with your workflow</b>, publish it. Then every time a change is detected, the workflow will execute. These executions will show up in the <a data-key='executions'>executions list</a>, but not in the editor.",
+				active:
+					"<b>While building your workflow</b>, click the 'execute step' button, then trigger an MQTT event. This will trigger an execution, which will show up in this editor.<br /> <br /><b>Your workflow will also execute automatically</b>, since it's activated. Every time a change is detected, this node will trigger an execution. These executions will show up in the <a data-key='executions'>executions list</a>, but not in the editor.",
+			},
+			activationHint:
+				'Once you’ve finished building your workflow, publish it to have it also listen continuously (you just won’t see those executions here).',
+		},
+		inputs: [],
+		outputs: [NodeConnectionTypes.Main],
+		credentials: [
+			{
+				name: 'mqtt',
+				required: true,
+			},
+		],
+		properties: [
+			{
+				displayName: 'Topics',
+				name: 'topics',
+				type: 'string',
+				default: '',
+				description:
+					'Topics to subscribe to, multiple can be defined with comma. Wildcard characters are supported (+ - for single level and # - for multi level). By default all subscription used QoS=0. To set a different QoS, write the QoS desired after the topic preceded by a colom. For Example: topicA:1,topicB:2',
+			},
+			{
+				displayName: 'Options',
+				name: 'options',
+				type: 'collection',
+				placeholder: 'Add option',
+				default: {},
+				options: [
+					{
+						displayName: 'JSON Parse Body',
+						name: 'jsonParseBody',
+						type: 'boolean',
+						default: false,
+						description: 'Whether to try parse the message to an object',
+					},
+					{
+						displayName: 'Only Message',
+						name: 'onlyMessage',
+						type: 'boolean',
+						default: false,
+						description: 'Whether to return only the message property',
+					},
+					{
+						displayName: 'Parallel Processing',
+						name: 'parallelProcessing',
+						type: 'boolean',
+						default: true,
+						description:
+							'Whether to process messages in parallel or by keeping the message in order',
+					},
+				],
+			},
+		],
+	};
+
+	async trigger(this: ITriggerFunctions): Promise<ITriggerResponse> {
+		const topics = (this.getNodeParameter('topics') as string).split(',');
+		if (!topics?.length) {
+			throw new NodeOperationError(this.getNode(), 'Topics are mandatory!');
+		}
+
+		const topicsQoS: ISubscriptionMap = {};
+		for (const data of topics) {
+			const [topic, qosString] = data.split(':');
+			let qos = qosString ? parseInt(qosString, 10) : 0;
+			if (qos < 0 || qos > 2) qos = 0;
+			topicsQoS[topic] = { qos: qos as QoS };
+		}
+
+		const options = this.getNodeParameter('options') as Options;
+		const credentials = await this.getCredentials<MqttCredential>('mqtt');
+		const client = await createClient(credentials);
+
+		const parsePayload = (topic: string, payload: Buffer) => {
+			let message = payload.toString();
+
+			if (options.jsonParseBody) {
+				try {
+					message = JSON.parse(message);
+				} catch (e) {}
+			}
+
+			let result: IDataObject = { message, topic };
+
+			if (options.onlyMessage) {
+				//@ts-ignore
+				result = [message];
+			}
+
+			return [this.helpers.returnJsonArray([result])];
+		};
+
+		const manualTriggerFunction = async () =>
+			await new Promise<void>(async (resolve) => {
+				client.once('message', (topic, payload) => {
+					this.emit(parsePayload(topic, payload));
+					resolve();
+				});
+				await client.subscribeAsync(topicsQoS);
+			});
+
+		if (this.getMode() === 'trigger') {
+			const donePromise = !options.parallelProcessing
+				? this.helpers.createDeferredPromise<IRun>()
+				: undefined;
+			client.on('message', async (topic, payload) => {
+				this.emit(parsePayload(topic, payload), undefined, donePromise);
+				await donePromise?.promise;
+			});
+			await client.subscribeAsync(topicsQoS);
+		}
+
+		async function closeFunction() {
+			await client.endAsync();
+		}
+
+		return {
+			closeFunction,
+			manualTriggerFunction,
+		};
+	}
+}