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packages/@n8n/utils/src/event-queue.ts

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+/**
+ * Create an event queue that processes events sequentially.
+ *
+ * @param processEvent - Async function that processes a single event.
+ * @returns A function that enqueues events for processing.
+ */
+export function createEventQueue<T>(processEvent: (event: T) => Promise<void>) {
+	// The internal queue holding events.
+	const queue: T[] = [];
+
+	// Flag to indicate whether an event is currently being processed.
+	let processing = false;
+
+	/**
+	 * Process the next event in the queue (if not already processing).
+	 */
+	async function processNext(): Promise<void> {
+		if (processing || queue.length === 0) {
+			return;
+		}
+
+		processing = true;
+		const currentEvent = queue.shift();
+
+		if (currentEvent !== undefined) {
+			try {
+				await processEvent(currentEvent);
+			} catch (error) {
+				console.error('Error processing event:', error);
+			}
+		}
+
+		processing = false;
+
+		// Recursively process the next event.
+		await processNext();
+	}
+
+	/**
+	 * Enqueue an event and trigger processing.
+	 *
+	 * @param event - The event to enqueue.
+	 */
+	function enqueue(event: T): void {
+		queue.push(event);
+		void processNext();
+	}
+
+	return { enqueue };
+}