Class Delayer

src/vs/base/common/async.ts:332–399

 * 		}
 */
export class Delayer<T> implements IDisposable {

	private deferred: IScheduledLater | null;
	private completionPromise: Promise<any> | null;
	private doResolve: ((value?: any | Promise<any>) => void) | null;
	private doReject: ((err: any) => void) | null;
	private task: ITask<T | Promise<T>> | null;

	constructor(public defaultDelay: number | typeof MicrotaskDelay) {
		this.deferred = null;
		this.completionPromise = null;
		this.doResolve = null;
		this.doReject = null;
		this.task = null;
	}

	trigger(task: ITask<T | Promise<T>>, delay = this.defaultDelay): Promise<T> {
		this.task = task;
		this.cancelTimeout();

		if (!this.completionPromise) {
			this.completionPromise = new Promise((resolve, reject) => {
				this.doResolve = resolve;
				this.doReject = reject;
			}).then(() => {
				this.completionPromise = null;
				this.doResolve = null;
				if (this.task) {
					const task = this.task;
					this.task = null;
					return task();
				}
				return undefined;
			});
		}

		const fn = () => {
			this.deferred = null;
			this.doResolve?.(null);
		};

		this.deferred = delay === MicrotaskDelay ? microtaskDeferred(fn) : timeoutDeferred(delay, fn);

		return this.completionPromise;
	}

	isTriggered(): boolean {
		return !!this.deferred?.isTriggered();
	}

	cancel(): void {
		this.cancelTimeout();

		if (this.completionPromise) {
			this.doReject?.(new CancellationError());
			this.completionPromise = null;
		}
	}