upstream-rocketchat/apps/meteor/lib/utils/highOrderFunctions.ts

export const withThrottling =
	({ wait, leading, trailing }: { wait: number; leading?: boolean; trailing?: boolean }) =>
	<TFunction extends (...args: any[]) => any>(fn: TFunction) => {
		let timer: ReturnType<typeof setTimeout> | undefined = undefined;
		let result: ReturnType<TFunction>;
		let previous = 0;

		function throttled(this: ThisParameterType<TFunction>, ...args: Parameters<TFunction>) {
			const now = Date.now();
			if (!previous && leading === false) previous = now;
			const remaining = wait - (now - previous);

			if (remaining <= 0 || remaining > wait) {
				if (timer) clearTimeout(timer);
				timer = undefined;
				previous = now;
				result = fn.apply(this, args);
			} else if (!timer && trailing !== false) {
				const later = () => {
					previous = leading === false ? 0 : Date.now();
					result = fn.apply(this, args);
					timer = undefined;
				};
				timer = setTimeout(later, remaining);
			}
			return result;
		}

		const cancel = () => {
			if (timer) clearTimeout(timer);
			previous = 0;
			timer = undefined;
		};

		return Object.assign(throttled, { cancel });
	};

export const withDebouncing =
	({ wait, immediate }: { wait: number; immediate?: boolean }) =>
	<TFunction extends (...args: any[]) => any>(fn: TFunction) => {
		let timer: ReturnType<typeof setTimeout> | undefined = undefined;
		let result: ReturnType<TFunction>;
		let previous: number;

		function debounced(this: ThisParameterType<TFunction>, ...args: Parameters<TFunction>) {
			previous = Date.now();
			if (!timer) {
				const later = () => {
					const passed = Date.now() - previous;
					if (wait > passed) {
						timer = setTimeout(later, wait - passed);
					} else {
						timer = undefined;
						if (!immediate) result = fn.apply(this, args);
					}
				};
				timer = setTimeout(later, wait);
				if (immediate) result = fn.apply(this, args);
			}
			return result;
		}

		const cancel = () => {
			clearTimeout(timer);
			timer = undefined;
		};

		return Object.assign(debounced, { cancel });
	};