Function debounce

src/settings/components/settingHelpers.ts:420–461

(
	func: T,
	wait: number,
	immediate = false
)

 * Returns a debounced function with a flush() method to immediately execute pending calls
 */
export function debounce<T extends (...args: never[]) => unknown>(
	func: T,
	wait: number,
	immediate = false
): DebouncedFunction<T> {
	let timeout: number | undefined;
	let lastArgs: Parameters<T> | undefined;
	let lastThis: unknown;

	const debounced = function (this: unknown, ...args: Parameters<T>) {
		lastArgs = args;
		// eslint-disable-next-line @typescript-eslint/no-this-alias -- Debounce preserves the caller's this binding for later invocation.
		lastThis = this;

		const later = () => {
			timeout = undefined;
			lastArgs = undefined;
			if (!immediate) {
				func.apply(lastThis, args);
			}
		};

		const callNow = immediate && !timeout;
		window.clearTimeout(timeout);
		timeout = window.setTimeout(later, wait);

		if (callNow) {
			func.apply(this, args);
		}
	} as DebouncedFunction<T>;

	debounced.flush = () => {
		if (timeout && lastArgs) {
			window.clearTimeout(timeout);
			timeout = undefined;
			func.apply(lastThis, lastArgs);
			lastArgs = undefined;
		}
	};

	return debounced;
}