/**
 * throttle limits the number of times a function can be called to a
 * given threshhold (100ms by default). The function is always called
 * on the leading and trailing edge.
 */

type Arguments = ReadonlyArray<Event | string | number | boolean | null>;
export type ThrottleReturn = {
  (...args: Arguments): void;
  clearTimeout: () => void;
};

export default function throttle(
  fn: (...args: Arguments) => void,
  threshhold: number = 100,
): ThrottleReturn {
  let last: number | undefined;
  let deferTimer: number | undefined;
  const throttled = (...args: Arguments) => {
    const now = Date.now();
    if (last !== undefined && now - last < threshhold) {
      clearTimeout(deferTimer);
      // @ts-expect-error - TS2322 - Type 'Timeout' is not assignable to type 'number'.
      deferTimer = setTimeout(() => {
        last = now;
        fn(...args);
      }, threshhold - (now - (last ?? 0)));
    } else {
      last = now;
      fn(...args);
    }
  };

  throttled.clearTimeout = () => {
    if (deferTimer) {
      clearTimeout(deferTimer);
    }
  };

  return throttled;
}