useCountdown Hook

import { useState, useRef, useCallback } from 'react';

export function useCountdown(initialSeconds: number) {
  const [remaining, setRemaining] = useState(initialSeconds);
  const [isRunning, setIsRunning] = useState(false);
  const intervalRef = useRef<ReturnType<typeof setInterval>>();

  const start = useCallback(() => {
    if (isRunning || remaining <= 0) return;
    setIsRunning(true);
    intervalRef.current = setInterval(() => {
      setRemaining(prev => {
        if (prev <= 1) {
          clearInterval(intervalRef.current);
          setIsRunning(false);
          return 0;
        }
        return prev - 1;
      });
    }, 1000);
  }, [isRunning, remaining]);

  const pause = useCallback(() => {
    clearInterval(intervalRef.current);
    setIsRunning(false);
  }, []);

  const reset = useCallback(() => {
    clearInterval(intervalRef.current);
    setIsRunning(false);
    setRemaining(initialSeconds);
  }, [initialSeconds]);

  const minutes = Math.floor(remaining / 60);
  const seconds = remaining % 60;
  const formatted = `${String(minutes).padStart(2, '0')}:${String(seconds).padStart(2, '0')}`;

  return { remaining, formatted, isRunning, start, pause, reset };
}