src/hooks/useTimer.ts

import { useState, useRef } from "react";

export function useTimer() {
  const [seconds, setSeconds] = useState(0);
  const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null);

  function startTimer() {
    setSeconds(0);
    intervalRef.current = setInterval(() => {
      setSeconds((prev) => prev + 1);
    }, 1000);
  }

  function stopTimer() {
    if (intervalRef.current) {
      clearInterval(intervalRef.current);
    }
    setSeconds(0);
  }

  function formatTime(seconds: number) {
    const hrs = Math.floor(seconds / 3600);
    const mins = Math.floor((seconds % 3600) / 60);
    const secs = seconds % 60;
    return `${String(hrs).padStart(2, "0")}:${String(mins).padStart(2, "0")}:${String(secs).padStart(2, "0")}`;
  }

  return { timer: formatTime(seconds), startTimer, stopTimer };
}