import { useEffect, useState } from "react";

/** Live elapsed seconds since `startedAt`, ticking every second. */
export function useRunningElapsed(startedAt?: string | Date | null) {
  const [elapsed, setElapsed] = useState(0);

  useEffect(() => {
    if (!startedAt) {
      setElapsed(0);
      return;
    }

    const startMs = new Date(startedAt).getTime();
    if (Number.isNaN(startMs)) {
      setElapsed(0);
      return;
    }

    const tick = () => {
      setElapsed(Math.max(0, Math.floor((Date.now() - startMs) / 1000)));
    };

    tick();
    const id = setInterval(tick, 1000);
    return () => clearInterval(id);
  }, [startedAt]);

  return elapsed;
}