// Formats a non-negative number of seconds as `mm:ss` when under an hour,
// `h:mm:ss` otherwise. Negative values clamp to zero (callers shouldn't
// pass them, but the UI shouldn't crash if they do).
export function formatDuration(seconds: number): string {
  const total = Math.max(0, Math.floor(seconds));
  const h = Math.floor(total / 3600);
  const m = Math.floor((total % 3600) / 60);
  const s = total % 60;
  const ss = String(s).padStart(2, '0');
  if (h > 0) {
    const mm = String(m).padStart(2, '0');
    return `${h}:${mm}:${ss}`;
  }
  return `${m}:${ss}`;
}