export function timeAgo(iso: string): string {
  const s = Math.max(0, (Date.now() - new Date(iso).getTime()) / 1000);
  if (s < 60) return 'just now';
  if (s < 3600) return `${Math.floor(s / 60)}m ago`;
  if (s < 86400) return `${Math.floor(s / 3600)}h ago`;
  return `${Math.floor(s / 86400)}d ago`;
}

/** "until 5:30 PM", "until tomorrow 1:00 AM", or "until you turn it back on" for an indefinite pause. */
export function pausedUntilLabel(iso: string, now = new Date()): string {
  const until = new Date(iso);
  if (until.getTime() - now.getTime() > 30 * 86_400_000) return 'until you turn it back on';
  const time = until.toLocaleTimeString([], { hour: 'numeric', minute: '2-digit' });
  return until.toDateString() === now.toDateString() ? `until ${time}` : `until tomorrow ${time}`;
}