/**
 * Compact relative time ("just now", "5m ago", "3h ago", "2d ago"), falling
 * back to a locale date for anything older than a week. Shared across the
 * notification feed, the comments drawer, and anywhere else that shows a
 * timestamp tail.
 */
export function timeAgo(iso: string): string {
  const then = new Date(iso).getTime();
  if (Number.isNaN(then)) return "";
  const secs = Math.max(0, Math.floor((Date.now() - then) / 1000));
  if (secs < 45) return "just now";
  const mins = Math.floor(secs / 60);
  if (mins < 60) return `${mins}m ago`;
  const hours = Math.floor(mins / 60);
  if (hours < 24) return `${hours}h ago`;
  const days = Math.floor(hours / 24);
  if (days < 7) return `${days}d ago`;
  return new Date(iso).toLocaleDateString();
}