/**
 * Human-readable relative time for activity feeds (e.g. "2m ago").
 */
export function formatRelativeTime(isoString) {
  if (!isoString) return '';
  const then = new Date(isoString).getTime();
  if (Number.isNaN(then)) return '';

  const diffMs = Date.now() - then;
  if (diffMs < 0) return 'Just now';

  const mins = Math.floor(diffMs / 60000);
  if (mins < 1) return 'Just now';
  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(isoString).toLocaleDateString(undefined, {
    month: 'short',
    day: 'numeric',
  });
}