// Relative-time formatting shared by the monitor widget and the dashboard
// cockpit, so their "5m ago" labels never drift.

// Compact relative label. `deltaMs = now - target`: positive is past ("5m
// ago"), negative is future ("in 5m"). Steps s → m → h → d.
export function relativeTime(deltaMs: number): string {
  const past = deltaMs >= 0;
  const s = Math.round(Math.abs(deltaMs) / 1000);
  const val =
    s < 60
      ? `${s}s`
      : s < 3600
        ? `${Math.round(s / 60)}m`
        : s < 86400
          ? `${Math.round(s / 3600)}h`
          : `${Math.round(s / 86400)}d`;
  return past ? `${val} ago` : `in ${val}`;
}

// Format an epoch-ms marker per an absolute/relative flag. Absolute is
// now-independent (locale string); relative depends on the live clock, so it
// returns null until `now` is set (post-mount) to avoid an SSR/hydration
// mismatch and a nonsensical "0s ago" flash. Callers render "…" for null.
export function fmtTime(
  ms: number,
  now: number | null,
  absolute: boolean,
): string | null {
  if (absolute) return new Date(ms).toLocaleString();
  if (now === null) return null;
  return relativeTime(now - ms);
}