// Time formatting helpers. Relative for at-a-glance scanning, absolute (mono)
// for the precise value on hover.

const UNITS: [Intl.RelativeTimeFormatUnit, number][] = [
  ["year", 60 * 60 * 24 * 365],
  ["month", 60 * 60 * 24 * 30],
  ["day", 60 * 60 * 24],
  ["hour", 60 * 60],
  ["minute", 60],
  ["second", 1],
];

const rtf = new Intl.RelativeTimeFormat(undefined, { numeric: "auto" });

/**
 * Human relative time, e.g. "3 minutes ago" / "in 2 days". Returns "—" for
 * missing input and "just now" for sub-10-second deltas.
 */
export function relativeTime(iso: string | null | undefined): string {
  if (!iso) return "—";
  const then = new Date(iso).getTime();
  if (Number.isNaN(then)) return "—";

  const deltaSec = Math.round((then - Date.now()) / 1000);
  const abs = Math.abs(deltaSec);
  if (abs < 10) return "just now";

  for (const [unit, secs] of UNITS) {
    if (abs >= secs || unit === "second") {
      return rtf.format(Math.round(deltaSec / secs), unit);
    }
  }
  return "just now";
}

/** Absolute local timestamp for tooltips / mono display. */
export function absoluteTime(iso: string | null | undefined): string {
  if (!iso) return "—";
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return "—";
  return d.toLocaleString(undefined, {
    year: "numeric",
    month: "short",
    day: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
  });
}

/** Format a duration in seconds as a compact "1h 04m" / "47s" string. */
export function formatDuration(secs: number | null | undefined): string {
  if (secs == null || secs < 0) return "—";
  const h = Math.floor(secs / 3600);
  const m = Math.floor((secs % 3600) / 60);
  const s = secs % 60;
  if (h > 0) return `${h}h ${String(m).padStart(2, "0")}m`;
  if (m > 0) return `${m}m ${String(s).padStart(2, "0")}s`;
  return `${s}s`;
}