// Lightweight date/time helpers — shared across server components so we
// don't reinvent toLocaleString conventions per page.

export function formatRelative(iso: string, now: number = Date.now()): string {
  const t = new Date(iso).getTime();
  if (Number.isNaN(t)) return iso;
  const diff = t - now;
  const abs = Math.abs(diff);
  const ago = diff < 0;
  const units: [string, number][] = [
    ["second", 1000],
    ["minute", 60 * 1000],
    ["hour", 3600 * 1000],
    ["day", 24 * 3600 * 1000],
    ["week", 7 * 24 * 3600 * 1000],
    ["month", 30 * 24 * 3600 * 1000],
    ["year", 365 * 24 * 3600 * 1000],
  ];
  let unit = "second";
  let n = Math.round(abs / 1000);
  for (let i = units.length - 1; i >= 0; i--) {
    if (abs >= units[i][1]) {
      unit = units[i][0];
      n = Math.round(abs / units[i][1]);
      break;
    }
  }
  const suffix = n === 1 ? unit : `${unit}s`;
  return ago ? `${n} ${suffix} ago` : `in ${n} ${suffix}`;
}

export function formatDateTime(iso: string): string {
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return iso;
  // YYYY-MM-DD HH:MM:SS — locale-stable, sortable, no surprises.
  const pad = (n: number) => String(n).padStart(2, "0");
  return (
    d.getUTCFullYear() +
    "-" +
    pad(d.getUTCMonth() + 1) +
    "-" +
    pad(d.getUTCDate()) +
    " " +
    pad(d.getUTCHours()) +
    ":" +
    pad(d.getUTCMinutes()) +
    ":" +
    pad(d.getUTCSeconds()) +
    " UTC"
  );
}

export function truncate(s: string, max = 40): string {
  if (s.length <= max) return s;
  return s.slice(0, max - 1) + "…";
}