export function formatDate(yyyymmdd: string): string {
  if (!/^\d{8}$/.test(yyyymmdd)) return yyyymmdd;
  return `${yyyymmdd.slice(0, 4)}-${yyyymmdd.slice(4, 6)}-${yyyymmdd.slice(6, 8)}`;
}

// Whole days between an upload date ("YYYYMMDD") and now. Returns null on a
// missing/malformed date. Used to flag VODs past their platform's retention
// window (see vodExpiry). Interpreted as UTC midnight to match yt-dlp's
// upload_date (a date, not a timestamp).
export function daysSince(yyyymmdd: string | undefined | null): number | null {
  if (!yyyymmdd || !/^\d{8}$/.test(yyyymmdd)) return null;
  const y = Number(yyyymmdd.slice(0, 4));
  const m = Number(yyyymmdd.slice(4, 6));
  const d = Number(yyyymmdd.slice(6, 8));
  const then = Date.UTC(y, m - 1, d);
  if (Number.isNaN(then)) return null;
  return Math.floor((Date.now() - then) / 86_400_000);
}

export function formatBytes(bytes: number): string {
  if (!Number.isFinite(bytes)) return "∞";
  if (bytes < 1024) return `${bytes} B`;
  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
  if (bytes < 1024 * 1024 * 1024)
    return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
  return `${(bytes / (1024 * 1024 * 1024)).toFixed(2)} GB`;
}

export function formatDuration(seconds: number): string {
  if (!seconds) return "";
  const h = Math.floor(seconds / 3600);
  const m = Math.floor((seconds % 3600) / 60);
  const s = Math.floor(seconds % 60);
  const mm = String(m).padStart(2, "0");
  const ss = String(s).padStart(2, "0");
  return h > 0 ? `${h}:${mm}:${ss}` : `${m}:${ss}`;
}