const FALLBACK_TZ = "Asia/Tehran";

const TZ_ALIASES: Record<string, string> = {
  "Asia/Esfahan": FALLBACK_TZ,
  "Asia/Isfahan": FALLBACK_TZ,
  "Asia/Mashhad": FALLBACK_TZ,
  "Asia/Shiraz": FALLBACK_TZ,
  "Asia/Tabriz": FALLBACK_TZ,
  Iran: FALLBACK_TZ,
};

export function resolveTimezone(input?: string | null): string {
  const raw = (input || FALLBACK_TZ).trim() || FALLBACK_TZ;
  const candidate = TZ_ALIASES[raw] || raw;
  try {
    Intl.DateTimeFormat("en-US", { timeZone: candidate });
    return candidate;
  } catch {
    return FALLBACK_TZ;
  }
}

export function formatClock(date: Date, timezone?: string | null, locale = "fa-IR") {
  const tz = resolveTimezone(timezone);
  return new Intl.DateTimeFormat(locale, {
    timeZone: tz,
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
    hour12: false,
  }).format(date);
}