function localeFor(lang: string): string {
  if (lang === "zh-TW") return "zh-TW";
  if (lang === "zh-CN") return "zh-CN";
  return "en-US";
}

function formatDate(iso: string, lang: string): string {
  const d = new Date(iso);
  return new Intl.DateTimeFormat(localeFor(lang), {
    year: "numeric",
    month: lang === "en" ? "short" : "numeric",
    day: "numeric",
  }).format(d);
}

export function formatTime(iso: string, lang: string): string {
  const d = new Date(iso);
  return new Intl.DateTimeFormat(localeFor(lang), {
    hour: "numeric",
    minute: "2-digit",
    hour12: lang === "en",
  }).format(d);
}

export function formatDateTime(iso: string, lang: string): string {
  return `${formatDate(iso, lang)} ${formatTime(iso, lang)}`;
}