/** 内容翻译 fallback：当前语言 → 英文 → 中文 */
export function resolveTranslationFallback(
  map: Record<string, string | undefined | null>,
  locale: string,
): string {
  const chain = [locale, 'en-US', 'zh-CN'];
  const seen = new Set<string>();
  for (const loc of chain) {
    if (seen.has(loc)) continue;
    seen.add(loc);
    const v = map[loc];
    if (v != null && String(v).trim() !== '') return String(v).trim();
  }
  for (const v of Object.values(map)) {
    if (v != null && String(v).trim() !== '') return String(v).trim();
  }
  return '';
}

/** 前台语言显示名（PRD 3.1） */
export const LOCALE_UI_LABELS: Record<string, string> = {
  'zh-CN': '中文',
  'ms-MY': 'Bahasa Melayu',
  'en-US': 'English',
};

/** vue-i18n 缺 key 时：en-US → zh-CN */
export const VUE_I18N_FALLBACK_LOCALES = ['en-US', 'zh-CN'] as const;