feat: added i18n support; added Simplified Chinese support

src/i18n/locale.ts

@@ -0,0 +1,40 @@
+import type { LanguageSetting, ResolvedLocaleCode } from './types';
+
+const CHINESE_LANGUAGE_PREFIX = 'zh';
+const DEFAULT_LOCALE: ResolvedLocaleCode = 'en_us';
+
+export function normalizeLanguageSetting(value: unknown): LanguageSetting {
+  return value === 'zh_cn' || value === 'en_us' || value === 'auto' ? value : 'auto';
+}
+
+export function getBrowserLocales(): string[] {
+  if (typeof navigator === 'undefined') {
+    return [];
+  }
+
+  if (Array.isArray(navigator.languages) && navigator.languages.length > 0) {
+    return navigator.languages.filter((value): value is string => typeof value === 'string' && value.length > 0);
+  }
+
+  return typeof navigator.language === 'string' && navigator.language.length > 0
+    ? [navigator.language]
+    : [];
+}
+
+export function resolveLanguageSetting(
+  setting: LanguageSetting,
+  browserLocales: string[] = getBrowserLocales(),
+): ResolvedLocaleCode {
+  if (setting === 'en_us' || setting === 'zh_cn') {
+    return setting;
+  }
+
+  for (const locale of browserLocales) {
+    const normalizedLocale = locale.trim().toLowerCase();
+    if (normalizedLocale === CHINESE_LANGUAGE_PREFIX || normalizedLocale.startsWith(`${CHINESE_LANGUAGE_PREFIX}-`)) {
+      return 'zh_cn';
+    }
+  }
+
+  return DEFAULT_LOCALE;
+}