初步集成next-intl支持多语言

src/lib/i18n.ts

@@ -0,0 +1,84 @@
+import type { AppLocale, SystemLanguageSettings } from "@/lib/types"
+
+export const APP_LOCALES: readonly AppLocale[] = ["en", "zh_cn", "zh_tw"]
+const FALLBACK_APP_LOCALE: AppLocale = "en"
+
+export const DEFAULT_LANGUAGE_SETTINGS: SystemLanguageSettings = {
+  mode: "system",
+  language: FALLBACK_APP_LOCALE,
+}
+
+export const APP_LOCALE_TO_INTL_LOCALE: Record<AppLocale, string> = {
+  en: "en",
+  zh_cn: "zh-CN",
+  zh_tw: "zh-TW",
+}
+
+export function isAppLocale(value: unknown): value is AppLocale {
+  return APP_LOCALES.includes(value as AppLocale)
+}
+
+export function normalizeLanguageSettings(
+  settings: Partial<SystemLanguageSettings> | null | undefined
+): SystemLanguageSettings {
+  const mode = settings?.mode === "manual" ? "manual" : "system"
+  const language = isAppLocale(settings?.language)
+    ? settings.language
+    : FALLBACK_APP_LOCALE
+
+  return {
+    mode,
+    language,
+  }
+}
+
+function mapSystemLocaleToAppLocale(localeTag: string): AppLocale | null {
+  const normalized = localeTag.trim().toLowerCase().replace(/_/g, "-")
+
+  if (!normalized) return null
+  if (normalized.startsWith("en")) return "en"
+
+  if (
+    normalized.startsWith("zh-hant") ||
+    normalized.endsWith("-tw") ||
+    normalized.endsWith("-hk") ||
+    normalized.endsWith("-mo")
+  ) {
+    return "zh_tw"
+  }
+
+  if (normalized.startsWith("zh")) return "zh_cn"
+
+  return null
+}
+
+export function getSystemLocaleCandidates(): string[] {
+  if (typeof navigator === "undefined") return []
+
+  const candidates = [
+    ...(navigator.languages ?? []),
+    navigator.language,
+  ].filter((value): value is string => Boolean(value))
+
+  return [...new Set(candidates)]
+}
+
+export function resolveSystemLocale(candidates: string[]): AppLocale | null {
+  for (const candidate of candidates) {
+    const resolved = mapSystemLocaleToAppLocale(candidate)
+    if (resolved) return resolved
+  }
+
+  return null
+}
+
+export function resolveAppLocale(
+  settings: SystemLanguageSettings,
+  systemLocaleCandidates: string[]
+): AppLocale {
+  if (settings.mode === "manual") {
+    return settings.language
+  }
+
+  return resolveSystemLocale(systemLocaleCandidates) ?? FALLBACK_APP_LOCALE
+}