feat: Implement the PolyWeather dashboard including frontend components, data collection, analysis, and API endpoints.

frontend/hooks/useI18n.tsx

@@ -0,0 +1,57 @@
+"use client";
+
+import { createContext, useContext, useEffect, useMemo, useState } from "react";
+import {
+  formatMessage,
+  getInitialLocaleFromNavigator,
+  Locale,
+  LOCALE_STORAGE_KEY,
+  normalizeLocale,
+} from "@/lib/i18n";
+
+interface I18nContextValue {
+  locale: Locale;
+  setLocale: (locale: Locale) => void;
+  toggleLocale: () => void;
+  t: (key: string, params?: Record<string, string | number>) => string;
+}
+
+const I18nContext = createContext<I18nContextValue | null>(null);
+
+export function I18nProvider({ children }: { children: React.ReactNode }) {
+  const [locale, setLocale] = useState<Locale>(() => {
+    if (typeof window === "undefined") {
+      return "zh-CN";
+    }
+    const stored = window.localStorage.getItem(LOCALE_STORAGE_KEY);
+    return stored ? normalizeLocale(stored) : getInitialLocaleFromNavigator();
+  });
+
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+    window.localStorage.setItem(LOCALE_STORAGE_KEY, locale);
+    document.documentElement.lang = locale;
+  }, [locale]);
+
+  const value = useMemo<I18nContextValue>(
+    () => ({
+      locale,
+      setLocale,
+      t: (key, params) => formatMessage(locale, key, params),
+      toggleLocale: () => {
+        setLocale((current) => (current === "zh-CN" ? "en-US" : "zh-CN"));
+      },
+    }),
+    [locale],
+  );
+
+  return <I18nContext.Provider value={value}>{children}</I18nContext.Provider>;
+}
+
+export function useI18n() {
+  const context = useContext(I18nContext);
+  if (!context) {
+    throw new Error("useI18n must be used within I18nProvider");
+  }
+  return context;
+}