"use client";

import {
  createContext,
  useContext,
  useCallback,
  type ReactNode,
} from "react";

export type Locale = "zh" | "en";

const LOCALES: Locale[] = ["zh", "en"];
const DEFAULT_LOCALE: Locale = "zh";

type Messages = Record<string, unknown>;

type LocaleContextValue = {
  locale: Locale;
  messages: Messages;
  t: (key: string) => string;
  setLocale: (locale: Locale) => void;
};

const LocaleContext = createContext<LocaleContextValue | null>(null);

function getNested(obj: unknown, path: string): string | undefined {
  const keys = path.split(".");
  let current: unknown = obj;
  for (const key of keys) {
    if (current == null || typeof current !== "object") return undefined;
    current = (current as Record<string, unknown>)[key];
  }
  return typeof current === "string" ? current : undefined;
}

export function LocaleProvider({
  locale,
  messages,
  children,
}: {
  locale: Locale;
  messages: Messages;
  children: ReactNode;
}) {
  const t = useCallback(
    (key: string) => {
      const value = getNested(messages, key);
      return value ?? key;
    },
    [messages]
  );

  const setLocale = useCallback((newLocale: Locale) => {
    const path = window.location.pathname;
    const newPath = path.replace(/^\/(zh|en)/, `/${newLocale}`);
    void import("@/app/lib/navigation-loading").then(({ startNavigation }) => {
      startNavigation();
      window.location.href = newPath || `/${newLocale}/digital`;
    });
  }, []);

  const value: LocaleContextValue = {
    locale,
    messages,
    t,
    setLocale,
  };

  return (
    <LocaleContext.Provider value={value}>{children}</LocaleContext.Provider>
  );
}

export function useLocale() {
  const ctx = useContext(LocaleContext);
  if (!ctx) throw new Error("useLocale must be used within LocaleProvider");
  return ctx.locale;
}

export function useTranslation(namespace?: string) {
  const ctx = useContext(LocaleContext);
  if (!ctx) throw new Error("useTranslation must be used within LocaleProvider");
  return {
    t: (key: string) => {
      const fullKey = namespace ? `${namespace}.${key}` : key;
      return ctx.t(fullKey);
    },
  };
}

export function useLocaleRouter() {
  const locale = useLocale();
  return {
    replace: (pathname: string, opts?: { locale?: Locale }) => {
      const newLocale = opts?.locale ?? locale;
      const cleanPath = pathname.replace(/^\/(zh|en)/, "") || "/";
      const digitalPath = cleanPath.startsWith("/digital")
        ? cleanPath
        : `/digital${cleanPath === "/" ? "" : cleanPath}`;
      const newPath = `/${newLocale}${digitalPath}`;
      void import("@/app/lib/navigation-loading").then(({ startNavigation }) => {
        startNavigation();
        window.location.href = newPath;
      });
    },
  };
}

export { LOCALES, DEFAULT_LOCALE };