import {
  createContext,
  useContext,
  useState,
  useCallback,
  useMemo,
  useEffect,
  type ReactNode,
} from "react";
import { login as loginApi, getMe } from "../services/authApi";

// ============================================================
// 类型
// ============================================================

export interface UserInfo {
  id: string;
  username: string;
  display_name: string;
  role: string;
}

interface AuthState {
  user: UserInfo | null;
  token: string | null;
  loading: boolean; // 初始化时检查 token
}

interface AuthContextValue extends AuthState {
  login: (username: string, password: string) => Promise<void>;
  logout: () => void;
  isAuthenticated: boolean;
}

// ============================================================
// Token 存储 key
// ============================================================

const TOKEN_KEY = "track_admin_token";
const USER_KEY = "track_admin_user";

// ============================================================
// Context
// ============================================================

const AuthContext = createContext<AuthContextValue | null>(null);

export function useAuth() {
  const ctx = useContext(AuthContext);
  if (!ctx) throw new Error("useAuth 必须在 AuthProvider 内使用");
  return ctx;
}

// ============================================================
// Provider
// ============================================================

export function AuthProvider({ children }: { children: ReactNode }) {
  const [state, setState] = useState<AuthState>({
    user: null,
    token: null,
    loading: true,
  });

  // 初始化：从 localStorage 恢复 token
  useEffect(() => {
    const savedToken = localStorage.getItem(TOKEN_KEY);
    const savedUser = localStorage.getItem(USER_KEY);
    if (savedToken && savedUser) {
      try {
        const user = JSON.parse(savedUser) as UserInfo;
        setState({ user, token: savedToken, loading: false });
        // 可选：后端验证 token 是否仍有效
        getMe(savedToken)
          .then((fresh) => {
            setState((prev) => ({ ...prev, user: fresh }));
            localStorage.setItem(USER_KEY, JSON.stringify(fresh));
          })
          .catch(() => {
            // token 过期，清除
            logoutInternal();
          });
      } catch {
        logoutInternal();
      }
    } else {
      setState((prev) => ({ ...prev, loading: false }));
    }
  }, []);

  function logoutInternal() {
    localStorage.removeItem(TOKEN_KEY);
    localStorage.removeItem(USER_KEY);
    setState({ user: null, token: null, loading: false });
  }

  const login = useCallback(async (username: string, password: string) => {
    const result = await loginApi(username, password);
    const token = result.access_token;
    const user: UserInfo = result.user;

    localStorage.setItem(TOKEN_KEY, token);
    localStorage.setItem(USER_KEY, JSON.stringify(user));
    setState({ user, token, loading: false });
  }, []);

  const logout = useCallback(() => {
    logoutInternal();
  }, []);

  // 🚀 稳定 Context value 引用，避免消费者不必要的 re-render
  const ctxValue = useMemo<AuthContextValue>(
    () => ({
      ...state,
      login,
      logout,
      isAuthenticated: !!state.token && !!state.user,
    }),
    [state, login, logout],
  );

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