// Who is signed in. Checks the session on startup and exposes signIn/logout so
// every sign-in path (startup, login form, 2FA) runs the same follow-up work.
import { useEffect, useRef, useState } from 'react';
import { getCurrentUser, logoutUser } from '../syncService.js';

// onSignIn(user) runs right after a user becomes signed in (switch local
// storage to their account, load their data). onSignOut() runs after logout.
export function useAuth({ onSignIn, onSignOut }) {
  // authUser: undefined = still checking · null = signed out · object = signed in
  const [authUser, setAuthUser] = useState(undefined);
  const [authServerDown, setAuthServerDown] = useState(false);

  // Callbacks come from App and close over its latest state; read them through
  // a ref so signIn/logout never call a stale copy.
  const callbacksRef = useRef({ onSignIn, onSignOut });
  callbacksRef.current = { onSignIn, onSignOut };

  const signIn = (user) => {
    setAuthUser(user);
    callbacksRef.current.onSignIn(user);
  };

  const logout = async () => {
    await logoutUser();
    setAuthUser(null);
    callbacksRef.current.onSignOut();
  };

  useEffect(() => {
    getCurrentUser().then((result) => {
      if (result.ok) {
        if (result.user) signIn(result.user);
        else setAuthUser(null);
      } else {
        // Genuine network failure (server unreachable) — fall back to local-only mode.
        setAuthServerDown(true);
        setAuthUser(null);
      }
    });
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return { authUser, setAuthUser, authServerDown, signIn, logout };
}