firebaseAuth.js

import { Platform } from 'react-native';
import { getApp } from '@react-native-firebase/app';
import {
  getAuth,
  signInWithCredential,
  signOut,
  getIdToken,
  GoogleAuthProvider,
  OAuthProvider,
} from '@react-native-firebase/auth';
import { GoogleSignin } from '@react-native-google-signin/google-signin';
import {
  appleAuth,
  appleAuthAndroid,
} from '@invertase/react-native-apple-authentication';

// Replace these three constants with values from your own Firebase / Apple
// Developer / Google Cloud console before running on a real device.
//   APPLE_SERVICES_ID     — Apple "Services ID" used for Sign in with Apple
//                           on Android (`com.your.app.signin`).
//   APPLE_REDIRECT_URI    — Firebase Auth handler URL for your project,
//                           shape: `https://<firebase-project-id>.firebaseapp.com/__/auth/handler`.
//   GOOGLE_WEB_CLIENT_ID  — OAuth 2.0 Web client id from Google Cloud
//                           console (Firebase auto-creates one).
const APPLE_SERVICES_ID = 'REPLACE_WITH_APPLE_SERVICES_ID';
const APPLE_REDIRECT_URI =
  'https://your-firebase-project-id.firebaseapp.com/__/auth/handler';
const GOOGLE_WEB_CLIENT_ID = 'REPLACE_WITH_GOOGLE_WEB_CLIENT_ID';

const randomNonce = () => {
  let s = '';
  for (let i = 0; i < 32; i++) s += Math.floor(Math.random() * 16).toString(16);
  return s;
};

const auth = () => getAuth(getApp());

/**
 * Sign in with Google → Firebase credential → Firebase ID token.
 * @returns {Promise<{firebaseIdToken: string, appleRefreshToken: null}>}
 */
export const signInWithGoogle = async () => {
  GoogleSignin.configure({ webClientId: GOOGLE_WEB_CLIENT_ID });
  await GoogleSignin.hasPlayServices({ showPlayServicesUpdateDialog: true });
  const result = await GoogleSignin.signIn();
  const idToken = result?.idToken ?? result?.data?.idToken;
  if (!idToken) throw new Error('Google Sign-In returned no ID token');
  const cred = GoogleAuthProvider.credential(idToken);
  const { user } = await signInWithCredential(auth(), cred);
  const firebaseIdToken = await getIdToken(user);
  return { firebaseIdToken, appleRefreshToken: null };
};

/**
 * Sign in with Apple → Firebase credential → Firebase ID token.
 * On iOS: native Apple sheet. On Android: web-based OAuth via Services ID.
 * @returns {Promise<{firebaseIdToken: string, appleRefreshToken: string|null}>}
 */
export const signInWithApple = async () => {
  if (Platform.OS === 'ios') {
    const res = await appleAuth.performRequest({
      requestedOperation: appleAuth.Operation.LOGIN,
      requestedScopes: [appleAuth.Scope.EMAIL, appleAuth.Scope.FULL_NAME],
    });
    if (!res.identityToken)
      throw new Error('Apple Sign-In returned no identity token');
    const provider = new OAuthProvider('apple.com');
    const cred = provider.credential({
      rawNonce: res.nonce,
      idToken: res.identityToken,
    });
    const { user } = await signInWithCredential(auth(), cred);
    return {
      firebaseIdToken: await getIdToken(user),
      appleRefreshToken: res.authorizationCode ?? null,
    };
  }

  if (Platform.OS === 'android') {
    appleAuthAndroid.configure({
      nonce: randomNonce(),
      clientId: APPLE_SERVICES_ID,
      redirectUri: APPLE_REDIRECT_URI,
      scope: appleAuthAndroid.Scope.ALL,
      responseType: appleAuthAndroid.ResponseType.ALL,
    });
    const res = await appleAuthAndroid.signIn();
    if (!res.id_token)
      throw new Error('Apple Sign-In (Android) returned no ID token');
    const provider = new OAuthProvider('apple.com');
    const cred = provider.credential({
      rawNonce: res.nonce,
      idToken: res.id_token,
    });
    const { user } = await signInWithCredential(auth(), cred);
    return {
      firebaseIdToken: await getIdToken(user),
      appleRefreshToken: res.code ?? null,
    };
  }

  throw new Error('Apple Sign-In not supported on this platform');
};

/**
 * Sign out of Firebase + Google. Apple has no client-side sign-out — token
 * revocation happens server-side during account deletion.
 */
export const signOutFirebase = async () => {
  try {
    await signOut(auth());
  } catch {}
  try {
    await GoogleSignin.signOut();
  } catch {}
};