// ABOUTME: Firebase SDK configuration and authentication utilities for React Native
// ABOUTME: Provides Google Sign-In via Firebase and expo-auth-session for the Pierre mobile app
import { initializeApp, type FirebaseApp } from 'firebase/app';
import {
getAuth,
onAuthStateChanged,
signOut,
GoogleAuthProvider,
signInWithCredential,
type Auth,
type User,
} from 'firebase/auth';
import * as Google from 'expo-auth-session/providers/google';
import * as WebBrowser from 'expo-web-browser';
import type { AuthSessionResult } from 'expo-auth-session';
import { Platform } from 'react-native';
// Complete any pending auth sessions on app load
WebBrowser.maybeCompleteAuthSession();
// Firebase configuration - all values from environment variables
// Set these in your .env file with EXPO_PUBLIC_ prefix
const firebaseConfig = {
apiKey: process.env.EXPO_PUBLIC_FIREBASE_API_KEY,
authDomain: process.env.EXPO_PUBLIC_FIREBASE_AUTH_DOMAIN,
projectId: process.env.EXPO_PUBLIC_FIREBASE_PROJECT_ID,
storageBucket: process.env.EXPO_PUBLIC_FIREBASE_STORAGE_BUCKET,
messagingSenderId: process.env.EXPO_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
appId: process.env.EXPO_PUBLIC_FIREBASE_APP_ID,
};
// Google OAuth client IDs - needed for expo-auth-session
const googleClientIds = {
iosClientId: process.env.EXPO_PUBLIC_GOOGLE_IOS_CLIENT_ID,
androidClientId: process.env.EXPO_PUBLIC_GOOGLE_ANDROID_CLIENT_ID,
webClientId: process.env.EXPO_PUBLIC_GOOGLE_WEB_CLIENT_ID,
};
// Check if Firebase is configured
const isFirebaseConfigured = Boolean(
firebaseConfig.apiKey &&
firebaseConfig.authDomain &&
firebaseConfig.projectId
);
// Check if Google OAuth is configured for the current platform
// iOS requires iosClientId, Android requires androidClientId, web uses webClientId
function isPlatformGoogleOAuthConfigured(): boolean {
if (Platform.OS === 'ios') {
return Boolean(googleClientIds.iosClientId);
}
if (Platform.OS === 'android') {
return Boolean(googleClientIds.androidClientId);
}
// Web/other platforms can use webClientId
return Boolean(googleClientIds.webClientId);
}
let app: FirebaseApp | null = null;
let auth: Auth | null = null;
/**
* Check if Firebase is properly configured via environment variables
* Returns true only if both Firebase and platform-specific Google OAuth are configured
*/
export function isFirebaseEnabled(): boolean {
return isFirebaseConfigured && isPlatformGoogleOAuthConfigured();
}
/**
* Initialize Firebase app (lazy initialization)
* Returns null if Firebase is not configured
*/
export function getFirebaseApp(): FirebaseApp | null {
if (!isFirebaseConfigured) {
return null;
}
if (!app) {
app = initializeApp(firebaseConfig);
}
return app;
}
/**
* Get Firebase Auth instance
* Returns null if Firebase is not configured
*/
export function getFirebaseAuth(): Auth | null {
if (!isFirebaseConfigured) {
return null;
}
if (!auth) {
const firebaseApp = getFirebaseApp();
if (!firebaseApp) {
return null;
}
auth = getAuth(firebaseApp);
}
return auth;
}
/**
* Build Google OAuth config with only the defined client IDs
* expo-auth-session throws if iosClientId is passed but undefined on iOS
*/
function buildGoogleOAuthConfig(): Record<string, string> {
const config: Record<string, string> = {};
if (googleClientIds.iosClientId) {
config.iosClientId = googleClientIds.iosClientId;
}
if (googleClientIds.androidClientId) {
config.androidClientId = googleClientIds.androidClientId;
}
if (googleClientIds.webClientId) {
config.webClientId = googleClientIds.webClientId;
}
// Provide a generic clientId fallback when platform-specific IDs are missing.
// expo-auth-session's Google.useAuthRequest validates that the platform's
// clientId exists (e.g., iosClientId on iOS), falling back to generic clientId.
// Since hooks must be called unconditionally per React rules, this placeholder
// prevents the invariant crash in CI/test environments where Google OAuth
// credentials are not configured. The auth result is discarded when
// isFirebaseEnabled() returns false.
if (!isPlatformGoogleOAuthConfigured()) {
config.clientId = 'not-configured';
}
return config;
}
/**
* Hook to get Google auth request for expo-auth-session
* This should be called at the top level of a component (unconditionally)
* Returns null values when Firebase is not enabled
*/
export function useGoogleAuth() {
// Always call the hook unconditionally (React Rules of Hooks requirement)
// webClientId is used with the Expo auth proxy (https://auth.expo.io/@owner/slug)
// iosClientId/androidClientId are used for native redirects in standalone builds
// Only include client IDs that are actually configured (prevents expo-auth-session errors)
const [request, response, promptAsync] = Google.useAuthRequest({
...buildGoogleOAuthConfig(),
scopes: ['email', 'profile'],
});
// Return null-like values if Firebase is not enabled
if (!isFirebaseEnabled()) {
return { request: null, response: null, promptAsync: null };
}
return { request, response, promptAsync };
}
/**
* Exchange Google auth response for Firebase credential and sign in
* Returns the Firebase ID token for backend authentication
*/
export async function signInWithGoogleResponse(
response: AuthSessionResult
): Promise<{ idToken: string; email: string; displayName: string | null } | null> {
if (response.type !== 'success') {
return null;
}
const firebaseAuth = getFirebaseAuth();
if (!firebaseAuth) {
throw new Error('Google Sign-In is not available. Firebase is not configured.');
}
const { id_token: googleIdToken } = response.params;
if (!googleIdToken) {
throw new Error('No ID token received from Google');
}
// Create Firebase credential from Google ID token
const credential = GoogleAuthProvider.credential(googleIdToken);
// Sign in to Firebase with the credential
const userCredential = await signInWithCredential(firebaseAuth, credential);
// Get Firebase ID token for backend authentication
const firebaseIdToken = await userCredential.user.getIdToken();
return {
idToken: firebaseIdToken,
email: userCredential.user.email || '',
displayName: userCredential.user.displayName,
};
}
/**
* Sign out from Firebase
* No-op if Firebase is not configured
*/
export async function signOutFromFirebase(): Promise<void> {
const firebaseAuth = getFirebaseAuth();
if (!firebaseAuth) {
return;
}
await signOut(firebaseAuth);
}
/**
* Subscribe to Firebase auth state changes
* Returns an unsubscribe function (no-op if Firebase not configured)
*/
export function subscribeToAuthState(
callback: (user: User | null) => void
): () => void {
const firebaseAuth = getFirebaseAuth();
if (!firebaseAuth) {
return () => {};
}
return onAuthStateChanged(firebaseAuth, callback);
}
/**
* Get the current Firebase user (if signed in)
* Returns null if Firebase not configured
*/
export function getCurrentFirebaseUser(): User | null {
const firebaseAuth = getFirebaseAuth();
if (!firebaseAuth) {
return null;
}
return firebaseAuth.currentUser;
}
/**
* Get ID token for current user
* Returns null if Firebase not configured or no user
*/
export async function getFirebaseIdToken(): Promise<string | null> {
const user = getCurrentFirebaseUser();
if (!user) {
return null;
}
return user.getIdToken();
}
// Re-export auth session types for convenience
export type { AuthSessionResult } from 'expo-auth-session';
