How to Manage Large-Scale User Authentication with Firebase in FlutterFlow

1// functions/setUserRole.js
2const { onCall } = require('firebase-functions/v2/https');
3const { getAuth } = require('firebase-admin/auth');
4const { initializeApp } = require('firebase-admin/app');
5
6initializeApp();
7
8const VALID_ROLES = ['user', 'moderator', 'admin', 'enterprise'];
9
10exports.setUserRole = onCall(async (request) => {
11  // Only admins can set roles
12  if (request.auth?.token?.role !== 'admin') {
13    throw new Error('Unauthorized');
14  }
15  const { targetUid, role } = request.data;
16  if (!VALID_ROLES.includes(role)) {
17    throw new Error(`Invalid role: ${role}`);
18  }
19  await getAuth().setCustomUserClaims(targetUid, { role });
20  return { success: true, uid: targetUid, role };
21});

1// Custom Action: initAppCheck.dart
2import 'package:firebase_app_check/firebase_app_check.dart';
3import 'package:flutter/foundation.dart';
4
5Future<void> initAppCheck() async {
6  await FirebaseAppCheck.instance.activate(
7    androidProvider: kDebugMode
8        ? AndroidProvider.debug
9        : AndroidProvider.playIntegrity,
10    appleProvider: kDebugMode
11        ? AppleProvider.debug
12        : AppleProvider.deviceCheck,
13    webProvider: ReCaptchaV3Provider('YOUR_SITE_KEY'),
14  );
15}

1// functions/revokeUserSession.js
2const { onCall } = require('firebase-functions/v2/https');
3const { getAuth } = require('firebase-admin/auth');
4const { getFirestore } = require('firebase-admin/firestore');
5
6exports.revokeUserSession = onCall(async (request) => {
7  if (request.auth?.token?.role !== 'admin') {
8    throw new Error('Unauthorized');
9  }
10  const { targetUid, reason } = request.data;
11  await getAuth().revokeRefreshTokens(targetUid);
12  // Mark all sessions as revoked
13  const db = getFirestore();
14  const sessionsSnap = await db.collection('sessions')
15    .where('userId', '==', targetUid)
16    .where('isRevoked', '==', false).get();
17  const batch = db.batch();
18  sessionsSnap.docs.forEach(doc => {
19    batch.update(doc.ref, {
20      isRevoked: true,
21      revokedAt: new Date(),
22      revokedReason: reason,
23    });
24  });
25  await batch.commit();
26  return { revoked: sessionsSnap.size };
27});

1// Custom Action: handleAccountLinking.dart
2import 'package:firebase_auth/firebase_auth.dart';
3
4Future<String> getSignInMethodsForEmail(String email) async {
5  try {
6    final methods = await FirebaseAuth.instance
7        .fetchSignInMethodsForEmail(email);
8    return methods.join(','); // e.g., 'google.com,password'
9  } catch (e) {
10    return 'error:$e';
11  }
12}
13
14Future<bool> linkEmailPasswordToCurrentUser(
15    String email, String password) async {
16  try {
17    final credential = EmailAuthProvider.credential(
18        email: email, password: password);
19    await FirebaseAuth.instance.currentUser
20        ?.linkWithCredential(credential);
21    return true;
22  } on FirebaseAuthException catch (e) {
23    // credential-already-in-use means another account has this email
24    return false;
25  }
26}

1// functions/bulkUserExport.js
2const { onCall } = require('firebase-functions/v2/https');
3const { getAuth } = require('firebase-admin/auth');
4
5exports.exportAllUsers = onCall(async (request) => {
6  if (request.auth?.token?.role !== 'admin') {
7    throw new Error('Unauthorized');
8  }
9  const users = [];
10  let pageToken;
11  do {
12    const result = await getAuth().listUsers(1000, pageToken);
13    result.users.forEach(user => {
14      users.push({
15        uid: user.uid,
16        email: user.email,
17        createdAt: user.metadata.creationTime,
18        lastSignIn: user.metadata.lastSignInTime,
19        disabled: user.disabled,
20        customClaims: user.customClaims,
21      });
22    });
23    pageToken = result.pageToken;
24  } while (pageToken);
25  return { count: users.length, users };
26});