Able to assign host and port for emualtor

packages/dart_firebase_admin/lib/src/app.dart

@@ -13,3 +13,4 @@ import 'package:meta/meta.dart';
 part 'app/credential.dart';
 part 'app/exception.dart';
 part 'app/firebase_admin.dart';
+part 'app/emulator.dart';

packages/dart_firebase_admin/lib/src/app/emulator.dart

@@ -0,0 +1,62 @@
+part of '../app.dart';
+
+/// Represents a Firebase Emulator.
+/// Now for Auth and Firestore.
+class Emulator {
+  /// If there is no environment variable set, please use this constructor.
+  /// For example, gcloud firestore emulators.
+  const Emulator(this.host, this.port);
+
+  /// Creates an [Emulator] from an environment variable.
+  /// For example, env key for auth is: FIREBASE_AUTH_EMULATOR_HOST
+  @internal
+  factory Emulator.fromEnvString(String envString) {
+    final parts = envString.split(':');
+    if (parts.length != 2) {
+      throw ArgumentError.value(envString, 'envString', 'Invalid format');
+    }
+    final host = parts[0];
+    final port = int.tryParse(parts[1]);
+    if (port == null) {
+      throw ArgumentError.value(envString, 'envString', 'Invalid port');
+    }
+    return Emulator(host, port);
+  }
+
+  /// The default Auth Emulator.
+  const Emulator._defaultAuth()
+      : host = '127.0.0.1',
+        port = 9099;
+
+  /// The default Firestore Emulator.
+  const Emulator._defaultFirestore()
+      : host = '127.0.0.1',
+        port = 8080;
+
+  /// Try to get the Auth Emulator from the environment variable.
+  /// If not found, use the default Auth Emulator.
+  factory Emulator.auth() {
+    if (!Platform.environment.containsKey('FIREBASE_AUTH_EMULATOR_HOST')) {
+      return const Emulator._defaultAuth();
+    } else {
+      return Emulator.fromEnvString(
+        Platform.environment['FIREBASE_AUTH_EMULATOR_HOST']!,
+      );
+    }
+  }
+
+  /// Try to get the Firestore Emulator from the environment variable.
+  /// If not found, use the default Firestore Emulator.
+  factory Emulator.firestore() {
+    if (!Platform.environment.containsKey('FIRESTORE_EMULATOR_HOST')) {
+      return const Emulator._defaultFirestore();
+    } else {
+      return Emulator.fromEnvString(
+        Platform.environment['FIRESTORE_EMULATOR_HOST']!,
+      );
+    }
+  }
+
+  final String host;
+  final int port;
+}

packages/dart_firebase_admin/lib/src/app/firebase_admin.dart

@@ -9,19 +9,46 @@ class FirebaseAdminApp {
   /// The [Credential] used to authenticate the Admin SDK.
   final Credential credential;
 
-  bool get isUsingEmulator => _isUsingEmulator;
-  var _isUsingEmulator = false;
+  bool get isUsingAuthEmulator => _isUsingAuthEmulator;
+
+  bool get isUsingFirestoreEmulator => _isUsingFirestoreEmulator;
+
+  bool get isUsingEmulator => _isUsingAuthEmulator || _isUsingFirestoreEmulator;
+
+  var _isUsingAuthEmulator = false;
+  var _isUsingFirestoreEmulator = false;
 
   @internal
   Uri authApiHost = Uri.https('identitytoolkit.googleapis.com', '/');
   @internal
   Uri firestoreApiHost = Uri.https('firestore.googleapis.com', '/');
 
-  /// Use the Firebase Emulator Suite to run the app locally.
-  void useEmulator() {
-    _isUsingEmulator = true;
-    authApiHost = Uri.http('127.0.0.1:9099', 'identitytoolkit.googleapis.com/');
-    firestoreApiHost = Uri.http('127.0.0.1:8080', '/');
+  /// Use the Firebase Emulator suite to run the app locally.
+  void useEmulator({
+    Emulator? authEmulator,
+    Emulator? firestoreEmulator,
+  }) {
+    useAuthEmulator(emulator: authEmulator);
+    useFirestoreEmulator(emulator: firestoreEmulator);
+  }
+
+  /// Use the Firebase Auth Emulator to run the app locally.
+  void useAuthEmulator({
+    Emulator? emulator
+  }) {
+    _isUsingAuthEmulator = true;
+    emulator ??= Emulator.auth();
+    authApiHost = Uri.http(
+        '${emulator.host}:${emulator.port}', 'identitytoolkit.googleapis.com/');
+  }
+
+  /// Use the Firebase Firestore Emulator to run the app locally.
+  void useFirestoreEmulator({
+    Emulator? emulator,
+  }) {
+    _isUsingFirestoreEmulator = true;
+    emulator ??= Emulator.firestore();
+    firestoreApiHost = Uri.http('${emulator.host}:${emulator.port}', '/');
   }
 
   @internal

packages/dart_firebase_admin/test/firebase_admin_app_test.dart

@@ -18,13 +18,18 @@ void main() {
     });
 
     test('useEmulator() sets the apiHost to the emulator', () {
-      final app = FirebaseAdminApp.initializeApp(
+      var app = FirebaseAdminApp.initializeApp(
         'dart-firebase-admin',
         Credential.fromApplicationDefaultCredentials(),
       );
 
+      /// Use both auth and firestore emulator.
       app.useEmulator();
 
+      expect(app.isUsingAuthEmulator, true);
+      expect(app.isUsingFirestoreEmulator, true);
+      expect(app.isUsingEmulator, true);
+
       expect(
         app.authApiHost,
         Uri.http('127.0.0.1:9099', 'identitytoolkit.googleapis.com/'),
@@ -33,6 +38,66 @@ void main() {
         app.firestoreApiHost,
         Uri.http('127.0.0.1:8080', '/'),
       );
+
+      /// Use only auth emulator.
+      app = FirebaseAdminApp.initializeApp(
+        'dart-firebase-admin',
+        Credential.fromApplicationDefaultCredentials(),
+      );
+
+      app.useAuthEmulator(
+        emulator: const Emulator('192.168.1.1', 9),
+      );
+
+      expect(app.isUsingAuthEmulator, true);
+      expect(app.isUsingFirestoreEmulator, false);
+      expect(app.isUsingEmulator, true);
+
+      expect(
+        app.authApiHost,
+        Uri.http('192.168.1.1:9', 'identitytoolkit.googleapis.com/'),
+      );
+      expect(
+        app.firestoreApiHost,
+        Uri.https('firestore.googleapis.com', '/'),
+      );
+
+      /// Use only firestore emulator.
+      app = FirebaseAdminApp.initializeApp(
+        'dart-firebase-admin',
+        Credential.fromApplicationDefaultCredentials(),
+      );
+
+      app.useFirestoreEmulator();
+
+      expect(app.isUsingAuthEmulator, false);
+      expect(app.isUsingFirestoreEmulator, true);
+      expect(app.isUsingEmulator, true);
+
+      expect(
+        app.authApiHost,
+        Uri.https('identitytoolkit.googleapis.com', '/'),
+      );
+      expect(
+        app.firestoreApiHost,
+        Uri.http('127.0.0.1:8080', '/'),
+      );
+    });
+
+    test('Emulator is initiated as expected', () {
+      /// Test the parsing part of env string to Uri.
+      var emulator = Emulator.fromEnvString('192.168.0.1:9999');
+      expect(emulator.host, '192.168.0.1');
+      expect(emulator.port, 9999);
+
+      /// Test the default auth emulator is using the default host and port.
+      emulator = Emulator.auth();
+      expect(emulator.host, '127.0.0.1');
+      expect(emulator.port, 9099);
+
+      emulator = Emulator.firestore();
+      expect(emulator.host, '127.0.0.1');
+      expect(emulator.port, 8080);
     });
   });
 }