[WIP] Google sign in platform interface

packages/google_sign_in/google_sign_in/lib/google_sign_in.dart

@@ -5,38 +5,38 @@
 import 'dart:async';
 import 'dart:ui' show hashValues;
 
-import 'package:flutter/services.dart' show MethodChannel, PlatformException;
-import 'package:meta/meta.dart' show visibleForTesting;
+import 'package:flutter/services.dart' show PlatformException;
+import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart';
 
 import 'src/common.dart';
 
 export 'src/common.dart';
 export 'widgets.dart';
 
-enum SignInOption { standard, games }
+// enum SignInOption { standard, games }
 
 class GoogleSignInAuthentication {
   GoogleSignInAuthentication._(this._data);
 
-  final Map<String, dynamic> _data;
+  final GoogleSignInTokenData _data;
 
   /// An OpenID Connect ID token that identifies the user.
-  String get idToken => _data['idToken'];
+  String get idToken => _data.idToken;
 
   /// The OAuth2 access token to access Google services.
-  String get accessToken => _data['accessToken'];
+  String get accessToken => _data.accessToken;
 
   @override
   String toString() => 'GoogleSignInAuthentication:$_data';
 }
 
 class GoogleSignInAccount implements GoogleIdentity {
-  GoogleSignInAccount._(this._googleSignIn, Map<String, dynamic> data)
-      : displayName = data['displayName'],
-        email = data['email'],
-        id = data['id'],
-        photoUrl = data['photoUrl'],
-        _idToken = data['idToken'] {
+  GoogleSignInAccount._(this._googleSignIn, GoogleSignInUserData data)
+      : displayName = data.displayName,
+        email = data.email,
+        id = data.id,
+        photoUrl = data.photoUrl,
+        _idToken = data.idToken {
     assert(id != null);
   }
 
@@ -78,18 +78,12 @@ class GoogleSignInAccount implements GoogleIdentity {
       throw StateError('User is no longer signed in.');
     }
 
-    final Map<String, dynamic> response =
-        await GoogleSignIn.channel.invokeMapMethod<String, dynamic>(
-      'getTokens',
-      <String, dynamic>{
-        'email': email,
-        'shouldRecoverAuth': true,
-      },
-    );
+    final GoogleSignInTokenData response = await GoogleSignInPlatform.instance.getTokens(email: email, shouldRecoverAuth: true);
+
     // On Android, there isn't an API for refreshing the idToken, so re-use
     // the one we obtained on login.
-    if (response['idToken'] == null) {
-      response['idToken'] = _idToken;
+    if (response.idToken == null) {
+      response.idToken = _idToken;
     }
     return GoogleSignInAuthentication._(response);
   }
@@ -108,10 +102,7 @@ class GoogleSignInAccount implements GoogleIdentity {
   /// this method and grab `authHeaders` once again.
   Future<void> clearAuthCache() async {
     final String token = (await authentication).accessToken;
-    await GoogleSignIn.channel.invokeMethod<void>(
-      'clearAuthCache',
-      <String, dynamic>{'token': token},
-    );
+    await GoogleSignInPlatform.instance.clearAuthCache(token: token);
   }
 
   @override
@@ -146,7 +137,7 @@ class GoogleSignIn {
   /// Initializes global sign-in configuration settings.
   ///
   /// The [signInOption] determines the user experience. [SigninOption.games]
-  /// must not be used on iOS.
+  /// must not be used on iOS or Web.
   ///
   /// The list of [scopes] are OAuth scope codes to request when signing in.
   /// These scope codes will determine the level of data access that is granted
@@ -157,7 +148,7 @@ class GoogleSignIn {
   /// The [hostedDomain] argument specifies a hosted domain restriction. By
   /// setting this, sign in will be restricted to accounts of the user in the
   /// specified domain. By default, the list of accounts will not be restricted.
-  GoogleSignIn({this.signInOption, this.scopes, this.hostedDomain});
+  GoogleSignIn({this.signInOption = SignInOption.standard, this.scopes = const <String>[], this.hostedDomain});
 
   /// Factory for creating default sign in user experience.
   factory GoogleSignIn.standard({List<String> scopes, String hostedDomain}) {
@@ -168,7 +159,7 @@ class GoogleSignIn {
   }
 
   /// Factory for creating sign in suitable for games. This option must not be
-  /// used on iOS because the games API is not supported.
+  /// used on iOS or Web because the games API is not supported.
   factory GoogleSignIn.games() {
     return GoogleSignIn(signInOption: SignInOption.games);
   }
@@ -186,11 +177,6 @@ class GoogleSignIn {
   /// Error code indicating that attempt to sign in failed.
   static const String kSignInFailedError = 'sign_in_failed';
 
-  /// The [MethodChannel] over which this class communicates.
-  @visibleForTesting
-  static const MethodChannel channel =
-      MethodChannel('plugins.flutter.io/google_sign_in');
-
   /// Option to determine the sign in user experience. [SignInOption.games] must
   /// not be used on iOS.
   final SignInOption signInOption;
@@ -211,14 +197,12 @@ class GoogleSignIn {
   // Future that completes when we've finished calling `init` on the native side
   Future<void> _initialization;
 
-  Future<GoogleSignInAccount> _callMethod(String method) async {
+  Future<GoogleSignInAccount> _callMethod(Function method) async {
     await _ensureInitialized();
 
-    final Map<String, dynamic> response =
-        await channel.invokeMapMethod<String, dynamic>(method);
-    return _setCurrentUser(response != null && response.isNotEmpty
-        ? GoogleSignInAccount._(this, response)
-        : null);
+    final dynamic response = await method();
+
+    return _setCurrentUser(response != null && response is GoogleSignInUserData ? GoogleSignInAccount._(this, response) : null);
   }
 
   GoogleSignInAccount _setCurrentUser(GoogleSignInAccount currentUser) {
@@ -230,16 +214,14 @@ class GoogleSignIn {
   }
 
   Future<void> _ensureInitialized() {
-    return _initialization ??=
-        channel.invokeMethod<void>('init', <String, dynamic>{
-      'signInOption': (signInOption ?? SignInOption.standard).toString(),
-      'scopes': scopes ?? <String>[],
-      'hostedDomain': hostedDomain,
-    })
-          ..catchError((dynamic _) {
-            // Invalidate initialization if it errored out.
-            _initialization = null;
-          });
+    return _initialization ??= GoogleSignInPlatform.instance.init(
+      signInOption: signInOption,
+      scopes: scopes,
+      hostedDomain: hostedDomain,
+    )..catchError((dynamic _) {
+      // Invalidate initialization if it errored out.
+      _initialization = null;
+    });
   }
 
   /// The most recently scheduled method call.
@@ -251,6 +233,7 @@ class GoogleSignIn {
     final Completer<void> completer = Completer<void>();
     future.whenComplete(completer.complete).catchError((dynamic _) {
       // Ignore if previous call completed with an error.
+      // TODO: Should we log errors here?
     });
     return completer.future;
   }
@@ -259,26 +242,20 @@ class GoogleSignIn {
   ///
   /// At most one in flight call is allowed to prevent concurrent (out of order)
   /// updates to [currentUser] and [onCurrentUserChanged].
-  Future<GoogleSignInAccount> _addMethodCall(String method) async {
+  Future<GoogleSignInAccount> _addMethodCall(Function method, {bool canSkipCall = false}) async {
     Future<GoogleSignInAccount> response;
     if (_lastMethodCall == null) {
+      // First call
       response = _callMethod(method);
     } else {
       response = _lastMethodCall.then((_) {
-        // If after the last completed call `currentUser` is not `null` and requested
-        // method is a sign in method, re-use the same authenticated user
-        // instead of making extra call to the native side.
-        const List<String> kSignInMethods = <String>[
-          'signIn',
-          'signInSilently'
-        ];
-        if (kSignInMethods.contains(method) && _currentUser != null) {
+        if (canSkipCall && _currentUser != null) {
           return _currentUser;
-        } else {
-          return _callMethod(method);
         }
+        return _callMethod(method);
       });
     }
+    // Enqueue the response as the last method call
     _lastMethodCall = _waitFor(response);
     return response;
   }
@@ -306,7 +283,7 @@ class GoogleSignIn {
   Future<GoogleSignInAccount> signInSilently(
       {bool suppressErrors = true}) async {
     try {
-      return await _addMethodCall('signInSilently');
+      return _addMethodCall(GoogleSignInPlatform.instance.signInSilently, canSkipCall: true);
     } catch (_) {
       if (suppressErrors) {
         return null;
@@ -319,7 +296,7 @@ class GoogleSignIn {
   /// Returns a future that resolves to whether a user is currently signed in.
   Future<bool> isSignedIn() async {
     await _ensureInitialized();
-    return await channel.invokeMethod<bool>('isSignedIn');
+    return GoogleSignInPlatform.instance.isSignedIn();
   }
 
   /// Starts the interactive sign-in process.
@@ -333,16 +310,16 @@ class GoogleSignIn {
   ///
   /// Re-authentication can be triggered only after [signOut] or [disconnect].
   Future<GoogleSignInAccount> signIn() {
-    final Future<GoogleSignInAccount> result = _addMethodCall('signIn');
+    final Future<GoogleSignInAccount> result = _addMethodCall(GoogleSignInPlatform.instance.signIn, canSkipCall: true);
     bool isCanceled(dynamic error) =>
         error is PlatformException && error.code == kSignInCanceledError;
     return result.catchError((dynamic _) => null, test: isCanceled);
   }
 
   /// Marks current user as being in the signed out state.
-  Future<GoogleSignInAccount> signOut() => _addMethodCall('signOut');
+  Future<GoogleSignInAccount> signOut() => _addMethodCall(GoogleSignInPlatform.instance.signOut);
 
   /// Disconnects the current user from the app and revokes previous
   /// authentication.
-  Future<GoogleSignInAccount> disconnect() => _addMethodCall('disconnect');
+  Future<GoogleSignInAccount> disconnect() => _addMethodCall(GoogleSignInPlatform.instance.disconnect);
 }

packages/google_sign_in/google_sign_in/pubspec.yaml

@@ -15,6 +15,8 @@ dependencies:
   flutter:
     sdk: flutter
   meta: ^1.0.4
+  google_sign_in_platform_interface:
+    path: ../google_sign_in_platform_interface
 
 dev_dependencies:
   http: ^0.12.0

packages/google_sign_in/google_sign_in_platform_interface/CHANGELOG.md

@@ -0,0 +1,3 @@
+## 1.0.0
+
+* Initial release.

packages/google_sign_in/google_sign_in_platform_interface/LICENSE

@@ -0,0 +1,27 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/google_sign_in/google_sign_in_platform_interface/README.md

@@ -0,0 +1,26 @@
+# google_sign_in_platform_interface
+
+A common platform interface for the [`google_sign_in`][1] plugin.
+
+This interface allows platform-specific implementations of the `google_sign_in`
+plugin, as well as the plugin itself, to ensure they are supporting the
+same interface.
+
+# Usage
+
+To implement a new platform-specific implementation of `google_sign_in`, extend
+[`GoogleSignInPlatform`][2] with an implementation that performs the
+platform-specific behavior, and when you register your plugin, set the default
+`GoogleSignInPlatform` by calling
+`GoogleSignInPlatform.instance = MyPlatformGoogleSignIn()`.
+
+# Note on breaking changes
+
+Strongly prefer non-breaking changes (such as adding a method to the interface)
+over breaking changes for this package.
+
+See https://flutter.dev/go/platform-interface-breaking-changes for a discussion
+on why a less-clean interface is preferable to a breaking change.
+
+[1]: ../google_sign_in
+[2]: lib/google_sign_in_platform_interface.dart

packages/google_sign_in/google_sign_in_platform_interface/lib/google_sign_in_platform_interface.dart

@@ -0,0 +1,83 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:meta/meta.dart' show required;
+
+import 'method_channel_google_sign_in.dart';
+
+enum SignInOption { standard, games }
+
+class GoogleSignInUserData {
+  GoogleSignInUserData(
+      {this.displayName, this.email, this.id, this.photoUrl, this.idToken});
+  String displayName;
+  String email;
+  String id;
+  String photoUrl;
+  String idToken;
+}
+
+class GoogleSignInTokenData {
+  GoogleSignInTokenData({this.idToken, this.accessToken});
+  String idToken;
+  String accessToken;
+}
+
+/// The interface that implementations of google_sign_in must implement.
+///
+/// Platform implementations that live in a separate package should extend this
+/// class rather than implement it as `google_sign_in` does not consider newly
+/// added methods to be breaking changes. Extending this class (using `extends`)
+/// ensures that the subclass will get the default implementation, while
+/// platform implementations that `implements` this interface will be broken by
+/// newly added [GoogleSignInPlatform] methods.
+abstract class GoogleSignInPlatform {
+  /// The default instance of [GoogleSignInPlatform] to use.
+  ///
+  /// Platform-specific plugins should override this with their own
+  /// platform-specific class that extends [GoogleSignInPlatform] when they
+  /// register themselves.
+  ///
+  /// Defaults to [MethodChannelGoogleSignIn].
+  static GoogleSignInPlatform instance = MethodChannelGoogleSignIn();
+
+  Future<void> init(
+      {@required String hostedDomain,
+      List<String> scopes,
+      SignInOption signInOption,
+      String clientId}) async {
+    throw UnimplementedError('init() has not been implemented.');
+  }
+
+  Future<GoogleSignInUserData> signInSilently() async {
+    throw UnimplementedError('signInSilently() has not been implemented.');
+  }
+
+  Future<GoogleSignInUserData> signIn() async {
+    throw UnimplementedError('signIn() has not been implemented.');
+  }
+
+  Future<GoogleSignInTokenData> getTokens(
+      {@required String email, bool shouldRecoverAuth}) async {
+    throw UnimplementedError('getTokens() has not been implemented.');
+  }
+
+  Future<void> signOut() async {
+    throw UnimplementedError('signOut() has not been implemented.');
+  }
+
+  Future<void> disconnect() async {
+    throw UnimplementedError('disconnect() has not been implemented.');
+  }
+
+  Future<bool> isSignedIn() async {
+    throw UnimplementedError('isSignedIn() has not been implemented.');
+  }
+
+  Future<void> clearAuthCache({@required String token}) async {
+    throw UnimplementedError('clearAuthCache() has not been implemented.');
+  }
+}