Started to handle rate limiting

Fixed bug in early disposal of the photo card

lib/src/model/photo_card_producer.dart

@@ -3,7 +3,6 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:flutter/scheduler.dart';
-import 'package:flutter/widgets.dart';
 import 'package:path/path.dart' as path;
 import 'package:path_provider/path_provider.dart';
 
@@ -19,15 +18,17 @@ typedef PhotoCardProducerBuilder = PhotoCardProducer Function(
   PhotoMontage montage,
 );
 
-class PhotoCardProducer {
-  PhotoCardProducer(this.model, this.montage) {
-    debugPrint('creating new producer - ${StackTrace.current}');
-  }
+abstract class PhotoCardProducer {
+  factory PhotoCardProducer(
+    PhotosLibraryApiModel model,
+    PhotoMontage montage,
+  ) = _ApiPhotoCardProducer;
 
-  static const Duration interval = Duration(seconds: 1, milliseconds: 750);
+  factory PhotoCardProducer.asset(PhotoMontage montage) = _StaticPhotoCardProducer;
 
-  final PhotosLibraryApiModel model;
-  final PhotoMontage montage;
+  PhotoCardProducer._();
+
+  static const Duration interval = Duration(seconds: 1, milliseconds: 750);
 
   Timer _timer;
 
@@ -51,6 +52,16 @@ class PhotoCardProducer {
     _timer = Timer(interval * timeDilation, _addCard);
   }
 
+  Future<void> _addCard();
+}
+
+class _ApiPhotoCardProducer extends PhotoCardProducer {
+  _ApiPhotoCardProducer(this.model, this.montage) : super._();
+
+  final PhotosLibraryApiModel model;
+  final PhotoMontage montage;
+
+  @override
   Future<void> _addCard() async {
     Directory documentsDirectory = await getApplicationDocumentsDirectory();
     File photosFile = File(path.join(documentsDirectory.path, 'photos'));
@@ -87,3 +98,13 @@ class PhotoCardProducer {
     _scheduleProduce();
   }
 }
+
+class _StaticPhotoCardProducer extends PhotoCardProducer {
+  _StaticPhotoCardProducer(this.montage) : super._();
+
+  final PhotoMontage montage;
+
+  @override
+  Future<void> _addCard() async {
+  }
+}

lib/src/model/photo_cards.dart

@@ -1,4 +1,4 @@
-import 'dart:io';
+import 'dart:typed_data';
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
@@ -7,7 +7,6 @@ import 'package:flutter/scheduler.dart';
 import 'package:scoped_model/scoped_model.dart';
 
 import '../photos_library_api/media_item.dart';
-import 'http_status_exception.dart';
 import 'photo.dart';
 import 'random.dart';
 
@@ -55,32 +54,24 @@ class PhotoMontage extends Model {
     }
 
     PhotoColumn column = candidates[random.nextInt(candidates.length)];
-    Photo photo = await _loadPhoto(mediaItem, column);
+    Size sizeConstraints = Size.square(column.width * window.physicalSize.width);
+    Photo photo = await _loadPhoto(mediaItem, sizeConstraints);
 
     PhotoCard card = PhotoCard._(photo: photo, column: column);
     column._cards.insert(0, card);
     notifyListeners();
     return card;
   }
 
-  Future<Photo> _loadPhoto(MediaItem mediaItem, PhotoColumn column) async {
-    Size sizeConstraints = Size.square(column.width * window.physicalSize.width);
+  Future<Photo> _loadPhoto(MediaItem mediaItem, Size sizeConstraints) async {
     Size photoSize = applyBoxFit(BoxFit.scaleDown, mediaItem.size, sizeConstraints).destination;
-    String url = '${mediaItem.baseUrl}=w${photoSize.width.toInt()}-h${photoSize.height.toInt()}';
-
-    final HttpClient httpClient = HttpClient();
-    final Uri resolved = Uri.base.resolve(url);
-    final HttpClientRequest request = await httpClient.getUrl(resolved);
-    final HttpClientResponse response = await request.close();
-    if (response.statusCode != HttpStatus.ok) {
-      throw HttpStatusException(response.statusCode);
-    }
+    Uint8List bytes = await mediaItem.load(photoSize);
 
     return Photo(
       mediaItem,
       photoSize / window.devicePixelRatio,
       window.devicePixelRatio,
-      await consolidateHttpClientResponseBytes(response),
+      bytes,
     );
   }
 

lib/src/model/photos_library_api_model.dart

@@ -16,14 +16,27 @@ import '../photos_library_api/photos_library_api_client.dart';
 import '../photos_library_api/search_media_items_request.dart';
 import '../photos_library_api/search_media_items_response.dart';
 
-enum AuthState {
-  pending,
+enum PhotosLibraryApiState {
+  /// The user has not yet attempted authentication or is in the process of
+  /// authenticating.
+  pendingAuthentication,
+
+  /// The user has authenticated and is in possession of a valid OAuth 2.0
+  /// access token.
   authenticated,
+
+  /// The user has attempted authentication and failed, or their OAuth access
+  /// token has expired and in need of renewal.
   unauthenticated,
+
+  /// The user has successfully authenticated, but they are being rate limited
+  /// by the Google Photos API and are temporarily not allowed to make further
+  /// API requests.
+  rateLimited,
 }
 
 class PhotosLibraryApiModel extends Model {
-  AuthState _authState = AuthState.pending;
+  PhotosLibraryApiState _state = PhotosLibraryApiState.pendingAuthentication;
   PhotosLibraryApiClient _client;
   GoogleSignInAccount _currentUser;
 
@@ -33,22 +46,19 @@ class PhotosLibraryApiModel extends Model {
 
   Future<void> _onSignInComplete({bool fetchPhotos = true}) async {
     _currentUser = _googleSignIn.currentUser;
-    AuthState newAuthState;
+    PhotosLibraryApiState newState;
     if (_currentUser == null) {
-      newAuthState = AuthState.unauthenticated;
+      newState = PhotosLibraryApiState.unauthenticated;
       _client = null;
     } else {
-      newAuthState = AuthState.authenticated;
+      newState = PhotosLibraryApiState.authenticated;
       _client = PhotosLibraryApiClient(_currentUser.authHeaders);
     }
-    if (fetchPhotos && newAuthState == AuthState.authenticated) {
+    if (fetchPhotos && newState == PhotosLibraryApiState.authenticated) {
       // TODO(tvolkert): don't delete, but don't blindly append
       await _populatePhotosFile(delete: false);
     }
-    if (_authState != newAuthState) {
-      _authState = newAuthState;
-      notifyListeners();
-    }
+    state = newState;
   }
 
   Future<void> _populatePhotosFile({bool delete = false}) async {
@@ -89,25 +99,32 @@ class PhotosLibraryApiModel extends Model {
     }
   }
 
-  AuthState get authState => _authState;
+  PhotosLibraryApiState get state => _state;
+  set state(PhotosLibraryApiState value) {
+    assert(value != null);
+    if (_state != value) {
+      _state = value;
+      notifyListeners();
+    }
+  }
 
   Future<bool> signIn() async {
     if (_currentUser != null) {
-      assert(authState == AuthState.authenticated);
+      assert(state == PhotosLibraryApiState.authenticated);
       return true;
     }
 
-    assert(authState != AuthState.authenticated);
+    assert(state != PhotosLibraryApiState.authenticated);
     await _googleSignIn.signIn();
     await _onSignInComplete();
-    return authState == AuthState.authenticated;
+    return state == PhotosLibraryApiState.authenticated;
   }
 
   Future<void> signOut() async {
     await _googleSignIn.disconnect();
     _currentUser = null;
-    _authState = AuthState.unauthenticated;
     _client = null;
+    state = PhotosLibraryApiState.unauthenticated;
   }
 
   Future<void> signInSilently({bool fetchPhotosAfterSignIn = true}) async {
@@ -134,17 +151,21 @@ class PhotosLibraryApiModel extends Model {
       try {
         result = await _client.getMediaItem(id);
       } on GetMediaItemException catch (error) {
-        if (error.statusCode == HttpStatus.unauthorized) {
-          // Need to renew our OAuth access token.
-          debugPrint('Renewing OAuth access token...');
-          await signInSilently(fetchPhotosAfterSignIn: false);
-          if (authState == AuthState.unauthenticated) {
-            // Unable to renew OAuth token.
-            debugPrint('Unable to renew OAuth access token; bailing out');
+        switch (error.statusCode) {
+          case HttpStatus.unauthorized:
+            debugPrint('Renewing OAuth access token...');
+            await signInSilently(fetchPhotosAfterSignIn: false);
+            if (state == PhotosLibraryApiState.unauthenticated) {
+              debugPrint('Unable to renew OAuth access token; bailing out');
+              return null;
+            }
+            break;
+          case HttpStatus.tooManyRequests:
+            state = PhotosLibraryApiState.rateLimited;
             return null;
-          }
-        } else {
-          rethrow;
+            break;
+          default:
+            rethrow;
         }
       }
     }

lib/src/pages/home_page.dart

@@ -36,19 +36,27 @@ class HomePage extends StatelessWidget {
   Widget build(BuildContext context) {
     return ScopedModelDescendant<PhotosLibraryApiModel>(
       builder: (BuildContext context, Widget child, PhotosLibraryApiModel apiModel) {
-        switch (apiModel.authState) {
-          case AuthState.pending:
+        switch (apiModel.state) {
+          case PhotosLibraryApiState.pendingAuthentication:
             // Show a blank screen while we try to non-interactively sign in.
             return Container();
-          case AuthState.unauthenticated:
+          case PhotosLibraryApiState.unauthenticated:
             return interactive ? LoginPage() : InteractiveLoginRequiredPage();
-          case AuthState.authenticated:
+          case PhotosLibraryApiState.authenticated:
             return PhotosHome(
               montageBuilder: montageBuilder,
               producerBuilder: producerBuilder,
             );
+          case PhotosLibraryApiState.rateLimited:
+            return PhotosHome(
+              montageBuilder: montageBuilder,
+              producerBuilder: (PhotosLibraryApiModel model, PhotoMontage montage) {
+                return PhotoCardProducer.asset(montage);
+              },
+            );
+            break;
           default:
-            throw StateError('Auth state not supported: ${apiModel.authState}');
+            throw StateError('Auth state not supported: ${apiModel.state}');
         }
       },
     );

lib/src/pages/photos_page.dart

@@ -116,6 +116,7 @@ class _FLoatingPhotoState extends State<FLoatingPhoto> with SingleTickerProvider
         height: widget.card.column.width * screenSize.width,
         child: Image.memory(
           widget.card.photo.bytes,
+          alignment: Alignment.topCenter,
           scale: widget.card.photo.scale,
         ),
       ),

lib/src/photos_library_api/media_item.dart

@@ -1,7 +1,11 @@
+import 'dart:io';
+import 'dart:typed_data';
 import 'dart:ui';
 
+import 'package:flutter/foundation.dart';
 import 'package:json_annotation/json_annotation.dart';
 
+import 'http_status_exception.dart';
 import 'media_metadata.dart';
 
 part 'media_item.g.dart';
@@ -67,5 +71,19 @@ class MediaItem {
     return Size(width.toDouble(), height.toDouble());
   }
 
+  Future<Uint8List> load(Size size) async {
+    String url = '$baseUrl=w${size.width.toInt()}-h${size.height.toInt()}';
+
+    final HttpClient httpClient = HttpClient();
+    final Uri resolved = Uri.base.resolve(url);
+    final HttpClientRequest request = await httpClient.getUrl(resolved);
+    final HttpClientResponse response = await request.close();
+    if (response.statusCode != HttpStatus.ok) {
+      throw HttpStatusException(response.statusCode);
+    }
+
+    return await consolidateHttpClientResponseBytes(response);
+  }
+
   Map<String, dynamic> toJson() => _$MediaItemToJson(this);
 }