Developed the business logic of offline detection mechanism (GSoC)

lib/locator.dart

@@ -1,5 +1,6 @@
 import 'package:connectivity_plus/connectivity_plus.dart';
 import 'package:get_it/get_it.dart';
+import 'package:http/http.dart' as http;
 import 'package:image_cropper/image_cropper.dart';
 import 'package:image_picker/image_picker.dart';
 import 'package:talawa/main.dart';
@@ -14,6 +15,7 @@ import 'package:talawa/services/org_service.dart';
 import 'package:talawa/services/post_service.dart';
 import 'package:talawa/services/session_manager.dart';
 import 'package:talawa/services/size_config.dart';
+import 'package:talawa/services/third_party_service/connectivity_service.dart';
 import 'package:talawa/services/third_party_service/multi_media_pick_service.dart';
 import 'package:talawa/services/user_config.dart';
 import 'package:talawa/utils/queries.dart';
@@ -68,6 +70,9 @@ final queries = locator<Queries>();
 ///GetIt for Connectivity.
 final connectivity = locator<Connectivity>();
 
+///GetIt for ConnectivityService.
+final connectivityService = locator<ConnectivityService>();
+
 ///GetIt for OrganizationService.
 final organizationService = locator<OrganizationService>();
 
@@ -111,6 +116,8 @@ void setupLocator() {
   locator.registerLazySingleton(() => ImagePicker());
   locator.registerLazySingleton(() => ImageCropper());
 
+  locator.registerSingleton(ConnectivityService(client: http.Client()));
+
   //graphql
   locator.registerSingleton(GraphqlConfig());
 

lib/services/third_party_service/connectivity_service.dart

@@ -0,0 +1,175 @@
+import 'dart:async';
+
+import 'package:connectivity_plus/connectivity_plus.dart';
+import 'package:http/http.dart' as http;
+import 'package:talawa/locator.dart';
+
+/// This class provides services related to network connectivity monitoring and handling.
+///
+/// It includes methods for:
+/// * Initializing the network service - [initConnectivity]
+/// * Monitoring connectivity changes - [enableSubscription]
+/// * Handling online and offline states - [_handleOnline], [_handleOffline]
+/// * Checking reachability of a given URI - [isReachable]
+/// * Handling the device's connectivity status - [handleConnection]
+/// * Checking if the device has any type of network connection - [hasConnection]
+class ConnectivityService {
+  /// This function is used to initialize the network service.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  ConnectivityService({required http.Client client}) {
+    _client = client;
+    _connectionStatusController = StreamController<ConnectivityResult>();
+    initConnectivity();
+  }
+
+  /// Stream controller for network status changes
+  late StreamController<ConnectivityResult> _connectionStatusController;
+
+  /// Getter for the stream of connection status changes.
+  Stream<ConnectivityResult> get connectionStream =>
+      _connectionStatusController.stream;
+
+  /// Client to access internet.
+  late final http.Client _client;
+
+  /// This function initializes connectivity monitoring.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> initConnectivity() async {
+    /// Try getting initial connectivity status
+    checkInitialConnection();
+
+    /// Listen for future changes in connectivity
+    enableSubscription();
+  }
+
+  /// This function checks the initial connection status.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> checkInitialConnection() async {
+    try {
+      final result = await connectivity.checkConnectivity();
+      print(result);
+      _connectionStatusController.add(result);
+      handleConnection(result);
+    } catch (e) {
+      // Handle other exceptions
+      print('Error checking connectivity: $e');
+      _connectionStatusController
+          .add(ConnectivityResult.none); // Assume no connection on error
+      handleConnection(ConnectivityResult.none);
+    }
+  }
+
+  /// This function enables the subscription to connectivity changes.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> enableSubscription() async {
+    connectivity.onConnectivityChanged.listen(
+      (ConnectivityResult result) {
+        print(result);
+        _connectionStatusController.add(result);
+        handleConnection(result);
+      },
+      onError: (error) {
+        // Handle errors during listening for changes
+        print('Error listening for connectivity changes: $error');
+      },
+    );
+  }
+
+  /// This function handles the actions to be taken when the device is online.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> _handleOnline() async {
+    // To be implemented.
+  }
+
+  /// This function handles the actions to be taken when the device is offline.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> _handleOffline() async {
+    // To be implemented.
+  }
+
+  /// This function checks if a given URI is reachable within a specified timeout period.
+  ///
+  /// **params**:
+  /// * `client`: An instance of `http.Client` to make the HTTP request.
+  /// * `uriString`: An optional `String` specifying the URI to check.
+  /// Defaults to 'http://www.google.com' if not provided.
+  ///
+  /// **returns**:
+  /// * `Future<bool>`: indicates if the url is reachable.
+  Future<bool> isReachable({
+    http.Client? client,
+    String? uriString,
+  }) async {
+    try {
+      client ??= _client;
+      await client
+          .get(Uri.parse(uriString ?? 'http://www.google.com'))
+          .timeout(const Duration(seconds: 5));
+      return true;
+    } catch (e) {
+      print('Timeout while checking reachability: $e');
+      return false;
+    }
+  }
+
+  /// This function handles the device's connectivity status based on the provided `ConnectivityResult`.
+  ///
+  /// **params**:
+  /// * `result`: A `ConnectivityResult` indicating the current connectivity status.
+  ///
+  /// **returns**:
+  ///   None
+  Future<void> handleConnection(ConnectivityResult result) async {
+    if (await hasConnection() && await isReachable(client: _client)) {
+      _handleOnline();
+    } else {
+      _handleOffline();
+    }
+  }
+
+  /// This function checks if the device currently has any type of network connection.
+  ///
+  /// **params**:
+  ///   None
+  ///
+  /// **returns**:
+  /// * `Future<bool>`: indicating whether the device has a network connection.
+  Future<bool> hasConnection() async {
+    try {
+      final result = await connectivity.checkConnectivity();
+      return result != ConnectivityResult.none;
+    } catch (e) {
+      return false;
+    }
+  }
+}

test/helpers/test_helpers.dart

@@ -27,6 +27,7 @@ import 'package:talawa/services/org_service.dart';
 import 'package:talawa/services/post_service.dart';
 import 'package:talawa/services/session_manager.dart';
 import 'package:talawa/services/size_config.dart';
+import 'package:talawa/services/third_party_service/connectivity_service.dart';
 import 'package:talawa/services/third_party_service/multi_media_pick_service.dart';
 import 'package:talawa/services/user_config.dart';
 import 'package:talawa/utils/event_queries.dart';
@@ -50,6 +51,7 @@ import 'package:talawa/view_model/widgets_view_models/like_button_view_model.dar
 import 'package:talawa/view_model/widgets_view_models/progress_dialog_view_model.dart';
 
 import '../service_tests/image_service_test.dart';
+import '../service_tests/third_party_service_test.dart/connectivity_service_test.dart';
 import '../service_tests/user_config_test.dart';
 import '../views/main_screen_test.dart';
 import 'test_helpers.mocks.dart';
@@ -68,7 +70,6 @@ import 'test_helpers.mocks.dart';
     MockSpec<ChatService>(onMissingStub: OnMissingStub.returnDefault),
     MockSpec<UserConfig>(onMissingStub: OnMissingStub.returnDefault),
     MockSpec<AppLanguage>(onMissingStub: OnMissingStub.returnDefault),
-    MockSpec<Connectivity>(onMissingStub: OnMissingStub.returnDefault),
     MockSpec<SignupDetailsViewModel>(
       onMissingStub: OnMissingStub.returnDefault,
     ),
@@ -650,20 +651,35 @@ EventService getAndRegisterEventService() {
   return service;
 }
 
-/// `getAndRegisterConnectivityService` returns a mock instance of the `Connectivity` class.
+/// `getAndRegisterConnectivity` returns a mock instance of the `Connectivity` class.
 ///
 /// **params**:
 ///   None
 ///
 /// **returns**:
 /// * `Connectivity`: A mock instance of the `Connectivity` class.
-Connectivity getAndRegisterConnectivityService() {
+Connectivity getAndRegisterConnectivity() {
   _removeRegistrationIfExists<Connectivity>();
   final service = MockConnectivity();
   locator.registerSingleton<Connectivity>(service);
   return service;
 }
 
+/// `getAndRegisterConnectivityService` returns a mock instance of the `ConnectivityService` class.
+///
+/// **params**:
+///   None
+///
+/// **returns**:
+/// * `ConnectivityService`: A mock instance of the `ConnectivityService` class.
+ConnectivityService getAndRegisterConnectivityService() {
+  _removeRegistrationIfExists<ConnectivityService>();
+  final service = MockConnectivityService();
+  locator.registerSingleton<ConnectivityService>(service);
+  // when(service.)
+  return service;
+}
+
 /// `getPostMockModel` returns a mock instance of the `Post` class.
 ///
 /// **params**:
@@ -862,6 +878,7 @@ void registerServices() {
   getAndRegisterPostService();
   getAndRegisterEventService();
   getAndRegisterMultiMediaPickerService();
+  getAndRegisterConnectivity();
   getAndRegisterConnectivityService();
   getAndRegisterDatabaseMutationFunctions();
   getAndRegisterOrganizationService();
@@ -886,6 +903,7 @@ void unregisterServices() {
   locator.unregister<EventService>();
   locator.unregister<MultiMediaPickerService>();
   locator.unregister<Connectivity>();
+  locator.unregister<ConnectivityService>();
   locator.unregister<DataBaseMutationFunctions>();
   locator.unregister<OrganizationService>();
   locator.unregister<CommentService>();