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TF-3157 Update web socket with background service worker

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TF-3157 Stub BroadcastChannel for mobile build
This commit is contained in:
DatDang
2024-09-27 10:42:10 +07:00
committed by Dat H. Pham
parent c4d0c27603
commit 7d59982cc9
16 changed files with 414 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files
core/lib/data/constants/constant.dart
+1
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@@ -7,4 +7,5 @@ class Constant {
static const octetStreamMimeType = 'application/octet-stream';
static const pdfExtension = '.pdf';
static const imageType = 'image';
static const wsServiceWorkerBroadcastChannel = 'background-message';
}
fcm/lib/model/type_name.dart
+4 -4
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@@ -2,13 +2,13 @@
import 'package:equatable/equatable.dart';
class TypeName with EquatableMixin {
static final mailboxType = TypeName('Mailbox');
static final emailType = TypeName('Email');
static final emailDelivery = TypeName('EmailDelivery');
static const mailboxType = TypeName('Mailbox');
static const emailType = TypeName('Email');
static const emailDelivery = TypeName('EmailDelivery');
final String value;
TypeName(this.value);
const TypeName(this.value);
@override
List<Object?> get props => [value];
lib/features/push_notification/data/datasource_impl/remote_web_socket_datasource_impl.dart → lib/features/push_notification/data/datasource_impl/web_socket_datasource_impl.dart
+31 -17
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@@ -1,6 +1,7 @@
import 'dart:convert';
import 'package:core/data/constants/constant.dart';
import 'package:core/utils/app_logger.dart';
import 'package:core/utils/broadcast_channel/broadcast_channel.dart';
import 'package:jmap_dart_client/jmap/account_id.dart';
import 'package:jmap_dart_client/jmap/core/capability/capability_identifier.dart';
import 'package:jmap_dart_client/jmap/core/capability/websocket_capability.dart';
@@ -8,17 +9,21 @@ import 'package:jmap_dart_client/jmap/core/session/session.dart';
import 'package:model/extensions/session_extension.dart';
import 'package:rxdart/transformers.dart';
import 'package:tmail_ui_user/features/push_notification/data/datasource/web_socket_datasource.dart';
import 'package:tmail_ui_user/features/push_notification/data/model/connect_web_socket_message.dart';
import 'package:tmail_ui_user/features/push_notification/data/network/web_socket_api.dart';
import 'package:tmail_ui_user/features/push_notification/domain/exceptions/web_socket_exceptions.dart';
import 'package:tmail_ui_user/features/push_notification/domain/model/web_socket_action.dart';
import 'package:tmail_ui_user/main/error/capability_validator.dart';
import 'package:tmail_ui_user/main/exceptions/exception_thrower.dart';
import 'package:web_socket_channel/web_socket_channel.dart';
import 'package:universal_html/html.dart';
class RemoteWebSocketDatasourceImpl implements WebSocketDatasource {
class WebSocketDatasourceImpl implements WebSocketDatasource {
final WebSocketApi _webSocketApi;
final ExceptionThrower _exceptionThrower;
const RemoteWebSocketDatasourceImpl(this._webSocketApi, this._exceptionThrower);
const WebSocketDatasourceImpl(this._webSocketApi, this._exceptionThrower);
static const String _webSocketClosed = 'webSocketClosed';
@override
Stream getWebSocketChannel(Session session, AccountId accountId) {
@@ -30,32 +35,31 @@ class RemoteWebSocketDatasourceImpl implements WebSocketDatasource {
Stream _getWebSocketChannel(
Session session,
AccountId accountId,
[int retryRemained = 3]
) async* {
) async* {
final broadcastChannel = BroadcastChannel(Constant.wsServiceWorkerBroadcastChannel);
try {
_verifyWebSocketCapabilities(session, accountId);
final webSocketTicket = await _webSocketApi.getWebSocketTicket(session, accountId);
final webSocketUri = _getWebSocketUri(session, accountId);
window.navigator.serviceWorker?.controller?.postMessage(ConnectWebSocketMessage(
webSocketAction: WebSocketAction.connect,
webSocketUrl: webSocketUri.toString(),
webSocketTicket: webSocketTicket
).toJson());
final webSocketChannel = WebSocketChannel.connect(
Uri.parse('$webSocketUri?ticket=$webSocketTicket'));
await webSocketChannel.ready;
webSocketChannel.sink.add(jsonEncode({"@type": "WebSocketPushEnable"}));
yield* webSocketChannel.stream;
yield* _webSocketListener(broadcastChannel);
} catch (e) {
logError('RemoteWebSocketDatasourceImpl::getWebSocketChannel():error: $e');
if (retryRemained > 0) {
yield* _getWebSocketChannel(session, accountId, retryRemained - 1);
} else {
rethrow;
}
rethrow;
}
}
void _verifyWebSocketCapabilities(Session session, AccountId accountId) {
if (!CapabilityIdentifier.jmapWebSocket.isSupported(session, accountId)
|| !CapabilityIdentifier.jmapWebSocketTicket.isSupported(session, accountId)
|| session.getCapabilityProperties<WebSocketCapability>(
accountId,
CapabilityIdentifier.jmapWebSocket)?.supportsPush != true
) {
throw WebSocketPushNotSupportedException();
}
@@ -73,4 +77,14 @@ class RemoteWebSocketDatasourceImpl implements WebSocketDatasource {
return webSocketUri;
}
Stream _webSocketListener(BroadcastChannel broadcastChannel) {
return broadcastChannel.onMessage.map((event) {
if (event.data == _webSocketClosed) {
throw WebSocketClosedException();
}
return event.data;
});
}
}
lib/features/push_notification/data/model/connect_web_socket_message.dart
+28
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@@ -0,0 +1,28 @@
import 'package:equatable/equatable.dart';
import 'package:json_annotation/json_annotation.dart';
import 'package:tmail_ui_user/features/push_notification/domain/model/web_socket_action.dart';
part 'connect_web_socket_message.g.dart';
@JsonSerializable()
class ConnectWebSocketMessage with EquatableMixin {
@JsonKey(name: 'action')
final WebSocketAction webSocketAction;
@JsonKey(name: 'url')
final String webSocketUrl;
@JsonKey(name: 'ticket')
final String webSocketTicket;
ConnectWebSocketMessage({
required this.webSocketAction,
required this.webSocketUrl,
required this.webSocketTicket,
});
factory ConnectWebSocketMessage.fromJson(Map<String, dynamic> json)
=> _$ConnectWebSocketMessageFromJson(json);
Map<String, dynamic> toJson() => _$ConnectWebSocketMessageToJson(this);
@override
List<Object?> get props => [webSocketAction, webSocketUrl, webSocketTicket];
}
lib/features/push_notification/data/model/web_socket_echo.dart
+31
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@@ -0,0 +1,31 @@
import 'package:json_annotation/json_annotation.dart';
part 'web_socket_echo.g.dart';
@JsonSerializable(includeIfNull: false)
class WebSocketEcho {
@JsonKey(name: '@type')
final String? type;
final String? requestId;
final List<List<dynamic>>? methodResponses;
WebSocketEcho({
this.type,
this.requestId,
this.methodResponses,
});
factory WebSocketEcho.fromJson(Map<String, dynamic> json) => _$WebSocketEchoFromJson(json);
Map<String, dynamic> toJson() => _$WebSocketEchoToJson(this);
static bool isValid(Map<String, dynamic> json) {
try {
final webSocketEcho = WebSocketEcho.fromJson(json);
final listResponses = webSocketEcho.methodResponses?.firstOrNull;
return listResponses?.contains('Core/echo') ?? false;
} catch (_) {
return false;
}
}
}
lib/features/push_notification/domain/exceptions/web_socket_exceptions.dart
+3 -1
View File
@@ -2,4 +2,6 @@ class WebSocketPushNotSupportedException implements Exception {}
class WebSocketUriUnavailableException implements Exception {}
class WebSocketTicketUnavailableException implements Exception {}
class WebSocketTicketUnavailableException implements Exception {}
class WebSocketClosedException implements Exception {}
lib/features/push_notification/domain/model/web_socket_action.dart
+1
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@@ -0,0 +1 @@
enum WebSocketAction {connect, disconnect}
lib/features/push_notification/domain/state/web_socket_push_state.dart
+2 -2
View File
@@ -5,12 +5,12 @@ import 'package:jmap_dart_client/jmap/push/state_change.dart';
class InitializingWebSocketPushChannel extends LoadingState {}
class WebSocketPushStateReceived extends UIState {
final StateChange stateChange;
final StateChange? stateChange;
WebSocketPushStateReceived(this.stateChange);
@override
List<Object> get props => [stateChange];
List<Object?> get props => [stateChange];
}
class WebSocketConnectionFailed extends FeatureFailure {
lib/features/push_notification/domain/usecases/connect_web_socket_interactor.dart
+16 -3
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@@ -7,6 +7,7 @@ import 'package:dartz/dartz.dart';
import 'package:jmap_dart_client/jmap/account_id.dart';
import 'package:jmap_dart_client/jmap/core/session/session.dart';
import 'package:jmap_dart_client/jmap/push/state_change.dart';
import 'package:tmail_ui_user/features/push_notification/data/model/web_socket_echo.dart';
import 'package:tmail_ui_user/features/push_notification/domain/repository/web_socket_repository.dart';
import 'package:tmail_ui_user/features/push_notification/domain/state/web_socket_push_state.dart';
@@ -31,9 +32,21 @@ class ConnectWebSocketInteractor {
}
Either<Failure, Success> _toStateChange(dynamic data) {
if (data is String) {
data = jsonDecode(data);
StateChange? possibleStateChange;
try {
if (data is String) {
data = jsonDecode(data);
}
possibleStateChange = StateChange.fromJson(data);
return Right(WebSocketPushStateReceived(possibleStateChange));
} catch (e) {
logError('ConnectWebSocketInteractor::_toStateChange: '
'websocket message is not StateChange: $data');
final dataIsWebSocketEcho = WebSocketEcho.isValid(data);
if (dataIsWebSocketEcho) {
return Right(WebSocketPushStateReceived(null));
}
return Left(WebSocketConnectionFailed(exception: e));
}
return Right(WebSocketPushStateReceived(StateChange.fromJson(data)));
}
}
lib/features/push_notification/presentation/bindings/web_socket_interactor_bindings.dart
+3 -3
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@@ -1,7 +1,7 @@
import 'package:get/get.dart';
import 'package:tmail_ui_user/features/base/interactors_bindings.dart';
import 'package:tmail_ui_user/features/push_notification/data/datasource/web_socket_datasource.dart';
import 'package:tmail_ui_user/features/push_notification/data/datasource_impl/remote_web_socket_datasource_impl.dart';
import 'package:tmail_ui_user/features/push_notification/data/datasource_impl/web_socket_datasource_impl.dart';
import 'package:tmail_ui_user/features/push_notification/data/network/web_socket_api.dart';
import 'package:tmail_ui_user/features/push_notification/data/repository/web_socket_repository_impl.dart';
import 'package:tmail_ui_user/features/push_notification/domain/repository/web_socket_repository.dart';
@@ -11,12 +11,12 @@ import 'package:tmail_ui_user/main/exceptions/remote_exception_thrower.dart';
class WebSocketInteractorBindings extends InteractorsBindings {
@override
void bindingsDataSource() {
Get.lazyPut<WebSocketDatasource>(() => Get.find<RemoteWebSocketDatasourceImpl>());
Get.lazyPut<WebSocketDatasource>(() => Get.find<WebSocketDatasourceImpl>());
}
@override
void bindingsDataSourceImpl() {
Get.lazyPut(() => RemoteWebSocketDatasourceImpl(
Get.lazyPut(() => WebSocketDatasourceImpl(
Get.find<WebSocketApi>(),
Get.find<RemoteExceptionThrower>(),
));
lib/features/push_notification/presentation/controller/push_base_controller.dart
+29 -20
View File
@@ -1,3 +1,5 @@
import 'dart:async';
import 'package:collection/collection.dart';
import 'package:core/presentation/state/failure.dart';
import 'package:core/presentation/state/success.dart';
@@ -17,12 +19,12 @@ abstract class PushBaseController {
Session? session;
AccountId? accountId;
StreamSubscription<Either<Failure, Success>>? _stateStreamSubscription;
void consumeState(Stream<Either<Failure, Success>> newStateStream) {
newStateStream.listen(
_stateStreamSubscription = newStateStream.listen(
_handleStateStream,
onError: (error, stackTrace) {
logError('PushBaseController::consumeState():onError:error: $error | stackTrace: $stackTrace');
}
onError: handleErrorViewState,
);
}
@@ -34,6 +36,15 @@ abstract class PushBaseController {
void handleSuccessViewState(Success success);
void handleErrorViewState(Object error, StackTrace stackTrace) {
logError('PushBaseController::handleErrorViewState():error: $error | stackTrace: $stackTrace');
}
void cancelStateStreamSubscription() {
_stateStreamSubscription?.cancel();
_stateStreamSubscription = null;
}
void initialize({AccountId? accountId, Session? session}) {
this.accountId = accountId;
this.session = session;
@@ -87,22 +98,20 @@ abstract class PushBaseController {
{Session? session}
) {
final newState = jmap.State(mapTypeState[typeName.value]);
if (typeName == TypeName.emailType) {
if (isForeground) {
return SynchronizeEmailOnForegroundAction(typeName, newState, accountId, session);
} else {
return StoreEmailStateToRefreshAction(typeName, newState, accountId, userName, session);
}
} else if (typeName == TypeName.emailDelivery) {
if (!isForeground) {
return PushNotificationAction(typeName, newState, session, accountId, userName);
}
} else if (typeName == TypeName.mailboxType) {
if (isForeground) {
return SynchronizeMailboxOnForegroundAction(typeName, newState, accountId);
} else {
return StoreMailboxStateToRefreshAction(typeName, newState, accountId, userName);
}
switch (typeName) {
case TypeName.emailType:
return isForeground
? SynchronizeEmailOnForegroundAction(typeName, newState, accountId, session)
: StoreEmailStateToRefreshAction(typeName, newState, accountId, userName, session);
case TypeName.emailDelivery:
if (!isForeground) {
return PushNotificationAction(typeName, newState, session, accountId, userName);
}
break;
case TypeName.mailboxType:
return isForeground
? SynchronizeMailboxOnForegroundAction(typeName, newState, accountId)
: StoreMailboxStateToRefreshAction(typeName, newState, accountId, userName);
}
return null;
}
lib/features/push_notification/presentation/controller/web_socket_controller.dart
+25
View File
@@ -3,6 +3,7 @@ import 'package:core/presentation/state/success.dart';
import 'package:core/utils/app_logger.dart';
import 'package:jmap_dart_client/jmap/account_id.dart';
import 'package:jmap_dart_client/jmap/core/session/session.dart';
import 'package:tmail_ui_user/features/push_notification/domain/exceptions/web_socket_exceptions.dart';
import 'package:tmail_ui_user/features/push_notification/domain/state/web_socket_push_state.dart';
import 'package:tmail_ui_user/features/push_notification/domain/usecases/connect_web_socket_interactor.dart';
import 'package:tmail_ui_user/features/push_notification/presentation/controller/push_base_controller.dart';
@@ -20,9 +21,15 @@ class WebSocketController extends PushBaseController {
ConnectWebSocketInteractor? _connectWebSocketInteractor;
int _retryRemained = 3;
@override
void handleFailureViewState(Failure failure) {
logError('WebSocketController::handleFailureViewState():Failure $failure');
cancelStateStreamSubscription();
if (failure is WebSocketConnectionFailed) {
_handleWebSocketConnectionRetry();
}
}
@override
@@ -33,6 +40,15 @@ class WebSocketController extends PushBaseController {
}
}
@override
void handleErrorViewState(Object error, StackTrace stackTrace) {
super.handleErrorViewState(error, stackTrace);
cancelStateStreamSubscription();
if (error is WebSocketClosedException) {
_handleWebSocketConnectionRetry();
}
}
@override
void initialize({AccountId? accountId, Session? session}) {
super.initialize(accountId: accountId, session: session);
@@ -51,8 +67,10 @@ class WebSocketController extends PushBaseController {
void _handleWebSocketPushStateReceived(WebSocketPushStateReceived success) {
log('WebSocketController::_handleWebSocketPushStateReceived(): $success');
_retryRemained = 3;
if (accountId == null || session == null) return;
final stateChange = success.stateChange;
if (stateChange == null) return;
final mapTypeState = stateChange.getMapTypeState(accountId!);
mappingTypeStateToAction(
mapTypeState,
@@ -62,4 +80,11 @@ class WebSocketController extends PushBaseController {
session!.username,
session: session);
}
void _handleWebSocketConnectionRetry() {
if (_retryRemained > 0) {
_retryRemained--;
_connectWebSocket(accountId, session);
}
}
}
test/features/push_notification/data/model/web_socket_echo_test.dart
+44
View File
@@ -0,0 +1,44 @@
import 'package:flutter_test/flutter_test.dart';
import 'package:tmail_ui_user/features/push_notification/data/model/web_socket_echo.dart';
void main() {
group('web socket echo test:', () {
group('isValid():', () {
test(
'should return true '
'when json is web socket echo',
() {
// arrange
final json = {
"@type": "Response",
"requestId": "R1",
"methodResponses": [["Core/echo", {}, "c0"]]
};
// act
final result = WebSocketEcho.isValid(json);
// assert
expect(result, true);
});
test(
'should return false '
'when json is not web socket echo',
() {
// arrange
final json = {
"@type": "Response",
"requestId": "R1",
"methodResponses": [["Core/not-echo", {}, "c0"]]
};
// act
final result = WebSocketEcho.isValid(json);
// assert
expect(result, false);
});
});
});
}
test/features/push_notification/domain/usecases/connect_web_socket_interactor_test.dart
+121
View File
@@ -0,0 +1,121 @@
import 'package:dartz/dartz.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:jmap_dart_client/jmap/push/state_change.dart';
import 'package:mockito/annotations.dart';
import 'package:mockito/mockito.dart';
import 'package:tmail_ui_user/features/push_notification/domain/repository/web_socket_repository.dart';
import 'package:tmail_ui_user/features/push_notification/domain/state/web_socket_push_state.dart';
import 'package:tmail_ui_user/features/push_notification/domain/usecases/connect_web_socket_interactor.dart';
import '../../../../fixtures/account_fixtures.dart';
import '../../../../fixtures/session_fixtures.dart';
import 'connect_web_socket_interactor_test.mocks.dart';
@GenerateNiceMocks([MockSpec<WebSocketRepository>()])
void main() {
late MockWebSocketRepository webSocketRepository;
late ConnectWebSocketInteractor connectWebSocketInteractor;
setUp(() {
webSocketRepository = MockWebSocketRepository();
connectWebSocketInteractor = ConnectWebSocketInteractor(webSocketRepository);
});
group('connect web socket interactor test:', () {
test(
'should yield WebSocketPushStateReceived with StateChange '
'when web socket repository yield StateChange',
() {
// arrange
final stateChangeJson = {
"@type": "StateChange",
"changed": <String, dynamic>{}
};
when(webSocketRepository.getWebSocketChannel(any, any))
.thenAnswer((_) => Stream.value(stateChangeJson));
// assert
expect(
connectWebSocketInteractor.execute(
SessionFixtures.aliceSession,
AccountFixtures.aliceAccountId),
emitsInOrder([
Right(InitializingWebSocketPushChannel()),
Right(WebSocketPushStateReceived(StateChange.fromJson(stateChangeJson))),
]));
});
test(
'should yield WebSocketPushStateReceived with null '
'when web socket repository yield WebSocketEcho',
() {
// arrange
final webSocketEchoJson = {
"@type": "Response",
"requestId": "R1",
"methodResponses": [["Core/echo", {}, "c0"]]
};
when(webSocketRepository.getWebSocketChannel(any, any))
.thenAnswer((_) => Stream.value(webSocketEchoJson));
// assert
expect(
connectWebSocketInteractor.execute(
SessionFixtures.aliceSession,
AccountFixtures.aliceAccountId),
emitsInOrder([
Right(InitializingWebSocketPushChannel()),
Right(WebSocketPushStateReceived(null)),
]));
});
test(
'should yield WebSocketConnectionFailed '
'when web socket repository throws exception',
() {
// arrange
final exception = Exception();
when(webSocketRepository.getWebSocketChannel(any, any))
.thenThrow(exception);
// assert
expect(
connectWebSocketInteractor.execute(
SessionFixtures.aliceSession,
AccountFixtures.aliceAccountId),
emitsInOrder([
Right(InitializingWebSocketPushChannel()),
Left(WebSocketConnectionFailed(exception: exception)),
]));
});
test(
'should yield WebSocketConnectionFailed '
'when web socket repository yield data '
'and data is not web socket echo',
() async {
// arrange
final notWebSocketEchoJson = {
"@type": "Response",
"requestId": "R1",
"methodResponses": [["Core/not-echo", {}, "c0"]]
};
when(webSocketRepository.getWebSocketChannel(any, any))
.thenAnswer((_) => Stream.value(notWebSocketEchoJson));
// act
final lastState = await connectWebSocketInteractor.execute(
SessionFixtures.aliceSession,
AccountFixtures.aliceAccountId).last;
// assert
expect(
lastState.fold(
(failure) => failure is WebSocketConnectionFailed,
(success) => false,
),
true
);
});
});
}
web/web-sockets-worker.js
+74
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@@ -0,0 +1,74 @@
importScripts('flutter_service_worker.js?v={{flutter_service_worker_version}}');
var webSocket;
const broadcast = new BroadcastChannel("background-message");
var intervalId;
const pingIntervalInMs = 10000;
function connect(url, ticket) {
webSocket = new WebSocket(`${url}?ticket=${ticket}`, "jmap");
webSocket.onopen = () => {
console.log("websocket open");
webSocket.send(
JSON.stringify({
"@type": "WebSocketPushEnable",
dataTypes: ["Mailbox", "Email"],
})
);
intervalId = setInterval(() => {
webSocket.send(
JSON.stringify({
"@type": "Request",
id: "R1",
using: ["urn:ietf:params:jmap:core"],
methodCalls: [["Core/echo", {}, "c0"]],
})
);
}, pingIntervalInMs);
};
webSocket.onmessage = (event) => {
console.log(`websocket received message: ${event.data}`);
broadcast.postMessage(event.data);
};
webSocket.onclose = (event) => {
console.log(
`websocket connection closed with code: "${event.code}" reason: "${event.reason}" and cleanly: "${event.wasClean}"`
);
broadcast.postMessage("webSocketClosed");
webSocket = null;
clearInterval(intervalId);
};
}
function disconnect() {
if (webSocket == null) {
return;
}
webSocket.close();
}
self.addEventListener("install", (event) => {
self.skipWaiting().then(() => {
console.log("Service worker installed");
});
});
self.addEventListener("activate", (event) => {
event.waitUntil(
self.clients.claim().then(() => {
console.log("Service worker activated");
})
);
});
self.addEventListener("message", (event) => {
console.log(`web socket worker received message: ${event.data}`);
if (event.data.action === "connect") {
connect(event.data.url, event.data.ticket);
} else if (event.data.action === "disconnect") {
disconnect();
}
});
web/worker_service/worker_service.js
+1 -17
View File
@@ -4,7 +4,6 @@ const iosPlatform = 'iOS';
const androidPlatform = 'android';
const otherPlatform = 'other';
const timeoutDuration = 4000;
var serviceWorkerVersion = null;
var scriptLoaded = false;
function loadMainDartJs() {
@@ -24,16 +23,7 @@ function fetchServiceWorker() {
// Wait for registration to finish before dropping the <script>tag.
// Otherwise, the browser will load the script multiple times,
// potentially different versions.
navigator.serviceWorker.register('firebase-messaging-sw.js').then(serviceWorkerRegistration => {
console.info('[TwakeMail] fetchServiceWorker(): Service worker firebase-messaging was registered.');
}).catch(error => {
console.error(
'[TwakeMail] fetchServiceWorker(): An error occurred while registering the service worker firebase-messaging.'
);
console.error(error);
});
var serviceWorkerUrl = 'flutter_service_worker.js?v=' + serviceWorkerVersion;
navigator.serviceWorker.register(serviceWorkerUrl)
navigator.serviceWorker.register('web-sockets-worker.js')
.then((reg) => {
function waitForActivation(serviceWorker) {
serviceWorker.addEventListener('statechange', () => {
@@ -47,12 +37,6 @@ function fetchServiceWorker() {
// No active web worker and we have installed or are installing
// one for the first time. Simply wait for it to activate.
waitForActivation(reg.installing || reg.waiting);
} else if (!reg.active.scriptURL.endsWith(serviceWorkerVersion)) {
// When the app updates the serviceWorkerVersion changes, so we
// need to ask the service worker to update.
console.log('[TwakeMail] fetchServiceWorker(): New service worker available.');
reg.update();
waitForActivation(reg.installing);
} else {
// Existing service worker is still good.
console.log('[TwakeMail] fetchServiceWorker(): Loading app from service worker.');