Add Future.delays to json->obj conversion in Notifications and Timelines to reduce freezing

lib/friendica_client/friendica_client.dart

@@ -41,6 +41,9 @@ import '../services/network_status_service.dart';
 import '../utils/network_utils.dart';
 import 'paging_data.dart';
 
+const _maxProcessingMillis = 3;
+const _processingSleep = Duration(milliseconds: 1);
+
 class DirectMessagingClient extends FriendicaClient {
   static final _logger = Logger('$DirectMessagingClient');
 
@@ -378,13 +381,22 @@ class NotificationsClient extends FriendicaClient {
     final url = 'https://$serverName/api/v1/notifications?include_all=true';
     final request = Uri.parse('$url&${page.toQueryParameters()}');
     _logger.finest(() => 'Getting new notifications');
-    final result = await _getApiListRequest(request);
+    final result =
+        await _getApiListRequest(request).transformAsync((response) async {
+      final notifications = <UserNotification>[];
+
+      final st = Stopwatch()..start();
+      for (final json in response.data) {
+        if (st.elapsedMilliseconds > _maxProcessingMillis) {
+          await Future.delayed(_processingSleep, () => st.reset());
+        }
+        notifications.add(NotificationMastodonExtension.fromJson(json));
+      }
+      return PagedResponse(notifications,
+          id: response.id, previous: response.previous, next: response.next);
+    });
     _networkStatusService.finishNotificationUpdate();
-    return result
-        .andThenSuccess((response) => response.map((jsonArray) => jsonArray
-            .map((json) => NotificationMastodonExtension.fromJson(json))
-            .toList()))
-        .execErrorCast();
+    return result.execErrorCast();
   }
 
   FutureResult<bool, ExecError> clearNotifications() async {
@@ -894,13 +906,12 @@ class TimelineClient extends FriendicaClient {
         ? '$baseUrl$pagingData'
         : '${baseUrl}screen_name=$userId$pagingData';
     final request = Uri.parse(url);
-    final result = (await _getApiListRequest(request).andThenSuccessAsync(
-            (postsJson) async => postsJson.data
-                .map((json) => TimelineEntryMastodonExtensions.fromJson(json))
-                .toList()))
-        .execErrorCast();
+    final result = await _getApiListRequest(request).transformAsync(
+      (postsJson) async => await _timelineEntriesFromJson(postsJson.data),
+    );
+
     _networkStatusService.finishTimelineLoading();
-    return result;
+    return result.execErrorCast();
   }
 
   FutureResult<List<TimelineEntry>, ExecError> getTimeline(
@@ -913,13 +924,26 @@ class TimelineClient extends FriendicaClient {
         '$baseUrl?exclude_replies=true&${page.toQueryParameters()}&$timelineQPs';
     final request = Uri.parse(url);
     _logger.finest(() => 'Getting ${type.toHumanKey()} with paging data $page');
-    final result = (await _getApiListRequest(request).andThenSuccessAsync(
-            (postsJson) async => postsJson.data
-                .map((json) => TimelineEntryMastodonExtensions.fromJson(json))
-                .toList()))
-        .execErrorCast();
+    final result = await _getApiListRequest(request).transformAsync(
+      (postsJson) async => await _timelineEntriesFromJson(postsJson.data),
+    );
     _networkStatusService.finishTimelineLoading();
-    return result;
+    return result.execErrorCast();
+  }
+
+  Future<List<TimelineEntry>> _timelineEntriesFromJson(
+    List<dynamic> postsJson,
+  ) async {
+    final finalResult = <TimelineEntry>[];
+    final st = Stopwatch()..start();
+    for (final json in postsJson) {
+      if (st.elapsedMilliseconds > _maxProcessingMillis) {
+        await Future.delayed(_processingSleep, () => st.reset());
+      }
+      finalResult.add(TimelineEntryMastodonExtensions.fromJson(json));
+    }
+
+    return finalResult;
   }
 
   String _typeToTimelinePath(TimelineIdentifiers type) {