style: format

Author: fulleni

lib/discover/bloc/discover_bloc.dart

@@ -68,9 +68,7 @@ class DiscoverBloc extends Bloc<DiscoverEvent, DiscoverState> {
       emit(
         state.copyWith(
           status: DiscoverStatus.failure,
-          error: UnknownException(
-            'An unexpected error occurred: $e',
-          ),
+          error: UnknownException('An unexpected error occurred: $e'),
         ),
       );
     }

lib/discover/bloc/source_list_bloc.dart

@@ -298,8 +298,9 @@ class SourceListBloc extends Bloc<SourceListEvent, SourceListState> {
     Emitter<SourceListState> emit,
   ) async {
     if (!state.countriesHasMore ||
-        state.status == SourceListStatus.loadingMoreCountries)
+        state.status == SourceListStatus.loadingMoreCountries) {
       return;
+    }
 
     _logger.fine('Load more countries for source list filter requested.');
     emit(state.copyWith(status: SourceListStatus.loadingMoreCountries));

lib/discover/view/source_list_filter_page.dart

@@ -1,3 +1,4 @@
+import 'package:collection/collection.dart';
 import 'package:core/core.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
@@ -33,14 +34,26 @@ class _SourceListFilterView extends StatefulWidget {
 }
 
 class _SourceListFilterViewState extends State<_SourceListFilterView> {
+  late final Set<Country> _initialSelection;
+  late Set<Country> _currentSelection;
   final _scrollController = ScrollController();
 
   @override
   void initState() {
     super.initState();
+    // Store the initial and current selections locally to track changes.
+    _initialSelection = context.read<SourceListBloc>().state.selectedCountries;
+    _currentSelection = Set.from(_initialSelection);
     _scrollController.addListener(_onScroll);
   }
 
+  bool get _hasChanges {
+    return !const SetEquality<Country>().equals(
+      _initialSelection,
+      _currentSelection,
+    );
+  }
+
   @override
   void dispose() {
     _scrollController
@@ -79,7 +92,20 @@ class _SourceListFilterViewState extends State<_SourceListFilterView> {
           IconButton(
             icon: const Icon(Icons.check),
             tooltip: l10n.headlinesFeedFilterApplyButton,
-            onPressed: () => Navigator.of(context).pop(),
+            // The button is enabled only if the selection has changed.
+            onPressed: _hasChanges
+                ? () {
+                    // When applying, dispatch a single event with the final
+                    // selection and then pop the page.
+                    context.read<SourceListBloc>().add(
+                      SourceListCountryFilterChanged(
+                        selectedCountries: _currentSelection,
+                      ),
+                    );
+                    Navigator.of(context).pop();
+                  }
+                // If there are no changes, the button is disabled.
+                : null,
           ),
         ],
       ),
@@ -115,7 +141,7 @@ class _SourceListFilterViewState extends State<_SourceListFilterView> {
                     : const SizedBox.shrink();
               }
               final country = state.countries[index];
-              final isSelected = state.selectedCountries.contains(country);
+              final isSelected = _currentSelection.contains(country);
 
               return CheckboxListTile(
                 title: Text(country.name, style: textTheme.titleMedium),
@@ -138,19 +164,15 @@ class _SourceListFilterViewState extends State<_SourceListFilterView> {
                 value: isSelected,
                 onChanged: (bool? value) {
                   if (value == null) return;
-                  final newSelection = Set<Country>.from(
-                    state.selectedCountries,
-                  );
-                  if (value) {
-                    newSelection.add(country);
-                  } else {
-                    newSelection.remove(country);
-                  }
-                  context.read<SourceListBloc>().add(
-                    SourceListCountryFilterChanged(
-                      selectedCountries: newSelection,
-                    ),
-                  );
+                  // Update the local selection state, which will trigger a
+                  // rebuild and enable/disable the apply button.
+                  setState(() {
+                    if (value) {
+                      _currentSelection.add(country);
+                    } else {
+                      _currentSelection.remove(country);
+                    }
+                  });
                 },
                 controlAffinity: ListTileControlAffinity.leading,
               );

lib/headlines-feed/view/source_list_filter_page.dart

@@ -4,8 +4,8 @@ import 'package:core/core.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/l10n/l10n.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/router/routes.dart';
-import 'package:go_router/go_router.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/shared/extensions/extensions.dart';
+import 'package:go_router/go_router.dart';
 import 'package:ui_kit/ui_kit.dart';
 
 /// {@template source_list_filter_page}