refactor(content_management): simplify country dropdown pagination

- Remove background fetching mechanism for countries list
- Load all countries at once in EditHeadlineBloc initialization
- Update EditHeadlineState to remove pagination-related variables
- Modify EditHeadlinePage to use a predefined list of countries
- Remove loading indicator and related logic from the dropdown

Author: fulleni

lib/content_management/bloc/edit_headline/edit_headline_bloc.dart

@@ -7,25 +7,20 @@ import 'package:flutter/foundation.dart';
 part 'edit_headline_event.dart';
 part 'edit_headline_state.dart';
 
-final class _FetchNextCountryPage extends EditHeadlineEvent {
-  const _FetchNextCountryPage();
-}
-
 /// A BLoC to manage the state of editing a single headline.
 class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
   /// {@macro edit_headline_bloc}
   EditHeadlineBloc({
     required DataRepository<Headline> headlinesRepository,
     required DataRepository<Source> sourcesRepository,
     required DataRepository<Topic> topicsRepository,
-    required DataRepository<Country> countriesRepository,
+    required List<Country> countries,
     required String headlineId,
-  }) : _headlinesRepository = headlinesRepository,
-       _sourcesRepository = sourcesRepository,
-       _topicsRepository = topicsRepository,
-       _countriesRepository = countriesRepository,
-       _headlineId = headlineId,
-       super(const EditHeadlineState()) {
+  })  : _headlinesRepository = headlinesRepository,
+        _sourcesRepository = sourcesRepository,
+        _topicsRepository = topicsRepository,
+        _headlineId = headlineId,
+        super(EditHeadlineState(countries: countries)) {
     on<EditHeadlineLoaded>(_onLoaded);
     on<EditHeadlineTitleChanged>(_onTitleChanged);
     on<EditHeadlineExcerptChanged>(_onExcerptChanged);
@@ -36,13 +31,11 @@ class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
     on<EditHeadlineCountryChanged>(_onCountryChanged);
     on<EditHeadlineStatusChanged>(_onStatusChanged);
     on<EditHeadlineSubmitted>(_onSubmitted);
-    on<_FetchNextCountryPage>(_onFetchNextCountryPage);
   }
 
   final DataRepository<Headline> _headlinesRepository;
   final DataRepository<Source> _sourcesRepository;
   final DataRepository<Topic> _topicsRepository;
-  final DataRepository<Country> _countriesRepository;
   final String _headlineId;
 
   Future<void> _onLoaded(
@@ -67,10 +60,6 @@ class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
       final sources = (responses[1] as PaginatedResponse<Source>).items;
       final topics = (responses[2] as PaginatedResponse<Topic>).items;
 
-      final countriesResponse = await _countriesRepository.readAll(
-        sort: [const SortOption('name', SortOrder.asc)],
-      );
-
       emit(
         state.copyWith(
           status: EditHeadlineStatus.initial,
@@ -84,18 +73,9 @@ class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
           eventCountry: () => headline.eventCountry,
           sources: sources,
           topics: topics,
-          countries: countriesResponse.items,
-          countriesCursor: countriesResponse.cursor,
-          countriesHasMore: countriesResponse.hasMore,
           contentStatus: headline.status,
         ),
       );
-
-      // After the initial page of countries is loaded, start a background
-      // process to fetch all remaining pages.
-      if (state.countriesHasMore) {
-        add(const _FetchNextCountryPage());
-      }
     } on HttpException catch (e) {
       emit(state.copyWith(status: EditHeadlineStatus.failure, exception: e));
     } catch (e) {
@@ -197,49 +177,6 @@ class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
   }
 
   // --- Background Data Fetching for Dropdown ---
-  // The DropdownButtonFormField widget does not natively support on-scroll
-  // pagination. To preserve UI consistency across the application, this BLoC
-  // employs an event-driven background fetching mechanism.
-  //
-  // After the first page of items is loaded, a chain of events is initiated
-  // to progressively fetch all remaining pages. This process is throttled
-  // and runs in the background, ensuring the UI remains responsive while the
-  // full list of dropdown options is populated over time.
-  Future<void> _onFetchNextCountryPage(
-    _FetchNextCountryPage event,
-    Emitter<EditHeadlineState> emit,
-  ) async {
-    if (!state.countriesHasMore || state.countriesIsLoadingMore) return;
-
-    try {
-      emit(state.copyWith(countriesIsLoadingMore: true));
-
-      // ignore: inference_failure_on_instance_creation
-      await Future.delayed(const Duration(milliseconds: 400));
-
-      final nextCountries = await _countriesRepository.readAll(
-        pagination: PaginationOptions(cursor: state.countriesCursor),
-        sort: [const SortOption('name', SortOrder.asc)],
-      );
-
-      emit(
-        state.copyWith(
-          countries: List.of(state.countries)..addAll(nextCountries.items),
-          countriesCursor: nextCountries.cursor,
-          countriesHasMore: nextCountries.hasMore,
-          countriesIsLoadingMore: false,
-        ),
-      );
-
-      if (nextCountries.hasMore) {
-        add(const _FetchNextCountryPage());
-      }
-    } catch (e) {
-      emit(state.copyWith(countriesIsLoadingMore: false));
-      // Optionally log the error without disrupting the user
-    }
-  }
-
   Future<void> _onSubmitted(
     EditHeadlineSubmitted event,
     Emitter<EditHeadlineState> emit,

lib/content_management/bloc/edit_headline/edit_headline_state.dart

@@ -33,9 +33,6 @@ final class EditHeadlineState extends Equatable {
     this.sources = const [],
     this.topics = const [],
     this.countries = const [],
-    this.countriesHasMore = true,
-    this.countriesIsLoadingMore = false,
-    this.countriesCursor,
     this.contentStatus = ContentStatus.active,
     this.exception,
     this.updatedHeadline,
@@ -53,9 +50,6 @@ final class EditHeadlineState extends Equatable {
   final List<Source> sources;
   final List<Topic> topics;
   final List<Country> countries;
-  final bool countriesHasMore;
-  final bool countriesIsLoadingMore;
-  final String? countriesCursor;
   final ContentStatus contentStatus;
   final HttpException? exception;
   final Headline? updatedHeadline;
@@ -83,9 +77,6 @@ final class EditHeadlineState extends Equatable {
     List<Source>? sources,
     List<Topic>? topics,
     List<Country>? countries,
-    bool? countriesHasMore,
-    bool? countriesIsLoadingMore,
-    String? countriesCursor,
     ContentStatus? contentStatus,
     HttpException? exception,
     Headline? updatedHeadline,
@@ -103,10 +94,6 @@ final class EditHeadlineState extends Equatable {
       sources: sources ?? this.sources,
       topics: topics ?? this.topics,
       countries: countries ?? this.countries,
-      countriesHasMore: countriesHasMore ?? this.countriesHasMore,
-      countriesIsLoadingMore:
-          countriesIsLoadingMore ?? this.countriesIsLoadingMore,
-      countriesCursor: countriesCursor ?? this.countriesCursor,
       contentStatus: contentStatus ?? this.contentStatus,
       exception: exception,
       updatedHeadline: updatedHeadline ?? this.updatedHeadline,
@@ -127,9 +114,6 @@ final class EditHeadlineState extends Equatable {
     sources,
     topics,
     countries,
-    countriesHasMore,
-    countriesIsLoadingMore,
-    countriesCursor,
     contentStatus,
     exception,
     updatedHeadline,

lib/content_management/view/edit_headline_page.dart

@@ -23,12 +23,17 @@ class EditHeadlinePage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    // The list of all countries is fetched once and cached in the
+    // ContentManagementBloc. We read it here and provide it to the
+    // EditHeadlineBloc.
+    final allCountries =
+        context.read<ContentManagementBloc>().state.allCountries;
     return BlocProvider(
       create: (context) => EditHeadlineBloc(
         headlinesRepository: context.read<DataRepository<Headline>>(),
         sourcesRepository: context.read<DataRepository<Source>>(),
         topicsRepository: context.read<DataRepository<Topic>>(),
-        countriesRepository: context.read<DataRepository<Country>>(),
+        countries: allCountries,
         headlineId: headlineId,
       )..add(const EditHeadlineLoaded()),
       child: const _EditHeadlineView(),
@@ -288,9 +293,6 @@ class _EditHeadlineViewState extends State<_EditHeadlineView> {
                       decoration: InputDecoration(
                         labelText: l10n.countryName,
                         border: const OutlineInputBorder(),
-                        helperText: state.countriesIsLoadingMore
-                            ? l10n.loadingFullList
-                            : null,
                       ),
                       items: [
                         DropdownMenuItem(value: null, child: Text(l10n.none)),
@@ -317,11 +319,9 @@ class _EditHeadlineViewState extends State<_EditHeadlineView> {
                           ),
                         ),
                       ],
-                      onChanged: state.countriesIsLoadingMore
-                          ? null
-                          : (value) => context.read<EditHeadlineBloc>().add(
-                              EditHeadlineCountryChanged(value),
-                            ),
+                      onChanged: (value) => context
+                          .read<EditHeadlineBloc>()
+                          .add(EditHeadlineCountryChanged(value)),
                     ),
                     const SizedBox(height: AppSpacing.lg),
                     DropdownButtonFormField<ContentStatus>(