refactor(content_management): simplify source editing process

- Remove pagination and background fetching for countries and languages
- Load full lists of countries and languages at once
- Cache countries and languages in ContentManagementBloc
- Update EditSourceBloc to use cached lists
- Simplify UI by removing loading indicators for dropdowns

Author: fulleni

lib/content_management/bloc/edit_source/edit_source_bloc.dart

@@ -7,27 +7,22 @@ import 'package:flutter/foundation.dart';
 part 'edit_source_event.dart';
 part 'edit_source_state.dart';
 
-final class _FetchNextCountryPage extends EditSourceEvent {
-  const _FetchNextCountryPage();
-}
-
-final class _FetchNextLanguagePage extends EditSourceEvent {
-  const _FetchNextLanguagePage();
-}
-
 /// A BLoC to manage the state of editing a single source.
 class EditSourceBloc extends Bloc<EditSourceEvent, EditSourceState> {
   /// {@macro edit_source_bloc}
   EditSourceBloc({
     required DataRepository<Source> sourcesRepository,
-    required DataRepository<Country> countriesRepository,
-    required DataRepository<Language> languagesRepository,
+    required List<Country> countries,
+    required List<Language> languages,
     required String sourceId,
-  }) : _sourcesRepository = sourcesRepository,
-       _countriesRepository = countriesRepository,
-       _languagesRepository = languagesRepository,
-       _sourceId = sourceId,
-       super(const EditSourceState()) {
+  })  : _sourcesRepository = sourcesRepository,
+        _sourceId = sourceId,
+        super(
+          EditSourceState(
+            countries: countries,
+            languages: languages,
+          ),
+        ) {
     on<EditSourceLoaded>(_onLoaded);
     on<EditSourceNameChanged>(_onNameChanged);
     on<EditSourceDescriptionChanged>(_onDescriptionChanged);
@@ -37,13 +32,9 @@ class EditSourceBloc extends Bloc<EditSourceEvent, EditSourceState> {
     on<EditSourceHeadquartersChanged>(_onHeadquartersChanged);
     on<EditSourceStatusChanged>(_onStatusChanged);
     on<EditSourceSubmitted>(_onSubmitted);
-    on<_FetchNextCountryPage>(_onFetchNextCountryPage);
-    on<_FetchNextLanguagePage>(_onFetchNextLanguagePage);
   }
 
   final DataRepository<Source> _sourcesRepository;
-  final DataRepository<Country> _countriesRepository;
-  final DataRepository<Language> _languagesRepository;
   final String _sourceId;
 
   Future<void> _onLoaded(
@@ -52,32 +43,7 @@ class EditSourceBloc extends Bloc<EditSourceEvent, EditSourceState> {
   ) async {
     emit(state.copyWith(status: EditSourceStatus.loading));
     try {
-      final responses = await Future.wait<dynamic>([
-        _sourcesRepository.read(id: _sourceId),
-        _countriesRepository.readAll(
-          sort: [const SortOption('name', SortOrder.asc)],
-          filter: {'status': ContentStatus.active.name},
-        ),
-        _languagesRepository.readAll(
-          sort: [const SortOption('name', SortOrder.asc)],
-          filter: {'status': ContentStatus.active.name},
-        ),
-      ]);
-
-      final source = responses[0] as Source;
-      final countriesPaginated = responses[1] as PaginatedResponse<Country>;
-      final languagesPaginated = responses[2] as PaginatedResponse<Language>;
-
-      Language? selectedLanguage;
-      try {
-        // Find the equivalent language object from the full list.
-        // This ensures the DropdownButton can identify it by reference.
-        selectedLanguage = languagesPaginated.items.firstWhere(
-          (listLanguage) => listLanguage.id == source.language.id,
-        );
-      } catch (_) {
-        selectedLanguage = source.language;
-      }
+      final source = await _sourcesRepository.read(id: _sourceId);
 
       emit(
         state.copyWith(
@@ -87,26 +53,11 @@ class EditSourceBloc extends Bloc<EditSourceEvent, EditSourceState> {
           description: source.description,
           url: source.url,
           sourceType: () => source.sourceType,
-          language: () => selectedLanguage,
+          language: () => source.language,
           headquarters: () => source.headquarters,
           contentStatus: source.status,
-          countries: countriesPaginated.items,
-          countriesCursor: countriesPaginated.cursor,
-          countriesHasMore: countriesPaginated.hasMore,
-          languages: languagesPaginated.items,
-          languagesCursor: languagesPaginated.cursor,
-          languagesHasMore: languagesPaginated.hasMore,
         ),
       );
-
-      // After the initial page is loaded, start background processes to
-      // fetch all remaining pages for countries and languages.
-      if (state.countriesHasMore) {
-        add(const _FetchNextCountryPage());
-      }
-      if (state.languagesHasMore) {
-        add(const _FetchNextLanguagePage());
-      }
     } on HttpException catch (e) {
       emit(state.copyWith(status: EditSourceStatus.failure, exception: e));
     } catch (e) {
@@ -194,84 +145,6 @@ class EditSourceBloc extends Bloc<EditSourceEvent, EditSourceState> {
   }
 
   // --- 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<EditSourceState> 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> _onFetchNextLanguagePage(
-    _FetchNextLanguagePage event,
-    Emitter<EditSourceState> emit,
-  ) async {
-    if (!state.languagesHasMore || state.languagesIsLoadingMore) return;
-
-    try {
-      emit(state.copyWith(languagesIsLoadingMore: true));
-
-      // ignore: inference_failure_on_instance_creation
-      await Future.delayed(const Duration(milliseconds: 400));
-
-      final nextLanguages = await _languagesRepository.readAll(
-        pagination: PaginationOptions(cursor: state.languagesCursor),
-        sort: [const SortOption('name', SortOrder.asc)],
-      );
-
-      emit(
-        state.copyWith(
-          languages: List.of(state.languages)..addAll(nextLanguages.items),
-          languagesCursor: nextLanguages.cursor,
-          languagesHasMore: nextLanguages.hasMore,
-          languagesIsLoadingMore: false,
-        ),
-      );
-
-      if (nextLanguages.hasMore) {
-        add(const _FetchNextLanguagePage());
-      }
-    } catch (e) {
-      emit(state.copyWith(languagesIsLoadingMore: false));
-      // Optionally log the error without disrupting the user
-    }
-  }
-
   Future<void> _onSubmitted(
     EditSourceSubmitted event,
     Emitter<EditSourceState> emit,

lib/content_management/bloc/edit_source/edit_source_state.dart

@@ -30,13 +30,7 @@ final class EditSourceState extends Equatable {
     this.language,
     this.headquarters,
     this.countries = const [],
-    this.countriesHasMore = true,
-    this.countriesIsLoadingMore = false,
-    this.countriesCursor,
     this.languages = const [],
-    this.languagesHasMore = true,
-    this.languagesIsLoadingMore = false,
-    this.languagesCursor,
     this.contentStatus = ContentStatus.active,
     this.exception,
     this.updatedSource,
@@ -51,13 +45,7 @@ final class EditSourceState extends Equatable {
   final Language? language;
   final Country? headquarters;
   final List<Country> countries;
-  final bool countriesHasMore;
-  final bool countriesIsLoadingMore;
-  final String? countriesCursor;
   final List<Language> languages;
-  final bool languagesHasMore;
-  final bool languagesIsLoadingMore;
-  final String? languagesCursor;
   final ContentStatus contentStatus;
   final HttpException? exception;
   final Source? updatedSource;
@@ -81,13 +69,7 @@ final class EditSourceState extends Equatable {
     ValueGetter<Language?>? language,
     ValueGetter<Country?>? headquarters,
     List<Country>? countries,
-    bool? countriesHasMore,
-    bool? countriesIsLoadingMore,
-    String? countriesCursor,
     List<Language>? languages,
-    bool? languagesHasMore,
-    bool? languagesIsLoadingMore,
-    String? languagesCursor,
     ContentStatus? contentStatus,
     HttpException? exception,
     Source? updatedSource,
@@ -102,15 +84,7 @@ final class EditSourceState extends Equatable {
       language: language != null ? language() : this.language,
       headquarters: headquarters != null ? headquarters() : this.headquarters,
       countries: countries ?? this.countries,
-      countriesHasMore: countriesHasMore ?? this.countriesHasMore,
-      countriesIsLoadingMore:
-          countriesIsLoadingMore ?? this.countriesIsLoadingMore,
-      countriesCursor: countriesCursor ?? this.countriesCursor,
       languages: languages ?? this.languages,
-      languagesHasMore: languagesHasMore ?? this.languagesHasMore,
-      languagesIsLoadingMore:
-          languagesIsLoadingMore ?? this.languagesIsLoadingMore,
-      languagesCursor: languagesCursor ?? this.languagesCursor,
       contentStatus: contentStatus ?? this.contentStatus,
       exception: exception,
       updatedSource: updatedSource ?? this.updatedSource,
@@ -128,13 +102,7 @@ final class EditSourceState extends Equatable {
     language,
     headquarters,
     countries,
-    countriesHasMore,
-    countriesIsLoadingMore,
-    countriesCursor,
     languages,
-    languagesHasMore,
-    languagesIsLoadingMore,
-    languagesCursor,
     contentStatus,
     exception,
     updatedSource,

lib/content_management/view/edit_source_page.dart

@@ -24,11 +24,18 @@ class EditSourcePage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    // The lists of all countries and languages are fetched once and cached in
+    // the ContentManagementBloc. We read them here and provide them to the
+    // EditSourceBloc.
+    final contentManagementState = context.read<ContentManagementBloc>().state;
+    final allCountries = contentManagementState.allCountries;
+    final allLanguages = contentManagementState.allLanguages;
+
     return BlocProvider(
       create: (context) => EditSourceBloc(
         sourcesRepository: context.read<DataRepository<Source>>(),
-        countriesRepository: context.read<DataRepository<Country>>(),
-        languagesRepository: context.read<DataRepository<Language>>(),
+        countries: allCountries,
+        languages: allLanguages,
         sourceId: sourceId,
       )..add(const EditSourceLoaded()),
       child: const _EditSourceView(),
@@ -197,9 +204,6 @@ class _EditSourceViewState extends State<_EditSourceView> {
                       decoration: InputDecoration(
                         labelText: l10n.language,
                         border: const OutlineInputBorder(),
-                        helperText: state.languagesIsLoadingMore
-                            ? l10n.loadingFullList
-                            : null,
                       ),
                       items: [
                         DropdownMenuItem(value: null, child: Text(l10n.none)),
@@ -210,11 +214,9 @@ class _EditSourceViewState extends State<_EditSourceView> {
                           ),
                         ),
                       ],
-                      onChanged: state.languagesIsLoadingMore
-                          ? null
-                          : (value) => context.read<EditSourceBloc>().add(
-                              EditSourceLanguageChanged(value),
-                            ),
+                      onChanged: (value) => context
+                          .read<EditSourceBloc>()
+                          .add(EditSourceLanguageChanged(value)),
                     ),
                     const SizedBox(height: AppSpacing.lg),
                     DropdownButtonFormField<SourceType?>(
@@ -242,9 +244,6 @@ class _EditSourceViewState extends State<_EditSourceView> {
                       decoration: InputDecoration(
                         labelText: l10n.headquarters,
                         border: const OutlineInputBorder(),
-                        helperText: state.countriesIsLoadingMore
-                            ? l10n.loadingFullList
-                            : null,
                       ),
                       items: [
                         DropdownMenuItem(value: null, child: Text(l10n.none)),
@@ -271,11 +270,9 @@ class _EditSourceViewState extends State<_EditSourceView> {
                           ),
                         ),
                       ],
-                      onChanged: state.countriesIsLoadingMore
-                          ? null
-                          : (value) => context.read<EditSourceBloc>().add(
-                              EditSourceHeadquartersChanged(value),
-                            ),
+                      onChanged: (value) => context
+                          .read<EditSourceBloc>()
+                          .add(EditSourceHeadquartersChanged(value)),
                     ),
                     const SizedBox(height: AppSpacing.lg),
                     DropdownButtonFormField<ContentStatus>(