feat: Implement EditHeadlineBloc

- Manages headline editing state
- Handles loading data
- Handles form submissions
- Implements state updates

Author: fulleni

lib/content_management/bloc/edit_headline/edit_headline_bloc.dart

@@ -0,0 +1,200 @@
+import 'package:bloc/bloc.dart';
+import 'package:equatable/equatable.dart';
+import 'package:flutter/foundation.dart' hide Category;
+import 'package:ht_data_repository/ht_data_repository.dart';
+import 'package:ht_shared/ht_shared.dart';
+
+part 'edit_headline_event.dart';
+part 'edit_headline_state.dart';
+
+/// A BLoC to manage the state of editing a single headline.
+class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
+  /// {@macro edit_headline_bloc}
+  EditHeadlineBloc({
+    required HtDataRepository<Headline> headlinesRepository,
+    required HtDataRepository<Source> sourcesRepository,
+    required HtDataRepository<Category> categoriesRepository,
+    required String headlineId,
+  }) : _headlinesRepository = headlinesRepository,
+       _sourcesRepository = sourcesRepository,
+       _categoriesRepository = categoriesRepository,
+       _headlineId = headlineId,
+       super(const EditHeadlineState()) {
+    on<EditHeadlineLoaded>(_onLoaded);
+    on<EditHeadlineTitleChanged>(_onTitleChanged);
+    on<EditHeadlineDescriptionChanged>(_onDescriptionChanged);
+    on<EditHeadlineUrlChanged>(_onUrlChanged);
+    on<EditHeadlineImageUrlChanged>(_onImageUrlChanged);
+    on<EditHeadlineSourceChanged>(_onSourceChanged);
+    on<EditHeadlineCategoryChanged>(_onCategoryChanged);
+    on<EditHeadlineSubmitted>(_onSubmitted);
+  }
+
+  final HtDataRepository<Headline> _headlinesRepository;
+  final HtDataRepository<Source> _sourcesRepository;
+  final HtDataRepository<Category> _categoriesRepository;
+  final String _headlineId;
+
+  Future<void> _onLoaded(
+    EditHeadlineLoaded event,
+    Emitter<EditHeadlineState> emit,
+  ) async {
+    emit(state.copyWith(status: EditHeadlineStatus.loading));
+    try {
+      final [
+        headlineResponse,
+        sourcesResponse,
+        categoriesResponse,
+      ] = await Future.wait([
+        _headlinesRepository.read(id: _headlineId),
+        _sourcesRepository.readAll(),
+        _categoriesRepository.readAll(),
+      ]);
+
+      final headline = headlineResponse as Headline;
+      final sources = (sourcesResponse as PaginatedResponse<Source>).items;
+      final categories =
+          (categoriesResponse as PaginatedResponse<Category>).items;
+
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.initial,
+          initialHeadline: headline,
+          title: headline.title,
+          description: headline.description ?? '',
+          url: headline.url ?? '',
+          imageUrl: headline.imageUrl ?? '',
+          source: () => headline.source,
+          category: () => headline.category,
+          sources: sources,
+          categories: categories,
+        ),
+      );
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+
+  void _onTitleChanged(
+    EditHeadlineTitleChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(
+      state.copyWith(title: event.title, status: EditHeadlineStatus.initial),
+    );
+  }
+
+  void _onDescriptionChanged(
+    EditHeadlineDescriptionChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        description: event.description,
+        status: EditHeadlineStatus.initial,
+      ),
+    );
+  }
+
+  void _onUrlChanged(
+    EditHeadlineUrlChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(state.copyWith(url: event.url, status: EditHeadlineStatus.initial));
+  }
+
+  void _onImageUrlChanged(
+    EditHeadlineImageUrlChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        imageUrl: event.imageUrl,
+        status: EditHeadlineStatus.initial,
+      ),
+    );
+  }
+
+  void _onSourceChanged(
+    EditHeadlineSourceChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        source: () => event.source,
+        status: EditHeadlineStatus.initial,
+      ),
+    );
+  }
+
+  void _onCategoryChanged(
+    EditHeadlineCategoryChanged event,
+    Emitter<EditHeadlineState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        category: () => event.category,
+        status: EditHeadlineStatus.initial,
+      ),
+    );
+  }
+
+  Future<void> _onSubmitted(
+    EditHeadlineSubmitted event,
+    Emitter<EditHeadlineState> emit,
+  ) async {
+    if (!state.isFormValid) return;
+
+    final initialHeadline = state.initialHeadline;
+    if (initialHeadline == null) {
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.failure,
+          errorMessage: 'Cannot update: Original headline data not loaded.',
+        ),
+      );
+      return;
+    }
+
+    emit(state.copyWith(status: EditHeadlineStatus.submitting));
+    try {
+      final updatedHeadline = initialHeadline.copyWith(
+        title: state.title,
+        description: state.description.isNotEmpty ? state.description : null,
+        url: state.url.isNotEmpty ? state.url : null,
+        imageUrl: state.imageUrl.isNotEmpty ? state.imageUrl : null,
+        source: state.source,
+        category: state.category,
+      );
+
+      await _headlinesRepository.update(id: _headlineId, item: updatedHeadline);
+      emit(state.copyWith(status: EditHeadlineStatus.success));
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: EditHeadlineStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+}