feat(entity_details): create entity details state

- Define states and statuses
- Add copyWith method
- Implement Equatable

Author: fulleni

lib/entity_details/bloc/entity_details_state.dart

@@ -0,0 +1,84 @@
+part of 'entity_details_bloc.dart';
+
+/// Status for the overall entity details page.
+enum EntityDetailsStatus {
+  initial,
+  loading,
+  success,
+  failure,
+}
+
+/// Status for fetching headlines within the entity details page.
+enum EntityHeadlinesStatus {
+  initial,
+  loadingMore,
+  success,
+  failure,
+}
+
+class EntityDetailsState extends Equatable {
+  const EntityDetailsState({
+    this.status = EntityDetailsStatus.initial,
+    this.entityType,
+    this.entity,
+    this.isFollowing = false,
+    this.headlines = const [],
+    this.headlinesStatus = EntityHeadlinesStatus.initial,
+    this.hasMoreHeadlines = true,
+    this.headlinesCursor,
+    this.errorMessage,
+  });
+
+  final EntityDetailsStatus status;
+  final EntityType? entityType;
+  final dynamic entity; // Will be Category or Source
+  final bool isFollowing;
+  final List<Headline> headlines;
+  final EntityHeadlinesStatus headlinesStatus;
+  final bool hasMoreHeadlines;
+  final String? headlinesCursor;
+  final String? errorMessage;
+
+  EntityDetailsState copyWith({
+    EntityDetailsStatus? status,
+    EntityType? entityType,
+    dynamic entity,
+    bool? isFollowing,
+    List<Headline>? headlines,
+    EntityHeadlinesStatus? headlinesStatus,
+    bool? hasMoreHeadlines,
+    String? headlinesCursor,
+    String? errorMessage,
+    bool clearErrorMessage = false,
+    bool clearEntity = false,
+    bool clearHeadlinesCursor = false,
+  }) {
+    return EntityDetailsState(
+      status: status ?? this.status,
+      entityType: entityType ?? this.entityType,
+      entity: clearEntity ? null : entity ?? this.entity,
+      isFollowing: isFollowing ?? this.isFollowing,
+      headlines: headlines ?? this.headlines,
+      headlinesStatus: headlinesStatus ?? this.headlinesStatus,
+      hasMoreHeadlines: hasMoreHeadlines ?? this.hasMoreHeadlines,
+      headlinesCursor: clearHeadlinesCursor
+          ? null
+          : headlinesCursor ?? this.headlinesCursor,
+      errorMessage:
+          clearErrorMessage ? null : errorMessage ?? this.errorMessage,
+    );
+  }
+
+  @override
+  List<Object?> get props => [
+        status,
+        entityType,
+        entity,
+        isFollowing,
+        headlines,
+        headlinesStatus,
+        hasMoreHeadlines,
+        headlinesCursor,
+        errorMessage,
+      ];
+}