init

client/lib/features/writing/providers/writing_provider.dart

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+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../models/writing_task.dart';
+import '../models/writing_submission.dart';
+import '../services/writing_service.dart';
+
+/// 写作任务状态
+class WritingTasksState {
+  final List<WritingTask> tasks;
+  final bool isLoading;
+  final String? error;
+
+  WritingTasksState({
+    this.tasks = const [],
+    this.isLoading = false,
+    this.error,
+  });
+
+  WritingTasksState copyWith({
+    List<WritingTask>? tasks,
+    bool? isLoading,
+    String? error,
+  }) {
+    return WritingTasksState(
+      tasks: tasks ?? this.tasks,
+      isLoading: isLoading ?? this.isLoading,
+      error: error,
+    );
+  }
+}
+
+/// 写作任务 Notifier
+class WritingTasksNotifier extends StateNotifier<WritingTasksState> {
+  final WritingService _writingService;
+
+  WritingTasksNotifier(this._writingService) : super(WritingTasksState());
+
+  /// 加载写作任务列表
+  Future<void> loadTasks({
+    WritingType? type,
+    WritingDifficulty? difficulty,
+    int page = 1,
+    bool forceRefresh = false,
+  }) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      final tasks = await _writingService.getWritingTasks(
+        type: type,
+        difficulty: difficulty,
+        page: page,
+        forceRefresh: forceRefresh,
+      );
+      
+      state = state.copyWith(tasks: tasks, isLoading: false);
+    } catch (e) {
+      state = state.copyWith(
+        isLoading: false,
+        error: e.toString(),
+      );
+    }
+  }
+
+  /// 获取推荐任务
+  Future<void> loadRecommendedTasks(String userId, {bool forceRefresh = false}) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      final tasks = await _writingService.getRecommendedWritingTasks(
+        userId: userId,
+        limit: 5,
+        forceRefresh: forceRefresh,
+      );
+      
+      state = state.copyWith(tasks: tasks, isLoading: false);
+    } catch (e) {
+      state = state.copyWith(
+        isLoading: false,
+        error: e.toString(),
+      );
+    }
+  }
+}
+
+/// 写作服务 Provider
+final writingServiceProvider = Provider<WritingService>((ref) {
+  return WritingService();
+});
+
+/// 写作任务列表 Provider
+final writingTasksProvider = StateNotifierProvider<WritingTasksNotifier, WritingTasksState>((ref) {
+  final service = ref.watch(writingServiceProvider);
+  return WritingTasksNotifier(service);
+});
+
+/// 按考试类型获取写作任务
+final examWritingTasksProvider = FutureProvider.family<List<WritingTask>, ExamType>((ref, examType) async {
+  final service = ref.watch(writingServiceProvider);
+  
+  try {
+    // 从后端获取所有任务，然后在前端过滤
+    final tasks = await service.getWritingTasks(limit: 100);
+    return tasks.where((task) => task.examType == examType).toList();
+  } catch (e) {
+    return [];
+  }
+});
+
+/// 用户写作历史 Provider
+final userWritingHistoryProvider = FutureProvider.family<List<WritingSubmission>, String>((ref, userId) async {
+  final service = ref.watch(writingServiceProvider);
+  
+  try {
+    return await service.getUserWritingHistory(userId: userId, limit: 3);
+  } catch (e) {
+    return [];
+  }
+});