japp_flutter/lib/features/challenge/view_models/challenge_add_vm.dart

// features/challenge/add/add_challenge_viewmodel.dart
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:japp_flutter/core/models/challenge_model.dart';
import 'package:japp_flutter/core/proviers/repository_providers.dart';
import 'package:japp_flutter/core/repositories/challenge_repository.dart';

final addChallengeProvider = AsyncNotifierProvider<AddChallengeViewModel, ChallengeModel>(
  AddChallengeViewModel.new,
);

class AddChallengeViewModel extends AsyncNotifier<ChallengeModel> {
  ChallengeRepository get _repository => ref.read(challengeRepositoryProvider);

  @override
  Future<ChallengeModel> build() async {
    // 初始化为空挑战模板
    return ChallengeModel(
      id: null,
      title: '',
      description: '',
      startDate: DateTime.now(),
      endDate: DateTime.now().add(const Duration(days: 30)),
      participants: 0,
      completed: false,
      difficulty: '中等',
    );
  }

  /// 更新挑战标题
  void updateTitle(String title) {
    state = AsyncData(state.value!.copyWith(title: title));
  }

  /// 更新挑战描述
  void updateDescription(String description) {
    state = AsyncData(state.value!.copyWith(description: description));
  }

  /// 更新难度级别
  void updateDifficulty(String difficulty) {
    state = AsyncData(state.value!.copyWith(difficulty: difficulty));
  }

  /// 更新日期范围
  void updateDateRange(DateTime start, DateTime end) {
    state = AsyncData(state.value!.copyWith(
      startDate: start,
      endDate: end,
    ));
  }

  /// 提交新挑战
  Future<void> submitChallenge() async {
    if (state.value == null) return;

    state = const AsyncLoading();
    state = await AsyncValue.guard(() => _repository.addChallenge(state.value!));
  }
}