import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../models/message.dart';
import '../services/api_service.dart';

class ChatState {
  final List<ChatMessage> messages;
  final bool isLoading;
  final String? error;

  const ChatState({this.messages = const [], this.isLoading = false, this.error});

  ChatState copyWith({List<ChatMessage>? messages, bool? isLoading, String? error}) {
    return ChatState(
      messages: messages ?? this.messages,
      isLoading: isLoading ?? this.isLoading,
      error: error,
    );
  }
}

class ChatNotifier extends StateNotifier<ChatState> {
  ChatNotifier() : super(const ChatState()) {
    _loadHistory();
  }

  Future<void> _loadHistory() async {
    try {
      final messages = await apiService.getChatHistory();
      state = state.copyWith(messages: messages);
    } catch (_) {}
  }

  Future<void> sendMessage(String content) async {
    if (content.trim().isEmpty) return;

    final userMessage = ChatMessage(
      id: 'msg_user_${DateTime.now().millisecondsSinceEpoch}',
      content: content.trim(),
      type: MessageType.text,
      sender: MessageSender.user,
      timestamp: DateTime.now(),
    );

    state = state.copyWith(
      messages: [...state.messages, userMessage],
      isLoading: true,
    );

    final loadingMessage = ChatMessage(
      id: 'msg_loading_${DateTime.now().millisecondsSinceEpoch}',
      content: '',
      type: MessageType.loading,
      sender: MessageSender.ai,
      timestamp: DateTime.now(),
    );

    state = state.copyWith(
      messages: [...state.messages, loadingMessage],
    );

    try {
      final response = await apiService.sendMessage(content);
      final updatedMessages = [...state.messages];
      updatedMessages.removeLast();
      updatedMessages.add(response);
      state = state.copyWith(messages: updatedMessages, isLoading: false);
    } catch (e) {
      final updatedMessages = [...state.messages];
      updatedMessages.removeLast();
      updatedMessages.add(ChatMessage(
        id: 'msg_err_${DateTime.now().millisecondsSinceEpoch}',
        content: '抱歉，消息发送失败，请稍后重试。',
        type: MessageType.text,
        sender: MessageSender.ai,
        timestamp: DateTime.now(),
      ));
      state = state.copyWith(messages: updatedMessages, isLoading: false, error: e.toString());
    }
  }

  void clearMessages() {
    state = const ChatState();
    _loadHistory();
  }
}

final chatProvider = StateNotifierProvider<ChatNotifier, ChatState>((ref) {
  return ChatNotifier();
});