AI-Health/health_app/lib/providers/chat_provider.dart

import 'dart:async';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'auth_provider.dart';
import '../utils/sse_handler.dart';

class ChatMessage {
  final String id;
  final String role;
  String content;
  final DateTime createdAt;
  ChatMessage(
      {required this.id,
      required this.role,
      required this.content,
      required this.createdAt});
  bool get isUser => role == 'user';
}

enum ActiveAgent { default_, consultation, health, diet, medication, report, exercise }

class ChatState {
  final ActiveAgent activeAgent;
  final List<ChatMessage> messages;
  final String? conversationId;
  final bool isStreaming;
  final String? noticeText;
  const ChatState({
    this.activeAgent = ActiveAgent.default_,
    this.messages = const [],
    this.conversationId,
    this.isStreaming = false,
    this.noticeText,
  });
  ChatState copyWith({ActiveAgent? activeAgent, List<ChatMessage>? messages,
      String? conversationId, bool? isStreaming, String? noticeText,
      bool clearNotice = false}) =>
      ChatState(
        activeAgent: activeAgent ?? this.activeAgent,
        messages: messages ?? this.messages,
        conversationId: conversationId ?? this.conversationId,
        isStreaming: isStreaming ?? this.isStreaming,
        noticeText: clearNotice ? null : (noticeText ?? this.noticeText),
      );
}

class SelectedAgentNotifier extends Notifier<ActiveAgent?> {
  @override
  ActiveAgent? build() => null;
  void select(ActiveAgent? a) => state = a;
}

final selectedAgentProvider =
    NotifierProvider<SelectedAgentNotifier, ActiveAgent?>(SelectedAgentNotifier.new);
final chatProvider = NotifierProvider<ChatNotifier, ChatState>(ChatNotifier.new);

class ChatNotifier extends Notifier<ChatState> {
  StreamSubscription<Map<String, dynamic>>? _subscription;

  @override
  ChatState build() => const ChatState();

  void setAgent(ActiveAgent a) {
    _subscription?.cancel();
    state = state.activeAgent == a ? const ChatState() : ChatState(activeAgent: a);
  }

  Future<void> sendMessage(String text) async {
    if (text.trim().isEmpty || state.isStreaming) return;

    final userMsg = ChatMessage(
      id: '${DateTime.now().millisecondsSinceEpoch}',
      role: 'user',
      content: text,
      createdAt: DateTime.now(),
    );
    state = state.copyWith(
        messages: [...state.messages, userMsg], isStreaming: true);

    final aiMsg = ChatMessage(
      id: '${DateTime.now().millisecondsSinceEpoch}_ai',
      role: 'assistant',
      content: '',
      createdAt: DateTime.now(),
    );

    try {
      final token = await ref.read(apiClientProvider).accessToken;
      if (token == null) {
        _addError(aiMsg, '未登录，请重新登录');
        return;
      }

      final agentPath =
          state.activeAgent.name.replaceFirst('default_', 'default');
      final stream = SseHandler.connect(
        agentType: agentPath,
        message: text,
        conversationId: state.conversationId,
        token: token,
      );

      await for (final event in stream) {
        _processEvent(event, aiMsg);
      }
    } catch (e) {
      _addError(aiMsg, '网络异常，请稍后重试');
    }
  }

  void _addError(ChatMessage aiMsg, String errorText) {
    state = state.copyWith(
      messages: [
        ...state.messages,
        ChatMessage(
          id: 'err_${DateTime.now().millisecondsSinceEpoch}',
          role: 'assistant',
          content: errorText,
          createdAt: DateTime.now(),
        ),
      ],
      isStreaming: false,
      clearNotice: true,
    );
  }

  void _processEvent(Map<String, dynamic> j, ChatMessage aiMsg) {
    final a = j['action'] as String?;
    switch (a) {
      case 'conversation_id':
        state = state.copyWith(conversationId: j['data']?.toString());
      case 'answer':
        aiMsg.content += (j['data'] as String?) ?? '';
        _update(aiMsg);
      case 'notice':
        state = state.copyWith(noticeText: j['message'] as String?);
      case 'status':
        _done(aiMsg);
      case 'error':
        _done(aiMsg);
    }
  }

  void _update(ChatMessage m) {
    final u = state.messages.toList();
    final i = u.indexWhere((x) => x.id == m.id);
    if (i >= 0) {
      u[i] = m;
    } else if (m.content.isNotEmpty) {
      u.add(m);
    }
    state = state.copyWith(messages: u);
  }

  void _done(ChatMessage m) {
    final u = state.messages.toList();
    if (!u.any((x) => x.id == m.id) && m.content.isNotEmpty) u.add(m);
    state = state.copyWith(messages: u, isStreaming: false, clearNotice: true);
  }
}