import 'package:flutter/material.dart';
import 'package:drift/drift.dart';
import 'package:trainhub_flutter/database/database.dart';

class ChatProvider extends ChangeNotifier {
  final AppDatabase database;

  List<ChatSession> _sessions = [];
  List<ChatMessage> _currentMessages = [];
  ChatSession? _activeSession;

  List<ChatSession> get sessions => _sessions;
  List<ChatMessage> get currentMessages => _currentMessages;
  ChatSession? get activeSession => _activeSession;

  bool _isTyping = false;
  bool get isTyping => _isTyping;

  ChatProvider(this.database) {
    _loadSessions();
  }

  Future<void> _loadSessions() async {
    _sessions =
        await (database.select(database.chatSessions)..orderBy([
              (t) => OrderingTerm(
                expression: t.createdAt,
                mode: OrderingMode.desc,
              ),
            ]))
            .get();
    notifyListeners();
  }

  Future<void> createSession() async {
    final id = DateTime.now().toIso8601String();
    final session = ChatSessionsCompanion.insert(
      id: id,
      title: const Value('New Chat'),
      createdAt: DateTime.now().toIso8601String(),
      updatedAt: DateTime.now().toIso8601String(),
    );
    await database.into(database.chatSessions).insert(session);
    await _loadSessions();
    await loadSession(id);
  }

  Future<void> deleteSession(String id) async {
    await (database.delete(
      database.chatSessions,
    )..where((t) => t.id.equals(id))).go();
    if (_activeSession?.id == id) {
      _activeSession = null;
      _currentMessages = [];
    }
    await _loadSessions();
  }

  Future<void> loadSession(String id) async {
    final session = await (database.select(
      database.chatSessions,
    )..where((t) => t.id.equals(id))).getSingleOrNull();
    if (session != null) {
      _activeSession = session;
      await _loadMessages(id);
    }
  }

  Future<void> _loadMessages(String sessionId) async {
    _currentMessages =
        await (database.select(database.chatMessages)
              ..where((t) => t.sessionId.equals(sessionId))
              ..orderBy([
                (t) => OrderingTerm(
                  expression: t.createdAt,
                  mode: OrderingMode.asc,
                ),
              ]))
            .get();
    notifyListeners();
  }

  Future<void> sendMessage(String content) async {
    if (_activeSession == null) {
      await createSession();
    }
    final sessionId = _activeSession!.id;

    // User Message
    final userMsgId = DateTime.now().toIso8601String();
    await database
        .into(database.chatMessages)
        .insert(
          ChatMessagesCompanion.insert(
            id: userMsgId,
            sessionId: sessionId,
            role: 'user',
            content: content,
            createdAt: DateTime.now().toIso8601String(),
          ),
        );
    await _loadMessages(sessionId);

    // AI Response (Mock)
    _isTyping = true;
    notifyListeners();

    await Future.delayed(const Duration(seconds: 1)); // Simulate latency

    final aiMsgId = DateTime.now().toIso8601String();
    final response = _getMockResponse(content);

    await database
        .into(database.chatMessages)
        .insert(
          ChatMessagesCompanion.insert(
            id: aiMsgId,
            sessionId: sessionId,
            role: 'assistant',
            content: response,
            createdAt: DateTime.now().toIso8601String(),
          ),
        );

    // Update session title if it's the first message
    if (_currentMessages.length <= 2) {
      final newTitle = content.length > 30
          ? '${content.substring(0, 30)}...'
          : content;
      await (database.update(database.chatSessions)
            ..where((t) => t.id.equals(sessionId)))
          .write(ChatSessionsCompanion(title: Value(newTitle)));
      await _loadSessions();
    }

    _isTyping = false;
    await _loadMessages(sessionId);
  }

  String _getMockResponse(String input) {
    input = input.toLowerCase();
    if (input.contains('plan') || input.contains('program')) {
      return "I can help you design a training plan! What are your goals? Strength, hypertrophy, or endurance?";
    } else if (input.contains('squat') || input.contains('bench')) {
      return "Compound movements are great. Remember to maintain proper form. For squats, keep your chest up and knees tracking over toes.";
    } else if (input.contains('nutrition') || input.contains('eat')) {
      return "Nutrition is key. Aim for 1.6-2.2g of protein per kg of bodyweight if you're training hard.";
    }
    return "I'm your AI training assistant. How can I help you today?";
  }
}