import 'dart:io';
import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';

class DatabaseHelper {
  static final DatabaseHelper _instance = DatabaseHelper._internal();
  factory DatabaseHelper() => _instance;
  static Database? _database;

  DatabaseHelper._internal();

  Future<Database> get database async {
    if (_database != null) return _database!;
    _database = await _initDatabase();
    return _database!;
  }

  Future<Database> _initDatabase() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String path = join(documentsDirectory.path, 'chat.db');
    return await openDatabase(
      path,
      version: 1,
      onCreate: _onCreate,
    );
  }

  Future<void> _onCreate(Database db, int version) async {
    await db.execute('''
      CREATE TABLE messages (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        role TEXT NOT NULL,
        message TEXT NOT NULL,
        timestamp INTEGER DEFAULT (strftime('%s', 'now'))
      ''');
  }

  // 插入一条消息
  Future<int> insertMessage(Map<String, dynamic> message) async {
    Database db = await database;
    return await db.insert('messages', message);
  }

  // 获取所有消息（按时间排序）
  Future<List<Map<String, dynamic>>> getMessages() async {
    Database db = await database;
    return await db.query('messages', orderBy: 'timestamp ASC');
  }

  // 删除所有消息
  Future<int> clearMessages() async {
    Database db = await database;
    return await db.delete('messages');
  }
}