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

class DatabaseHelper {
  static final _databaseName = "my_database.db";
  static final _databaseVersion = 1;

  static final table = 'items';
  static final columnId = '_id';
  static final columnName = 'name';
  static final columnContext = 'context';

  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();
    print('初始化成功！');
    return _database!;
  }

  Future<Database> _initDatabase() async {
    final directory = await getApplicationDocumentsDirectory();
    final path = join(directory.path, _databaseName);
    print('${path}');
    return await openDatabase(
      path,
      version: _databaseVersion,
      onCreate: _onCreate,
    );
  }

  Future<void> _onCreate(Database db, int version) async {
    await db.execute('''
      CREATE TABLE $table (
        $columnId INTEGER PRIMARY KEY,
        $columnName TEXT NOT NULL,
        $columnContext
      )
    ''');
  }
}