Feat: DAL (Data Access Layer) Added

lib/services/database_helper.dart

@@ -0,0 +1,75 @@
+import 'package:sqflite_common_ffi/sqflite_ffi.dart';
+import 'package:path/path.dart';
+import '../models/product.dart';
+
+class DatabaseHelper {
+  static final DatabaseHelper _instance = DatabaseHelper._internal();
+  static Database? _database;
+
+  factory DatabaseHelper() {
+    return _instance;
+  }
+
+  DatabaseHelper._internal();
+
+  Future<Database> get database async {
+    if (_database != null) {
+      return _database!;
+    }
+    _database = await _initDatabase();
+    return _database!;
+  }
+
+  Future<Database> _initDatabase() async {
+    String documentsDirectory = await getDatabasesPath();
+    String path = join(documentsDirectory, 'product_database.db');
+
+    return await openDatabase(path, version: 1, onCreate: _onCreate);
+  }
+
+  Future<void> _onCreate(Database db, int version) async {
+    await db.execute('''
+      CREATE TABLE products(
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        name TEXT NOT NULL,
+        code TEXT NOT NULL,
+        quantity INTEGER NOT NULL,
+        price REAL NOT NULL,
+        description TEXT
+      )
+      ''');
+  }
+
+  Future<int> insertProduct(Product product) async {
+    final db = await database;
+    return await db.insert(
+      'products',
+      product.toMap(),
+      conflictAlgorithm: ConflictAlgorithm.replace,
+    );
+  }
+
+  Future<List<Product>> getProducts() async {
+    final db = await database;
+    final List<Map<String, dynamic>> maps = await db.query('products');
+
+    return List.generate(maps.length, (i) {
+      return Product.fromMap(maps[i]);
+    });
+  }
+
+  Future<int> updateProduct(Product product) async {
+    final db = await database;
+    return await db.update(
+      'products',
+      product.toMap(),
+      where: 'id = ?',
+      whereArgs: [product.id],
+    );
+  }
+
+  Future<int> deleteProduct(int id) async {
+    final db = await database;
+    return await db.delete('products', where: 'id = ?', whereArgs: [id]);
+  }
+}