Feat: DAL (Data Access Layer) Added

lib/database/database_helper.dart

@@ -0,0 +1,93 @@
+import 'package:sqflite_common_ffi/sqflite_ffi.dart';
+import 'package:path/path.dart';
+import '../models/contact.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 {
+    sqfliteFfiInit();
+    var databaseFactory = databaseFactoryFfi;
+
+    final databasePath = await getDatabasesPath();
+    final path = join(databasePath, 'contacts.db');
+
+    return await databaseFactory.openDatabase(
+      path,
+      options: OpenDatabaseOptions(
+        version: 1,
+        onCreate: (db, version) async {
+          await db.execute('''
+          CREATE TABLE contacts(
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            name TEXT NOT NULL,
+            phone TEXT,
+            email TEXT,
+            address TEXT,
+            company TEXT,
+            notes TEXT
+          )
+          ''');
+        },
+      ),
+    );
+  }
+
+  Future<int> insertContact(Contact contact) async {
+    final db = await database;
+    return await db.insert(
+      'contacts',
+      contact.toMap(),
+      conflictAlgorithm: ConflictAlgorithm.replace,
+    );
+  }
+
+  Future<List<Contact>> getContacts() async {
+    final db = await database;
+    final List<Map<String, dynamic>> maps = await db.query(
+      'contacts',
+      orderBy: 'name ASC',
+    ); // Order by name for display
+    return List.generate(maps.length, (i) {
+      return Contact.fromMap(maps[i]);
+    });
+  }
+
+  Future<int> updateContact(Contact contact) async {
+    final db = await database;
+    return await db.update(
+      'contacts',
+      contact.toMap(),
+      where: 'id = ?',
+      whereArgs: [contact.id],
+    );
+  }
+
+  Future<int> deleteContact(int id) async {
+    final db = await database;
+    return await db.delete('contacts', where: 'id = ?', whereArgs: [id]);
+  }
+
+  Future<void> closeDatabase() async {
+    final db = await _database;
+    if (db != null && db.isOpen) {
+      await db.close();
+      _database = null; // Clear the instance
+    }
+  }
+}