Adds drone model, db helper.

lib/db/db_helper.dart

@@ -0,0 +1,81 @@
+// Singleton to access database
+import 'dart:developer';
+import 'dart:io';
+import 'package:path/path.dart';
+import 'package:logging/logging.dart';
+import '../models/drone.dart';
+
+
+import 'package:path_provider/path_provider.dart';import 'package:sqflite/sqflite.dart';
+
+class DbHelper 
+{
+    static final DbHelper instance = DbHelper._internal();
+    static final log = Logger("DbHelper");
+    static Database? _database;
+
+    DbHelper._internal();
+
+    Future<Database> get database async
+    {
+        if (_database != null) return _database!;
+        await _initDb();
+        return _database!;
+    }
+
+    Future _initDb() async
+    {
+        final directory = await getApplicationDocumentsDirectory();
+        final db_name = "rtime.db";
+        final path = join(directory.path, db_name);
+        log.info("Opeing database file at $path");
+
+        _database = await openDatabase(
+            path,
+            version: 1,
+            onCreate: _onCreate,
+        );
+
+        log.info("Database opened successfully !");
+        log.info("${(await getDrones()).length} drones in DB.");
+    }
+
+    Future _onCreate(Database db, int version) async
+    {
+        log.info("Database does not exist, creating a new one.");
+        await db.execute('''
+            CREATE TABLE drones(
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                name TEXT NOT NULL,
+                image TEXT
+            )
+        ''');
+    }
+
+    Future<int> insertDrone(Drone drone) async
+    {
+        final db = await database;
+        return await db.insert("drones", drone.toMap());
+    }
+
+    Future<List<Drone>> getDrones() async
+    {
+        final db = await database;
+        final maps = await db.query("drones");
+        return maps.map((e) => Drone.fromMap(e)).toList();
+    }
+
+    Future<int> deleteItem(int drone_id) async
+    {
+        final db = await database;
+        return await db.delete("drones", where: "id = ?", whereArgs: [drone_id]);
+    }
+
+    Future closeDb() async
+    {
+        final db = await database;
+        log.info("Closing database.");
+        db.close();
+        _database = null;
+    }
+}