Initial version

lib/scooters/scooter.dart

@@ -0,0 +1,46 @@
+import 'package:flutter/foundation.dart';
+
+import '../models/scooter_state.dart';
+
+/// Result of a local scooter authentication attempt.
+///
+/// A missing response is deliberately NOT a value here: it surfaces as a
+/// [TimeoutException] so callers can tell "wrong PIN" from "no answer".
+enum AuthenticationResult {
+  success,
+  invalidCredential,
+}
+
+/// Base class for every supported scooter.
+///
+/// The current [state] is always available synchronously and the UI rebuilds
+/// through [ListenableBuilder]. There is no replay problem because there is
+/// no stream to miss.
+abstract class Scooter extends ChangeNotifier {
+  ScooterState get state;
+
+  Future<void> connect();
+  Future<void> disconnect();
+
+  Future<AuthenticationResult> authenticate(String credential);
+
+  Future<void> lock();
+  Future<void> unlock();
+
+  Future<void> setHeadlight(bool enabled);
+
+  /// True only when the implementation holds enough fresh scooter state to
+  /// build a safe control write AND control writes are enabled for this build.
+  bool get canWrite;
+
+  /// Disconnects and releases every resource. The object is unusable after.
+  Future<void> disposeScooter();
+}
+
+/// Thrown into any pending operation when the BLE link drops underneath it.
+class ScooterConnectionLostException implements Exception {
+  const ScooterConnectionLostException([this.message = 'Connection to the scooter was lost']);
+  final String message;
+  @override
+  String toString() => message;
+}