feat: add round bumper (#42)

* feat: add round bumper

* refactor: PR suggestions

* fix: remove unused import 🤦‍♀️

lib/game/components/components.dart

@@ -6,5 +6,6 @@ export 'flipper.dart';
 export 'joint_anchor.dart';
 export 'pathway.dart';
 export 'plunger.dart';
+export 'round_bumper.dart';
 export 'score_points.dart';
 export 'wall.dart';

lib/game/components/round_bumper.dart

@@ -0,0 +1,41 @@
+import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:pinball/game/game.dart';
+
+/// {@template round_bumper}
+/// Circular body that repels a [Ball] on contact, increasing the score.
+/// {@endtemplate}
+class RoundBumper extends BodyComponent with ScorePoints {
+  /// {@macro round_bumper}
+  RoundBumper({
+    required Vector2 position,
+    required double radius,
+    required int points,
+  })  : _position = position,
+        _radius = radius,
+        _points = points;
+
+  /// The position of the [RoundBumper] body.
+  final Vector2 _position;
+
+  /// The radius of the [RoundBumper].
+  final double _radius;
+
+  /// Points awarded from hitting this [RoundBumper].
+  final int _points;
+
+  @override
+  int get points => _points;
+
+  @override
+  Body createBody() {
+    final shape = CircleShape()..radius = _radius;
+
+    final fixtureDef = FixtureDef(shape)..restitution = 1;
+
+    final bodyDef = BodyDef()
+      ..position = _position
+      ..type = BodyType.static;
+
+    return world.createBody(bodyDef)..createFixture(fixtureDef);
+  }
+}

test/game/components/round_bumper_test.dart

@@ -0,0 +1,124 @@
+// ignore_for_file: cascade_invocations
+
+import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:flame_test/flame_test.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pinball/game/game.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  group('RoundBumper', () {
+    final flameTester = FlameTester(Forge2DGame.new);
+    const radius = 1.0;
+    const points = 1;
+
+    flameTester.test(
+      'loads correctly',
+      (game) async {
+        await game.ready();
+        final roundBumper = RoundBumper(
+          position: Vector2.zero(),
+          radius: radius,
+          points: points,
+        );
+        await game.ensureAdd(roundBumper);
+
+        expect(game.contains(roundBumper), isTrue);
+      },
+    );
+
+    flameTester.test(
+      'has points',
+      (game) async {
+        final roundBumper = RoundBumper(
+          position: Vector2.zero(),
+          radius: radius,
+          points: points,
+        );
+        await game.ensureAdd(roundBumper);
+
+        expect(roundBumper.points, equals(points));
+      },
+    );
+
+    group('body', () {
+      flameTester.test(
+        'positions correctly',
+        (game) async {
+          final position = Vector2.all(10);
+          final roundBumper = RoundBumper(
+            position: position,
+            radius: radius,
+            points: points,
+          );
+          await game.ensureAdd(roundBumper);
+          game.contains(roundBumper);
+
+          expect(roundBumper.body.position, equals(position));
+        },
+      );
+
+      flameTester.test(
+        'is static',
+        (game) async {
+          final roundBumper = RoundBumper(
+            position: Vector2.zero(),
+            radius: radius,
+            points: points,
+          );
+          await game.ensureAdd(roundBumper);
+
+          expect(roundBumper.body.bodyType, equals(BodyType.static));
+        },
+      );
+    });
+
+    group('fixture', () {
+      flameTester.test(
+        'exists',
+        (game) async {
+          final roundBumper = RoundBumper(
+            position: Vector2.zero(),
+            radius: radius,
+            points: points,
+          );
+          await game.ensureAdd(roundBumper);
+
+          expect(roundBumper.body.fixtures[0], isA<Fixture>());
+        },
+      );
+
+      flameTester.test(
+        'has restitution',
+        (game) async {
+          final roundBumper = RoundBumper(
+            position: Vector2.zero(),
+            radius: radius,
+            points: points,
+          );
+          await game.ensureAdd(roundBumper);
+
+          final fixture = roundBumper.body.fixtures[0];
+          expect(fixture.restitution, greaterThan(0));
+        },
+      );
+
+      flameTester.test(
+        'shape is circular',
+        (game) async {
+          final roundBumper = RoundBumper(
+            position: Vector2.zero(),
+            radius: radius,
+            points: points,
+          );
+          await game.ensureAdd(roundBumper);
+
+          final fixture = roundBumper.body.fixtures[0];
+          expect(fixture.shape.shapeType, equals(ShapeType.circle));
+          expect(fixture.shape.radius, equals(1));
+        },
+      );
+    });
+  });
+}