feat: implemented `ScorePoints` mixin and callback (#7)

* feat: implemented ScorePoints mixin

* refactor: renamed BallHasScoreCallback to BallScorePointsCallback

* feat: included test for end method

* chore: included TODO comment

* docs: included doc comments

* feat: set ScorePoints mixin on BodyComponent

* feat: rewrote test for mixin only extending BodyComponent

* feat: registered BallScorePointsCallback in PinballGame

* docs: improved BallScorePointsCallback doc comment

* docs: changed PR url to issue url

* refactor: fixed analyzer warnings

* refactor: used real class names instead of Mock class names

Co-authored-by: Allison Ryan <77211884+allisonryan0002@users.noreply.github.com>

Co-authored-by: Allison Ryan <77211884+allisonryan0002@users.noreply.github.com>

lib/game/components/ball.dart

@@ -1,8 +1,11 @@
+import 'package:flame_bloc/flame_bloc.dart';
 import 'package:flame_forge2d/body_component.dart';
 import 'package:flutter/material.dart';
 import 'package:forge2d/forge2d.dart';
+import 'package:pinball/game/game.dart';
 
-class Ball extends BodyComponent {
+class Ball extends BodyComponent<PinballGame>
+    with BlocComponent<GameBloc, GameState> {
   Ball({
     required Vector2 position,
   }) : _position = position {

lib/game/components/components.dart

@@ -1 +1,2 @@
 export 'ball.dart';
+export 'score_points.dart';

lib/game/components/score_points.dart

@@ -0,0 +1,30 @@
+// ignore_for_file: avoid_renaming_method_parameters
+
+import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:pinball/game/game.dart';
+
+/// {@template score_points}
+/// Specifies the amount of points received on [Ball] collision.
+/// {@endtemplate}
+mixin ScorePoints on BodyComponent {
+  /// {@macro score_points}
+  int get points;
+}
+
+/// Adds points to the score when a [Ball] collides with a [BodyComponent] that
+/// implements [ScorePoints].
+class BallScorePointsCallback extends ContactCallback<Ball, ScorePoints> {
+  @override
+  void begin(
+    Ball ball,
+    ScorePoints hasPoints,
+    Contact _,
+  ) {
+    ball.gameRef.read<GameBloc>().add(Scored(points: hasPoints.points));
+  }
+
+  // TODO(alestiago): remove once this issue is closed.
+  // https://github.com/flame-engine/flame/issues/1414
+  @override
+  void end(Ball _, ScorePoints __, Contact ___) {}
+}

lib/game/pinball_game.dart

@@ -1,4 +1,10 @@
 import 'package:flame_bloc/flame_bloc.dart';
 import 'package:flame_forge2d/forge2d_game.dart';
+import 'package:pinball/game/game.dart';
 
-class PinballGame extends Forge2DGame with FlameBloc {}
+class PinballGame extends Forge2DGame with FlameBloc {
+  @override
+  Future<void> onLoad() async {
+    addContactCallback(BallScorePointsCallback());
+  }
+}

test/game/components/score_points_test.dart

@@ -0,0 +1,80 @@
+import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:pinball/game/game.dart';
+
+class MockBall extends Mock implements Ball {}
+
+class MockGameBloc extends Mock implements GameBloc {}
+
+class MockPinballGame extends Mock implements PinballGame {}
+
+class FakeContact extends Fake implements Contact {}
+
+class FakeGameEvent extends Fake implements GameEvent {}
+
+class FakeScorePoints extends BodyComponent with ScorePoints {
+  @override
+  Body createBody() {
+    throw UnimplementedError();
+  }
+
+  @override
+  int get points => 2;
+}
+
+void main() {
+  group('BallScorePointsCallback', () {
+    late PinballGame game;
+    late GameBloc bloc;
+    late Ball ball;
+    late FakeScorePoints fakeScorePoints;
+
+    setUp(() {
+      game = MockPinballGame();
+      bloc = MockGameBloc();
+      ball = MockBall();
+      fakeScorePoints = FakeScorePoints();
+    });
+
+    setUpAll(() {
+      registerFallbackValue(FakeGameEvent());
+    });
+
+    group('begin', () {
+      test(
+        'emits Scored event with points',
+        () {
+          when<PinballGame>(() => ball.gameRef).thenReturn(game);
+          when<GameBloc>(game.read).thenReturn(bloc);
+
+          BallScorePointsCallback().begin(
+            ball,
+            fakeScorePoints,
+            FakeContact(),
+          );
+
+          verify(
+            () => bloc.add(
+              Scored(points: fakeScorePoints.points),
+            ),
+          ).called(1);
+        },
+      );
+    });
+
+    group('end', () {
+      test("doesn't add events to GameBloc", () {
+        BallScorePointsCallback().end(
+          ball,
+          fakeScorePoints,
+          FakeContact(),
+        );
+
+        verifyNever(
+          () => bloc.add(any()),
+        );
+      });
+    });
+  });
+}

test/game/pinball_game_test.dart

@@ -0,0 +1,9 @@
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('PinballGame', () {
+    // TODO(alestiago): test if [PinballGame] registers
+    // [BallScorePointsCallback] once the following issue is resolved:
+    // https://github.com/flame-engine/flame/issues/1416
+  });
+}