feat: bonus letter callback

lib/game/components/bonus_letter.dart

@@ -1,9 +1,20 @@
+// ignore_for_file: avoid_renaming_method_parameters
+
 import 'package:flame/components.dart';
+import 'package:flame_bloc/flame_bloc.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
 import 'package:flutter/material.dart';
 import 'package:pinball/game/game.dart';
 
-class BonusLetter extends BodyComponent<PinballGame> {
+/// {@template bonus_letter}
+/// A pass through, [BodyType.static] component, part of
+/// a word bonus, which will active its letter once a ball
+/// pass through it
+/// {@endtemplate}
+class BonusLetter extends BodyComponent<PinballGame>
+    with BlocComponent<GameBloc, GameState> {
+
+  /// {@macro bonus_letter}
   BonusLetter({
     required Vector2 position,
     required String letter,
@@ -14,6 +25,7 @@ class BonusLetter extends BodyComponent<PinballGame> {
     paint = _disablePaint;
   }
 
+  /// The area size of this bonus letter
   static final areaSize = Vector2.all(4);
 
   static final _activePaint = Paint()..color = Colors.green;
@@ -51,4 +63,22 @@ class BonusLetter extends BodyComponent<PinballGame> {
 
     return world.createBody(bodyDef)..createFixture(fixtureDef);
   }
+
+  /// When called, will activate this letter, if still not activated
+  void activate() {
+    // TODO
+    //gameRef.read<GameBloc>().add(BonusLetterActivated(_index));
+
+    paint = _activePaint;
+  }
+}
+
+/// Handles contact for [Ball] and [BonusLetter], which trigger [BonusLetter]
+/// activate method.
+class BonusLetterBallContactCallback
+    extends ContactCallback<Ball, BonusLetter> {
+  @override
+  void begin(Ball ball, BonusLetter bonusLetter, Contact contact) {
+    bonusLetter.activate();
+  }
 }

lib/game/pinball_game.dart

@@ -44,6 +44,7 @@ class PinballGame extends Forge2DGame
 
     unawaited(_addFlippers());
     _addBonusLetters();
+    addContactCallback(BonusLetterBallContactCallback());
   }
 
   void _addBonusLetters() {