feat: made ChromeDino sweep

lib/game/components/chrome_dino.dart

@@ -1,4 +1,8 @@
+import 'dart:async';
+import 'dart:math' as math;
+
 import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:flutter/material.dart';
 import 'package:pinball/game/game.dart';
 
 /// {@template chrome_dino}
@@ -7,11 +11,106 @@ import 'package:pinball/game/game.dart';
 /// {@endtemplate}
 class ChromeDino extends BodyComponent with InitialPosition {
   /// {@macro chrome_dino}
-  ChromeDino();
+  ChromeDino() {
+    // TODO(alestiago): Remove once sprites are defined.
+    paint = Paint()..color = Colors.blue;
+  }
+
+  static final size = Vector2(3, 1);
+
+  /// Anchors the [ChromeDino] to the [RevoluteJoint] that controls its arc
+  /// motion.
+  Future<void> _anchorToJoint() async {
+    final anchor = ChromeDinoAnchor(chromeDino: this);
+    await add(anchor);
+
+    final jointDef = ChromeDinoAnchorRevoluteJointDef(
+      chromeDino: this,
+      anchor: anchor,
+    );
+    final joint = world.createJoint(jointDef) as RevoluteJoint;
+
+    ChromeDinoAnchorRevoluteJointDef.spin(joint, removed);
+  }
+
+  Completer removed = Completer<bool>();
+
+  @override
+  void onRemove() {
+    super.onRemove();
+    removed.complete(true);
+  }
+
+  @override
+  Future<void> onLoad() async {
+    await super.onLoad();
+    await _anchorToJoint();
+  }
 
   @override
   Body createBody() {
-    // TODO: implement createBody
-    throw UnimplementedError();
+    final shape = PolygonShape()..setAsBoxXY(size.x, size.y);
+    final fixtureDef = FixtureDef(shape)..density = 1;
+
+    final bodyDef = BodyDef()
+      ..gravityScale = 0
+      ..position = initialPosition
+      ..type = BodyType.dynamic;
+
+    return world.createBody(bodyDef)..createFixture(fixtureDef);
+  }
+}
+
+/// {@template flipper_anchor}
+/// [JointAnchor] positioned at the end of a [ChromeDino].
+/// {@endtemplate}
+class ChromeDinoAnchor extends JointAnchor {
+  /// {@macro flipper_anchor}
+  ChromeDinoAnchor({
+    required ChromeDino chromeDino,
+  }) {
+    initialPosition = Vector2(
+      chromeDino.body.position.x + ChromeDino.size.x / 2,
+      chromeDino.body.position.y,
+    );
+  }
+}
+
+/// {@template chrome_dino_anchor_revolute_joint_def}
+/// Hinges a [ChromeDino] to a [ChromeDinoAnchor].
+/// {@endtemplate}
+class ChromeDinoAnchorRevoluteJointDef extends RevoluteJointDef {
+  /// {@macro chrome_dino_anchor_revolute_joint_def}
+  ChromeDinoAnchorRevoluteJointDef({
+    required ChromeDino chromeDino,
+    required ChromeDinoAnchor anchor,
+  }) {
+    initialize(
+      chromeDino.body,
+      anchor.body,
+      anchor.body.position,
+    );
+    enableLimit = true;
+    const halfAngle = _sweepingAngle / 2;
+    lowerAngle = -halfAngle;
+    upperAngle = halfAngle;
+
+    enableMotor = true;
+    maxMotorTorque = 999;
+    motorSpeed = 999;
   }
+
+  // TODO(alestiago): Refactor.
+  static void spin(RevoluteJoint joint, Completer completer) {
+    Future.doWhile(() async {
+      if (completer.isCompleted) return false;
+
+      await Future<void>.delayed(Duration(milliseconds: 1000));
+      joint.setMotorSpeed(-joint.motorSpeed);
+      return true;
+    });
+  }
+
+  /// The total angle of the arc motion.
+  static const _sweepingAngle = math.pi / 3.5;
 }