feat: implemented ChromeDino mechanics (#76)

* feat: included ChromeDino in Board

* feat: made ChromeDino sweep

* feat: enclosed ChromeDino

* feat: included ChromeDino in Board

* feat: included initial file

* feat: made ChromeDino sweep

* feat: enclosed ChromeDino

* feat: positioned and clean

* feat: used ChromeDinoJoint

* feat: used a Timer in ChromeDino animation

* feat: positioned ChromeDino

* feat: adjusted motor values

* feat: created test file

* feat: included tests

* refactor: used TimerComponent

* feat: adjusted ChromeDino

* refactor: renamed test variable

* refactor: removed redundant test

* fix: included components import

* refactor: removed joint member

* refactor: included missing new line

* docs: fixed "dinosaur" typo

Co-authored-by: Erick <erickzanardoo@gmail.com>
Co-authored-by: Rui Miguel Alonso <ruiskas@gmail.com>

lib/game/components/board.dart

@@ -21,8 +21,16 @@ class Board extends Component {
 
     final flutterForest = FlutterForest();
 
+    // TODO(alestiago): adjust positioning to real design.
+    final dino = ChromeDino()
+      ..initialPosition = Vector2(
+        PinballGame.boardBounds.center.dx + 25,
+        PinballGame.boardBounds.center.dy + 10,
+      );
+
     await addAll([
       bottomGroup,
+      dino,
       flutterForest,
     ]);
   }

lib/game/components/chrome_dino.dart

@@ -0,0 +1,169 @@
+import 'dart:async';
+import 'dart:math' as math;
+
+import 'package:flame/components.dart';
+import 'package:flame_forge2d/flame_forge2d.dart' hide Timer;
+import 'package:flutter/material.dart';
+import 'package:pinball/game/game.dart';
+import 'package:pinball_components/pinball_components.dart';
+
+/// {@template chrome_dino}
+/// Dinosaur that gobbles up a [Ball], swivel his head around, and shoots it
+/// back out.
+/// {@endtemplate}
+class ChromeDino extends BodyComponent with InitialPosition {
+  /// {@macro chrome_dino}
+  ChromeDino() {
+    // TODO(alestiago): Remove once sprites are defined.
+    paint = Paint()..color = Colors.blue;
+  }
+
+  /// The size of the dinosaur mouth.
+  static final size = Vector2(5, 2.5);
+
+  /// Anchors the [ChromeDino] to the [RevoluteJoint] that controls its arc
+  /// motion.
+  Future<_ChromeDinoJoint> _anchorToJoint() async {
+    final anchor = _ChromeDinoAnchor(chromeDino: this);
+    await add(anchor);
+
+    final jointDef = _ChromeDinoAnchorRevoluteJointDef(
+      chromeDino: this,
+      anchor: anchor,
+    );
+    final joint = _ChromeDinoJoint(jointDef);
+    world.createJoint2(joint);
+
+    return joint;
+  }
+
+  @override
+  Future<void> onLoad() async {
+    await super.onLoad();
+    final joint = await _anchorToJoint();
+    await add(
+      TimerComponent(
+        period: 1,
+        onTick: joint.swivel,
+        repeat: true,
+      ),
+    );
+  }
+
+  List<FixtureDef> _createFixtureDefs() {
+    final fixtureDefs = <FixtureDef>[];
+
+    // TODO(alestiago): Subject to change when sprites are added.
+    final box = PolygonShape()..setAsBoxXY(size.x / 2, size.y / 2);
+    final fixtureDef = FixtureDef(box)
+      ..shape = box
+      ..density = 999
+      ..friction = 0.3
+      ..restitution = 0.1
+      ..isSensor = true;
+    fixtureDefs.add(fixtureDef);
+
+    // FIXME(alestiago): Investigate why adding these fixtures is considered as
+    // an invalid contact type.
+    // final upperEdge = EdgeShape()
+    //   ..set(
+    //     Vector2(-size.x / 2, -size.y / 2),
+    //     Vector2(size.x / 2, -size.y / 2),
+    //   );
+    // final upperEdgeDef = FixtureDef(upperEdge)..density = 0.5;
+    // fixtureDefs.add(upperEdgeDef);
+
+    // final lowerEdge = EdgeShape()
+    //   ..set(
+    //     Vector2(-size.x / 2, size.y / 2),
+    //     Vector2(size.x / 2, size.y / 2),
+    //   );
+    // final lowerEdgeDef = FixtureDef(lowerEdge)..density = 0.5;
+    // fixtureDefs.add(lowerEdgeDef);
+
+    // final rightEdge = EdgeShape()
+    //   ..set(
+    //     Vector2(size.x / 2, -size.y / 2),
+    //     Vector2(size.x / 2, size.y / 2),
+    //   );
+    // final rightEdgeDef = FixtureDef(rightEdge)..density = 0.5;
+    // fixtureDefs.add(rightEdgeDef);
+
+    return fixtureDefs;
+  }
+
+  @override
+  Body createBody() {
+    final bodyDef = BodyDef()
+      ..gravityScale = 0
+      ..position = initialPosition
+      ..type = BodyType.dynamic;
+
+    final body = world.createBody(bodyDef);
+    _createFixtureDefs().forEach(body.createFixture);
+
+    return body;
+  }
+}
+
+/// {@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;
+    // TODO(alestiago): Apply design angle value.
+    const angle = math.pi / 3.5;
+    lowerAngle = -angle / 2;
+    upperAngle = angle / 2;
+
+    enableMotor = true;
+    // TODO(alestiago): Tune this values.
+    maxMotorTorque = motorSpeed = chromeDino.body.mass * 30;
+  }
+}
+
+class _ChromeDinoJoint extends RevoluteJoint {
+  _ChromeDinoJoint(_ChromeDinoAnchorRevoluteJointDef def) : super(def);
+
+  /// Sweeps the [ChromeDino] up and down repeatedly.
+  void swivel() {
+    setMotorSpeed(-motorSpeed);
+  }
+}
+
+extension on World {
+  // TODO(alestiago): Remove once Forge2D supports custom joints.
+  void createJoint2(Joint joint) {
+    assert(!isLocked, '');
+
+    joints.add(joint);
+
+    joint.bodyA.joints.add(joint);
+    joint.bodyB.joints.add(joint);
+  }
+}

lib/game/components/components.dart

@@ -3,6 +3,7 @@ export 'baseboard.dart';
 export 'board.dart';
 export 'board_side.dart';
 export 'bonus_word.dart';
+export 'chrome_dino.dart';
 export 'flipper.dart';
 export 'flutter_forest.dart';
 export 'jetpack_ramp.dart';

test/game/components/board_test.dart

@@ -86,6 +86,18 @@ void main() {
           expect(flutterForest.length, equals(1));
         },
       );
+
+      flameTester.test(
+        'has one ChromeDino',
+        (game) async {
+          final board = Board();
+          await game.ready();
+          await game.ensureAdd(board);
+
+          final chromeDino = board.descendants().whereType<ChromeDino>();
+          expect(chromeDino.length, equals(1));
+        },
+      );
     });
   });
 }

test/game/components/chrome_dino_test.dart

@@ -0,0 +1,23 @@
+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();
+  final flameTester = FlameTester(Forge2DGame.new);
+
+  group('ChromeDino', () {
+    flameTester.test(
+      'loads correctly',
+      (game) async {
+        final chromeDino = ChromeDino();
+
+        await game.ready();
+        await game.ensureAdd(chromeDino);
+
+        expect(game.contains(chromeDino), isTrue);
+      },
+    );
+  });
+}