refactor: changed Elevated mixin to Priority extension

lib/game/components/ball.dart

@@ -7,8 +7,7 @@ import 'package:pinball/gen/assets.gen.dart';
 /// A solid, [BodyType.dynamic] sphere that rolls and bounces along the
 /// [PinballGame].
 /// {@endtemplate}
-class Ball extends BodyComponent<PinballGame>
-    with InitialPosition, Layered, Elevated {
+class Ball extends BodyComponent<PinballGame> with InitialPosition, Layered {
   /// {@macro ball}
   Ball() {
     // TODO(ruimiguel): while developing Ball can be launched by clicking mouse,

lib/game/components/components.dart

@@ -3,7 +3,6 @@ export 'baseboard.dart';
 export 'board.dart';
 export 'board_side.dart';
 export 'bonus_word.dart';
-export 'elevation.dart';
 export 'flipper.dart';
 export 'initial_position.dart';
 export 'jetpack_ramp.dart';
@@ -13,6 +12,7 @@ export 'launcher_ramp.dart';
 export 'layer.dart';
 export 'pathway.dart';
 export 'plunger.dart';
+export 'priority.dart';
 export 'ramp_opening.dart';
 export 'round_bumper.dart';
 export 'score_points.dart';

lib/game/components/elevation.dart

@@ -1,71 +0,0 @@
-import 'package:flame_forge2d/flame_forge2d.dart';
-import 'package:flutter/material.dart';
-
-/// {@template elevated}
-/// Modifies priority of the [BodyComponent] to specify in which z-index level
-///  [BodyComponent] is.
-/// {@endtemplate}
-mixin Elevated<T extends Forge2DGame> on BodyComponent<T> {
-  int _elevation = Elevation.board.order;
-
-  /// {@macro elevated}
-  int get elevation => _elevation;
-
-  set elevation(int value) {
-    _elevation = value;
-    if (!isLoaded) {
-      // TODO(ruimiguel): Use loaded.whenComplete once provided.
-      mounted.whenComplete(_applyElevation);
-    } else {
-      _applyElevation();
-    }
-  }
-
-  void _applyElevation() {
-    priority = elevation;
-    reorderChildren();
-  }
-}
-
-/// The [Elevation]s a [BodyComponent] can be in.
-///
-/// Each [Elevation] is associated with a different board level from ground, to
-/// define several z-index heights.
-///
-/// Usually used with [Elevated].
-enum Elevation {
-  /// The ground level.
-  board,
-
-  /// Level for Jetpack group elements.
-  jetpack,
-
-  /// Level for Spaceship group elements.
-  spaceship,
-
-  /// Level for SpaceshipExitRail.
-  spaceshipExitRail,
-}
-
-/// {@template elevation_order}
-/// Specifies the order of each [Elevation].
-///
-/// Used by [Elevated] to specify what is the priority of [BodyComponent].
-/// {@endtemplate}
-@visibleForTesting
-extension ElevationOrder on Elevation {
-  /// {@macro elevation_order}
-
-  int get order {
-    switch (this) {
-      case Elevation.board:
-        return 1;
-      case Elevation.jetpack:
-        return 2;
-      case Elevation.spaceship:
-        return 3;
-      case Elevation.spaceshipExitRail:
-        return 2;
-    }
-  }
-}

lib/game/components/priority.dart

@@ -0,0 +1,32 @@
+// TODO(ruimiguel): move file to appropiate location.
+import 'dart:math' as math;
+import 'package:flame/components.dart';
+
+/// Helper methods to change the [priority] of a [Component].
+extension ComponentPriorityX on Component {
+  static const _lowestPriority = 0;
+
+  /// Changes the priority to the lowest possible.
+  void sendToBack() {
+    if (priority != _lowestPriority) {
+      priority = _lowestPriority;
+      reorderChildren();
+    }
+  }
+
+  /// Decreases the priority to be lower than another [Component].
+  void showBehindOf(Component other) {
+    if (priority >= other.priority) {
+      priority = math.max(other.priority - 1, _lowestPriority);
+      reorderChildren();
+    }
+  }
+
+  /// Increases the priority to be higher than another [Component].
+  void showInFrontOf(Component other) {
+    if (priority <= other.priority) {
+      priority = other.priority + 1;
+      reorderChildren();
+    }
+  }
+}

lib/game/components/spaceship.dart

@@ -1,4 +1,4 @@
-// ignore_for_file: avoid_renaming_method_parameters
+// ignore_for_file: avoid_renaming_method_parameters, avoid_function_literals_in_foreach_calls
 
 import 'dart:async';
 import 'dart:math';
@@ -26,14 +26,28 @@ class Spaceship extends Forge2DBlueprint {
       SpaceshipEntranceBallContactCallback(),
     ]);
 
-    addAll([
-      SpaceshipSaucer()..initialPosition = position,
+    const ballPriorityWhenOnSpaceship = 3;
+
+    final rendersBehindBall = [
       SpaceshipEntrance()..initialPosition = position,
+      SpaceshipSaucer()..initialPosition = position,
+    ]..forEach(
+        (component) => component.priority = ballPriorityWhenOnSpaceship - 1,
+      );
+
+    final rendersInFrontOfBall = [
       SpaceshipBridge()..initialPosition = position,
       SpaceshipBridgeTop()..initialPosition = position + Vector2(0, 5.5),
+      SpaceshipWall()..initialPosition = position,
+    ]..forEach(
+        (component) => component.priority = ballPriorityWhenOnSpaceship + 1,
+      );
+
+    addAll([
+      ...rendersBehindBall,
+      ...rendersInFrontOfBall,
       SpaceshipHole()..initialPosition = position - Vector2(5, 4),
       SpaceshipHole()..initialPosition = position - Vector2(-5, 4),
-      SpaceshipWall()..initialPosition = position,
     ]);
   }
 }
@@ -41,12 +55,10 @@ class Spaceship extends Forge2DBlueprint {
 /// {@template spaceship_saucer}
 /// A [BodyComponent] for the base, or the saucer of the spaceship
 /// {@endtemplate}
-class SpaceshipSaucer extends BodyComponent
-    with InitialPosition, Layered, Elevated {
+class SpaceshipSaucer extends BodyComponent with InitialPosition, Layered {
   /// {@macro spaceship_saucer}
   SpaceshipSaucer() {
     layer = Layer.spaceship;
-    elevation = Elevation.spaceship.order - 1;
   }
 
   @override
@@ -97,11 +109,9 @@ class SpaceshipSaucer extends BodyComponent
 /// The bridge of the spaceship (the android head) is divided in two
 // [BodyComponent]s, this is the top part of it which contains a single sprite
 /// {@endtemplate}
-class SpaceshipBridgeTop extends BodyComponent with InitialPosition, Elevated {
+class SpaceshipBridgeTop extends BodyComponent with InitialPosition {
   /// {@macro spaceship_bridge_top}
-  SpaceshipBridgeTop() {
-    elevation = Elevation.spaceship.order * 2;
-  }
+  SpaceshipBridgeTop();
 
   @override
   Future<void> onLoad() async {
@@ -134,12 +144,10 @@ class SpaceshipBridgeTop extends BodyComponent with InitialPosition, Elevated {
 /// The main part of the [SpaceshipBridge], this [BodyComponent]
 /// provides both the collision and the rotation animation for the bridge.
 /// {@endtemplate}
-class SpaceshipBridge extends BodyComponent
-    with InitialPosition, Layered, Elevated {
+class SpaceshipBridge extends BodyComponent with InitialPosition, Layered {
   /// {@macro spaceship_bridge}
   SpaceshipBridge() {
     layer = Layer.spaceship;
-    elevation = Elevation.spaceship.order;
   }
 
   @override
@@ -246,12 +254,10 @@ class SpaceshipHole extends BodyComponent with InitialPosition, Layered {
 /// [Ball] to get inside the spaceship saucer.
 /// It also contains the [SpriteComponent] for the lower wall
 /// {@endtemplate}
-class SpaceshipWall extends BodyComponent
-    with InitialPosition, Layered, Elevated {
+class SpaceshipWall extends BodyComponent with InitialPosition, Layered {
   /// {@macro spaceship_wall}
-  SpaceshipWall() : super(priority: 4) {
+  SpaceshipWall() {
     layer = Layer.spaceship;
-    elevation = Elevation.spaceship.order + 1;
   }
 
   @override
@@ -311,8 +317,8 @@ class SpaceshipEntranceBallContactCallback
   @override
   void begin(SpaceshipEntrance entrance, Ball ball, _) {
     ball
-      ..elevation = Elevation.spaceship.order
-      ..layer = Layer.spaceship;
+      ..layer = Layer.spaceship
+      ..showInFrontOf(entrance);
   }
 }
 
@@ -326,7 +332,7 @@ class SpaceshipHoleBallContactCallback
   @override
   void begin(SpaceshipHole hole, Ball ball, _) {
     ball
-      ..elevation = Elevation.board.order
-      ..layer = Layer.board;
+      ..layer = Layer.board
+      ..sendToBack();
   }
 }

test/game/components/priority_test.dart

@@ -2,10 +2,10 @@
 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/components/elevation.dart';
+import 'package:pinball/game/components/priority.dart';
 import 'package:pinball/game/game.dart';
 
-class TestBodyComponent extends BodyComponent with Elevated {
+class TestBodyComponent extends BodyComponent {
   @override
   Body createBody() {
     final fixtureDef = FixtureDef(CircleShape());
@@ -16,7 +16,7 @@ class TestBodyComponent extends BodyComponent with Elevated {
 void main() {
   final flameTester = FlameTester(Forge2DGame.new);
 
-  group('Elevated', () {
+  group('ComponentPriorityX', () {
     test('correctly sets and gets', () {
       final component = TestBodyComponent()
         ..elevation = Elevation.spaceship.order;