Spawn + shoot asteroids

* Add AsteroidSpawningSystem which adds asteroids to the game at a regular
  interval up to a set limit.
* Add EventFactory for generating entity-specific Collision events
* Detect asteroids being shot with BulletAsteroidCollisionEvent
* Add DEBUG output to creating entities
* New getPointAlongPolygon utils function

core/src/com/me/asteroids/EntityFactory.java

@@ -3,6 +3,7 @@ package com.me.asteroids;
 import com.badlogic.gdx.math.Polygon;
 import com.badlogic.gdx.math.Vector2;
 import com.me.asteroids.components.AccelerationComponent;
+import com.me.asteroids.components.AsteroidComponent;
 import com.me.asteroids.components.BulletComponent;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PlayerComponent;
@@ -11,8 +12,20 @@ import com.me.asteroids.components.VelocityComponent;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 
+import static com.me.asteroids.Constants.rand;
+
 public class EntityFactory {
 
+    private static final Vector2 tmp = new Vector2();
+
+    private static Entity createEntity(Engine engine) {
+        Entity entity = engine.createEntity();
+        if (Constants.DEBUG) {
+            System.out.println("Spawned entity: " + entity);
+        }
+        return entity;
+    }
+
     public static Entity createPlayer(Engine engine) {
         PositionComponent position = new PositionComponent();
         position.position = new Vector2(Constants.HALF_WIDTH, Constants.HALF_HEIGHT);
@@ -35,7 +48,7 @@ public class EntityFactory {
         AccelerationComponent accel = new AccelerationComponent();
         accel.acceleration = new Vector2(0,1f);
 
-        Entity player = engine.createEntity();
+        Entity player = createEntity(engine);
         player.addComponent(position);
         player.addComponent(velocity);
         player.addComponent(model);
@@ -45,26 +58,30 @@ public class EntityFactory {
     }
 
     public static Entity createBullet(Engine engine, Entity player) {
-        PositionComponent position = new PositionComponent();
         float[] modelVertices = player.getComponent(ModelComponent.class).model.getTransformedVertices();
-        position.position = new Vector2(modelVertices[0], modelVertices[1]);
-        position.rotation = player.getComponent(PositionComponent.class).rotation;
+        float rotation = player.getComponent(PositionComponent.class).rotation;
+
+        Vector2 direction = Utils.setUnitVectorAngle(tmp, rotation);
 
         VelocityComponent velocity = new VelocityComponent();
-        velocity.velocity = Utils.setUnitVectorAngle(new Vector2(), position.rotation).scl(500);
+        velocity.velocity = new Vector2(direction).scl(500);
+
+        PositionComponent position = new PositionComponent();
+        position.position = new Vector2(modelVertices[0], modelVertices[1]).add(direction.scl(4));
+        position.rotation = rotation;
 
         ModelComponent model = new ModelComponent();
         model.model = new Polygon(new float[] {
-                -1f, 2f,
-                1f, 2f,
-                1f, -2f,
-                -1f, -2f,
+                1f, 0f,
+                -1f, 0f,
+                -1f, -4f,
+                1f, -4f,
         });
         model.model.setRotation(position.rotation);
-        model.model.setPosition(position.position.x, position.position.x);
+        model.model.setPosition(position.position.x, position.position.y);
 
 
-        Entity bullet = engine.createEntity();
+        Entity bullet = createEntity(engine);
         bullet.addComponent(position);
         bullet.addComponent(velocity);
         bullet.addComponent(model);
@@ -72,4 +89,27 @@ public class EntityFactory {
         return bullet;
     }
 
+    public static Entity createAsteroid(Engine engine) {
+        // Creates an asteroid entity with position and velocity unset - the AsteroidSpawningSystem
+        // is responsible for setting its position and velocity
+        PositionComponent position = new PositionComponent();
+        VelocityComponent velocity = new VelocityComponent();
+
+        ModelComponent model = new ModelComponent();
+        int size = rand.nextInt(30, 60);
+        model.model = new AsteroidFactory()
+                .setVertexCount(rand.nextInt(16, 24))
+                .setSize(size)
+                .setSizeVariation(size * 0.7f)
+                .generate();
+        model.aabb = model.model.getBoundingRectangle();
+
+        Entity asteroid = createEntity(engine);
+        asteroid.addComponent(position);
+        asteroid.addComponent(velocity);
+        asteroid.addComponent(model);
+        asteroid.addComponent(new AsteroidComponent());
+        return asteroid;
+    }
+
 }

core/src/com/me/asteroids/EventFactory.java

@@ -0,0 +1,36 @@
+package com.me.asteroids;
+
+import com.me.asteroids.components.AsteroidComponent;
+import com.me.asteroids.components.BulletComponent;
+import com.me.asteroids.components.PlayerComponent;
+import com.me.asteroids.events.BulletAsteroidCollisionEvent;
+import com.me.asteroids.events.CollisionEvent;
+import com.me.asteroids.events.PlayerASteroidCollisionEvent;
+import com.me.common.ecs.Entity;
+
+public class EventFactory {
+
+    public static CollisionEvent getNewCollisionEvent(Entity a, Entity b) {
+        boolean isEntityAPlayer = a.hasComponent(PlayerComponent.class);
+        boolean isEntityBPlayer = b.hasComponent(PlayerComponent.class);
+        boolean isEntityABullet = !isEntityAPlayer && a.hasComponent(BulletComponent.class);
+        boolean isEntityBBullet = !isEntityBPlayer && b.hasComponent(BulletComponent.class);
+        boolean isEntityAAsteroid = !isEntityAPlayer && !isEntityABullet && a.hasComponent(AsteroidComponent.class);
+        boolean isEntityBAsteroid = !isEntityBPlayer && !isEntityBBullet && b.hasComponent(AsteroidComponent.class);
+
+        if (isEntityAAsteroid || isEntityBAsteroid) {
+            if (isEntityAPlayer && isEntityBAsteroid) {
+                return new PlayerASteroidCollisionEvent(a, b);
+            } else if (isEntityBPlayer && isEntityAAsteroid) {
+                return new PlayerASteroidCollisionEvent(b, a);
+            } else if (isEntityABullet && isEntityBAsteroid) {
+                return new BulletAsteroidCollisionEvent(a, b);
+            } else if (isEntityBBullet && isEntityAAsteroid) {
+                return new BulletAsteroidCollisionEvent(b, a);
+            }
+        }
+
+        return new CollisionEvent(a, b);
+    }
+
+}

core/src/com/me/asteroids/Utils.java

@@ -7,6 +7,8 @@ import java.lang.Math;
 
 public final class Utils {
 
+    private static final Vector2 tmp = new Vector2();
+
     public static float rotate(float rotation, float degrees) {
         rotation += degrees;
         if (rotation < 0) {
@@ -25,4 +27,21 @@ public final class Utils {
         return vector.set((float) Math.cos(radians), (float) Math.sin(radians));
     }
 
+    public static Vector2 getPointAlongPolygon(Vector2[] vertices, float distanceAlongPerimeter) {
+        for (int i = 0, n = vertices.length; i < n; i++) {
+            Vector2 a = vertices[i];
+            Vector2 b = vertices[i + 1 == n ? 0 : i + 1];
+            tmp.set(a).sub(b);
+            float len = tmp.len();
+
+            if (len < distanceAlongPerimeter) {
+                distanceAlongPerimeter -= len;
+                continue;
+            }
+
+            return a.add(tmp.set(tmp.x / len, tmp.y / len).scl(distanceAlongPerimeter));
+        }
+        return null;
+    }
+
 }

core/src/com/me/asteroids/components/AsteroidComponent.java

@@ -0,0 +1,7 @@
+package com.me.asteroids.components;
+
+import com.me.common.ecs.Component;
+
+public class AsteroidComponent implements Component {
+    // TODO: See PlayerComponent's TODO
+}

core/src/com/me/asteroids/events/BulletAsteroidCollisionEvent.java

@@ -0,0 +1,19 @@
+package com.me.asteroids.events;
+
+import com.me.common.ecs.Entity;
+
+public class BulletAsteroidCollisionEvent extends CollisionEvent {
+
+    public BulletAsteroidCollisionEvent(Entity bullet, Entity asteroid) {
+        super(bullet, asteroid);
+    }
+
+    public Entity getBullet() {
+        return entityA;
+    }
+
+    public Entity getAsteroid() {
+        return entityB;
+    }
+
+}

core/src/com/me/asteroids/events/PlayerASteroidCollisionEvent.java

@@ -0,0 +1,19 @@
+package com.me.asteroids.events;
+
+import com.me.common.ecs.Entity;
+
+public class PlayerASteroidCollisionEvent extends CollisionEvent {
+
+    public PlayerASteroidCollisionEvent(Entity player, Entity asteroid) {
+        super(player, asteroid);
+    }
+
+    public Entity getPlayer() {
+        return entityA;
+    }
+
+    public Entity getAsteroid() {
+        return entityB;
+    }
+
+}

core/src/com/me/asteroids/screens/GameScreen.java

@@ -4,22 +4,28 @@ import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.g2d.BitmapFont;
 import com.badlogic.gdx.graphics.g2d.SpriteBatch;
+import com.badlogic.gdx.math.Polygon;
+import com.badlogic.gdx.math.Vector2;
 import com.me.asteroids.Constants;
 import com.me.asteroids.EntityFactory;
 import com.me.asteroids.Graphics;
 import com.me.asteroids.components.AccelerationComponent;
+import com.me.asteroids.components.AsteroidComponent;
 import com.me.asteroids.components.BulletComponent;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PlayerComponent;
 import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.components.VelocityComponent;
+import com.me.asteroids.events.BulletAsteroidCollisionEvent;
 import com.me.asteroids.events.ScreenWrapEvent;
+import com.me.asteroids.systems.AsteroidSpawningSystem;
 import com.me.asteroids.systems.CollisionSystem;
 import com.me.asteroids.systems.ModelRenderSystem;
 import com.me.asteroids.systems.MovementSystem;
 import com.me.asteroids.systems.PlayerInputSystem;
 import com.me.asteroids.systems.ScreenWrapSystem;
 import com.me.common.Screen;
+import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.event.EventHandler;
@@ -48,18 +54,20 @@ public class GameScreen extends Screen implements Listener {
 
         engine.registerComponentClass(PlayerComponent.class);
         engine.registerComponentClass(BulletComponent.class);
+        engine.registerComponentClass(AsteroidComponent.class);
         engine.registerComponentClass(PositionComponent.class);
         engine.registerComponentClass(VelocityComponent.class);
         engine.registerComponentClass(AccelerationComponent.class);
         engine.registerComponentClass(ModelComponent.class);
 
         engine.registerSystem(new PlayerInputSystem(engine));
+        engine.registerSystem(new AsteroidSpawningSystem(engine));
         engine.registerSystem(new MovementSystem(engine));
         engine.registerSystem(new CollisionSystem(engine));
         engine.registerSystem(new ScreenWrapSystem(engine));
         engine.registerSystem(new ModelRenderSystem(engine, graphics));
 
-        engine.registerListener(this);
+        engine.registerListener(this.new EventListener(engine));
 
         engine.ready();
 
@@ -84,13 +92,40 @@ public class GameScreen extends Screen implements Listener {
 
     }
 
-    @EventHandler
-    public void onScreenWrap(ScreenWrapEvent event) {
-        if (event.entity.hasComponent(BulletComponent.class)) {
-            // Remove bullets when they leave the screen
-            event.setCancelled(true);
-            event.entity.remove();
+    private class EventListener implements Listener {
+
+        ComponentMapper<PositionComponent> positionMapper;
+        ComponentMapper<ModelComponent> modelMapper;
+        ComponentMapper<BulletComponent> bulletMapper;
+
+        EventListener(Engine engine) {
+            this.positionMapper = engine.getComponentMapper(PositionComponent.class);
+            this.modelMapper = engine.getComponentMapper(ModelComponent.class);
+            this.bulletMapper = engine.getComponentMapper(BulletComponent.class);
         }
+
+        @EventHandler
+        public void onScreenWrap(ScreenWrapEvent event) {
+            if (bulletMapper.has(event.entity)) {
+                // Remove bullets when they leave the screen
+                //event.setCancelled(true);
+                event.entity.remove();
+            }
+        }
+
+        @EventHandler
+        public void onBulletAsteroidCollision(BulletAsteroidCollisionEvent event) {
+            Vector2 bulletPosition = positionMapper.get(event.getBullet()).position;
+            Polygon asteroidModel = modelMapper.get(event.getAsteroid()).model;
+
+            if (asteroidModel.contains(bulletPosition)) {
+                // AABBs intersect but let's only consider it a hit if the bullet's position
+                // is actually inside the asteroid
+                event.getBullet().remove();
+                event.getAsteroid().remove();
+            }
+        }
+
     }
 
 

core/src/com/me/asteroids/systems/AsteroidSpawningSystem.java

@@ -0,0 +1,88 @@
+package com.me.asteroids.systems;
+
+import com.badlogic.gdx.math.Vector2;
+import com.badlogic.gdx.utils.Array;
+import com.me.asteroids.Constants;
+import com.me.asteroids.EntityFactory;
+import com.me.asteroids.Utils;
+import com.me.asteroids.components.AsteroidComponent;
+import com.me.asteroids.components.ModelComponent;
+import com.me.asteroids.components.PositionComponent;
+import com.me.asteroids.components.VelocityComponent;
+import com.me.common.ecs.BaseSystem;
+import com.me.common.ecs.ComponentMapper;
+import com.me.common.ecs.Engine;
+import com.me.common.ecs.Entity;
+
+import static com.me.asteroids.Constants.rand;
+
+public class AsteroidSpawningSystem extends BaseSystem {
+
+    private ComponentMapper<AsteroidComponent> asteroidMapper;
+    private ComponentMapper<PositionComponent> positionMapper;
+    private ComponentMapper<VelocityComponent> velocityMapper;
+    private ComponentMapper<ModelComponent> modelMapper;
+
+    private float asteroidSpawnDelay = 0f;
+
+    public AsteroidSpawningSystem(Engine engine) {
+        super(engine);
+        asteroidMapper = engine.getComponentMapper(AsteroidComponent.class);
+        positionMapper = engine.getComponentMapper(PositionComponent.class);
+        velocityMapper = engine.getComponentMapper(VelocityComponent.class);
+        modelMapper = engine.getComponentMapper(ModelComponent.class);
+    }
+
+    private Vector2 getRandomSpawnLocation(float asteroidWidth, float asteroidHeight) {
+        float halfWidth = asteroidWidth / 2;
+        float halfHeight = asteroidHeight / 2;
+
+        Vector2[] spawnPerimeter = new Vector2[]{
+                new Vector2(-halfWidth, -halfHeight),
+                new Vector2(-halfWidth, Constants.HEIGHT + halfHeight),
+                new Vector2(Constants.WIDTH + halfWidth, Constants.HEIGHT + halfHeight),
+                new Vector2(Constants.WIDTH + halfWidth, -halfHeight),
+        };
+
+        float perimeterLength = (Constants.WIDTH + Constants.HEIGHT + asteroidWidth + asteroidHeight) * 2;
+        float positionAlongPerimeter = rand.nextFloat(0, perimeterLength);
+
+        return Utils.getPointAlongPolygon(spawnPerimeter, positionAlongPerimeter);
+    }
+
+    private void spawnAsteroid() {
+        Entity asteroid = EntityFactory.createAsteroid(engine);
+
+        ModelComponent model = modelMapper.get(asteroid);
+        Vector2 position
+                = positionMapper.get(asteroid).position
+                = getRandomSpawnLocation(model.aabb.getWidth(), model.aabb.getHeight());
+        model.model.setPosition(position.x, position.y);
+        model.aabb = model.model.getBoundingRectangle();
+
+        VelocityComponent velocityComponent = velocityMapper.get(asteroid);
+        velocityComponent.velocity = new Vector2().setToRandomDirection().scl(rand.nextFloat(125, 175));
+
+        asteroid.activate();
+    }
+
+    @Override
+    public void process(float dt) {
+        Array<Entity> entities = engine.getEntities();
+        int asteroidCount = 0;
+        for (Entity entity : entities) {
+            // It's rather inefficient to have to check our entire entity list every frame
+            // to count how many entities have a specific component. Maybe we should keep a count of
+            // how many entites a given component?
+            if (asteroidMapper.has(entity)) {
+                asteroidCount++;
+            }
+        }
+
+        if (asteroidCount++ < 6 && (asteroidSpawnDelay -= dt) <= 0) {
+            spawnAsteroid();
+            asteroidSpawnDelay = Constants.ASTEROID_SPAWN_DELAY;
+        }
+    }
+
+}

core/src/com/me/asteroids/systems/CollisionSystem.java

@@ -1,6 +1,7 @@
 package com.me.asteroids.systems;
 
 import com.badlogic.gdx.math.Rectangle;
+import com.me.asteroids.EventFactory;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.events.CollisionEvent;
 import com.me.common.ecs.ComponentMapper;
@@ -29,8 +30,7 @@ public class CollisionSystem extends EntitySystem {
 
                 Rectangle aabbB = modelMapper.get(entityB).aabb;
                 if (aabbA.overlaps(aabbB)) {
-                    CollisionEvent event = new CollisionEvent(entityA, entityB);
-                    engine.callEvent(event);
+                    engine.callEvent(EventFactory.getNewCollisionEvent(entityA, entityB));
                 }
             }
         }