From b9148c028dded64cae30bfcb89502b5472a25a41 Mon Sep 17 00:00:00 2001
From: Matt Low <mattjlow94@gmail.com>
Date: Sat, 25 Jan 2020 17:26:44 +0400
Subject: [PATCH] Add CollisionSystem

---
 .../me/asteroids/events/CollisionEvent.java   | 16 +++++++
 .../com/me/asteroids/screens/GameScreen.java  |  2 +
 .../me/asteroids/systems/CollisionSystem.java | 42 +++++++++++++++++++
 3 files changed, 60 insertions(+)
 create mode 100644 core/src/com/me/asteroids/events/CollisionEvent.java
 create mode 100644 core/src/com/me/asteroids/systems/CollisionSystem.java

diff --git a/core/src/com/me/asteroids/events/CollisionEvent.java b/core/src/com/me/asteroids/events/CollisionEvent.java
new file mode 100644
index 0000000..d8118c7
--- /dev/null
+++ b/core/src/com/me/asteroids/events/CollisionEvent.java
@@ -0,0 +1,16 @@
+package com.me.asteroids.events;
+
+import com.me.common.ecs.Entity;
+import com.me.common.ecs.event.Event;
+
+public class CollisionEvent extends Event {
+
+    public Entity entityA;
+    public Entity entityB;
+
+    public CollisionEvent(Entity entityA, Entity entityB) {
+        this.entityA = entityA;
+        this.entityB = entityB;
+    }
+
+}
diff --git a/core/src/com/me/asteroids/screens/GameScreen.java b/core/src/com/me/asteroids/screens/GameScreen.java
index 598b380..c37f50d 100644
--- a/core/src/com/me/asteroids/screens/GameScreen.java
+++ b/core/src/com/me/asteroids/screens/GameScreen.java
@@ -12,6 +12,7 @@ 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.systems.CollisionSystem;
 import com.me.asteroids.systems.ModelRenderSystem;
 import com.me.asteroids.systems.MovementSystem;
 import com.me.asteroids.systems.PlayerInputSystem;
@@ -49,6 +50,7 @@ public class GameScreen extends Screen {
 
         engine.registerSystem(new PlayerInputSystem(engine));
         engine.registerSystem(new MovementSystem(engine));
+        engine.registerSystem(new CollisionSystem(engine));
         engine.registerSystem(new ScreenWrapSystem(engine));
         engine.registerSystem(new ModelRenderSystem(engine, graphics));
 
diff --git a/core/src/com/me/asteroids/systems/CollisionSystem.java b/core/src/com/me/asteroids/systems/CollisionSystem.java
new file mode 100644
index 0000000..50f1354
--- /dev/null
+++ b/core/src/com/me/asteroids/systems/CollisionSystem.java
@@ -0,0 +1,42 @@
+package com.me.asteroids.systems;
+
+import com.badlogic.gdx.math.Rectangle;
+import com.me.asteroids.components.ModelComponent;
+import com.me.asteroids.events.CollisionEvent;
+import com.me.common.ecs.ComponentMapper;
+import com.me.common.ecs.Engine;
+import com.me.common.ecs.Entity;
+import com.me.common.ecs.EntitySystem;
+
+public class CollisionSystem extends EntitySystem {
+
+    private ComponentMapper<ModelComponent> modelMapper;
+
+    public CollisionSystem(Engine engine) {
+        super(engine, ModelComponent.class);
+        modelMapper = engine.getComponentMapper(ModelComponent.class);
+    }
+
+    @Override
+    public void processEntities(float dt) {
+        Entity[] entities = getEntities().items;
+        for (int i = 0, n = getEntities().size; i < n-1; i++) {
+            Entity entityA = entities[i];
+            Rectangle aabbA = modelMapper.get(entityA).aabb;
+
+            for (int j = i + 1; j < n; j++) {
+                Entity entityB = entities[j];
+
+                Rectangle aabbB = modelMapper.get(entityB).aabb;
+                if (aabbA.overlaps(aabbB)) {
+                    CollisionEvent event = new CollisionEvent(entityA, entityB);
+                    engine.callEvent(event);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void processEntity(Entity entity, float dt) {}
+
+}