Health/damage system with unit tests

engine/src/main/java/org/destinationsol/components/Health.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.components;
+
+import org.terasology.gestalt.entitysystem.component.Component;
+
+/**
+ * Contains information about the health of an entity.
+ */
+public final class Health implements Component<Health> {
+
+    public int maxHealth = 30;
+    public int currentHealth = 30;
+
+    @Override
+    public void copy(Health other) {
+        this.maxHealth = other.maxHealth;
+        this.currentHealth = other.currentHealth;
+    }
+}

engine/src/main/java/org/destinationsol/entitysystem/EntitySystemManager.java

@@ -36,10 +36,10 @@
 public class EntitySystemManager {
 
     private static EntityManager entityManager;
-    private static EventSystem eventSystem = new EventSystemImpl();
+    private EventSystem eventSystem = new EventSystemImpl();
     private static EventReceiverMethodSupport eventReceiverMethodSupport = new EventReceiverMethodSupport();
 
-    public EntitySystemManager(ModuleEnvironment environment, ComponentManager componentManager){
+    public EntitySystemManager(ModuleEnvironment environment, ComponentManager componentManager) {
 
         List<ComponentStore<?>> stores = Lists.newArrayList();
         for (Class<? extends Component> componentType : environment.getSubtypesOf(Component.class)) {
@@ -51,9 +51,9 @@ public EntitySystemManager(ModuleEnvironment environment, ComponentManager compo
 
         entityManager = new CoreEntityManager(stores);
 
-        for (Class<?> eventReceivers : environment.getTypesAnnotatedWith(RegisterEventReceivers.class)) {
+        for (Class<? extends EventReceiver> eventReceiver : environment.getSubtypesOf(EventReceiver.class)) {
             try {
-                eventReceiverMethodSupport.register(eventReceivers.newInstance(), eventSystem);
+                eventReceiverMethodSupport.register(eventReceiver.newInstance(), eventSystem);
             } catch (Exception e) {
                 e.printStackTrace();
             }

engine/src/main/java/org/destinationsol/entitysystem/RegisterEventReceivers.java → engine/src/main/java/org/destinationsol/entitysystem/EventReceiver.java

@@ -15,5 +15,5 @@
  */
 package org.destinationsol.entitysystem;
 
-public @interface RegisterEventReceivers {
+public interface EventReceiver {
 }

engine/src/main/java/org/destinationsol/events/DamageEvent.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.events;
+
+import org.terasology.gestalt.entitysystem.event.Event;
+
+/**
+ * Event that contains information about the damage an entity receives.
+ */
+public class DamageEvent implements Event {
+
+    private int damage;
+
+    public DamageEvent(int damage) {
+        this.damage = damage;
+    }
+
+    public int getDamage() {
+        return damage;
+    }
+}

engine/src/main/java/org/destinationsol/systems/DamageSystem.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.systems;
+
+import org.destinationsol.components.Health;
+import org.destinationsol.entitysystem.ComponentSystem;
+import org.destinationsol.entitysystem.EventReceiver;
+import org.destinationsol.events.DamageEvent;
+import org.terasology.gestalt.entitysystem.entity.EntityRef;
+import org.terasology.gestalt.entitysystem.event.EventResult;
+import org.terasology.gestalt.entitysystem.event.ReceiveEvent;
+
+/**
+ * When a damage event happens to an entity with a health component, this system reads the damage from that event and
+ * lowers its health by that amount. If it would lower the health to less than zero, it's reduced to zero instead. If
+ * the damage is a negative amount, nothing happens.
+ */
+public class DamageSystem implements EventReceiver {
+
+    /**
+     * Handles a damage event done to an entity with a Health component.
+     *
+     * @param event  the damage event that is occurring
+     * @param entity the entity that the damage is happening to
+     * @return the event should be processed by other systems, if there are
+     */
+    @ReceiveEvent(components = Health.class)
+    public EventResult onDamage(DamageEvent event, EntityRef entity) {
+        if (event.getDamage() <= 0) {
+            return EventResult.CONTINUE;
+        }
+        if (entity.getComponent(Health.class).isPresent()) {
+            Health health = entity.getComponent(Health.class).get();
+            int newHealthAmount = health.currentHealth - event.getDamage();
+            if (newHealthAmount < 0) {
+                newHealthAmount = 0;
+            }
+            health.currentHealth = newHealthAmount;
+            entity.setComponent(health);
+        }
+        return EventResult.CONTINUE;
+    }
+}

engine/src/test/java/org/destinationsol/systems/DamageSystemTests/NonNegativeDamageTest.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.systems.DamageSystemTests;
+
+import org.destinationsol.components.Health;
+import org.destinationsol.entitysystem.EntitySystemManager;
+import org.destinationsol.events.DamageEvent;
+import org.destinationsol.modules.ModuleManager;
+import org.junit.Before;
+import org.junit.Test;
+import org.terasology.gestalt.entitysystem.component.management.ComponentManager;
+import org.terasology.gestalt.entitysystem.entity.EntityRef;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test to ensure that a damage event with a negative amount of damage doesn't add health.
+ */
+public class NonNegativeDamageTest {
+
+    private ModuleManager moduleManager;
+    private EntitySystemManager entitySystemManager;
+
+    @Before
+    public void setUp() throws Exception {
+        moduleManager = new ModuleManager();
+        moduleManager.init();
+        entitySystemManager = new EntitySystemManager(moduleManager.getEnvironment(), new ComponentManager());
+    }
+
+    @Test
+    public void testNegativeDamageHasNoEffect() {
+        EntityRef entity = entitySystemManager.getEntityManager().createEntity(new Health());
+        if (entity.getComponent(Health.class).isPresent()) {
+            Health health = entity.getComponent(Health.class).get();
+            health.maxHealth = 50;
+            health.currentHealth = 50;
+            entity.setComponent(health);
+        }
+        DamageEvent event = new DamageEvent(-30);
+
+        entitySystemManager.sendEvent(event, new Health());
+
+        assertEquals(50, entity.getComponent(Health.class).get().currentHealth);
+    }
+}

engine/src/test/java/org/destinationsol/systems/DamageSystemTests/NonNegativeHealthTest.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.systems.DamageSystemTests;
+
+import org.destinationsol.components.Health;
+import org.destinationsol.entitysystem.EntitySystemManager;
+import org.destinationsol.events.DamageEvent;
+import org.destinationsol.modules.ModuleManager;
+import org.junit.Before;
+import org.junit.Test;
+import org.terasology.gestalt.entitysystem.component.management.ComponentManager;
+import org.terasology.gestalt.entitysystem.entity.EntityRef;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test to ensure that a damage event that would make the health become negative reduces it to zero instead.
+ */
+public class NonNegativeHealthTest {
+    private ModuleManager moduleManager;
+    private EntitySystemManager entitySystemManager;
+
+    @Before
+    public void setUp() throws Exception {
+        moduleManager = new ModuleManager();
+        moduleManager.init();
+        entitySystemManager = new EntitySystemManager(moduleManager.getEnvironment(), new ComponentManager());
+    }
+
+    @Test
+    public void testDamageDoesntMakeHealthBecomeNegative() {
+        EntityRef entity = entitySystemManager.getEntityManager().createEntity(new Health());
+        if (entity.getComponent(Health.class).isPresent()) {
+            Health health = entity.getComponent(Health.class).get();
+            health.maxHealth = 50;
+            health.currentHealth = 50;
+            entity.setComponent(health);
+        }
+        DamageEvent event = new DamageEvent(60);
+
+        entitySystemManager.sendEvent(event, new Health());
+
+        assertEquals(0, entity.getComponent(Health.class).get().currentHealth);
+    }
+
+}

engine/src/test/java/org/destinationsol/systems/DamageSystemTests/OnDamageTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2020 The Terasology Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.destinationsol.systems.DamageSystemTests;
+
+import org.destinationsol.components.Health;
+import org.destinationsol.entitysystem.EntitySystemManager;
+import org.destinationsol.events.DamageEvent;
+import org.destinationsol.modules.ModuleManager;
+import org.junit.Before;
+import org.junit.Test;
+import org.terasology.gestalt.entitysystem.component.management.ComponentManager;
+import org.terasology.gestalt.entitysystem.entity.EntityRef;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test to ensure that a damage event to an entity lowers that entity's health by that amount.
+ */
+public class OnDamageTest {
+
+    private ModuleManager moduleManager;
+    private EntitySystemManager entitySystemManager;
+
+    @Before
+    public void setUp() throws Exception {
+        moduleManager = new ModuleManager();
+        moduleManager.init();
+        entitySystemManager = new EntitySystemManager(moduleManager.getEnvironment(), new ComponentManager());
+    }
+
+    @Test
+    public void testOnDamage() {
+        EntityRef entity = entitySystemManager.getEntityManager().createEntity(new Health());
+        if (entity.getComponent(Health.class).isPresent()) {
+            Health health = entity.getComponent(Health.class).get();
+            health.maxHealth = 50;
+            health.currentHealth = 50;
+            entity.setComponent(health);
+        }
+        DamageEvent event = new DamageEvent(30);
+
+        entitySystemManager.sendEvent(event, new Health());
+
+        assertEquals(20, entity.getComponent(Health.class).get().currentHealth);
+    }
+
+}