fix: Improve FindNearbyPlayersSystem performance

src/main/java/org/terasology/behaviors/actions/CheckAttackStopAction.java

@@ -15,6 +15,7 @@
  */
 package org.terasology.behaviors.actions;
 
+import org.terasology.behaviors.components.AttackInProximityComponent;
 import org.terasology.behaviors.components.AttackOnHitComponent;
 import org.terasology.logic.behavior.BehaviorAction;
 import org.terasology.logic.behavior.core.Actor;
@@ -40,9 +41,15 @@ public class CheckAttackStopAction extends BaseAction {
     public BehaviorState modify(Actor actor, BehaviorState state) {
         BehaviorState status = getBehaviorStateWithoutReturn(actor);
         if (status == BehaviorState.FAILURE) {
-            AttackOnHitComponent attackOnHitComponent = actor.getComponent(AttackOnHitComponent.class);
-            attackOnHitComponent.instigator = null;
-            actor.getEntity().saveComponent(attackOnHitComponent);
+            if (actor.hasComponent(AttackOnHitComponent.class)) {
+                AttackOnHitComponent attackOnHitComponent = actor.getComponent(AttackOnHitComponent.class);
+                attackOnHitComponent.instigator = null;
+                actor.getEntity().saveComponent(attackOnHitComponent);
+            } else if (actor.hasComponent(AttackInProximityComponent.class)) {
+                AttackInProximityComponent attackInProximityComponent = actor.getComponent(AttackInProximityComponent.class);
+                attackInProximityComponent.instigator = null;
+                actor.getEntity().saveComponent(attackInProximityComponent);
+            }
             actor.getEntity().removeComponent(FollowComponent.class);
         }
         return status;
@@ -54,7 +61,12 @@ private BehaviorState getBehaviorStateWithoutReturn(Actor actor) {
             return BehaviorState.FAILURE;
         }
         Vector3f actorPosition = actorLocationComponent.getWorldPosition();
-        float maxDistance = actor.hasComponent(AttackOnHitComponent.class) ? actor.getComponent(AttackOnHitComponent.class).maxDistance : this.maxDistance;
+        float maxDistance = this.maxDistance;
+        if (actor.hasComponent(AttackOnHitComponent.class)) {
+            maxDistance = actor.getComponent(AttackOnHitComponent.class).maxDistance;
+        } else if (actor.hasComponent(AttackInProximityComponent.class)) {
+            maxDistance = actor.getComponent(AttackInProximityComponent.class).maxDistance;
+        }
 
         float maxDistanceSquared = maxDistance * maxDistance;
         FollowComponent followWish = actor.getComponent(FollowComponent.class);

src/main/java/org/terasology/behaviors/components/AttackInProximityComponent.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2020 MovingBlocks
+ *
+ * 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.terasology.behaviors.components;
+
+import org.terasology.entitySystem.Component;
+import org.terasology.entitySystem.entity.EntityRef;
+
+/**
+ * Represents an NPC that will attack players when they enter {@code maxDistance} range.
+ */
+public class AttackInProximityComponent implements Component {
+    // Maximum distance from instigator after which the animal will stop chasing to attack
+    public float maxDistance = 10f;
+    // Speed factor by which attack speed increases
+    public float speedMultiplier = 1.2f;
+    public EntityRef instigator;
+    public long timeWhenHit;
+}

src/main/java/org/terasology/behaviors/system/FindNearbyPlayersSystem.java

@@ -15,7 +15,6 @@
  */
 package org.terasology.behaviors.system;
 
-import com.google.common.collect.Lists;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.terasology.entitySystem.entity.EntityManager;
@@ -31,9 +30,15 @@
 import org.terasology.registry.In;
 import org.terasology.behaviors.components.FindNearbyPlayersComponent;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 @RegisterSystem(RegisterMode.AUTHORITY)
 public class FindNearbyPlayersSystem extends BaseComponentSystem implements UpdateSubscriberSystem {
@@ -46,47 +51,48 @@ public class FindNearbyPlayersSystem extends BaseComponentSystem implements Upda
 
     @Override
     public void update(float delta) {
+        Iterable<EntityRef> clients = entityManager.getEntitiesWith(ClientComponent.class);
+        Map<Vector3f, EntityRef> clientLocationMap = new HashMap<>();
+
+        for (EntityRef client : clients) {
+            ClientComponent clientComponent = client.getComponent(ClientComponent.class);
+            EntityRef character = clientComponent.character;
+            AliveCharacterComponent aliveCharacterComponent = character.getComponent(AliveCharacterComponent.class);
+            if (aliveCharacterComponent == null) {
+                continue;
+            }
+            LocationComponent locationComponent = character.getComponent(LocationComponent.class);
+            if (locationComponent == null) {
+                continue;
+            }
+            clientLocationMap.put(locationComponent.getWorldPosition(), character);
+        }
+        Set<Vector3f> locationSet = clientLocationMap.keySet();
+
         for (EntityRef entity : entityManager.getEntitiesWith(FindNearbyPlayersComponent.class)) {
             Vector3f actorPosition = entity.getComponent(LocationComponent.class).getWorldPosition();
             FindNearbyPlayersComponent findNearbyPlayersComponent = entity.getComponent(FindNearbyPlayersComponent.class);
             float maxDistance = findNearbyPlayersComponent.searchRadius;
             float maxDistanceSquared = maxDistance * maxDistance;
-            Iterable<EntityRef> clients = entityManager.getEntitiesWith(ClientComponent.class);
-            List<EntityRef> charactersWithinRange = Lists.newArrayList();
-
-            EntityRef closestCharacter = EntityRef.NULL;
-            float minDistanceFromCharacter = 0.0f;
 
-            for (EntityRef client : clients) {
-                ClientComponent clientComponent = client.getComponent(ClientComponent.class);
-                EntityRef character = clientComponent.character;
-                AliveCharacterComponent aliveCharacterComponent = character.getComponent(AliveCharacterComponent.class);
-                if (aliveCharacterComponent == null) {
-                    continue;
-                }
-                LocationComponent locationComponent = character.getComponent(LocationComponent.class);
-                if (locationComponent == null) {
-                    continue;
-                }
-                if (locationComponent.getWorldPosition().distanceSquared(actorPosition) <= maxDistanceSquared) {
-                    if (charactersWithinRange.size() == 0) {
-                        closestCharacter = character;
-                        minDistanceFromCharacter = locationComponent.getWorldPosition().distanceSquared(actorPosition);
-                    } else {
-                        if (locationComponent.getWorldPosition().distanceSquared(actorPosition) < minDistanceFromCharacter) {
-                            closestCharacter = character;
-                            minDistanceFromCharacter = locationComponent.getWorldPosition().distanceSquared(actorPosition);
-                        }
-                    }
-                    charactersWithinRange.add(character);
-                }
+            List<Vector3f> inRange = locationSet.stream()
+                    .filter(loc -> loc.distanceSquared(actorPosition) <= maxDistanceSquared)
+                    .sorted(Comparator.comparingDouble(v3f -> v3f.distanceSquared(actorPosition)))
+                    .collect(Collectors.toList());
+            if (inRange.isEmpty()) {
+                findNearbyPlayersComponent.charactersWithinRange = Collections.emptyList();
+                findNearbyPlayersComponent.closestCharacter = EntityRef.NULL;
+                entity.saveComponent(findNearbyPlayersComponent);
+                continue;
             }
 
+            List<EntityRef> charactersWithinRange = 
+            	inRange.stream().map(clientLocationMap::get).collect(Collectors.toList());
+
             if (!isEqual(charactersWithinRange, findNearbyPlayersComponent.charactersWithinRange)) {
                 findNearbyPlayersComponent.charactersWithinRange = charactersWithinRange;
-                findNearbyPlayersComponent.closestCharacter = closestCharacter;
+                findNearbyPlayersComponent.closestCharacter = charactersWithinRange.get(0);
                 entity.saveComponent(findNearbyPlayersComponent);
-
             }
         }
     }