Optimize important code, add distance interaction check.

api/src/main/java/net/jitse/npclib/listeners/PacketListener.java

@@ -11,12 +11,11 @@ import net.jitse.npclib.api.events.NPCInteractEvent;
 import net.jitse.npclib.internal.NPCManager;
 import net.jitse.npclib.internal.SimpleNPC;
 import org.bukkit.Bukkit;
+import org.bukkit.Location;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.Plugin;
 
-import java.util.HashSet;
+import java.util.*;
-import java.util.Set;
-import java.util.UUID;
 
 /**
  * @author Jitse Boonstra
@@ -49,31 +48,66 @@ public class PacketListener {
 
     private boolean handleInteractPacket(Player player, Object packet) {
         if (packetPlayInUseEntityClazz.isInstance(packet)) {
-            SimpleNPC npc = NPCManager.getAllNPCs().stream().filter(
+            SimpleNPC npc = null;
-                    check -> check.isShown(player) && check.getEntityId() == (int) entityIdField.get(packet))
+            int packetEntityId = (int) entityIdField.get(packet);
-                    .findFirst().orElse(null);
+
+
+            // Not using streams here is an intentional choice.
+            // Packet listeners is one of the few places where it is important to write optimized code.
+            // Lambdas (And the stream api) create a massive amount of objects, especially if it isn't a static lambda.
+            // So, we're avoiding them here.
+            // ~ Kneesnap, 9 / 20 / 2019.
+
+            for (SimpleNPC testNPC : NPCManager.getAllNPCs()) {
+                if (testNPC.isShown(player) && testNPC.getEntityId() == packetEntityId) {
+                    npc = testNPC;
+                    break;
+                }
+            }
 
             if (npc == null) {
                 // Default player, not doing magic with the packet.
                 return true;
             }
 
-            if (delay.contains(player.getUniqueId())) {
+            if (delay.contains(player.getUniqueId())) { // There is an active delay.
                 return false;
             }
 
             NPCInteractEvent.ClickType clickType = actionField.get(packet).toString().equals("ATTACK")
                     ? NPCInteractEvent.ClickType.LEFT_CLICK : NPCInteractEvent.ClickType.RIGHT_CLICK;
 
-            Bukkit.getScheduler().runTask(plugin, () ->
+            delay.add(player.getUniqueId());
-                    Bukkit.getPluginManager().callEvent(new NPCInteractEvent(player, clickType, npc)));
+            Bukkit.getScheduler().runTask(plugin, new TaskCallNpcInteractEvent(new NPCInteractEvent(player, clickType, npc), this));
-
-            UUID uuid = player.getUniqueId();
-            delay.add(uuid);
-            Bukkit.getScheduler().runTask(plugin, () -> delay.remove(uuid));
             return false;
         }
 
         return true;
     }
+
+    // This would be a non-static lambda, and its usage matters, so we'll make it a full class.
+    private static final class TaskCallNpcInteractEvent implements Runnable {
+        private NPCInteractEvent eventToCall;
+        private PacketListener listener;
+
+        private static Location playerLocation = new Location(null, 0, 0, 0);
+
+        TaskCallNpcInteractEvent(NPCInteractEvent eventToCall, PacketListener listener) {
+            this.eventToCall = eventToCall;
+            this.listener = listener;
+        }
+
+        @Override
+        public void run() {
+            Player player = eventToCall.getWhoClicked();
+            this.listener.delay.remove(player.getUniqueId()); // Remove the NPC from the interact cooldown.
+
+            if (!Objects.equals(playerLocation.getWorld(), eventToCall.getNPC().getLocation().getWorld()))
+                return; // If the NPC and player are not in the same world, abort!
+
+            double distance = player.getLocation(playerLocation).distanceSquared(eventToCall.getNPC().getLocation());
+            if (distance <= 64) // Only handle the interaction if the player is within interaction range. This way, hacked clients can't interact with NPCs that they shouldn't be able to interact with.
+                Bukkit.getPluginManager().callEvent(this.eventToCall);
+        }
+    }
 }