extend leave viewer remover to all viewables

plugin/src/main/java/lol/pyr/znpcsplus/ZNpcsPlus.java

@@ -38,7 +38,7 @@ import lol.pyr.znpcsplus.scheduling.TaskScheduler;
 import lol.pyr.znpcsplus.skin.cache.MojangSkinCache;
 import lol.pyr.znpcsplus.skin.cache.SkinCacheCleanTask;
 import lol.pyr.znpcsplus.tasks.HologramRefreshTask;
-import lol.pyr.znpcsplus.tasks.NpcHideListener;
+import lol.pyr.znpcsplus.tasks.ViewableHideOnLeaveListener;
 import lol.pyr.znpcsplus.tasks.NpcProcessorTask;
 import lol.pyr.znpcsplus.updater.UpdateChecker;
 import lol.pyr.znpcsplus.updater.UpdateNotificationListener;
@@ -163,7 +163,7 @@ public class ZNpcsPlus extends JavaPlugin {
         scheduler.runDelayedTimerAsync(new NpcProcessorTask(npcRegistry, configManager, propertyRegistry), 60L, 3L);
         scheduler.runDelayedTimerAsync(new HologramRefreshTask(npcRegistry), 60L, 20L);
         scheduler.runDelayedTimerAsync(new SkinCacheCleanTask(skinCache), 1200, 1200);
-        pluginManager.registerEvents(new NpcHideListener(npcRegistry), this);
+        pluginManager.registerEvents(new ViewableHideOnLeaveListener(), this);
 
         log(ChatColor.WHITE + " * Loading data...");
         npcRegistry.reload();

plugin/src/main/java/lol/pyr/znpcsplus/tasks/NpcHideListener.java

@@ -1,21 +0,0 @@
-package lol.pyr.znpcsplus.tasks;
-
-import lol.pyr.znpcsplus.npc.NpcRegistryImpl;
-import org.bukkit.event.EventHandler;
-import org.bukkit.event.Listener;
-import org.bukkit.event.player.PlayerQuitEvent;
-
-public class NpcHideListener implements Listener {
-    private final NpcRegistryImpl registry;
-
-    public NpcHideListener(NpcRegistryImpl registry) {
-        this.registry = registry;
-    }
-
-    @EventHandler
-    public void onQuit(PlayerQuitEvent event) {
-        registry.getProcessable().forEach(entry -> {
-            if (entry.getNpc().isVisibleTo(event.getPlayer())) entry.getNpc().UNSAFE_removeViewer(event.getPlayer());
-        });
-    }
-}

plugin/src/main/java/lol/pyr/znpcsplus/tasks/ViewableHideOnLeaveListener.java

@@ -0,0 +1,15 @@
+package lol.pyr.znpcsplus.tasks;
+
+import lol.pyr.znpcsplus.util.Viewable;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerQuitEvent;
+
+public class ViewableHideOnLeaveListener implements Listener {
+    @EventHandler
+    public void onQuit(PlayerQuitEvent event) {
+        Viewable.all().forEach(viewable -> {
+            if (viewable.isVisibleTo(event.getPlayer())) viewable.UNSAFE_removeViewer(event.getPlayer());
+        });
+    }
+}

plugin/src/main/java/lol/pyr/znpcsplus/util/Viewable.java

@@ -2,13 +2,31 @@ package lol.pyr.znpcsplus.util;
 
 import org.bukkit.entity.Player;
 
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
 
 public abstract class Viewable {
+    private final static List<WeakReference<Viewable>> all = new ArrayList<>();
+
+    public static List<Viewable> all() {
+        all.removeIf(reference -> reference.get() == null);
+        return all.stream()
+                .map(Reference::get)
+                .collect(Collectors.toList());
+    }
+
     private final Set<Player> viewers = ConcurrentHashMap.newKeySet();
 
+    public Viewable() {
+        all.add(new WeakReference<>(this));
+    }
+
     public void delete() {
         UNSAFE_hideAll();
         viewers.clear();