Optimise handheld lights (#2927)

* Optimise handheld lights

* Woops also these

* Might as well do shutdown too

* Also these

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Server/GameObjects/EntitySystems/HandHeldLightSystem.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+using System.Linq;
 using Content.Server.GameObjects.Components.Interactable;
 using JetBrains.Annotations;
 using Robust.Shared.GameObjects.Systems;
@@ -7,11 +9,41 @@ namespace Content.Server.GameObjects.EntitySystems
     [UsedImplicitly]
     internal sealed class HandHeldLightSystem : EntitySystem
     {
+        // TODO: Ideally you'd be able to subscribe to power stuff to get events at certain percentages.. or something?
+        // But for now this will be better anyway.
+        private HashSet<HandheldLightComponent> _activeLights = new();
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeLocalEvent<ActivateHandheldLightMessage>(HandleActivate);
+            SubscribeLocalEvent<DeactivateHandheldLightMessage>(HandleDeactivate);
+        }
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+            _activeLights.Clear();
+            UnsubscribeLocalEvent<ActivateHandheldLightMessage>();
+            UnsubscribeLocalEvent<DeactivateHandheldLightMessage>();
+        }
+
+        private void HandleActivate(ActivateHandheldLightMessage message)
+        {
+            _activeLights.Add(message.Component);
+        }
+
+        private void HandleDeactivate(DeactivateHandheldLightMessage message)
+        {
+            _activeLights.Remove(message.Component);
+        }
+
         public override void Update(float frameTime)
         {
-            foreach (var comp in ComponentManager.EntityQuery<HandheldLightComponent>(false))
+            foreach (var handheld in _activeLights.ToArray())
             {
-                comp.OnUpdate(frameTime);
+                if (handheld.Deleted || handheld.Paused) continue;
+                handheld.OnUpdate(frameTime);
             }
         }
     }