Improve NPC proximity aggro responsiveness

* `AddToAggroList` now automatically switches to aggro state and reschedule the next think tick.
* `CheckPlayerAggro` and `CheckNpcAggro` are no longer be allowed to run if we're waiting for at least one los check. This relies on `LosCheckForAggroCallback` to be called for every successful call to `SendLosCheckForAggro`.
* Replaced various explicit calls to `Think` and `AttackMostWanted` by next think tick reschedule.

CoreServer/ConsolePacketLib.cs

@@ -199,7 +199,7 @@ public void SendMovingObjectCreate(GameMovingObject obj) { }
 		public void SendWarmapUpdate(ICollection<IGameKeep> list) { }
 		public void SendWarmapDetailUpdate(List<List<byte>> fights, List<List<byte>> groups) { }
 		public void SendWarmapBonuses() { }
-		public void SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback) { }
+		public bool SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback) { return true; }
 		public void SendLivingDataUpdate(GameLiving living, bool updateStrings) { }
 		public void SendPlayerTitles() { }
 		public void SendPlayerTitleUpdate(GamePlayer player) { }

GameServer/ECS-Effects/ConfusionECSEffect.cs

@@ -99,17 +99,8 @@ public override void OnEffectPulse()
                 brain.ClearAggroList();
                 npc.StopAttack();
                 npc.StopCurrentSpellcast();
-                GameLiving target = targetList[Util.Random(targetList.Count - 1)] as GameLiving;
+                GameLiving target = targetList[Util.Random(targetList.Count - 1)];
                 brain.ForceAddToAggroList(target, 1);
-
-                if (brain.HasAggro)
-                {
-                    if (brain.FSM.GetCurrentState() != brain.FSM.GetState(eFSMStateType.AGGRO))
-                        brain.FSM.SetCurrentState(eFSMStateType.AGGRO);
-
-                    brain.AttackMostWanted();
-                    brain.Think();
-                }
             }
         }
     }

GameServer/ai/brain/Animist/TurretFNFBrain.cs

@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using DOL.GS;
-using DOL.GS.PacketHandler;
 using DOL.GS.ServerProperties;
 
 namespace DOL.AI.Brain
@@ -21,7 +20,7 @@ public override bool CheckProximityAggro()
         {
             // FnF turrets need to add all players and NPCs to their aggro list to be able to switch target randomly and effectively.
             CheckPlayerAggro();
-            CheckNPCAggro();
+            CheckNpcAggro();
             return HasAggro;
         }
 
@@ -40,13 +39,13 @@ protected override void CheckPlayerAggro()
                     continue;
 
                 if (Properties.CHECK_LOS_BEFORE_AGGRO_FNF)
-                    player.Out.SendCheckLos(Body, player, new CheckLosResponse(LosCheckForAggroCallback));
+                    SendLosCheckForAggro(player, player);
                 else
                     AddToAggroList(player, 1);
             }
         }
 
-        protected override void CheckNPCAggro()
+        protected override void CheckNpcAggro()
         {
             // Copy paste of 'base.CheckNPCAggro()' except we add all NPCs in range.
             foreach (GameNPC npc in Body.GetNPCsInRadius((ushort) AggroRange))
@@ -61,12 +60,12 @@ protected override void CheckNPCAggro()
                 {
                     if (npc.Brain is ControlledMobBrain theirControlledNpcBrain && theirControlledNpcBrain.GetPlayerOwner() is GamePlayer theirOwner)
                     {
-                        theirOwner.Out.SendCheckLos(Body, npc, new CheckLosResponse(LosCheckForAggroCallback));
+                        SendLosCheckForAggro(theirOwner, npc);
                         continue;
                     }
                     else if (this is ControlledMobBrain ourControlledNpcBrain && ourControlledNpcBrain.GetPlayerOwner() is GamePlayer ourOwner)
                     {
-                        ourOwner.Out.SendCheckLos(Body, npc, new CheckLosResponse(LosCheckForAggroCallback));
+                        SendLosCheckForAggro(ourOwner, npc);
                         continue;
                     }
                 }
@@ -75,17 +74,7 @@ protected override void CheckNPCAggro()
             }
         }
 
-        protected override void LosCheckForAggroCallback(GamePlayer player, eLosCheckResponse response, ushort sourceOID, ushort targetOID)
-        {
-            // Copy paste of 'base.LosCheckForAggroCallback()' except we don't care if we already have aggro.
-            if (response is eLosCheckResponse.TRUE)
-            {
-                GameObject gameObject = Body.CurrentRegion.GetObject(targetOID);
-
-                if (gameObject is GameLiving gameLiving)
-                    AddToAggroList(gameLiving, 1);
-            }
-        }
+        protected override bool CanAddToAggroListFromMultipleLosChecks => true;
 
         protected override bool ShouldBeIgnoredFromAggroList(GameLiving living)
         {

GameServer/ai/brain/GuardBrain.cs

@@ -1,5 +1,4 @@
 using DOL.GS;
-using DOL.GS.PacketHandler;
 
 namespace DOL.AI.Brain
 {
@@ -24,12 +23,12 @@ protected override void CheckPlayerAggro()
 				if (player.effectListComponent.ContainsEffectForEffectType(eEffect.Shade))
 					continue;
 
-				player.Out.SendCheckLos(Body, player, new CheckLosResponse(LosCheckForAggroCallback));
+				SendLosCheckForAggro(player, player);
 				// We don't know if the LoS check will be positive, so we have to ask other players
 			}
 		}
 
-		protected override void CheckNPCAggro()
+		protected override void CheckNpcAggro()
 		{
 			foreach (GameNPC npc in Body.GetNPCsInRadius((ushort)AggroRange))
 			{

GameServer/ai/brain/Guards/KeepGuardBrain.cs

@@ -84,15 +84,15 @@ protected override void CheckPlayerAggro()
 					continue;
 
 				WarMapMgr.AddGroup((byte) player.CurrentZone.ID, player.X, player.Y, player.Name, (byte) player.Realm);
-				player.Out.SendCheckLos(Body, player, new CheckLosResponse(LosCheckForAggroCallback));
+				SendLosCheckForAggro(player, player);
 				// We don't know if the LoS check will be positive, so we have to ask other players
 			}
 		}
 
 		/// <summary>
 		/// Check area for NPCs to attack
 		/// </summary>
-		protected override void CheckNPCAggro()
+		protected override void CheckNpcAggro()
 		{
 			foreach (GameNPC npc in Body.GetNPCsInRadius((ushort)AggroRange))
 			{
@@ -108,7 +108,7 @@ protected override void CheckNPCAggro()
 					continue;
 
 				WarMapMgr.AddGroup((byte)player.CurrentZone.ID, player.X, player.Y, player.Name, (byte)player.Realm);
-				player.Out.SendCheckLos(Body, npc, new CheckLosResponse(LosCheckForAggroCallback));
+				SendLosCheckForAggro(player, npc);
 				// We don't know if the LoS check will be positive, so we have to ask other players
 			}
 		}

GameServer/ai/brain/Scout/ScoutMobBrainState.cs

@@ -112,14 +112,10 @@ void ReportToFriends()
                     return;
 
                 _brain.AddAggroListTo(_friend);
-                _friend.AttackMostWanted();
 
+                // This includes us.
                 foreach (StandardMobBrain otherFriendlyBrain in _friend.GetFriendlyAndAvailableBrainsInRadiusOrderedByDistance(ADDS_RADIUS, MAX_ADDS))
-                {
-                    // This includes us.
                     _brain.AddAggroListTo(otherFriendlyBrain);
-                    otherFriendlyBrain.AttackMostWanted();
-                }
 
                 _state = ScoutMobState.FIGHTING;
             }

GameServer/ai/brain/Special/AlluvianGlobuleBrain.cs

@@ -58,7 +58,7 @@ public override void Think()
 				if (!Body.attackComponent.AttackState && AggroLevel > 0)
 				{
 					CheckPlayerAggro();
-					CheckNPCAggro();
+					CheckNpcAggro();
 				}
 				if (HasAggro)
 				{
@@ -142,4 +142,4 @@ public void Grow()
 			hasGrown = true;
 		}
 	}
-}
+}

GameServer/ai/brain/StandardMob/StandardMobBrain.cs

@@ -79,10 +79,10 @@ public virtual bool CheckProximityAggro()
             FireAmbientSentence();
 
             // Check aggro only if our aggro list is empty and we're not in combat.
-            if (AggroLevel > 0 && AggroRange > 0 && !HasAggro && Body.CurrentSpellHandler == null)
+            if (AggroLevel > 0 && AggroRange > 0 && Body.CurrentSpellHandler == null && !HasAggro && !IsWaitingForLosCheck)
             {
                 CheckPlayerAggro();
-                CheckNPCAggro();
+                CheckNpcAggro();
             }
 
             // Some calls rely on this method to return if there's something in the aggro list, not necessarily to perform a proximity aggro check.
@@ -118,20 +118,21 @@ protected virtual void CheckPlayerAggro()
                     continue;
 
                 if (Properties.CHECK_LOS_BEFORE_AGGRO)
-                    // We don't know if the LoS check will be positive, so we have to ask other players
-                    player.Out.SendCheckLos(Body, player, new CheckLosResponse(LosCheckForAggroCallback));
+                    SendLosCheckForAggro(player, player);
                 else
                 {
                     AddToAggroList(player, 1);
                     return;
                 }
+
+                // We don't know if the LoS check will be positive, so we have to ask other players
             }
         }
 
         /// <summary>
         /// Check for aggro against close NPCs
         /// </summary>
-        protected virtual void CheckNPCAggro()
+        protected virtual void CheckNpcAggro()
         {
             foreach (GameNPC npc in Body.GetNPCsInRadius((ushort) AggroRange))
             {
@@ -146,12 +147,12 @@ protected virtual void CheckNPCAggro()
                     // Check LoS if either the target or the current mob is a pet
                     if (npc.Brain is ControlledMobBrain theirControlledNpcBrain && theirControlledNpcBrain.GetPlayerOwner() is GamePlayer theirOwner)
                     {
-                        theirOwner.Out.SendCheckLos(Body, npc, new CheckLosResponse(LosCheckForAggroCallback));
+                        SendLosCheckForAggro(theirOwner, npc);
                         continue;
                     }
                     else if (this is ControlledMobBrain ourControlledNpcBrain && ourControlledNpcBrain.GetPlayerOwner() is GamePlayer ourOwner)
                     {
-                        ourOwner.Out.SendCheckLos(Body, npc, new CheckLosResponse(LosCheckForAggroCallback));
+                        SendLosCheckForAggro(ourOwner, npc);
                         continue;
                     }
                 }
@@ -332,6 +333,13 @@ public void ForceAddToAggroList(GameLiving living, long aggroAmount)
                 }
             }
 
+            // Change state and reschedule the next think tick to improve responsiveness.
+            if (FSM.GetCurrentState() != FSM.GetState(eFSMStateType.AGGRO) && HasAggro)
+            {
+                FSM.SetCurrentState(eFSMStateType.AGGRO);
+                NextThinkTick = GameLoop.GameLoopTime;
+            }
+
             static AggroAmount Add(GameLiving key, long arg)
             {
                 return new(Math.Max(0, arg));
@@ -389,8 +397,7 @@ public bool UnsetTemporaryAggroList()
                 if (FSM.GetCurrentState() != FSM.GetState(eFSMStateType.AGGRO))
                     FSM.SetCurrentState(eFSMStateType.AGGRO);
 
-                AttackMostWanted();
-                Think();
+                NextThinkTick = GameLoop.GameLoopTime;
             }
 
             return true;
@@ -440,13 +447,23 @@ public virtual void AttackMostWanted()
         }
 
         private long _isHandlingAdditionToAggroListFromLosCheck;
+        private long _losCheckCount;
         private bool StartAddToAggroListFromLosCheck => Interlocked.Exchange(ref _isHandlingAdditionToAggroListFromLosCheck, 1) == 0; // Returns true the first time it's called.
+        private bool IsWaitingForLosCheck => Interlocked.Read(ref _losCheckCount) > 0;
+        protected virtual bool CanAddToAggroListFromMultipleLosChecks => false;
 
-        protected virtual void LosCheckForAggroCallback(GamePlayer player, eLosCheckResponse response, ushort sourceOID, ushort targetOID)
+        protected void SendLosCheckForAggro(GamePlayer player, GameObject target)
+        {
+            if (player.Out.SendCheckLos(Body, target, new CheckLosResponse(LosCheckForAggroCallback)))
+                Interlocked.Increment(ref _losCheckCount);
+        }
+
+        protected void LosCheckForAggroCallback(GamePlayer player, eLosCheckResponse response, ushort sourceOID, ushort targetOID)
         {
             // Make sure only one thread can enter this block to prevent multiple entities from being added to the aggro list.
             // Otherwise mobs could kill one player and immediately go for another one.
-            if (response is eLosCheckResponse.TRUE && StartAddToAggroListFromLosCheck)
+            // This method should not be allowed to be executed at the same time as `CheckPlayerAggro` or `CheckNPCAggro`.
+            if (response is eLosCheckResponse.TRUE && (CanAddToAggroListFromMultipleLosChecks || StartAddToAggroListFromLosCheck))
             {
                 if (!HasAggro)
                 {
@@ -458,6 +475,8 @@ protected virtual void LosCheckForAggroCallback(GamePlayer player, eLosCheckResp
 
                 _isHandlingAdditionToAggroListFromLosCheck = 0;
             }
+
+            Interlocked.Decrement(ref _losCheckCount);
         }
 
         protected virtual bool ShouldBeRemovedFromAggroList(GameLiving living)
@@ -594,12 +613,6 @@ public virtual void OnAttackedByEnemy(AttackData ad)
 
             if (ad.GeneratesAggro)
                 ConvertDamageToAggroAmount(ad.Attacker, Math.Max(1, ad.Damage + ad.CriticalDamage));
-
-            if (FSM.GetCurrentState() != FSM.GetState(eFSMStateType.AGGRO) && HasAggro)
-            {
-                FSM.SetCurrentState(eFSMStateType.AGGRO);
-                Think();
-            }
         }
 
         /// <summary>
@@ -698,7 +711,6 @@ protected virtual void BringFriends(GameLiving puller)
                     target = puller;
 
                 brain.AddToAggroList(target, 1);
-                brain.AttackMostWanted();
             }
 
             int GetMaxAddsCountFromBaf(GameLiving puller, out List<GamePlayer> otherTargets)

GameServer/packets/Client/168/CheckLosResponseHandler.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Linq;
 
 namespace DOL.GS.PacketHandler.Client.v168
 {
@@ -45,10 +44,10 @@ public bool TryAddCallback(CheckLosResponse callback)
                 {
                     if (Callbacks == null)
                     {
-                        Callbacks ??= new();
+                        Callbacks ??= [];
                         Callbacks.Add(callback);
                     }
-                    else if (Callbacks.Any())
+                    else if (Callbacks.Count != 0)
                         Callbacks.Add(callback);
                     else
                         return false;

GameServer/packets/Server/IPacketLib.cs

@@ -694,7 +694,7 @@ void SendDialogBox(eDialogCode code, ushort data1, ushort data2, ushort data3, u
 		                   bool autoWrapText, string message);
 
 		void SendCustomDialog(string msg, CustomDialogResponse callback);
-		void SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback);
+		bool SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback);
 		void SendGuildLeaveCommand(GamePlayer invitingPlayer, string inviteMessage);
 		void SendGuildInviteCommand(GamePlayer invitingPlayer, string inviteMessage);
 		void SendQuestOfferWindow(GameNPC questNPC, GamePlayer player, RewardQuest quest);

GameServer/packets/Server/PacketLib168.cs

@@ -1489,16 +1489,16 @@ public virtual void SendCustomDialog(string msg, CustomDialogResponse callback)
 			}
 		}
 
-		public virtual void SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback)
+		public virtual bool SendCheckLos(GameObject source, GameObject target, CheckLosResponse callback)
 		{
 			if (m_gameClient.Player == null || source == null || target == null)
-				return;
+				return false;
 
 			ushort sourceObjectId = (ushort) source.ObjectID;
 			ushort targetObjectId = (ushort) target.ObjectID;
 
 			if (!HandleCallback(m_gameClient, sourceObjectId, targetObjectId, callback))
-				return;
+				return false;
 
 			using (var pak = new GSTCPPacketOut(GetPacketCode(eServerPackets.CheckLOSRequest)))
 			{
@@ -1509,6 +1509,8 @@ public virtual void SendCheckLos(GameObject source, GameObject target, CheckLosR
 				SendTCP(pak);
 			}
 
+			return true;
+
 			static bool HandleCallback(GameClient client, ushort sourceObjectId, ushort targetObjectId, CheckLosResponse callback)
 			{
 				CheckLosResponseHandler.TimeoutTimer timer;

GameServer/scripts/namedmobs/Dodens/AI/ArosBrain/ArosBrain.cs

@@ -133,7 +133,7 @@ public void ResistsTwo()
                 Body.AbilityBonus[(int)eProperty.StyleAbsorb] = 10;
             }
         }
-        protected override void CheckNPCAggro()
+        protected override void CheckNpcAggro()
         {
             if (Body.attackComponent.AttackState)
                 return;

GameServer/scripts/namedmobs/Dodens/MistressOfRunes.cs

@@ -179,7 +179,7 @@ public override void Think()
 			base.Think();
 		}
 
-		protected override void CheckNPCAggro()
+		protected override void CheckNpcAggro()
 		{
 			if (Body.attackComponent.AttackState)
 				return;

GameServer/spells/Masterlevel/Convoker.cs

@@ -864,7 +864,7 @@ public override int AggroRange
 	{
 		get { return 400; }
 	}
-	protected override void CheckNPCAggro()
+	protected override void CheckNpcAggro()
 	{
 		//Check if we are already attacking, return if yes
 		if (Body.attackComponent.AttackState)