fix: Cleans up potential memory leak in monster abilities. (#2185)

Projects/UOContent/Mobiles/Abilities/MonsterAbility.cs

@@ -1,12 +1,13 @@
 using System;
 using System.Collections.Generic;
+using ModernUO.CodeGeneratedEvents;
 
 namespace Server.Mobiles;
 
 /// <summary>
 /// Abstract class used to build singletons for managing a specific monster ability.
 /// </summary>
-public abstract partial class MonsterAbility
+public abstract class MonsterAbility
 {
     private Dictionary<BaseCreature, long> _nextTriggerTicks;
 
@@ -18,39 +19,34 @@ public abstract partial class MonsterAbility
     public virtual TimeSpan MinTriggerCooldown => TimeSpan.Zero;
     public virtual TimeSpan MaxTriggerCooldown => TimeSpan.Zero;
 
-    public bool WillTrigger(MonsterAbilityTrigger trigger) => (AbilityTrigger & trigger) != 0;
-
     /// <summary>
     /// Returns true if ability is not on cooldown, and the chance to trigger succeeds.
     /// </summary>
     /// <returns>Boolean indicating the ability can trigger.</returns>
     public virtual bool CanTrigger(BaseCreature source, MonsterAbilityTrigger trigger)
     {
-        if (source is not { Alive: true, Deleted: false })
+        if ((AbilityTrigger & trigger) == 0 || source is not { Alive: true, Deleted: false })
         {
             return false;
         }
 
-        if (_nextTriggerTicks?.TryGetValue(source, out var nextTrigger) == true && nextTrigger - Core.TickCount > 0)
+        if (_nextTriggerTicks?.TryGetValue(source, out var nextTrigger) == true)
         {
-            return false;
+            if (nextTrigger - Core.TickCount > 0)
+            {
+                return false;
+            }
+
+            _nextTriggerTicks.Remove(source);
+            if (_nextTriggerTicks.Count == 0)
+            {
+                _nextTriggerTicks = null;
+            }
         }
 
         var c = ChanceToTrigger;
 
-        if (c >= 1)
+        return c >= 1 || c > 0 && c > Utility.RandomDouble();
-        {
-            return true;
-        }
-
-        if (c <= 0)
-        {
-            return false;
-        }
-
-        var rnd = Utility.RandomDouble();
-
-        return c > rnd;
     }
 
     /// <summary>
@@ -99,7 +95,23 @@ public abstract partial class MonsterAbility
     {
     }
 
-    public virtual void Move(BaseCreature creature, Direction d)
+    public virtual void Move(BaseCreature source, Direction d)
     {
     }
+
+    [OnEvent(nameof(BaseCreature.CreatureDeathEvent))]
+    [OnEvent(nameof(BaseCreature.CreatureDeletedEvent))]
+    public static void InvalidateNextAbilityTriggers(BaseCreature source)
+    {
+        var abilities = source.GetMonsterAbilities();
+        if (abilities == null || abilities.Length == 0)
+        {
+            return;
+        }
+
+        for (var i = 0; i < abilities.Length; i++)
+        {
+            abilities[i]._nextTriggerTicks?.Remove(source);
+        }
+    }
 }

Projects/UOContent/Mobiles/Abilities/MonsterAbilityGroup.cs

@@ -1,15 +1,14 @@
 using System;
-using Server.Random;
 using WeightedMonsterAbility = Server.Random.WeightedValue<Server.Mobiles.MonsterAbility>;
 
 namespace Server.Mobiles;
 
 public class MonsterAbilityGroup : MonsterAbility
 {
-    private WeightedMonsterAbility[] _weightedAbilities;
+    private readonly WeightedMonsterAbility[] _weightedAbilities;
-    private WeightedMonsterAbility[] _availableToTrigger;
+    private readonly WeightedMonsterAbility[] _availableToTrigger;
+    private readonly MonsterAbilityTrigger _triggers;
     private int _availableToTriggerCount;
-    private MonsterAbilityTrigger _triggers;
 
     public MonsterAbilityGroup(params WeightedMonsterAbility[] weightedAbilities)
     {
@@ -18,8 +17,7 @@ public class MonsterAbilityGroup : MonsterAbility
 
         for (var i = 0; i < _weightedAbilities.Length; i++)
         {
-            var weightedAbility = _weightedAbilities[i];
+            _triggers |= _weightedAbilities[i].Value.AbilityTrigger;
-            _triggers |= weightedAbility.Value.AbilityTrigger;
         }
     }
 
@@ -66,7 +64,7 @@ public class MonsterAbilityGroup : MonsterAbility
         for (var i = 0; i < _weightedAbilities.Length; i++)
         {
             var weightedAbility = _weightedAbilities[i];
-            if (weightedAbility.Value.WillTrigger(trigger) && weightedAbility.Value.CanTrigger(source, trigger))
+            if (weightedAbility.Value.CanTrigger(source, trigger))
             {
                 _availableToTrigger[_availableToTriggerCount++] = weightedAbility;
             }
@@ -83,7 +81,7 @@ public class MonsterAbilityGroup : MonsterAbility
             return;
         }
 
-        var slice = new ReadOnlySpan<WeightedValue<MonsterAbility>>(_availableToTrigger, 0, _availableToTriggerCount);
+        var slice = new ReadOnlySpan<WeightedMonsterAbility>(_availableToTrigger, 0, _availableToTriggerCount);
         var chosenAbility = slice.RandomWeightedElement().Value;
 
         // Just in case?

Projects/UOContent/Mobiles/Abilities/ReflectPhysicalDamage.cs

@@ -8,4 +8,8 @@ public class ReflectPhysicalDamage : MonsterAbility
     public override MonsterAbilityType AbilityType => MonsterAbilityType.ReflectPhysicalDamage;
 
     public virtual int PercentReflected => 10;
+
+    public override void Trigger(MonsterAbilityTrigger trigger, BaseCreature source, Mobile target)
+    {
+    }
 }

Projects/UOContent/Mobiles/BaseCreature.cs

@@ -1216,7 +1216,7 @@ namespace Server.Mobiles
             for (var i = 0; i < abilities.Length; i++)
             {
                 var ability = abilities[i];
-                if (ability.WillTrigger(trigger) && ability.CanTrigger(this, trigger))
+                if (ability.CanTrigger(this, trigger))
                 {
                     ability.Trigger(trigger, this, defender);
                     triggered = true;
@@ -1238,7 +1238,7 @@ namespace Server.Mobiles
             for (var i = 0; i < abilities.Length; i++)
             {
                 var ability = abilities[i];
-                if (ability.WillTrigger(trigger) && ability.CanTrigger(this, trigger))
+                if (ability.CanTrigger(this, trigger))
                 {
                     ability.Move(this, d);
                 }
@@ -1257,7 +1257,7 @@ namespace Server.Mobiles
             for (var i = 0; i < abilities.Length; i++)
             {
                 var ability = abilities[i];
-                if (ability.WillTrigger(trigger) && ability.CanTrigger(this, trigger))
+                if (ability.CanTrigger(this, trigger))
                 {
                     if ((trigger & MonsterAbilityTrigger.GiveMeleeDamage) != 0)
                     {
@@ -1298,7 +1298,7 @@ namespace Server.Mobiles
             for (var i = 0; i < abilities.Length; i++)
             {
                 var ability = abilities[i];
-                if (ability.WillTrigger(trigger) && ability.CanTrigger(this, trigger))
+                if (ability.CanTrigger(this, trigger))
                 {
                     if ((trigger & MonsterAbilityTrigger.GiveSpellDamage) != 0)
                     {
@@ -3263,7 +3263,7 @@ namespace Server.Mobiles
         }
 
         [GeneratedEvent(nameof(CreatureDeathEvent))]
-        public static partial void CreatureDeathEvent(Mobile m);
+        public static partial void CreatureDeathEvent(BaseCreature bc);
 
         public override void OnDeath(Container c)
         {
@@ -3454,8 +3454,13 @@ namespace Server.Mobiles
             CreatureDeathEvent(this);
         }
 
+        [GeneratedEvent(nameof(CreatureDeletedEvent))]
+        public static partial void CreatureDeletedEvent(BaseCreature bc);
+
         public override void OnDelete()
         {
+            CreatureDeletedEvent(this);
+
             var m = m_ControlMaster;
             SetControlMaster(null);