Core/Spells: Corrected aura SPELL_AURA_MOD_CASTING_SPEED_NOT_STACK handling for auras with very high values

Port From (https://github.com/TrinityCore/TrinityCore/commit/9842ca3f4a843e97815512e84e9860737ab5db21)

Source/Game/Entities/Unit/Unit.Fields.cs

@@ -131,6 +131,7 @@ namespace Game.Entities
         uint m_transform;
         bool m_cleanupDone; // lock made to not add stuff after cleanup before delete
         bool m_duringRemoveFromWorld; // lock made to not add stuff after begining removing from world
+        bool _instantCast;
 
         ushort _aiAnimKitId;
         ushort _movementAnimKitId;

Source/Game/Entities/Unit/Unit.Spells.cs

@@ -35,6 +35,9 @@ namespace Game.Entities
             return false;
         }
 
+        public void SetInstantCast(bool set) { _instantCast = set; }
+        public bool CanInstantCast() { return _instantCast; }
+        
         // function uses real base points (typically value - 1)
         public int CalculateSpellDamage(Unit target, SpellInfo spellProto, uint effect_index, int? basePoints = null, uint castItemId = 0, int itemLevel = -1)
         {
@@ -1954,7 +1957,7 @@ namespace Game.Entities
 
             if (!(spellInfo.HasAttribute(SpellAttr0.Ability | SpellAttr0.Tradespell) || spellInfo.HasAttribute(SpellAttr3.NoDoneBonus))
                 && (IsTypeId(TypeId.Player) && spellInfo.SpellFamilyName != 0) || IsTypeId(TypeId.Unit))
-                castTime = (int)(castTime * m_unitData.ModCastingSpeed);
+                castTime = CanInstantCast() ? 0 : (int)(castTime * m_unitData.ModCastingSpeed);
             else if (spellInfo.HasAttribute(SpellAttr0.ReqAmmo) && !spellInfo.HasAttribute(SpellAttr2.AutorepeatFlag))
                 castTime = (int)(castTime * m_modAttackSpeedPct[(int)WeaponAttackType.RangedAttack]);
             else if (Global.SpellMgr.IsPartOfSkillLine(SkillType.Cooking, spellInfo.Id) && HasAura(67556)) // cooking with Chef Hat.

Source/Game/Spells/Auras/AuraEffect.cs

@@ -3777,6 +3777,34 @@ namespace Game.Spells
 
             Unit target = aurApp.GetTarget();
 
+            // Do not apply such auras in normal way
+            if (GetAmount() >= 1000)
+            {
+                if (apply)
+                    target.SetInstantCast(true);
+                else
+                {
+                    // only SPELL_AURA_MOD_CASTING_SPEED_NOT_STACK can have this high amount
+                    // it's some rare case that you have 2 auras like that, but just in case ;)
+
+                    bool remove = true;
+                    var castingSpeedNotStack = target.GetAuraEffectsByType(AuraType.ModCastingSpeedNotStack);
+                    foreach (AuraEffect aurEff in castingSpeedNotStack)
+                    {
+                        if (aurEff != this && aurEff.GetAmount() >= 1000)
+                        {
+                            remove = false;
+                            break;
+                        }
+                    }
+
+                    if (remove)
+                        target.SetInstantCast(false);
+                }
+
+                return;
+            }
+
             target.ApplyCastTimePercentMod(GetAmount(), apply);
         }