Core/Spells: unify OnSpellCastInterrupt and OnSuccessfulSpellCast hooks into OnSpellCastFinished

Port From (https://github.com/TrinityCore/TrinityCore/commit/d1594c7295f1ca3f21a63a13895abf371d8bd3e0)

Source/Framework/Constants/Spells/SpellConst.cs

@@ -98,6 +98,13 @@ namespace Framework.Constants
         Ranged = 2      //hunter range and ranged weapon
     }
 
+    public enum SpellFinishReason
+    {
+        SuccessfulCast = 0, // spell has sucessfully launched
+        Canceled = 1, // spell has been canceled (interrupts)
+        ChannelingComplete = 2  // spell channeling has been finished
+    }
+
     [Flags]
     public enum SpellInterruptFlags
     {

Source/Game/AI/CoreAI/CreatureAI.cs

@@ -492,11 +492,8 @@ namespace Game.AI
         // Called when spell hits a target
         public virtual void SpellHitTarget(WorldObject target, SpellInfo spellInfo) { }
 
-        // Called when a spell cast gets interrupted
-        public virtual void OnSpellCastInterrupt(SpellInfo spell) { }
-
-        // Called when a spell cast has been successfully finished
-        public virtual void OnSuccessfulSpellCast(SpellInfo spell) { }
+        // Called when a spell either finishes, interrupts or cancels a spell cast
+        public virtual void OnSpellCastFinished(SpellInfo spell, SpellFinishReason reason) { }
 
         // Should return true if the NPC is currently being escorted
         public virtual bool IsEscorted() { return false; }

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

@@ -2422,7 +2422,7 @@ namespace Game.Entities
                 }
 
                 if (IsCreature() && IsAIEnabled())
-                    ToCreature().GetAI().OnSpellCastInterrupt(spell.GetSpellInfo());
+                    ToCreature().GetAI().OnSpellCastFinished(spell.GetSpellInfo(), SpellFinishReason.Canceled);
             }
         }
         public void UpdateInterruptMask()

Source/Game/Spells/Spell.cs

@@ -2904,7 +2904,7 @@ namespace Game.Spells
             Creature caster = m_originalCaster.ToCreature();
             if (caster)
                 if (caster.IsAIEnabled())
-                    caster.GetAI().OnSuccessfulSpellCast(GetSpellInfo());
+                    caster.GetAI().OnSpellCastFinished(GetSpellInfo(), SpellFinishReason.SuccessfulCast);
         }
 
         void DoProcessTargetContainer<T>(List<T> targetContainer) where T : TargetInfoBase
@@ -3267,6 +3267,12 @@ namespace Game.Spells
                     {
                         SendChannelUpdate(0);
                         Finish();
+
+                        // We call the hook here instead of in Spell::finish because we only want to call it for completed channeling. Everything else is handled by interrupts
+                        Creature creatureCaster = m_caster.ToCreature();
+                        if (creatureCaster != null)
+                            if (creatureCaster.IsAIEnabled())
+                                creatureCaster.GetAI().OnSpellCastFinished(m_spellInfo, SpellFinishReason.ChannelingComplete);
                     }
                     break;
                 }