feat(Core/Scripting): Implement SetInvincibility() to prevent creatur… (#20508)

src/server/game/AI/ScriptedAI/ScriptedCreature.cpp

@@ -194,6 +194,7 @@ ScriptedAI::ScriptedAI(Creature* creature) : CreatureAI(creature),
 {
     _isHeroic = me->GetMap()->IsHeroic();
     _difficulty = Difficulty(me->GetMap()->GetSpawnMode());
+    _invincible = false;
 }
 
 void ScriptedAI::AttackStartNoMove(Unit* who)
@@ -222,6 +223,12 @@ void ScriptedAI::UpdateAI(uint32 /*diff*/)
     DoMeleeAttackIfReady();
 }
 
+void ScriptedAI::DamageTaken(Unit* /*attacker*/, uint32& damage, DamageEffectType /*damagetype*/, SpellSchoolMask /*damageSchoolMask*/)
+{
+    if (IsInvincible() && damage >= me->GetHealth())
+        damage = me->GetHealth() - 1;
+}
+
 void ScriptedAI::DoStartMovement(Unit* victim, float distance, float angle)
 {
     if (victim)
@@ -732,8 +739,10 @@ void BossAI::UpdateAI(uint32 diff)
     DoMeleeAttackIfReady();
 }
 
-void BossAI::DamageTaken(Unit* /*attacker*/, uint32& damage, DamageEffectType /*damagetype*/, SpellSchoolMask /*damageSchoolMask*/)
+void BossAI::DamageTaken(Unit* attacker, uint32& damage, DamageEffectType damagetype, SpellSchoolMask damageSchoolMask)
 {
+    ScriptedAI::DamageTaken(attacker, damage, damagetype, damageSchoolMask);
+
     if (_nextHealthCheck._valid)
         if (me->HealthBelowPctDamaged(_nextHealthCheck._healthPct, damage))
         {

src/server/game/AI/ScriptedAI/ScriptedCreature.h

@@ -198,7 +198,7 @@ struct ScriptedAI : public CreatureAI
     void AttackStartNoMove(Unit* target);
 
     // Called at any Damage from any attacker (before damage apply)
-    void DamageTaken(Unit* /*attacker*/, uint32& /*damage*/, DamageEffectType /*damagetype*/, SpellSchoolMask /*damageSchoolMask*/) override {}
+    void DamageTaken(Unit* /*attacker*/, uint32& /*damage*/, DamageEffectType /*damagetype*/, SpellSchoolMask /*damageSchoolMask*/) override;
 
     //Called at World update tick
     void UpdateAI(uint32 diff) override;
@@ -438,9 +438,14 @@ struct ScriptedAI : public CreatureAI
 
     Player* SelectTargetFromPlayerList(float maxdist, uint32 excludeAura = 0, bool mustBeInLOS = false) const;
 
+    // Allows dropping to 1 HP but prevents creature from dying.
+    void SetInvincibility(bool apply) { _invincible = apply; };
+    [[nodiscard]] bool IsInvincible() const { return _invincible; };
+
 private:
     Difficulty _difficulty;
     bool _isHeroic;
+    bool _invincible;
     std::unordered_set<uint32> _uniqueTimedEvents;
 };
 

src/server/scripts/EasternKingdoms/BlackrockMountain/BlackrockSpire/boss_gyth.cpp

@@ -62,13 +62,20 @@ public:
 
         void Reset() override
         {
-            _summonedRend = false;
             if (instance->GetBossState(DATA_GYTH) == IN_PROGRESS)
             {
                 instance->SetBossState(DATA_GYTH, NOT_STARTED);
                 summons.DespawnAll();
                 me->DespawnOrUnsummon();
             }
+
+            SetInvincibility(true); // Don't let boss die before summoning Rend.
+
+            ScheduleHealthCheckEvent(25, [&] {
+                DoCastAOE(SPELL_SUMMON_REND, true);
+                me->RemoveAura(SPELL_REND_MOUNTS);
+                SetInvincibility(false);
+            });
         }
 
         void JustEngagedWith(Unit* /*who*/) override
@@ -104,21 +111,6 @@ public:
             instance->SetBossState(DATA_GYTH, DONE);
         }
 
-        void DamageTaken(Unit* /*attacker*/, uint32& damage, DamageEffectType /*type*/, SpellSchoolMask /*school*/) override
-        {
-            if (!_summonedRend && me->HealthBelowPctDamaged(25, damage))
-            {
-                if (damage >= me->GetHealth())
-                {
-                    // Let creature fall to 1 HP but prevent it from dying before boss is summoned.
-                    damage = me->GetHealth() - 1;
-                }
-                DoCast(me, SPELL_SUMMON_REND, true);
-                me->RemoveAura(SPELL_REND_MOUNTS);
-                _summonedRend = true;
-            }
-        }
-
         void UpdateAI(uint32 diff) override
         {
             if (!UpdateVictim())
@@ -173,9 +165,6 @@ public:
             }
             DoMeleeAttackIfReady();
         }
-
-        private:
-            bool _summonedRend;
     };
 
     CreatureAI* GetAI(Creature* creature) const override