refactor(Core/Unit): minor changes for the combat system (#11904)

Cherry-pick from TC: https://github.com/TrinityCore/TrinityCore/pull/19966

Co-authored-by: Treeston <treeston.nmoc@gmail.com>

src/server/game/Entities/Creature/Creature.cpp

@@ -704,7 +704,7 @@ void Creature::Update(uint32 diff)
                 }
 
                 // periodic check to see if the creature has passed an evade boundary
-                if (IsAIEnabled && !IsInEvadeMode() && IsInCombat())
+                if (IsAIEnabled && !IsInEvadeMode() && IsEngaged())
                 {
                     if (diff >= m_boundaryCheckTime)
                     {
@@ -1838,7 +1838,7 @@ bool Creature::CanStartAttack(Unit const* who) const
     // pussywizard: at this point we are either hostile to who or friendly to who->getAttackerForHelper()
     // pussywizard: if who is in combat and has an attacker, help him if the distance is right (help because who is hostile or help because attacker is friendly)
     bool assist = false;
-    if (who->IsInCombat() && IsWithinDist(who, ATTACK_DISTANCE))
+    if (who->IsEngaged() && IsWithinDist(who, ATTACK_DISTANCE))
         if (Unit* victim = who->getAttackerForHelper())
             if (IsWithinDistInMap(victim, sWorld->getFloatConfig(CONFIG_CREATURE_FAMILY_ASSISTANCE_RADIUS)))
                 assist = true;
@@ -2357,7 +2357,7 @@ bool Creature::CanAssistTo(Unit const* u, Unit const* enemy, bool checkfaction /
         return false;
 
     // skip fighting creature
-    if (IsInCombat())
+    if (IsEngaged())
         return false;
 
     // only free creature
@@ -2408,11 +2408,10 @@ bool Creature::_IsTargetAcceptable(Unit const* target) const
             return false;
     }
 
-    Unit const* myVictim = getAttackerForHelper();
     Unit const* targetVictim = target->getAttackerForHelper();
 
     // if I'm already fighting target, or I'm hostile towards the target, the target is acceptable
-    if (myVictim == target || targetVictim == this || IsHostileTo(target))
+    if (IsEngagedBy(target) || IsHostileTo(target))
         return true;
 
     // if the target's victim is friendly, and the target is neutral, the target is acceptable

src/server/game/Entities/Creature/CreatureGroups.cpp

@@ -190,7 +190,7 @@ void CreatureGroup::RemoveMember(Creature* member)
     member->SetFormation(nullptr);
 }
 
-void CreatureGroup::MemberAttackStart(Creature* member, Unit* target)
+void CreatureGroup::MemberEngagingTarget(Creature* member, Unit* target)
 {
     uint8 const groupAI = sFormationMgr->CreatureGroupMap[member->GetSpawnId()].groupAI;
     if (member == m_leader)

src/server/game/Entities/Creature/CreatureGroups.h

@@ -106,7 +106,7 @@ public:
     void FormationReset(bool dismiss, bool initMotionMaster);
 
     void LeaderMoveTo(float x, float y, float z, bool run);
-    void MemberAttackStart(Creature* member, Unit* target);
+    void MemberEngagingTarget(Creature* member, Unit* target);
     void MemberEvaded(Creature* member);
 
 private:

src/server/game/Entities/Unit/Unit.cpp

@@ -13150,7 +13150,7 @@ void Unit::SetInCombatState(bool PvP, Unit* enemy, uint32 duration)
                 creature->AI()->EnterCombat(enemy);
 
             if (creature->GetFormation())
-                creature->GetFormation()->MemberAttackStart(creature, enemy);
+                creature->GetFormation()->MemberEngagingTarget(creature, enemy);
         }
 
         creature->RefreshSwimmingFlag();

src/server/game/Entities/Unit/Unit.h

@@ -1326,6 +1326,7 @@ public:
     bool IsWithinCombatRange(Unit const* obj, float dist2compare) const;
     bool IsWithinMeleeRange(Unit const* obj, float dist = 0.f) const;
     float GetMeleeRange(Unit const* target) const;
+    [[nodiscard]] virtual SpellSchoolMask GetMeleeDamageSchoolMask() const;
     bool GetRandomContactPoint(Unit const* target, float& x, float& y, float& z, bool force = false) const;
     uint32 m_extraAttacks;
     bool m_canDualWield;
@@ -1343,6 +1344,9 @@ public:
         if (GetVictim() != nullptr)
             return GetVictim();
 
+        if (!IsEngaged())
+            return nullptr;
+
         if (!m_attackers.empty())
             return *(m_attackers.begin());
 
@@ -1643,6 +1647,9 @@ public:
 
     [[nodiscard]] bool IsInFlight()  const { return HasUnitState(UNIT_STATE_IN_FLIGHT); }
 
+    bool IsEngaged() const { return IsInCombat(); }
+    bool IsEngagedBy(Unit const* who) const { return IsInCombatWith(who); }
+
     [[nodiscard]] bool IsInCombat() const { return HasUnitFlag(UNIT_FLAG_IN_COMBAT); }
     bool IsInCombatWith(Unit const* who) const;
 
@@ -2103,6 +2110,7 @@ public:
     void TauntApply(Unit* victim);
     void TauntFadeOut(Unit* taunter);
     ThreatMgr& GetThreatMgr() { return m_ThreatMgr; }
+    ThreatMgr const& GetThreatMgr() const { return m_ThreatMgr; }
     void addHatedBy(HostileReference* pHostileReference) { m_HostileRefMgr.insertFirst(pHostileReference); };
     void removeHatedBy(HostileReference* /*pHostileReference*/) { /* nothing to do yet */ }
     HostileRefMgr& getHostileRefMgr() { return m_HostileRefMgr; }
@@ -2473,8 +2481,6 @@ protected:
     CharmInfo* m_charmInfo;
     SharedVisionList m_sharedVision;
 
-    [[nodiscard]] virtual SpellSchoolMask GetMeleeDamageSchoolMask() const;
-
     MotionMaster* i_motionMaster;
 
     uint32 m_reactiveTimer[MAX_REACTIVE];