Entities/Player: Clean up client control handling behavior around possession. Mind Control should no longer cause various weirdness. Closes #23539.

src/server/game/AI/CreatureAI.cpp

@@ -152,7 +152,7 @@ void CreatureAI::TriggerAlert(Unit const* who) const
     me->GetMotionMaster()->MoveDistract(5 * IN_MILLISECONDS, me->GetAbsoluteAngle(who));
 }
 
-// adapted from logic in Spell:EffectSummonType
+// adapted from logic in Spell:EffectSummonType before commit 8499434
 static bool ShouldFollowOnSpawn(SummonPropertiesEntry const* properties)
 {
     // Summons without SummonProperties are generally scripted summons that don't belong to any owner

src/server/game/Entities/Player/Player.cpp

@@ -23876,24 +23876,38 @@ void Player::ResurrectUsingRequestDataImpl()
 
 void Player::SetClientControl(Unit* target, bool allowMove)
 {
-    // still affected by some aura that shouldn't allow control, only allow on last such aura to be removed
-    if (allowMove && target->HasUnitState(UNIT_STATE_CANT_CLIENT_CONTROL))
+    // a player can never client control nothing
+    ASSERT(target);
+
+    // don't allow possession to be overridden
+    if (target->HasUnitState(UNIT_STATE_CHARMED) && (GetGUID() != target->GetCharmerGUID()))
     {
-        // this should never happen, otherwise m_unitBeingMoved might be left dangling!
-        ASSERT(GetUnitBeingMoved() == target);
+        TC_LOG_ERROR("entities.player", "Player '%s' attempt to client control '%s', which is charmed by GUID %s",
+                     GetName().c_str(), target->GetName().c_str(), target->GetCharmerGUID().ToString().c_str());
         return;
     }
 
+    // still affected by some aura that shouldn't allow control, only allow on last such aura to be removed
+    if (target->HasUnitState(UNIT_STATE_CONTROLLED))
+        allowMove = false;
+
     WorldPacket data(SMSG_CLIENT_CONTROL_UPDATE, target->GetPackGUID().size()+1);
     data << target->GetPackGUID();
     data << uint8(allowMove ? 1 : 0);
     SendDirectMessage(&data);
 
-    if (this != target)
-        SetViewpoint(target, allowMove);
+    WorldObject* viewpoint = GetViewpoint();
+    if (!viewpoint)
+        viewpoint = this;
+    if (target != viewpoint)
+    {
+        if (viewpoint != this)
+            SetViewpoint(viewpoint, false);
+        if (target != this)
+            SetViewpoint(target, true);
+    }
 
-    if (allowMove)
-        SetMovedUnit(target);
+    SetMovedUnit(target);
 }
 
 void Player::UpdateZoneDependentAuras(uint32 newZone)

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

@@ -455,7 +455,7 @@ void Unit::Update(uint32 p_time)
     UpdateSplineMovement(p_time);
     i_motionMaster->Update(p_time);
 
-    if (!GetAI() && (GetTypeId() != TYPEID_PLAYER || IsCharmed()))
+    if (!GetAI() && (GetTypeId() != TYPEID_PLAYER || (IsCharmed() && GetCharmerGUID().IsCreature())))
         UpdateCharmAI();
     RefreshAI();
 }

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

@@ -249,7 +249,6 @@ enum UnitState : uint32
     UNIT_STATE_UNATTACKABLE        = UNIT_STATE_IN_FLIGHT,
     UNIT_STATE_MOVING              = UNIT_STATE_ROAMING_MOVE | UNIT_STATE_CONFUSED_MOVE | UNIT_STATE_FLEEING_MOVE | UNIT_STATE_CHASE_MOVE | UNIT_STATE_FOLLOW_MOVE,
     UNIT_STATE_CONTROLLED          = UNIT_STATE_CONFUSED | UNIT_STATE_STUNNED | UNIT_STATE_FLEEING,
-    UNIT_STATE_CANT_CLIENT_CONTROL = UNIT_STATE_CHARMED | UNIT_STATE_FLEEING | UNIT_STATE_CONFUSED | UNIT_STATE_POSSESSED,
     UNIT_STATE_LOST_CONTROL        = UNIT_STATE_CONTROLLED | UNIT_STATE_POSSESSED | UNIT_STATE_JUMPING | UNIT_STATE_CHARGING,
     UNIT_STATE_CANNOT_AUTOATTACK   = UNIT_STATE_CONTROLLED | UNIT_STATE_CHARGING | UNIT_STATE_CASTING,
     UNIT_STATE_SIGHTLESS           = UNIT_STATE_LOST_CONTROL | UNIT_STATE_EVADE,