The following stealth changes are implemented.

 - Combat no longer removes stealth, only damage does
 - Creatures will pursue a stealthed unit they cannot see if they're already in combat with them
 - When a player is ~~3 yards~~ 8% + 1.5 yards away from the usual stealth detection distance, the creature will perform the "alerted" effect.
 - When sitting/sleeping creatures are distracted or alerted, they will stand up
 - Idle movement creatures will return to their original (spawn) orientation after distract/alert
 - When entering combat with a distracted/alerted creature, distract state is removed
 - NPC no longer have a limit to stealth visibility (granted by stealth modifier spells/buffs)
 - If alert visibility is greater than aggro range, no alert sent

11 files changed, 108 insertions, 14 deletions

diff --git a/src/server/game/AI/CreatureAI.cpp b/src/server/game/AI/CreatureAI.cpp
index 96a25588120..d76d106e81a 100644
--- a/src/server/game/AI/CreatureAI.cpp
+++ b/src/server/game/AI/CreatureAI.cpp
@@ -140,6 +140,30 @@ void CreatureAI::MoveInLineOfSight(Unit* who)
     //    me->GetMotionMaster()->MoveChase(who->GetVictim());
 }
 
+// Distract creature, if player gets too close while stealthed/prowling
+void CreatureAI::TriggerAlert(Unit const* who) const
+{
+    // If there's no target, or target isn't a player do nothing
+    if (!who || who->GetTypeId() != TYPEID_PLAYER)
+        return;
+
+    // If this unit isn't an NPC, is already distracted, is in combat, is confused, stunned or fleeing, do nothing
+    if (me->GetTypeId() != TYPEID_UNIT || me->IsInCombat() || me->HasUnitState(UNIT_STATE_CONFUSED | UNIT_STATE_STUNNED | UNIT_STATE_FLEEING | UNIT_STATE_DISTRACTED))
+        return;
+
+    // Only alert for hostiles!
+    if (me->IsCivilian() || me->HasReactState(REACT_PASSIVE) || !me->IsHostileTo(who) || !me->_IsTargetAcceptable(who))
+        return;
+
+    // Send alert sound (if any) for this creature
+    me->SendAIReaction(AI_REACTION_ALERT);
+
+    // Face the unit (stealthed player) and set distracted state for 5 seconds
+    me->SetFacingTo(me->GetAngle(who->GetPositionX(), who->GetPositionY()));
+    me->StopMoving();
+    me->GetMotionMaster()->MoveDistract(5 * IN_MILLISECONDS);
+}
+
 void CreatureAI::EnterEvadeMode()
 {
     if (!_EnterEvadeMode())
diff --git a/src/server/game/AI/CreatureAI.h b/src/server/game/AI/CreatureAI.h
index 2e862c37c0e..33616d076e7 100644
--- a/src/server/game/AI/CreatureAI.h
+++ b/src/server/game/AI/CreatureAI.h
@@ -89,6 +89,9 @@ class CreatureAI : public UnitAI
         // Called if IsVisible(Unit* who) is true at each who move, reaction at visibility zone enter
         void MoveInLineOfSight_Safe(Unit* who);
 
+        // Trigger Creature "Alert" state (creature can see stealthed unit)
+        void TriggerAlert(Unit const* who) const;
+
         // Called in Creature::Update when deathstate = DEAD. Inherited classes may maniuplate the ability to respawn based on scripted events.
         virtual bool CanRespawn() { return true; }
 
diff --git a/src/server/game/AI/ScriptedAI/ScriptedEscortAI.cpp b/src/server/game/AI/ScriptedAI/ScriptedEscortAI.cpp
index ed87804474a..f1c53e2f9eb 100644
--- a/src/server/game/AI/ScriptedAI/ScriptedEscortAI.cpp
+++ b/src/server/game/AI/ScriptedAI/ScriptedEscortAI.cpp
@@ -120,7 +120,13 @@ void npc_escortAI::MoveInLineOfSight(Unit* who)
             {
                 if (!me->GetVictim())
                 {
-                    who->RemoveAurasByType(SPELL_AURA_MOD_STEALTH);
+                    // Clear distracted state on combat
+                    if (me->HasUnitState(UNIT_STATE_DISTRACTED))
+                    {
+                        me->ClearUnitState(UNIT_STATE_DISTRACTED);
+                        me->GetMotionMaster()->Clear();
+                    }
+
                     AttackStart(who);
                 }
                 else if (me->GetMap()->IsDungeon())
diff --git a/src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp b/src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp
index 7fd21a8f791..8985f722cf2 100644
--- a/src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp
+++ b/src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp
@@ -117,7 +117,13 @@ void FollowerAI::MoveInLineOfSight(Unit* who)
             {
                 if (!me->GetVictim())
                 {
-                    who->RemoveAurasByType(SPELL_AURA_MOD_STEALTH);
+                    // Clear distracted state on combat
+                    if (me->HasUnitState(UNIT_STATE_DISTRACTED))
+                    {
+                        me->ClearUnitState(UNIT_STATE_DISTRACTED);
+                        me->GetMotionMaster()->Clear();
+                    }
+
                     AttackStart(who);
                 }
                 else if (me->GetMap()->IsDungeon())
diff --git a/src/server/game/AI/SmartScripts/SmartAI.cpp b/src/server/game/AI/SmartScripts/SmartAI.cpp
index 21a15fa4f99..97d2d718ff0 100644
--- a/src/server/game/AI/SmartScripts/SmartAI.cpp
+++ b/src/server/game/AI/SmartScripts/SmartAI.cpp
@@ -469,7 +469,13 @@ void SmartAI::MoveInLineOfSight(Unit* who)
         {
             if (!me->GetVictim())
             {
-                who->RemoveAurasByType(SPELL_AURA_MOD_STEALTH);
+                // Clear distracted state on combat
+                if (me->HasUnitState(UNIT_STATE_DISTRACTED))
+                {
+                   me->ClearUnitState(UNIT_STATE_DISTRACTED);
+                   me->GetMotionMaster()->Clear();
+                }
+
                 AttackStart(who);
             }
             else/* if (me->GetMap()->IsDungeon())*/
diff --git a/src/server/game/Entities/Object/Object.cpp b/src/server/game/Entities/Object/Object.cpp
index 6392c3ee51b..fc55c09bffa 100644
--- a/src/server/game/Entities/Object/Object.cpp
+++ b/src/server/game/Entities/Object/Object.cpp
@@ -1539,7 +1539,7 @@ float WorldObject::GetSightRange(const WorldObject* target) const
     return 0.0f;
 }
 
-bool WorldObject::CanSeeOrDetect(WorldObject const* obj, bool ignoreStealth, bool distanceCheck) const
+bool WorldObject::CanSeeOrDetect(WorldObject const* obj, bool ignoreStealth, bool distanceCheck, bool checkAlert) const
 {
     if (this == obj)
         return true;
@@ -1611,7 +1611,7 @@ bool WorldObject::CanSeeOrDetect(WorldObject const* obj, bool ignoreStealth, boo
     if (obj->IsInvisibleDueToDespawn())
         return false;
 
-    if (!CanDetect(obj, ignoreStealth))
+    if (!CanDetect(obj, ignoreStealth, checkAlert))
         return false;
 
     return true;
@@ -1622,7 +1622,7 @@ bool WorldObject::CanNeverSee(WorldObject const* obj) const
     return GetMap() != obj->GetMap() || !InSamePhase(obj);
 }
 
-bool WorldObject::CanDetect(WorldObject const* obj, bool ignoreStealth) const
+bool WorldObject::CanDetect(WorldObject const* obj, bool ignoreStealth, bool checkAlert) const
 {
     const WorldObject* seer = this;
 
@@ -1637,7 +1637,7 @@ bool WorldObject::CanDetect(WorldObject const* obj, bool ignoreStealth) const
     if (!ignoreStealth && !seer->CanDetectInvisibilityOf(obj))
         return false;
 
-    if (!ignoreStealth && !seer->CanDetectStealthOf(obj))
+    if (!ignoreStealth && !seer->CanDetectStealthOf(obj, checkAlert))
         return false;
 
     return true;
@@ -1674,7 +1674,7 @@ bool WorldObject::CanDetectInvisibilityOf(WorldObject const* obj) const
     return true;
 }
 
-bool WorldObject::CanDetectStealthOf(WorldObject const* obj) const
+bool WorldObject::CanDetectStealthOf(WorldObject const* obj, bool checkAlert) const
 {
     // Combat reach is the minimal distance (both in front and behind),
     //   and it is also used in the range calculation.
@@ -1724,9 +1724,19 @@ bool WorldObject::CanDetectStealthOf(WorldObject const* obj) const
         // Calculate max distance
         float visibilityRange = float(detectionValue) * 0.3f + combatReach;
 
-        if (visibilityRange > MAX_PLAYER_STEALTH_DETECT_RANGE)
+        // If this unit is an NPC then player detect range doesn't apply
+        if (unit && unit->GetTypeId() == TYPEID_PLAYER && visibilityRange > MAX_PLAYER_STEALTH_DETECT_RANGE)
             visibilityRange = MAX_PLAYER_STEALTH_DETECT_RANGE;
 
+        // When checking for alert state, look 8% further, and then 1.5 yards more than that.
+        if (checkAlert)
+            visibilityRange += (visibilityRange * 0.08f) + 1.5f;
+
+        // If checking for alert, and creature's visibility range is greater than aggro distance, No alert
+        Unit const* tunit = obj->ToUnit();
+        if (checkAlert && unit && unit->ToCreature() && visibilityRange >= unit->ToCreature()->GetAttackDistance(tunit) + unit->ToCreature()->m_CombatDistance)
+            return false;
+
         if (distance > visibilityRange)
             return false;
     }
diff --git a/src/server/game/Entities/Object/Object.h b/src/server/game/Entities/Object/Object.h
index a560afa7f1b..e673e346a5f 100644
--- a/src/server/game/Entities/Object/Object.h
+++ b/src/server/game/Entities/Object/Object.h
@@ -514,7 +514,7 @@ class WorldObject : public Object, public WorldLocation
         float GetGridActivationRange() const;
         float GetVisibilityRange() const;
         float GetSightRange(WorldObject const* target = NULL) const;
-        bool CanSeeOrDetect(WorldObject const* obj, bool ignoreStealth = false, bool distanceCheck = false) const;
+        bool CanSeeOrDetect(WorldObject const* obj, bool ignoreStealth = false, bool distanceCheck = false, bool checkAlert = false) const;
 
         FlaggedValuesArray32<int32, uint32, StealthType, TOTAL_STEALTH_TYPES> m_stealth;
         FlaggedValuesArray32<int32, uint32, StealthType, TOTAL_STEALTH_TYPES> m_stealthDetect;
@@ -634,9 +634,9 @@ class WorldObject : public Object, public WorldLocation
 
         bool CanNeverSee(WorldObject const* obj) const;
         virtual bool CanAlwaysSee(WorldObject const* /*obj*/) const { return false; }
-        bool CanDetect(WorldObject const* obj, bool ignoreStealth) const;
+        bool CanDetect(WorldObject const* obj, bool ignoreStealth, bool checkAlert = false) const;
         bool CanDetectInvisibilityOf(WorldObject const* obj) const;
-        bool CanDetectStealthOf(WorldObject const* obj) const;
+        bool CanDetectStealthOf(WorldObject const* obj, bool checkAlert = false) const;
 };
 
 namespace Trinity
diff --git a/src/server/game/Entities/Unit/Unit.cpp b/src/server/game/Entities/Unit/Unit.cpp
index 17915e53cfb..f551df6c260 100644
--- a/src/server/game/Entities/Unit/Unit.cpp
+++ b/src/server/game/Entities/Unit/Unit.cpp
@@ -288,6 +288,28 @@ Unit::~Unit()
     ASSERT(m_dynObj.empty());
 }
 
+// Check if unit in combat with specific unit
+bool Unit::IsInCombatWith(Unit const* who) const
+{
+    // Check target exists
+    if (!who)
+        return false;
+
+    // Search in threat list
+    ObjectGuid guid = who->GetGUID();
+    for (ThreatContainer::StorageType::const_iterator i = m_ThreatManager.getThreatList().begin(); i != m_ThreatManager.getThreatList().end(); ++i)
+    {
+        HostileReference* ref = (*i);
+
+        // Return true if the unit matches
+        if (ref && ref->getUnitGuid() == guid)
+            return true;
+    }
+
+    // Nothing found, false.
+    return false;
+}
+
 void Unit::Update(uint32 p_time)
 {
     // WARNING! Order of execution here is important, do not change.
@@ -11885,8 +11907,8 @@ bool Unit::_IsValidAttackTarget(Unit const* target, SpellInfo const* bySpell, Wo
         if (IsOnVehicle(target) || m_vehicle->GetBase()->IsOnVehicle(target))
             return false;
 
-    // can't attack invisible (ignore stealth for aoe spells) also if the area being looked at is from a spell use the dynamic object created instead of the casting unit.
-    if ((!bySpell || !bySpell->HasAttribute(SPELL_ATTR6_CAN_TARGET_INVISIBLE)) && (obj ? !obj->CanSeeOrDetect(target, bySpell && bySpell->IsAffectingArea()) : !CanSeeOrDetect(target, bySpell && bySpell->IsAffectingArea())))
+    // can't attack invisible (ignore stealth for aoe spells) also if the area being looked at is from a spell use the dynamic object created instead of the casting unit. Ignore stealth if target is player and unit in combat with same player
+    if ((!bySpell || !bySpell->HasAttribute(SPELL_ATTR6_CAN_TARGET_INVISIBLE)) && (obj ? !obj->CanSeeOrDetect(target, bySpell && bySpell->IsAffectingArea()) : !CanSeeOrDetect(target, (bySpell && bySpell->IsAffectingArea()) || (target->GetTypeId() == TYPEID_PLAYER && target->HasStealthAura() && target->IsInCombat() && IsInCombatWith(target)))))
         return false;
 
     // can't attack dead
diff --git a/src/server/game/Entities/Unit/Unit.h b/src/server/game/Entities/Unit/Unit.h
index a61b406cbbd..39b1c34be55 100644
--- a/src/server/game/Entities/Unit/Unit.h
+++ b/src/server/game/Entities/Unit/Unit.h
@@ -1480,6 +1480,7 @@ class Unit : public WorldObject
         bool IsInFlight()  const { return HasUnitState(UNIT_STATE_IN_FLIGHT); }
 
         bool IsInCombat()  const { return HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_IN_COMBAT); }
+        bool IsInCombatWith(Unit const* who) const;
         void CombatStart(Unit* target, bool initialAggro = true);
         void SetInCombatState(bool PvP, Unit* enemy = NULL);
         void SetInCombatWith(Unit* enemy);
diff --git a/src/server/game/Grids/Notifiers/GridNotifiers.cpp b/src/server/game/Grids/Notifiers/GridNotifiers.cpp
index d52e559c408..15f3c7811cd 100644
--- a/src/server/game/Grids/Notifiers/GridNotifiers.cpp
+++ b/src/server/game/Grids/Notifiers/GridNotifiers.cpp
@@ -132,8 +132,13 @@ inline void CreatureUnitRelocationWorker(Creature* c, Unit* u)
         return;
 
     if (c->HasReactState(REACT_AGGRESSIVE) && !c->HasUnitState(UNIT_STATE_SIGHTLESS))
+    {
         if (c->IsAIEnabled && c->CanSeeOrDetect(u, false, true))
             c->AI()->MoveInLineOfSight_Safe(u);
+        else
+            if (u->GetTypeId() == TYPEID_PLAYER && u->HasStealthAura() && c->IsAIEnabled && c->CanSeeOrDetect(u, false, true, true))
+                c->AI()->TriggerAlert(u);
+    }
 }
 
 void PlayerRelocationNotifier::Visit(PlayerMapType &m)
diff --git a/src/server/game/Movement/MovementGenerators/IdleMovementGenerator.cpp b/src/server/game/Movement/MovementGenerators/IdleMovementGenerator.cpp
index 78d86fb7abb..2aaaa719e94 100755
--- a/src/server/game/Movement/MovementGenerators/IdleMovementGenerator.cpp
+++ b/src/server/game/Movement/MovementGenerators/IdleMovementGenerator.cpp
@@ -81,12 +81,23 @@ void RotateMovementGenerator::Finalize(Unit* unit)
 
 void DistractMovementGenerator::Initialize(Unit* owner)
 {
+    // Distracted creatures stand up if not standing
+    if (!owner->IsStandState())
+        owner->SetStandState(UNIT_STAND_STATE_STAND);
+
     owner->AddUnitState(UNIT_STATE_DISTRACTED);
 }
 
 void DistractMovementGenerator::Finalize(Unit* owner)
 {
     owner->ClearUnitState(UNIT_STATE_DISTRACTED);
+
+    // If this is a creature, then return orientation to original position (for idle movement creatures)
+    if (owner->GetTypeId() == TYPEID_UNIT && owner->ToCreature())
+    {
+        float angle = owner->ToCreature()->GetHomePosition().GetOrientation();
+        owner->SetFacingTo(angle);
+    }
 }
 
 bool DistractMovementGenerator::Update(Unit* /*owner*/, uint32 time_diff)