Core/Vehicles: Make the vehicle system more aura driven. Get rid of redundant checks and update relevant data.

Closes #805

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

@@ -2553,10 +2553,6 @@ SpellMissInfo Unit::MagicSpellHitResult(Unit *pVictim, SpellEntry const *spell)
 //   Resist
 SpellMissInfo Unit::SpellHitResult(Unit *pVictim, SpellEntry const *spell, bool CanReflect)
 {
-    // Return evade for units in evade mode
-    if (pVictim->GetTypeId() == TYPEID_UNIT && pVictim->ToCreature()->IsInEvadeMode() && this != pVictim)
-        return SPELL_MISS_EVADE;
-
     // Check for immune
     if (pVictim->IsImmunedToSpell(spell))
         return SPELL_MISS_IMMUNE;
@@ -2573,6 +2569,10 @@ SpellMissInfo Unit::SpellHitResult(Unit *pVictim, SpellEntry const *spell, bool
     if (this == pVictim)
         return SPELL_MISS_NONE;
 
+    // Return evade for units in evade mode
+    if (pVictim->GetTypeId() == TYPEID_UNIT && pVictim->ToCreature()->IsInEvadeMode())
+        return SPELL_MISS_EVADE;
+
     // Try victim reflect spell
     if (CanReflect)
     {
@@ -12347,7 +12347,6 @@ void Unit::setDeathState(DeathState s)
         UnsummonAllTotems();
         RemoveAllControlled();
         RemoveAllAurasOnDeath();
-        ExitVehicle();
     }
 
     if (s == JUST_DIED)
@@ -16512,14 +16511,20 @@ bool Unit::HandleSpellClick(Unit* clicker, int8 seatId)
         }
     }
 
-    if (this->ToCreature())
+    if (this->ToCreature() && this->ToCreature()->IsAIEnabled)
         this->ToCreature()->AI()->DoAction(EVENT_SPELLCLICK);
 
     return success;
 }
 
-void Unit::EnterVehicle(Vehicle *vehicle, int8 seatId, AuraApplication const * aurApp)
+void Unit::EnterVehicle(Unit *base, int8 seatId)
 {
+    CastCustomSpell(VEHICLE_SPELL_RIDE_HARDCODED, SPELLVALUE_BASE_POINT0, seatId+1, base, false);
+}
+
+void Unit::_EnterVehicle(Vehicle* vehicle, int8 seatId, AuraApplication const* aurApp)
+{
+    // Must be called only from aura handler
     if (!isAlive() || GetVehicleKit() == vehicle || vehicle->GetBase()->IsOnVehicle(this))
         return;
 
@@ -16541,6 +16546,9 @@ void Unit::EnterVehicle(Vehicle *vehicle, int8 seatId, AuraApplication const * a
         }
     }
 
+    if (aurApp && aurApp->GetRemoveMode())
+        return;
+
     if (Player* plr = ToPlayer())
     {
         if (vehicle->GetBase()->GetTypeId() == TYPEID_PLAYER && plr->isInCombat())
@@ -16557,11 +16565,6 @@ void Unit::EnterVehicle(Vehicle *vehicle, int8 seatId, AuraApplication const * a
             bg->EventPlayerDroppedFlag(plr);
     }
 
-    // vehicle is applied by aura, and aura effect remove handler was called during apply handler execution
-    // prevent undefined behaviour
-    if (aurApp && aurApp->GetRemoveMode())
-        return;
-
     if (Player* thisPlr = this->ToPlayer())
     {
         WorldPacket data(SMSG_ON_CANCEL_EXPECTED_RIDE_VEHICLE_AURA, 0);
@@ -16598,6 +16601,7 @@ void Unit::ChangeSeat(int8 seatId, bool next)
 
 void Unit::ExitVehicle(Position const* exitPosition)
 {
+    // This function can be called at upper level code to initialize an exit from the passenger's side.
     if (!m_vehicle)
         return;
 
@@ -16612,6 +16616,11 @@ void Unit::ExitVehicle(Position const* exitPosition)
         }
     }
 
+   _ExitVehicle(exitPosition);
+}
+
+void Unit::_ExitVehicle(Position const* exitPosition)
+{
     if (!m_vehicle)
         return;
 
@@ -16650,6 +16659,16 @@ void Unit::ExitVehicle(Position const* exitPosition)
     if (vehicle->GetBase()->HasUnitTypeMask(UNIT_MASK_MINION))
         if (((Minion*)vehicle->GetBase())->GetOwner() == this)
             vehicle->Dismiss();
+
+    if (HasUnitTypeMask(UNIT_MASK_ACCESSORY))
+    {
+        // Vehicle just died, we die too
+        if (vehicle->GetBase()->getDeathState() == JUST_DIED)
+            setDeathState(JUST_DIED);
+        // If for other reason we as minion are exiting the vehicle (ejected, master unmounted) - unsummon
+        else
+            ToTempSummon()->UnSummon();
+    }
 }
 
 void Unit::BuildMovementPacket(ByteBuffer *data) const