Core/Movement: ported and merged Follow and Chase movement generator rewrite

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

@@ -17,6 +17,7 @@
  */
 
 #include "Unit.h"
+#include "AbstractFollower.h"
 #include "Battlefield.h"
 #include "BattlefieldMgr.h"
 #include "Battleground.h"
@@ -623,14 +624,19 @@ bool Unit::IsWithinCombatRange(Unit const* obj, float dist2compare) const
     return distsq < maxdist * maxdist;
 }
 
-bool Unit::IsWithinMeleeRange(Unit const* obj) const
+bool Unit::IsWithinMeleeRangeAt(Position const& pos, Unit const* obj) const
 {
     if (!obj || !IsInMap(obj) || !IsInPhase(obj))
         return false;
 
-    float dx = GetPositionX() - obj->GetPositionX();
-    float dy = GetPositionY() - obj->GetPositionY();
-    float dz = GetPositionZMinusOffset() - obj->GetPositionZMinusOffset();
+    float dx = pos.GetPositionX() - obj->GetPositionX();
+    float dy = pos.GetPositionY() - obj->GetPositionY();
+
+    float z = pos.GetPositionZ();
+    if (HasUnitMovementFlag(MOVEMENTFLAG_HOVER))
+        z -= GetFloatValue(UNIT_FIELD_HOVERHEIGHT);
+
+    float dz = z - obj->GetPositionZMinusOffset();
     float distsq = dx*dx + dy*dy + dz*dz;
 
     float maxdist = GetMeleeRange(obj);
@@ -9008,25 +9014,7 @@ void Unit::UpdateSpeed(UnitMoveType mtype)
         {
             // Set creature speed rate
             if (GetTypeId() == TYPEID_UNIT)
-            {
-                Unit* pOwner = GetCharmerOrOwner();
-                if ((IsPet() || IsGuardian()) && !IsInCombat() && pOwner) // Must check for owner or crash on "Tame Beast"
-                {
-                    // For every yard over 5, increase speed by 0.01
-                    // to help prevent pet from lagging behind and despawning
-                    float dist = GetDistance(pOwner);
-                    float base_rate = 1.00f; // base speed is 100% of owner speed
-
-                    if (dist < 5)
-                        dist = 5;
-
-                    float mult = base_rate + ((dist - 5) * 0.01f);
-
-                    speed *= pOwner->GetSpeedRate(mtype) * mult; // pets derive speed from owner when not in combat
-                }
-                else
-                    speed *= ToCreature()->GetCreatureTemplate()->speed_run;    // at this point, MOVE_WALK is never reached
-            }
+                speed *= ToCreature()->GetCreatureTemplate()->speed_run;    // at this point, MOVE_WALK is never reached
 
             // Normalize speed by 191 aura SPELL_AURA_USE_NORMAL_MOVEMENT_SPEED if need
             /// @todo possible affect only on MOVE_RUN
@@ -9050,11 +9038,27 @@ void Unit::UpdateSpeed(UnitMoveType mtype)
             break;
     }
 
-    // for creature case, we check explicit if mob searched for assistance
-    if (GetTypeId() == TYPEID_UNIT)
+    if (Creature* creature = ToCreature())
     {
-        if (ToCreature()->HasSearchedAssistance())
+        // for creature case, we check explicit if mob searched for assistance
+        if (creature->HasSearchedAssistance())
             speed *= 0.66f;                                 // best guessed value, so this will be 33% reduction. Based off initial speed, mob can then "run", "walk fast" or "walk".
+
+        if (creature->HasUnitTypeMask(UNIT_MASK_MINION) && !creature->IsInCombat())
+        {
+            MovementGenerator* top = creature->GetMotionMaster()->topOrNull();
+            if (top && top->GetMovementGeneratorType() == FOLLOW_MOTION_TYPE)
+            {
+                Unit* followed = ASSERT_NOTNULL(dynamic_cast<AbstractFollower*>(top))->GetTarget();
+                if (followed && followed->GetGUID() == GetOwnerGUID() && !followed->IsInCombat())
+                {
+                    float ownerSpeed = followed->GetSpeedRate(mtype);
+                    if (speed < ownerSpeed || creature->IsWithinDist3d(followed, 10.0f))
+                        speed = ownerSpeed;
+                    speed *= std::min(std::max(1.0f, 0.75f + (GetDistance(followed) - PET_FOLLOW_DIST) * 0.05f), 1.3f);
+                }
+            }
+        }
     }
 
     // Apply strongest slow aura mod to speed
@@ -9130,6 +9134,12 @@ void Unit::SetSpeedRate(UnitMoveType mtype, float rate)
     Movement::PacketSender(this, moveTypeToOpcode[mtype][0], moveTypeToOpcode[mtype][1], moveTypeToOpcode[mtype][2], &extra).Send();
 }
 
+void Unit::RemoveAllFollowers()
+{
+    while (!m_followingMe.empty())
+        (*m_followingMe.begin())->SetTarget(nullptr);
+}
+
 void Unit::setDeathState(DeathState s)
 {
     // Death state needs to be updated before RemoveAllAurasOnDeath() is called, to prevent entering combat
@@ -10274,6 +10284,8 @@ void Unit::RemoveFromWorld()
 
         RemoveAreaAurasDueToLeaveWorld();
 
+        RemoveAllFollowers();
+
         if (GetCharmerGUID())
         {
             TC_LOG_FATAL("entities.unit", "Unit %u has charmer guid when removed from world", GetEntry());