Core/Movement: Added a wrapper method in MotionMaster for a unit to move toward another unit and stop once it reaches the target at a certain distance. (#16806)

(cherry picked from commit 97b053d2034825c58246d79ebdbb3eb23fc2f28f)

2 files changed, 27 insertions, 0 deletions

diff --git a/src/server/game/Movement/MotionMaster.cpp b/src/server/game/Movement/MotionMaster.cpp
index 931c3602612..da9cbed9374 100644
--- a/src/server/game/Movement/MotionMaster.cpp
+++ b/src/server/game/Movement/MotionMaster.cpp
@@ -296,6 +296,27 @@ void MotionMaster::MovePoint(uint32 id, float x, float y, float z, bool generate
     }
 }
 
+void MotionMaster::MoveCloserAndStop(uint32 id, Unit* target, float distance)
+{
+    float distanceToTravel = _owner->GetExactDist2d(target) - distance;
+    if (distanceToTravel > 0.0f)
+    {
+        float angle = _owner->GetAngle(target);
+        float destx = _owner->GetPositionX() + distanceToTravel * std::cos(angle);
+        float desty = _owner->GetPositionY() + distanceToTravel * std::sin(angle);
+        MovePoint(id, destx, desty, target->GetPositionZ());
+    }
+    else 
+    {
+        // we are already close enough. We just need to turn toward the target without changing position.
+        Movement::MoveSplineInit init(_owner);
+        init.MoveTo(_owner->GetPositionX(), _owner->GetPositionY(), _owner->GetPositionZMinusOffset());
+        init.SetFacing(target);
+        init.Launch();
+        Mutate(new EffectMovementGenerator(id), MOTION_SLOT_ACTIVE);
+    }
+}
+
 void MotionMaster::MoveLand(uint32 id, Position const& pos)
 {
     float x, y, z;
diff --git a/src/server/game/Movement/MotionMaster.h b/src/server/game/Movement/MotionMaster.h
index 4f396f80d3b..07c928da63b 100644
--- a/src/server/game/Movement/MotionMaster.h
+++ b/src/server/game/Movement/MotionMaster.h
@@ -173,6 +173,12 @@ class TC_GAME_API MotionMaster //: private std::stack<MovementGenerator *>
             { MovePoint(id, pos.m_positionX, pos.m_positionY, pos.m_positionZ, generatePath); }
         void MovePoint(uint32 id, float x, float y, float z, bool generatePath = true);
 
+        /*  Makes the unit move toward the target until it is at a certain distance from it. The unit then stops. 
+            Only works in 2D.
+            This method doesn't account for any movement done by the target. in other words, it only works if the target is stationary.
+        */
+        void MoveCloserAndStop(uint32 id, Unit* target, float distance);
+
         // These two movement types should only be used with creatures having landing/takeoff animations
         void MoveLand(uint32 id, Position const& pos);
         void MoveTakeoff(uint32 id, Position const& pos);