Core/Movement: Replace old TargetedMovementGenerator into ChaseMovementGenerator and FollowMovementGenerator, full rewrite for both.

- Chase to angle is now functional. Pets use this to chase behind the target. Closes #19925.
- Chase to arbitrary range interval works. Not used anywhere, but you can technically make hunter-like mobs.
- Pets now follow the hunter cleanly and without stutter stepping. Also fix some other things. Closes #8924.

(cherry picked from commit 2a84562dc85516f432bb1e5de9add23c28b26ce4)

1 files changed, 33 insertions, 2 deletions

diff --git a/src/server/game/Movement/MotionMaster.h b/src/server/game/Movement/MotionMaster.h
index 79050edadd5..f03f553e288 100644
--- a/src/server/game/Movement/MotionMaster.h
+++ b/src/server/game/Movement/MotionMaster.h
@@ -20,6 +20,7 @@
 
 #include "Common.h"
 #include "Errors.h"
+#include "ObjectDefines.h"
 #include "ObjectGuid.h"
 #include "Optional.h"
 #include "Position.h"
@@ -93,6 +94,35 @@ enum RotateDirection
     ROTATE_DIRECTION_RIGHT
 };
 
+struct ChaseRange
+{
+    ChaseRange(float range) : MinRange(range > CONTACT_DISTANCE ? 0 : range - CONTACT_DISTANCE), MinTolerance(range), MaxRange(range + CONTACT_DISTANCE), MaxTolerance(range) {}
+    ChaseRange(float min, float max) : MinRange(min), MinTolerance(std::min(min + CONTACT_DISTANCE, (min + max) / 2)), MaxRange(max), MaxTolerance(std::max(max - CONTACT_DISTANCE, MinTolerance)) {}
+    ChaseRange(float min, float tMin, float tMax, float max) : MinRange(min), MinTolerance(tMin), MaxRange(max), MaxTolerance(tMax) {}
+
+    // this contains info that informs how we should path!
+    float MinRange;     // we have to move if we are within this range...    (min. attack range)
+    float MinTolerance; // ...and if we are, we will move this far away
+    float MaxRange;     // we have to move if we are outside this range...   (max. attack range)
+    float MaxTolerance; // ...and if we are, we will move into this range
+};
+
+struct ChaseAngle
+{
+    ChaseAngle(float angle, float tol = M_PI_4) : RelativeAngle(Position::NormalizeOrientation(angle)), Tolerance(tol) {}
+
+    float RelativeAngle; // we want to be at this angle relative to the target (0 = front, M_PI = back)
+    float Tolerance;     // but we'll tolerate anything within +- this much
+
+    float UpperBound() const { return Position::NormalizeOrientation(RelativeAngle + Tolerance); }
+    float LowerBound() const { return Position::NormalizeOrientation(RelativeAngle - Tolerance); }
+    bool IsAngleOkay(float relAngle) const
+    {
+        float const diff = std::abs(relAngle - RelativeAngle);
+        return (std::min(diff, float(2 * M_PI) - diff) <= Tolerance);
+    }
+};
+
 struct JumpArrivalCastArgs
 {
     uint32 SpellId;
@@ -136,8 +166,9 @@ class TC_GAME_API MotionMaster
         void MoveIdle();
         void MoveTargetedHome();
         void MoveRandom(float spawndist = 0.0f);
-        void MoveFollow(Unit* target, float dist, float angle, MovementSlot slot = MOTION_SLOT_ACTIVE);
-        void MoveChase(Unit* target, float dist = 0.0f, float angle = 0.0f);
+        void MoveFollow(Unit* target, float dist, ChaseAngle angle, MovementSlot slot = MOTION_SLOT_ACTIVE);
+        void MoveChase(Unit* target, Optional<ChaseRange> dist = {}, Optional<ChaseAngle> angle = {});
+        void MoveChase(Unit* target, float dist, float angle = 0.0f) { MoveChase(target, Optional<ChaseRange>(dist), Optional<ChaseAngle>(angle)); }
         void MoveConfused();
         void MoveFleeing(Unit* enemy, uint32 time = 0);
         void MovePoint(uint32 id, Position const& pos, bool generatePath = true, Optional<float> finalOrient = {})