Core/Spells: Improve charge path logic, get a point to the target and then reduce it by the necessary distance

src/server/game/Movement/PathGenerator.cpp

@@ -882,3 +882,41 @@ float PathGenerator::Dist3DSqr(G3D::Vector3 const& p1, G3D::Vector3 const& p2) c
 {
     return (p1 - p2).squaredLength();
 }
+
+void PathGenerator::ReducePathLenghtByDist(float dist)
+{
+    if (GetPathType() == PATHFIND_BLANK)
+    {
+        TC_LOG_ERROR("maps", "PathGenerator::ReducePathLenghtByDist called before path was built");
+        return;
+    }
+
+    if (_pathPoints.size() < 2) // path building failure
+        return;
+
+    uint32 i = _pathPoints.size();
+    G3D::Vector3 nextVec = _pathPoints[--i];
+    while (i > 0)
+    {
+        G3D::Vector3 currVec = _pathPoints[--i];
+        G3D::Vector3 diffVec = (nextVec - currVec);
+        float len = diffVec.length();
+        if (len > dist)
+        {
+            float step = dist / len;
+            // same as nextVec
+            _pathPoints[i + 1] -= diffVec * step;
+            _pathPoints.resize(i + 2);
+            break;
+        }
+        else if (i == 0) // at second point
+        {
+            _pathPoints[1] = _pathPoints[0];
+            _pathPoints.resize(2);
+            break;
+        }
+
+        dist -= len;
+        nextVec = currVec; // we're going backwards
+    }
+}