public List<PathNode> Calculate(IGridShape start, IGridShape end, IGridManager gridManager)
        {
            var startNode = new PathNode {Position = start};
            startNode = CalculateFGH(startNode, startNode, end);

            _openList.Add(startNode);

            while (true)
            {
                _openList.Sort();

                if (_openList.Count == 0)
                    //_openList.Add(_closedList[0]);
                    return _closedList;

                var current = _openList[0];

                if (current.Position.Equals(end))
                    return _closedList;

                _closedList.Add(current);
                _openList.Remove(current);

                var neighbours = gridManager.GetNeighbours(current.Position);

                foreach (var g in neighbours)
                {
                    if (g == null) continue;

                    var c1 = _closedList.Where(x => x.Position.Equals(g)).FirstOrDefault();

                    if (!g.Blocked && (c1 == null))
                    {
                        var newNode = new PathNode { Position = g, Parent = current };
                        newNode = CalculateFGH(current, newNode, end);

                        if (!_openList.Contains(newNode))
                        {
                            newNode.Parent = current;
                            newNode = CalculateFGH(current, newNode, end);
                            _openList.Add(newNode);
                        }
                        else
                        {
                            var existingNode = _openList.First(x => x.Position.Id == newNode.Position.Id);
                            if (newNode.G < existingNode.G)
                            {
                                _openList.Remove(existingNode);
                                existingNode.Parent = current;
                                existingNode = CalculateFGH(current, existingNode, end);
                                _openList.Add(existingNode);
                                _openList.Sort();

                            }
                        }

                    }

                    //if (!g.Blocked && (c1 != null))
                    //{
                    //    var newNode = new PathNode { Position = g, Parent = current };
                    //    newNode = CalculateFGH(current, newNode, end);

                    //    if (newNode.G < c1.G)
                    //    {
                    //        _openList.Remove(c1);
                    //        _openList.Add(newNode);
                    //    }
                    //}

                }

            }
        }