AdventOfCode/AdventOfCode.Core/Shared/A-Star/AStarGrid.cs

namespace AdventOfCode.Core.Shared.A_Star
{
    public class AStarGrid(AStarNode[] data) : Grid<AStarNode>(data)
    {
        public int TileMoveCost { get; set; }

        public int MinimalSteps(AStarNode start, AStarNode destination)
        {
            List<AStarNode> openNodes = [start];
            List<AStarNode> closedNodes = [];

            while(openNodes.Count != 0)
            {
                // get the lowest F-cost node
                AStarNode current = openNodes.OrderBy(n => n.FCost).First();
                openNodes.Remove(current);
                current.CloseNode();
                closedNodes.Add(current);

                if (current == destination)
                {
                    //done
                    return 1;
                }

                var neighbors = GetNeighbors(current, false);
                neighbors = neighbors.Where(n => current.CanMoveTo(current));

                // calc costs
                foreach(AStarNode neighbor in neighbors)
                {
                    neighbor.ParentNode = current;
                    // since we only move straight the move cost is always the same
                    neighbor.GCost = current.GCost + TileMoveCost;
                    neighbor.HCost = neighbor.GetManhattanDistance(destination) * TileMoveCost;
                    neighbor.OpenNode();
                    openNodes.Add(neighbor);
                }
            }

            return -1;
        }
    }
}