//Source : http://en.wikipedia.org/wiki/Pathfinding
//TODO: Still needs improvement
//A good way to improve both this algorithm and the a* one, would be to load the Nodes when the map is created,
//and keep them either in TileMap or in each tile. Or something like that.
/// <summary>
/// Find the closest element or the chosen type from the from point.
/// </summary>
/// <typeparam name="T">Type of the object we are looking for.</typeparam>
/// <param name="from">The position we're starting from.</param>
/// <param name="validate">A lambda operation to validate if the object found is good. If the lamdba operation fails, the algorithm will look for another one. Note : Won't be tested if null.</param>
/// <returns>Return the closest object found. If none are found, returns null.</returns>
public static T FindClosest <T>(Point from, Func <T, bool> validate = null, bool includeChilds = false) where T : GameObject
{
int nbElements = TileMap.Width * TileMap.Height;
int nbSolidItems = 0;
List <DijkstraNode> nodes = new List <DijkstraNode>();
for (int i = 0; i < nbElements; i++)
{
int x = i % TileMap.Width;
int y = (int)Math.Floor((double)(i / TileMap.Width));
nodes.Add(new DijkstraNode()
{
Distance = int.MaxValue,
Position = new Point(x, y)
});
if (!IsWalkable(new Point(x, y)))
{
nbSolidItems++;
}
}
DijkstraNode start = nodes.FirstOrDefault(x => x.Position == from);
start.Distance = 0;
List <DijkstraNode> Q = nodes.ToList();
//We don't want to check the solid items in the path, but want to keep them
//because we may be looking for them.
while (Q.Count - nbSolidItems > 0)
{
//TODO : Improve it?
//DijkstraNode u =
// Q.Where(x => IsWalkable(x.Position)) //Get all non-solid items
// .MinBy(o => o.Distance);
//What is better : MinBy or Aggregate?
//.Aggregate((curmin, x) => (curmin == null || x.Distance < curmin.Distance ? x : curmin)); //Get the one with the smallest value
DijkstraNode u = Q[0];
for (int i = 1; i < Q.Count; i++)
{
DijkstraNode n = Q[i];
if (IsWalkable(n.Position) && n.Distance < u.Distance)
{
u = n;
}
}
Q.Remove(u);
if (u.Distance == int.MaxValue)
{
break;
}
u.SetNeighbors(nodes);
foreach (DijkstraNode v in u.Neighbors)
{
T obj = TileMap.Tiles[v.Position.X, v.Position.Y].GetFirstObject <T>(includeChilds);
if (obj != null)
{
if (validate == null ||
validate.Invoke(obj))
{
return(obj);
}
}
int alt = u.Distance + 1;
if (alt < v.Distance)
{
v.Distance = alt;
v.Previous = u;
}
}
}
return(null);
}
