Implementation of NearestNeighbour in Quadtree

[KovacicB]

Is there a way to implement NearestNeighbour method in Quadtree? As there is no method currently implemented in that class, I was trying to adjust STRTree's implementation to work with Quadtree but the issue I have is at defining and / or using Root.

1  public static TopologyNode[] NearestNeighbours(this Quadtree<TopologyNode> tree, TopologyNode item, IItemDistance dist, int k)
2  {
3    if (tree.IsEmpty)
4    {
5      return Array.Empty<TopologyNode>();
6    }

7    var bnd = new ItemBoundable<Envelope, TopologyNode> (item.Shape!.EnvelopeInternal, item);
8    var bp = new BoundablePair<TopologyNode>(tree.Root, bnd, dist); // Issue with tree.Root
9    return NearestNeighbourK(bp, k);
10 }

Issue is in line 8 as tree.Root is of type TopologyNode and not of type IBoundable<Envelope, TopologyNode>. If I created new ItemBoundable and then use it I don't have the slightest idea which item and its envelope to insert as parameters, e.g.:

1  public static TopologyNode[] NearestNeighbours(this Quadtree<TopologyNode> tree, TopologyNode item, IItemDistance dist, int k)
2  {
3    if (tree.IsEmpty)
4    {
5      return Array.Empty<TopologyNode>();
6    }

7    var root = new ItemBoundable<Envelope, TopologyNode> (...); // What to insert here?
8    var bnd = new ItemBoundable<Envelope, TopologyNode> (item.Shape!.EnvelopeInternal, item);
9    var bp = new BoundablePair<TopologyNode>(root, bnd, dist);
10   return NearestNeighbourK(bp, k);
11 }

It may be that I am not using the correct data structure but what I need is a data structure (tree) for:

1. Dinamically adding nodes into the tree (that's why STRTree is not suitable)
2. Executing NearestNeighbours on the tree.

I would greatly appreciate the help and ideas!

[KovacicB]

Resolved in #682.
If needed an extension method can be implemented.