private static TreeZipper FindNode(string value, TreeZipper zipper)
{
if (zipper == null || zipper.Focus.Value.CompareTo(value) == 0)
{
return(zipper);
}
return(FindNode(value, GoDown(zipper)) ?? FindNode(value, GoRight(zipper)));
}
private static TreeZipper GoDown(TreeZipper zipper)
{
if (zipper == null || !zipper.Focus.Children.Any())
{
return(null);
}
var focus = zipper.Focus;
var children = focus.Children;
var newCrumb = new TreeCrumb(focus.Value, Array.Empty <Tree>(), children.Skip(1).ToArray());
return(new TreeZipper(children.First(), new[] { newCrumb }.Concat(zipper.Crumbs)));
}
private static TreeZipper GoRight(TreeZipper zipper)
{
if (zipper == null || !zipper.Crumbs.Any() || !zipper.Crumbs.First().Right.Any())
{
return(null);
}
var crumbs = zipper.Crumbs;
var firstCrumb = crumbs.First();
var newCrumb = new TreeCrumb(firstCrumb.Value, firstCrumb.Left.Concat(new[] { zipper.Focus }).ToArray(), firstCrumb.Right.Skip(1).ToArray());
return(new TreeZipper(firstCrumb.Right.First(), new[] { newCrumb }.Concat(crumbs.Skip(1))));
}
private static Tree ChangeParent(TreeZipper zipper)
{
if (zipper == null)
{
return(null);
}
if (!zipper.Crumbs.Any())
{
return(zipper.Focus);
}
var firstCrumb = zipper.Crumbs.First();
var focus = zipper.Focus;
var newZipper = new TreeZipper(new Tree(firstCrumb.Value, firstCrumb.Left.Concat(firstCrumb.Right).ToArray()), zipper.Crumbs.Skip(1));
var parentGraph = ChangeParent(newZipper);
var ys = focus.Children.Concat(new[] { parentGraph }).ToArray();
return(new Tree(focus.Value, ys));
}
private static IEnumerable <string> ZipperToPath(TreeZipper zipper)
{
return(zipper?.Crumbs.Select(c => c.Value).Reverse().Concat(new[] { zipper.Focus.Value }));
}
