Beam/Beam.Dynamic/DataProviders/RelationalDataProvider.cs

using Beam.Abstractions;
using HtmlAgilityPack;

namespace Beam.Dynamic;

public enum RelationType {
    Parent,
    Child,
    NextSibling,
    PreviousSibling,
}

public class RelationalDataProvider : IComposableDataProvider<HtmlNode?> {
    
    public RelationType RelationType { get; set; } = RelationType.Parent;
    public int Distance { get; set; } = 1;
    public IBinding? Content { get; set; }
    
    public HtmlNode? Get(HtmlDocument document) {
        return Select(document);
    }
    public HtmlNode? Get(HtmlNode node) {
        return Select(node);
    }
    public HtmlNode? Select(HtmlDocument doc) {
        return Select(Content?.Select(doc) ?? doc.DocumentNode);
    }
    public HtmlNode? Select(HtmlNode node) {
        return _Select(node, Distance);
    }

    private HtmlNode? _Select(HtmlNode node, int distance = 0) {
        while (true) {
            if (distance == 0) return node;
            node = RelationType switch {
                RelationType.Parent => node.ParentNode,
                RelationType.Child => node.FirstChild,
                RelationType.NextSibling => node.NextSibling,
                RelationType.PreviousSibling => node.PreviousSibling,
                _ => throw new NotSupportedException()
            };
            distance = distance - 1;
        }
    }
}