DocsPageState.cs

using Microsoft.AspNetCore.Components;
using ShellDocs.Core;
using ShellDocs.Markdown;

namespace ShellDocs.Components;

// Populated by MarkdownContent on each page render, read by DocsLayout's chrome
// (TOC, PrevNext, Breadcrumb) so those components don't need per-page wiring.
public sealed class DocsPageState : IDisposable
{
 private readonly NavigationGraph _graph;
 private readonly NavigationManager _nav;

 public DocsPageState(NavigationGraph graph, NavigationManager nav)
 {
 _graph = graph;
 _nav = nav;
 _nav.LocationChanged += OnLocationChanged;
 }

 public RenderedDocument? Document { get; private set; }
 public NavigationNode? CurrentNode { get; private set; }
 public NavigationNode? Prev { get; private set; }
 public NavigationNode? Next { get; private set; }
 public IReadOnlyList<NavigationNode> Breadcrumbs { get; private set; } = Array.Empty<NavigationNode>();

 public event Action? OnChange;

 public void SetDocument(RenderedDocument? document)
 {
 Document = document;
 Recompute();
 }

 private void OnLocationChanged(object? sender, Microsoft.AspNetCore.Components.Routing.LocationChangedEventArgs e)
 => Recompute();

 private void Recompute()
 {
 var path = new Uri(_nav.Uri).AbsolutePath;
 CurrentNode = _graph.ResolveByUrl(path);
 if (CurrentNode is null)
 {
 Prev = Next = null;
 Breadcrumbs = Array.Empty<NavigationNode>();
 }
 else
 {
 (Prev, Next) = _graph.GetPrevNext(CurrentNode);
 Breadcrumbs = _graph.GetBreadcrumb(CurrentNode);
 }
 OnChange?.Invoke();
 }

 public void Dispose() => _nav.LocationChanged -= OnLocationChanged;
}