itc.pidi-3-docs/figures/code/share-page.cs

using Houston.Model.Documents;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace Houston.Pages.Document;

/// <summary>
/// Anonymous landing page for shared document links. It exposes only metadata derived from the
/// document id and never fetches or renders file contents.
/// </summary>
public class Share : PageModel
{
    [BindProperty(SupportsGet = true)]
    public string Id { get; set; } = String.Empty;

    public string Title { get; private set; } = "Dokument";

    public string ImageUrl { get; private set; } = String.Empty;

    public string ExplorerUrl { get; private set; } = String.Empty;

    public IActionResult OnGet()
    {
        var docId = new DocumentId(Id);

        if (!docId.TryDecode(out var relativePath))
            return NotFound();

        var type = relativePath.Value.Type;
        var name = relativePath.Value.Name;
        var iconPath = type.PreviewPath;

        Title = name.DisplayName;
        ImageUrl = AbsoluteUrl(iconPath);
        ExplorerUrl = AbsoluteUrl("/documents", BuildExplorerQuery(type, name), $"#{Documents.DocumentViewId(docId)}");

        return Page();
    }

    private static QueryString BuildExplorerQuery(DocumentType? type, DocumentName name)
    {
        return new QueryBuilder {
            { "q", name.DisplayName },
            { "types", type.Name }
        }.ToQueryString();
    }

    private string AbsoluteUrl(string path, QueryString query = default, string? fragment = null)
    {
        return UriHelper.BuildAbsolute(
            Request.Scheme,
            Request.Host,
            Request.PathBase,
            path,
            query,
            fragment: fragment is null ? default : new FragmentString(fragment)
        );
    }
}