using Elternbeirat.Contracts;

namespace Elternbeirat.Web.Features.Layout;

/// <summary>
/// Builds the header and footer navigation from the public pages. Every page
/// carries a required <see cref="Page.Location"/> ("header" or "footer") and an
/// <see cref="Page.Order"/>; this splits them into the two menus, each ordered.
/// </summary>
public static class NavBuilder
{
    /// <summary>Header links, ordered, built from pages with location "header".</summary>
    public static IReadOnlyList<NavLinkItem> Header(IReadOnlyList<Page> pages) =>
        Build(pages, "header");

    /// <summary>Footer links, ordered, built from pages with location "footer".</summary>
    public static IReadOnlyList<NavLinkItem> Footer(IReadOnlyList<Page> pages) =>
        Build(pages, "footer");

    private static List<NavLinkItem> Build(
        IReadOnlyList<Page> pages,
        string location) =>
        [.. pages
            .Where(page => string.Equals(page.Location, location, StringComparison.Ordinal))
            .OrderBy(page => page.Order)
            .Select(page => new NavLinkItem(HrefFor(page.Slug), page.Title))];

    // The home page owns "/" (served by the Home component); every other slug is
    // reached at "/{slug}", where either a literal route or the catch-all content
    // page renders it.
    private static string HrefFor(string slug) =>
        Page.IsHomeSlug(slug) ? "/" : $"/{slug}";
}