Add news post type with list and detail routes

Elternbeirat.Web/Services/PostService.cs

@@ -0,0 +1,86 @@
+using System.Globalization;
+using Markdig;
+
+namespace Elternbeirat.Web.Services;
+
+/// <summary>
+/// Reads the news posts from <c>Content/beitraege/*.md</c>, renders them to HTML
+/// once at startup and keeps them in memory, sorted newest first. Registered as
+/// a singleton because the content lives in the image and does not change at
+/// runtime.
+/// </summary>
+public sealed class PostService
+{
+    private readonly IReadOnlyList<Post> _posts;
+    private readonly IReadOnlyDictionary<string, Post> _postsBySlug;
+
+    /// <summary>
+    /// Reads every Markdown post from the <c>Content/beitraege</c> directory
+    /// below the application root and caches it.
+    /// </summary>
+    public PostService(IWebHostEnvironment environment)
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseYamlFrontMatter()
+            .Build();
+
+        var directory = Path.Combine(environment.ContentRootPath, "Content", "beitraege");
+        var posts = new List<Post>();
+
+        if (Directory.Exists(directory))
+        {
+            foreach (var path in Directory.EnumerateFiles(directory, "*.md"))
+            {
+                posts.Add(Read(path, pipeline));
+            }
+        }
+
+        // Newest first for the list; a stable slug order breaks date ties.
+        posts.Sort((a, b) =>
+        {
+            var byDate = b.Date.CompareTo(a.Date);
+            return byDate != 0 ? byDate : string.CompareOrdinal(a.Slug, b.Slug);
+        });
+
+        _posts = posts;
+        _postsBySlug = posts.ToDictionary(p => p.Slug, StringComparer.OrdinalIgnoreCase);
+    }
+
+    /// <summary>
+    /// All posts, newest first. Used for the overview list.
+    /// </summary>
+    public IReadOnlyList<Post> All => _posts;
+
+    /// <summary>
+    /// Returns the post for the given slug, or <c>null</c> if there is none.
+    /// The lookup is case-insensitive.
+    /// </summary>
+    public Post? Find(string slug) =>
+        _postsBySlug.GetValueOrDefault(slug);
+
+    private static Post Read(string path, MarkdownPipeline pipeline)
+    {
+        var slug = Path.GetFileNameWithoutExtension(path);
+        var source = File.ReadAllText(path);
+
+        var document = Markdown.Parse(source, pipeline);
+        var title = FrontMatter.Read("titel", document, source) ?? slug;
+        var date = ParseDate(FrontMatter.Read("datum", document, source));
+        var html = Markdown.ToHtml(source, pipeline);
+
+        return new Post { Slug = slug, Title = title, Date = date, ContentHtml = html };
+    }
+
+    /// <summary>
+    /// Parses the <c>datum:</c> value as an ISO date (yyyy-MM-dd). Falls back to
+    /// <see cref="DateOnly.MinValue"/> when the value is missing or malformed,
+    /// so a single bad file does not crash startup — it just sorts last.
+    /// </summary>
+    private static DateOnly ParseDate(string? value)
+    {
+        return DateOnly.TryParse(value, CultureInfo.InvariantCulture,
+            DateTimeStyles.None, out var date)
+            ? date
+            : DateOnly.MinValue;
+    }
+}