Add post and event cards, shared calendar sheet and per-event ICS; rework past events and next-event card

Elternbeirat.Web.Tests/MarkdownTests.cs

@@ -125,4 +125,63 @@ public class MarkdownTests
     [InlineData("::: hinweis\nText im Baustein.\n:::")]
     public void First_sentence_is_empty_without_a_top_level_paragraph(string? markdown) =>
         Markdown.FirstSentence(markdown).ShouldBe("");
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("## Nur eine Überschrift")]
+    public void Teaser_is_empty_without_paragraph_text(string? markdown) =>
+        Markdown.Teaser(markdown).ShouldBe("");
+
+    [Fact]
+    public void Teaser_keeps_a_short_body_whole() =>
+        Markdown.Teaser("Kurzer Text.").ShouldBe("Kurzer Text.");
+
+    [Fact]
+    public void Teaser_removes_markdown_and_skips_headings()
+    {
+        // Emphasis and link markup go, link text stays; the heading would repeat the
+        // card title, so it is left out. Paragraphs and list items are joined.
+        var teaser = Markdown.Teaser(
+            "## Rückblick\n\nDer **Basar** war ein [Erfolg](/posts).\n\n- Danke an alle\n- Bis bald");
+
+        teaser.ShouldBe("Der Basar war ein Erfolg. Danke an alle Bis bald");
+    }
+
+    [Fact]
+    public void Teaser_cuts_a_long_body_at_a_word_boundary()
+    {
+        var teaser = Markdown.Teaser("Der Basar war ein voller Erfolg.", 20);
+
+        // 20 characters end inside "voller"; the cut falls back to the space before it.
+        teaser.ShouldBe("Der Basar war ein…");
+    }
+
+    [Fact]
+    public void Teaser_keeps_a_word_that_ends_exactly_at_the_limit() =>
+        Markdown.Teaser("Der Basar war ein voller Erfolg.", 17).ShouldBe("Der Basar war ein…");
+
+    [Fact]
+    public void Teaser_drops_punctuation_left_at_the_cut() =>
+        Markdown.Teaser("Liebe Eltern, der Basar war schön.", 14).ShouldBe("Liebe Eltern…");
+
+    [Fact]
+    public void Teaser_cuts_a_single_overlong_word_hard() =>
+        Markdown.Teaser("Donaudampfschifffahrtsgesellschaft", 10).ShouldBe("Donaudampf…");
+
+    [Fact]
+    public void Teaser_defaults_to_160_characters_plus_ellipsis()
+    {
+        var body = string.Join(' ', Enumerable.Repeat("Wort", 100)); // 499 characters
+
+        var teaser = Markdown.Teaser(body);
+
+        teaser.Length.ShouldBeLessThanOrEqualTo(Markdown.TeaserLength + 1);
+        teaser.ShouldEndWith("Wort…");
+    }
+
+    [Fact]
+    public void Teaser_rejects_a_length_of_zero() =>
+        Should.Throw<ArgumentOutOfRangeException>(() => Markdown.Teaser("Text", 0));
 }