Added a way to read what the AI received from your sources (#1100)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/Tests/Components/ContentViewerTests.cs

@@ -0,0 +1,92 @@
+using AIStudio.Components;
+using AIStudio.Tools;
+
+using Markdig.Extensions.Mathematics;
+using Markdig.Syntax;
+
+namespace AIStudio.Tests.Components;
+
+/// <summary>
+/// Checks how much of a long text the content viewer shows.
+/// </summary>
+/// <remarks>
+/// The viewer shows only the beginning of a text which is too long to render, and it must not tear
+/// a line apart while doing so: a cut through a table row or a code fence would show the user a
+/// broken document, as if we had read it wrong.
+/// </remarks>
+[TestFixture]
+public sealed class ContentViewerTests
+{
+    [Test]
+    public void ATextWhichFitsIsShownEntirely()
+    {
+        const string TEXT = "# Heading\nA short passage.";
+
+        var shown = ContentViewer.CutAtLineBreak(TEXT, 100, out var cutOffCharacters);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(shown, Is.SameAs(TEXT));
+            Assert.That(cutOffCharacters, Is.Zero);
+        });
+    }
+
+    [Test]
+    public void ATextOfExactlyTheLimitIsShownEntirely()
+    {
+        var text = new string('a', 50);
+
+        var shown = ContentViewer.CutAtLineBreak(text, 50, out var cutOffCharacters);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(shown, Is.EqualTo(text));
+            Assert.That(cutOffCharacters, Is.Zero);
+        });
+    }
+
+    [Test]
+    public void ALongTextIsCutAfterTheLastLineBreakBeforeTheLimit()
+    {
+        const string TEXT = "| a | b |\n| 1 | 2 |\n| 3 | 4 |";
+
+        var shown = ContentViewer.CutAtLineBreak(TEXT, 25, out var cutOffCharacters);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(shown, Is.EqualTo("| a | b |\n| 1 | 2 |\n"), "The last table row would be torn apart, so it goes as a whole.");
+            Assert.That(cutOffCharacters, Is.EqualTo(TEXT.Length - shown.Length));
+        });
+    }
+
+    [Test]
+    public void DollarSignsInContentAreNoMath()
+    {
+        //
+        // Taken for math, the text would have MudMarkdown typeset the whole page with MathJax, which
+        // replaces elements Blazor renders, so that the next render of the viewer fails:
+        //
+        const string TEXT = "The budget $\\rho$ is spent on the hardest tokens.";
+        static bool HasMath(Markdig.MarkdownPipeline pipeline) => Markdig.Markdown.Parse(TEXT, pipeline).Descendants<MathInline>().Any();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(HasMath(Markdown.SAFE_MARKDOWN_PIPELINE), Is.True, "The safe pipeline reads this as math.");
+            Assert.That(HasMath(Markdown.CONTENT_MARKDOWN_PIPELINE), Is.False, "What AI Studio read from a document stays text.");
+        });
+    }
+
+    [Test]
+    public void ALongTextWithoutLineBreaksIsCutAtTheLimit()
+    {
+        var text = new string('a', 30);
+
+        var shown = ContentViewer.CutAtLineBreak(text, 20, out var cutOffCharacters);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(shown, Has.Length.EqualTo(20));
+            Assert.That(cutOffCharacters, Is.EqualTo(10));
+        });
+    }
+}