Added an optional notice for AI-generated content (#884)

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

app/Tests/Tools/AIGeneratedContentDisclosureServiceTests.cs

@@ -0,0 +1,82 @@
+using AIStudio.Settings;
+using AIStudio.Tools;
+using AIStudio.Tools.Services;
+
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks the notice which says that AI generated an answer the user copies or exports.
+/// </summary>
+/// <remarks>
+/// The notice must leave the answer itself untouched, and it must read as a notice: not as part of the
+/// last list item, not inside a code block the answer left open, and not with stray backslashes. Until
+/// somebody switches it on, it stays away entirely.
+/// </remarks>
+[TestFixture]
+public sealed class AIGeneratedContentDisclosureServiceTests
+{
+    private const string NOTICE = @"**This content was generated using artificial intelligence \(AI\)\.**";
+
+    [Test]
+    public void TheNoticeIsOffByDefault()
+    {
+        var settingsManager = CreateSettingsManager();
+        var service = new AIGeneratedContentDisclosureService(settingsManager);
+
+        Assert.That(settingsManager.ConfigurationData.App.AddAIGeneratedContentDisclosure, Is.False);
+        Assert.That(service.AddDisclosureToMarkdown("The answer."), Is.EqualTo("The answer."), "Without the setting, the answer leaves AI Studio as it is.");
+    }
+
+    [Test]
+    public void TheNoticeEndsTheAnswerAsAParagraphOfItsOwn()
+    {
+        var answer = Lines("- first point", "- second point");
+
+        Assert.That(CreateServiceWithNotice().AddDisclosureToMarkdown(answer), Is.EqualTo(Lines(answer, string.Empty, NOTICE)));
+    }
+
+    [Test]
+    public void TrailingLineBreaksDoNotWidenTheGap()
+    {
+        var answer = Lines("The answer.", string.Empty, string.Empty);
+
+        Assert.That(CreateServiceWithNotice().AddDisclosureToMarkdown(answer), Is.EqualTo(Lines("The answer.", string.Empty, NOTICE)));
+    }
+
+    [TestCase("")]
+    [TestCase("   ")]
+    public void AnEmptyAnswerStaysEmpty(string answer)
+    {
+        Assert.That(CreateServiceWithNotice().AddDisclosureToMarkdown(answer), Is.EqualTo(answer), "A notice alone would say that AI wrote something which is not there.");
+    }
+
+    [Test]
+    public void AnOpenCodeBlockIsClosedBeforeTheNotice()
+    {
+        var answer = Lines("Here is the code:", string.Empty, "```csharp", "var answer = 42;");
+
+        Assert.That(CreateServiceWithNotice().AddDisclosureToMarkdown(answer), Is.EqualTo(Lines(answer, "```", string.Empty, NOTICE)));
+    }
+
+    [Test]
+    public void TheNoticeIsShownAsBoldTextBelowTheCode()
+    {
+        var answer = Lines("```csharp", "var answer = 42;");
+        var html = Markdig.Markdown.ToHtml(CreateServiceWithNotice().AddDisclosureToMarkdown(answer), Markdown.SAFE_MARKDOWN_PIPELINE);
+
+        Assert.That(html.TrimEnd(), Does.EndWith("</code></pre>\n<p><strong>This content was generated using artificial intelligence (AI).</strong></p>"), "The escapes keep the parentheses and the period as plain text, and the closed fence keeps the notice out of the code block.");
+    }
+
+    private static AIGeneratedContentDisclosureService CreateServiceWithNotice()
+    {
+        var settingsManager = CreateSettingsManager();
+        settingsManager.ConfigurationData.App.AddAIGeneratedContentDisclosure = true;
+        return new AIGeneratedContentDisclosureService(settingsManager);
+    }
+
+    private static SettingsManager CreateSettingsManager() => new(NullLogger<SettingsManager>.Instance, null!);
+
+    private static string Lines(params string[] lines) => string.Join(Environment.NewLine, lines);
+}