Map code fence languages to export formats in one place

app/MindWork AI Studio/Tools/FileExportFormatExtensions.cs

@@ -103,6 +103,36 @@ public static class FileExportFormatExtensions
         _ => string.Empty,
     };
 
+    /// <summary>
+    /// Reads which format a model means when it names a language behind the opening fence of a
+    /// code block.
+    /// </summary>
+    /// <remarks>
+    /// A model which answers with a finished file puts it into a code block and names its language,
+    /// as in ```html. Models do not agree on the spelling, so we accept the usual names of a format
+    /// in any case. Only formats which are plain text appear here: a code block holds text, never
+    /// a Word document.
+    /// </remarks>
+    /// <param name="language">The language behind the opening fence, as Markdig reads it into
+    /// FencedCodeBlock.Info.</param>
+    /// <param name="format">The format the language names, or NONE when it names none of ours.</param>
+    /// <returns>True, when the language names a format AI Studio writes.</returns>
+    public static bool TryFromCodeFenceLanguage(string? language, out FileExportFormat format)
+    {
+        format = language?.Trim().ToLowerInvariant() switch
+        {
+            "html" => FileExportFormat.HTML,
+            "latex" or "tex" => FileExportFormat.LATEX,
+            "markdown" or "md" => FileExportFormat.MARKDOWN,
+            "csv" => FileExportFormat.CSV,
+            "tsv" => FileExportFormat.TSV,
+
+            _ => FileExportFormat.NONE,
+        };
+
+        return format is not FileExportFormat.NONE;
+    }
+
     /// <summary>
     /// Returns the file name the save dialog starts with.
     /// </summary>

app/MindWork AI Studio/Tools/PlainFileExport.cs

@@ -94,15 +94,7 @@ public static class PlainFileExport
     /// </summary>
     private static (string Fallback, FileExportFormat Format, string Text)? ToContent(FencedCodeBlock block)
     {
-        var format = block.Info?.Trim() switch
+        if (!FileExportFormatExtensions.TryFromCodeFenceLanguage(block.Info, out var format) || format is not (FileExportFormat.CSV or FileExportFormat.TSV))
-        {
-            "csv" => FileExportFormat.CSV,
-            "tsv" => FileExportFormat.TSV,
-
-            _ => FileExportFormat.NONE,
-        };
-
-        if (format is FileExportFormat.NONE)
             return null;
 
         var content = block.Lines.ToString();

app/Tests/Tools/FileExportFormatTests.cs

@@ -36,4 +36,37 @@ public sealed class FileExportFormatTests
             FileExportFormat.HTML,
         }), "A format was added to or removed from the export menu: say in FollowsPageAnchors whether its reader follows a page in a local link, then name it here.");
     }
+
+    [TestCase("html", FileExportFormat.HTML)]
+    [TestCase("latex", FileExportFormat.LATEX)]
+    [TestCase("tex", FileExportFormat.LATEX)]
+    [TestCase("markdown", FileExportFormat.MARKDOWN)]
+    [TestCase("md", FileExportFormat.MARKDOWN)]
+    [TestCase("csv", FileExportFormat.CSV)]
+    [TestCase("tsv", FileExportFormat.TSV)]
+    [TestCase("HTML", FileExportFormat.HTML, Description = "Models do not agree on the case.")]
+    [TestCase("LaTeX", FileExportFormat.LATEX)]
+    [TestCase("CSV", FileExportFormat.CSV)]
+    [TestCase(" md ", FileExportFormat.MARKDOWN, Description = "Space around the name is no part of it.")]
+    public void AFenceLanguageNamesItsFormat(string language, FileExportFormat expectedFormat)
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(FileExportFormatExtensions.TryFromCodeFenceLanguage(language, out var format), Is.True);
+            Assert.That(format, Is.EqualTo(expectedFormat));
+        });
+    }
+
+    [TestCase("css", TestName = "A language AI Studio writes no file for")]
+    [TestCase("docx", TestName = "A format no code block can hold")]
+    [TestCase("", TestName = "A fence without a language")]
+    [TestCase(null, TestName = "A fence Markdig read no language for")]
+    public void AnyOtherFenceLanguageNamesNoFormat(string? language)
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(FileExportFormatExtensions.TryFromCodeFenceLanguage(language, out var format), Is.False);
+            Assert.That(format, Is.EqualTo(FileExportFormat.NONE));
+        });
+    }
 }