Fix standalone HTML and LaTeX exports

app/MindWork AI Studio/Tools/PlainFileExport.cs

@@ -1,6 +1,7 @@
 using System.Text;
 
 using AIStudio.Tools.PluginSystem;
+using AIStudio.Tools.Rust;
 using AIStudio.Tools.Services;
 
 using Markdig.Extensions.Tables;
@@ -15,6 +16,42 @@ public static class PlainFileExport
 
     private static string TB(string fallbackEn) => I18N.I.T(fallbackEn, typeof(PlainFileExport).Namespace, nameof(PlainFileExport));
 
+    /// <summary>
+    /// Reads a complete HTML or LaTeX source file out of a message which consists only of the
+    /// matching fenced code block.
+    /// </summary>
+    /// <param name="markdown">The Markdown text the model wrote.</param>
+    /// <param name="format">The source format to extract.</param>
+    /// <param name="source">The contents inside the fence, or an empty string when the message is
+    /// not a standalone source file.</param>
+    /// <returns>True, when the message is a complete source file for the selected format.</returns>
+    internal static bool TryExtractStandaloneSource(string markdown, FileExportFormat format, out string source)
+    {
+        source = string.Empty;
+
+        var languages = format switch
+        {
+            FileExportFormat.HTML => new[] { "html" },
+            FileExportFormat.LATEX => new[] { "latex", "tex" },
+
+            _ => [],
+        };
+
+        if (languages.Length is 0 || string.IsNullOrWhiteSpace(markdown))
+            return false;
+
+        var document = Markdig.Markdown.Parse(markdown, Markdown.SAFE_MARKDOWN_PIPELINE);
+        if (document.Count is not 1 || document[0] is not FencedCodeBlock block || block.ClosingFencedCharCount is 0)
+            return false;
+
+        var language = block.Info?.Trim();
+        if (!languages.Any(candidate => string.Equals(candidate, language, StringComparison.OrdinalIgnoreCase)))
+            return false;
+
+        source = block.Lines.ToString();
+        return true;
+    }
+
     /// <summary>
     /// Reads every table a message holds, in the order they appear in it.
     /// </summary>
@@ -183,6 +220,30 @@ public static class PlainFileExport
         if (format.UsesPandoc() || format.ToFileTypeFilter() is not { } fileTypeFilter)
             throw new ArgumentOutOfRangeException(nameof(format), format, "AI Studio cannot write this format itself.");
 
+        return await WriteFile(rustService, dialogTitle, format, fileContent, fileTypeFilter, fileName);
+    }
+
+    /// <summary>
+    /// Writes HTML or LaTeX source authored by the model without converting it.
+    /// </summary>
+    /// <param name="rustService">The Rust service, used for the save dialog.</param>
+    /// <param name="dialogTitle">The title of the save dialog.</param>
+    /// <param name="format">The matching HTML or LaTeX format.</param>
+    /// <param name="source">The source text inside the model's code fence.</param>
+    /// <returns>True, when the file was written.</returns>
+    internal static async Task<bool> ToSourceFile(RustService rustService, string dialogTitle, FileExportFormat format, string source)
+    {
+        if (format is not (FileExportFormat.HTML or FileExportFormat.LATEX) || format.ToFileTypeFilter() is not { } fileTypeFilter)
+            throw new ArgumentOutOfRangeException(nameof(format), format, "AI Studio cannot write this format as an authored source file.");
+
+        return await WriteFile(rustService, dialogTitle, format, source, fileTypeFilter);
+    }
+
+    /// <summary>
+    /// Lets the user choose a path and writes text with the encoding of its format.
+    /// </summary>
+    private static async Task<bool> WriteFile(RustService rustService, string dialogTitle, FileExportFormat format, string fileContent, FileTypeFilter fileTypeFilter, string? fileName = null)
+    {
         var response = await rustService.SaveFile(dialogTitle, [fileTypeFilter], format.ToSuggestedFileName(fileName));
         if (response.UserCancelled)
         {
@@ -206,4 +267,4 @@ public static class PlainFileExport
             return false;
         }
     }
-}
+}