Added the Model Comparison assistant for blind comparisons of two models (#1009)

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

app/MindWork AI Studio/Chat/ChatTranscript.cs

@@ -0,0 +1,79 @@
+using System.Text;
+
+namespace AIStudio.Chat;
+
+/// <summary>
+/// Writes what the user sees of a chat as plain text, for a model which reads the chat, such as a judge.
+/// </summary>
+/// <remarks>
+/// Only the messages the user sees count: hidden requests, the results of tools, and the content of attached files
+/// stay out. A call of a tool is one line with its name and its arguments, each shortened, so that a reader learns what
+/// the model looked up without reading everything it got back. The thinking of a model stays out as well.
+/// </remarks>
+public static class ChatTranscript
+{
+    /// <summary>
+    /// How many characters of each argument of a tool call the transcript keeps.
+    /// </summary>
+    public const int MAX_ARGUMENT_LENGTH = 80;
+
+    /// <summary>
+    /// Writes the transcript of a chat.
+    /// </summary>
+    /// <param name="thread">The chat.</param>
+    /// <returns>The messages in their order, each below a line naming who wrote it.</returns>
+    public static string Of(ChatThread thread)
+    {
+        var transcript = new StringBuilder();
+        foreach (var block in thread.Blocks)
+        {
+            if (block is not { HideFromUser: false, Content: ContentText content })
+                continue;
+
+            var message = Message(block.Role, content);
+            if (message.Length == 0)
+                continue;
+
+            if (transcript.Length > 0)
+                transcript.AppendLineLF();
+
+            transcript.AppendLineLF(block.Role is ChatRole.USER ? "[User]" : "[Assistant]");
+            transcript.AppendLineLF(message);
+        }
+
+        return transcript.ToString().TrimEnd();
+    }
+
+    /// <summary>
+    /// Writes one message: the calls of tools first, since the model made them before it answered, then the text, then
+    /// the names of attached files.
+    /// </summary>
+    private static string Message(ChatRole role, ContentText content)
+    {
+        var lines = new List<string>();
+        if (role is ChatRole.AI)
+            lines.AddRange(content.ToolInvocations.OrderBy(call => call.Order).Select(call => $"[Tool call: {call.ToolName}({Arguments(call.Arguments)})]"));
+
+        var text = role is ChatRole.AI ? content.Text.RemoveThinkTags().Trim() : content.Text.Trim();
+        if (text.Length > 0)
+            lines.Add(text);
+
+        if (content.FileAttachments.Count > 0)
+            lines.Add($"[Attached files: {string.Join(", ", content.FileAttachments.Select(attachment => attachment.FileName))}]");
+
+        return string.Join('\n', lines);
+    }
+
+    private static string Arguments(IReadOnlyDictionary<string, string> arguments) => string.Join(", ", arguments.Select(argument => $"{argument.Key}={Shortened(argument.Value)}"));
+
+    private static string Shortened(string value)
+    {
+        var singleLine = value.ReplaceLineEndings(" ").Trim();
+        if (singleLine.Length <= MAX_ARGUMENT_LENGTH)
+            return singleLine;
+
+        // Cutting between the two halves of a character outside the basic plane would leave half of it:
+        var length = char.IsHighSurrogate(singleLine[MAX_ARGUMENT_LENGTH - 1]) ? MAX_ARGUMENT_LENGTH - 1 : MAX_ARGUMENT_LENGTH;
+        return singleLine[..length] + "…";
+    }
+}