Added the guided chat to the BeyondFacts Lab (#1177)

app/MindWork AI Studio/Assistants/BeyondFactsLab/BflTokenBudget.cs

@@ -0,0 +1,40 @@
+using AIStudio.Chat;
+
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Decides how much room a chat of the BeyondFacts Lab has left in the context of its model.
+/// </summary>
+/// <remarks>
+/// Every request carries the guide of the lab, so a conversation fills the context faster than an ordinary chat.
+/// A model which loses the beginning of its context loses its instructions first; therefore, the lab stops before.
+/// </remarks>
+public static class BflTokenBudget
+{
+    /// <summary>
+    /// From which share of the context on the lab warns.
+    /// </summary>
+    public const double WARNING_SHARE = 0.8;
+
+    /// <summary>
+    /// How many tokens the lab keeps free for the next message and its answer.
+    /// </summary>
+    public const int RESERVE_TOKENS = 4_096;
+
+    /// <summary>
+    /// Decides how much room a chat has left.
+    /// </summary>
+    /// <param name="tokens">What the conversation costs, with the system prompt, and the context of the model.</param>
+    /// <returns>The state of the budget.</returns>
+    public static BflTokenBudgetState Of(ConversationTokens tokens)
+    {
+        if (!tokens.IsKnown || !tokens.Window.IsKnown)
+            return BflTokenBudgetState.UNKNOWN;
+
+        var window = tokens.Window.DefaultTokens;
+        if (tokens.Tokens > window - RESERVE_TOKENS)
+            return BflTokenBudgetState.FULL;
+
+        return tokens.Tokens >= window * WARNING_SHARE ? BflTokenBudgetState.WARNING : BflTokenBudgetState.OK;
+    }
+}