Improved data security for chat threads (#317)

app/MindWork AI Studio/Chat/ChatThreadExtensions.cs

@@ -0,0 +1,58 @@
+using AIStudio.Provider.SelfHosted;
+using AIStudio.Settings.DataModel;
+
+namespace AIStudio.Chat;
+
+public static class ChatThreadExtensions
+{
+    /// <summary>
+    /// Checks if the specified provider is allowed for the chat thread.
+    /// </summary>
+    /// <remarks>
+    /// We don't check if the provider is allowed to use the data sources of the chat thread.
+    /// That kind of check is done in the RAG process itself.<br/><br/>
+    /// 
+    /// One thing which is not so obvious: after RAG was used on this thread, the entire chat
+    /// thread is kind of a data source by itself. Why? Because the augmentation data collected
+    /// from the data sources is stored in the chat thread. This means we must check if the
+    /// selected provider is allowed to use this thread's data.
+    /// </remarks>
+    /// <param name="chatThread">The chat thread to check.</param>
+    /// <param name="provider">The provider to check.</param>
+    /// <returns>True, when the provider is allowed for the chat thread. False, otherwise.</returns>
+    public static bool IsLLMProviderAllowed<T>(this ChatThread? chatThread, T provider)
+    {
+        // No chat thread available means we have a new chat. That's fine:
+        if (chatThread is null)
+            return true;
+        
+        // The chat thread is available, but the data security is not specified.
+        // Means, we never used RAG or RAG was enabled, but no data sources were selected.
+        // That's fine as well:
+        if (chatThread.DataSecurity is DataSourceSecurity.NOT_SPECIFIED)
+            return true;
+
+        //
+        // Is the provider self-hosted?
+        //
+        var isSelfHostedProvider = provider switch
+        {
+            ProviderSelfHosted => true,
+            AIStudio.Settings.Provider p => p.IsSelfHosted,
+            
+            _ => false,
+        };
+        
+        //
+        // Check the chat data security against the selected provider:
+        //
+        return isSelfHostedProvider switch
+        {
+            // The provider is self-hosted -- we can use any data source:
+            true => true,
+            
+            // The provider is not self-hosted -- it depends on the data security of the chat thread:
+            false => chatThread.DataSecurity is not DataSourceSecurity.SELF_HOSTED,
+        };
+    }
+}