Make state editable by the user, add deepcopy to fields that require it

LLama/ChatSession.cs

@@ -8,6 +8,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using LLama.Abstractions;
 using LLama.Common;
+using static LLama.Common.ChatHistory;
 using static LLama.InteractiveExecutor;
 using static LLama.LLamaContext;
 using static LLama.StatefulExecutorBase;
@@ -53,19 +54,16 @@ public class ChatSession
     /// </summary>
     /// <param name="executor">The executor for this session</param>
     /// <param name="history">History for this session</param>
-    /// <param name="cancellationToken">Cancellation token to stop session pre-processing</param>
     /// <returns></returns>
     public static async Task<ChatSession> InitializeSessionFromHistoryAsync(
-        ILLamaExecutor executor,
-        ChatHistory history,
-        CancellationToken cancellationToken = default)
+        ILLamaExecutor executor, ChatHistory history)
     {
         if (executor is not StatefulExecutorBase statefulExecutor)
         {
             throw new ArgumentException("Executor must have a StatefulExecutorBase", nameof(executor));
         }
         var session = new ChatSession(executor, history);
-        await statefulExecutor.AddPromptAsync(session.HistoryTransform.HistoryToText(history), cancellationToken);
+        await statefulExecutor.PrefillPromptAsync(session.HistoryTransform.HistoryToText(history));
         return session;
     }
 
@@ -164,13 +162,13 @@ public class ChatSession
     /// <returns>SessionState object representing session state in-memory</returns>
     public SessionState GetSessionState()
     {
-        return new SessionState(Executor.Context.GetState(), ((StatefulExecutorBase)Executor).GetStateData())
-        {
-            InputTransformPipeline = InputTransformPipeline,
-            OutputTransform = OutputTransform,
-            HistoryTransform = HistoryTransform,
-            History = History.ToJson()
-        };
+        return new SessionState(
+            Executor.Context.GetState(),
+            ((StatefulExecutorBase)Executor).GetStateData(),
+            History,
+            InputTransformPipeline,
+            OutputTransform,
+            HistoryTransform);
     }
 
     /// <summary>
@@ -183,18 +181,17 @@ public class ChatSession
     {
         if (Executor is StatefulExecutorBase statefulExecutor)
         {
-            statefulExecutor.LoadState(
-                JsonSerializer.Deserialize(
-                    state.ExecutorState, statefulExecutor.GetStateData().GetType()
-                ) as ExecutorBaseState ?? throw new ArgumentException("Executor state is invalid", nameof(state))
-            );
+            statefulExecutor.LoadState(state.ExecutorState);
         }
         else
         {
             throw new ArgumentException("Executor must be a StatefulExecutorBase to support loading of session state", nameof(state));
         }
         Executor.Context.LoadState(state.ContextState);
-        History = ChatHistory.FromJson(state.History) ?? new();
+        History = new ChatHistory(state.History);
+        InputTransformPipeline = state.InputTransformPipeline.ToList();
+        OutputTransform = state.OutputTransform;
+        HistoryTransform = state.HistoryTransform;
     }
 
     /// <summary>
@@ -288,7 +285,7 @@ public class ChatSession
             content = inputTransform.Transform(content);
         }
 
-        await statefulExecutor.AddPromptAsync(content);
+        await statefulExecutor.PrefillPromptAsync(content);
 
         History.AddMessage(AuthorRole.System, content);
         return this;
@@ -593,41 +590,52 @@ public record SessionState
     /// <summary>
     /// Saved executor state for the session in JSON format.
     /// </summary>
-    public string ExecutorState { get; init; }
+    public ExecutorBaseState ExecutorState { get; set; }
 
     /// <summary>
     /// Saved context state (KV cache) for the session.
     /// </summary>
-    public State ContextState { get; init; }
+    public State ContextState { get; set; }
 
     /// <summary>
     /// The input transform pipeline used in this session.
     /// </summary>
-    public List<ITextTransform> InputTransformPipeline { get; init; } = new();
+    public ITextTransform[] InputTransformPipeline { get; set; } = Array.Empty<ITextTransform>();
 
     /// <summary>
     /// The output transform used in this session.
     /// </summary>
-    public ITextStreamTransform OutputTransform { get; init; } = new LLamaTransforms.EmptyTextOutputStreamTransform();
+    public ITextStreamTransform OutputTransform { get; set; } = new LLamaTransforms.EmptyTextOutputStreamTransform();
 
     /// <summary>
     /// The history transform used in this session.
     /// </summary>
-    public IHistoryTransform HistoryTransform { get; init; } = new LLamaTransforms.DefaultHistoryTransform();
+    public IHistoryTransform HistoryTransform { get; set; } = new LLamaTransforms.DefaultHistoryTransform();
     
     /// <summary>
-    /// The JSON representation of the chat history for this session.
+    /// The the chat history messages for this session.
     /// </summary>
-    public string History { get; init; } = new ChatHistory().ToJson();
+    public Message[] History { get; set; } = Array.Empty<Message>();
 
     /// <summary>
     /// Create a new session state.
     /// </summary>
     /// <param name="contextState"></param>
     /// <param name="executorState"></param>
-    public SessionState(State contextState, ExecutorBaseState executorState)
+    /// <param name="history"></param>
+    /// <param name="inputTransformPipeline"></param>
+    /// <param name="outputTransform"></param>
+    /// <param name="historyTransform"></param>
+    public SessionState(
+        State contextState, ExecutorBaseState executorState, 
+        ChatHistory history, List<ITextTransform> inputTransformPipeline,
+        ITextStreamTransform outputTransform, IHistoryTransform historyTransform)
     {
         ContextState = contextState;
-        ExecutorState = JsonSerializer.Serialize(executorState);
+        ExecutorState = executorState;
+        History = history.Messages.ToArray();
+        InputTransformPipeline = inputTransformPipeline.ToArray();
+        OutputTransform = outputTransform;
+        HistoryTransform = historyTransform;
     }
 }

LLama/Common/ChatHistory.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -80,6 +81,15 @@ namespace LLama.Common
         [JsonConstructor]
         public ChatHistory() { }
 
+        /// <summary>
+        /// Create a new instance of the chat history from array of messages
+        /// </summary>
+        /// <param name="messageHistory"></param>
+        public ChatHistory(Message[] messageHistory)
+        {
+            this.Messages = messageHistory.ToList();
+        }
+
         /// <summary>
         /// Add a message to the chat history
         /// </summary>