Make text transform interfaces have explicit copy operation

LLama/Abstractions/IHistoryTransform.cs

@@ -21,5 +21,11 @@ namespace LLama.Abstractions
         /// <param name="text">The chat history as plain text.</param>
         /// <returns>The updated history.</returns>
         ChatHistory TextToHistory(AuthorRole role, string text);
+
+        /// <summary>
+        /// Copy the transform.
+        /// </summary>
+        /// <returns></returns>
+        IHistoryTransform Clone();
     }
 }

LLama/Abstractions/ITextStreamTransform.cs

@@ -13,5 +13,11 @@ namespace LLama.Abstractions
         /// <param name="tokens"></param>
         /// <returns></returns>
         IAsyncEnumerable<string> TransformAsync(IAsyncEnumerable<string> tokens);
+
+        /// <summary>
+        /// Copy the transform.
+        /// </summary>
+        /// <returns></returns>
+        ITextStreamTransform Clone();
     }
 }

LLama/Abstractions/ITextTransform.cs

@@ -17,5 +17,11 @@
         /// <param name="text"></param>
         /// <returns></returns>
         string Transform(string text);
+
+        /// <summary>
+        /// Copy the transform.
+        /// </summary>
+        /// <returns></returns>
+        ITextTransform Clone();
     }
 }

LLama/ChatSession.cs

@@ -189,9 +189,9 @@ public class ChatSession
         }
         Executor.Context.LoadState(state.ContextState);
         History = new ChatHistory(state.History);
-        InputTransformPipeline = state.InputTransformPipeline.ToList();
-        OutputTransform = state.OutputTransform;
-        HistoryTransform = state.HistoryTransform;
+        InputTransformPipeline = state.InputTransformPipeline.Select(t => t.Clone()).ToList();
+        OutputTransform = state.OutputTransform.Clone();
+        HistoryTransform = state.HistoryTransform.Clone();
     }
 
     /// <summary>
@@ -634,8 +634,8 @@ public record SessionState
         ContextState = contextState;
         ExecutorState = executorState;
         History = history.Messages.ToArray();
-        InputTransformPipeline = inputTransformPipeline.ToArray();
-        OutputTransform = outputTransform;
-        HistoryTransform = historyTransform;
+        InputTransformPipeline = inputTransformPipeline.Select(t => t.Clone()).ToArray();
+        OutputTransform = outputTransform.Clone();
+        HistoryTransform = historyTransform.Clone();
     }
 }

LLama/LLamaTransforms.cs

@@ -47,6 +47,12 @@ namespace LLama
                 _isInstructMode = isInstructMode;
             }
 
+            /// <inheritdoc />
+            public IHistoryTransform Clone()
+            {
+                return new DefaultHistoryTransform(_userName, _assistantName, _systemName, _unknownName, _isInstructMode);
+            }
+
             /// <inheritdoc />
             public virtual string HistoryToText(ChatHistory history)
             {
@@ -116,6 +122,12 @@ namespace LLama
             {
                 return text.Trim();
             }
+
+            /// <inheritdoc />
+            public ITextTransform Clone()
+            {
+                return new NaiveTextInputTransform();
+            }
         }
 
         /// <summary>
@@ -129,6 +141,12 @@ namespace LLama
             {
                 return tokens;
             }
+
+            /// <inheritdoc />
+            public ITextStreamTransform Clone()
+            {
+                return new EmptyTextOutputStreamTransform();
+            }
         }
 
         /// <summary>
@@ -157,6 +175,12 @@ namespace LLama
                 _removeAllMatchedTokens = removeAllMatchedTokens;
             }
 
+            /// <inheritdoc />
+            public ITextStreamTransform Clone()
+            {
+                return new KeywordTextOutputStreamTransform(_keywords, _maxKeywordLength, _removeAllMatchedTokens);
+            }
+
             /// <inheritdoc />
             public async IAsyncEnumerable<string> TransformAsync(IAsyncEnumerable<string> tokens)
             {