feat: add additional memory classes and do some cleanup

LangChain.sln

@@ -172,8 +172,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LangChain.Providers.Automat
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LangChain.Providers.Automatic1111.IntegrationTests", "src\tests\LangChain.Providers.Automatic1111.IntegrationTests\LangChain.Providers.Automatic1111.IntegrationTests.csproj", "{A6CF79BC-8365-46E8-9230-1A4AD615D40B}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LangChain.Samples.FileMemory", "examples\LangChain.Samples.FileMemory\LangChain.Samples.FileMemory.csproj", "{BA701280-0BEB-4DA4-92B3-9C777082C2AF}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LangChain.Providers.Bedrock.IntegrationTests", "src\tests\LangChain.Providers.Bedrock.IntegrationTests\LangChain.Providers.Bedrock.IntegrationTests.csproj", "{73C76E80-95C5-4C96-A319-4F32043C903E}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LangChain.Providers.Bedrock", "src\libs\Providers\LangChain.Providers.Bedrock\LangChain.Providers.Bedrock.csproj", "{67985CCB-F606-41F8-9D36-513459F58882}"
@@ -408,10 +406,6 @@ Global
 		{A6CF79BC-8365-46E8-9230-1A4AD615D40B}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A6CF79BC-8365-46E8-9230-1A4AD615D40B}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A6CF79BC-8365-46E8-9230-1A4AD615D40B}.Release|Any CPU.Build.0 = Release|Any CPU
-		{BA701280-0BEB-4DA4-92B3-9C777082C2AF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{BA701280-0BEB-4DA4-92B3-9C777082C2AF}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{BA701280-0BEB-4DA4-92B3-9C777082C2AF}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{BA701280-0BEB-4DA4-92B3-9C777082C2AF}.Release|Any CPU.Build.0 = Release|Any CPU
 		{73C76E80-95C5-4C96-A319-4F32043C903E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{73C76E80-95C5-4C96-A319-4F32043C903E}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{73C76E80-95C5-4C96-A319-4F32043C903E}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -488,7 +482,6 @@ Global
 		{4913844F-74EC-4E74-AE8A-EA825569E6BA} = {E55391DE-F8F3-4CC2-A0E3-2406C76E9C68}
 		{BF4C7B87-0997-4208-84EF-D368DF7B9861} = {E55391DE-F8F3-4CC2-A0E3-2406C76E9C68}
 		{A6CF79BC-8365-46E8-9230-1A4AD615D40B} = {FDEE2E22-C239-4921-83B2-9797F765FD6A}
-		{BA701280-0BEB-4DA4-92B3-9C777082C2AF} = {F17A86AE-A174-4B6C-BAA7-9D9A9704BE85}
 		{73C76E80-95C5-4C96-A319-4F32043C903E} = {FDEE2E22-C239-4921-83B2-9797F765FD6A}
 		{67985CCB-F606-41F8-9D36-513459F58882} = {E55391DE-F8F3-4CC2-A0E3-2406C76E9C68}
 	EndGlobalSection

examples/LangChain.Samples.Memory/Program.cs

@@ -1,13 +1,176 @@
 using LangChain.Memory;
+using LangChain.Providers;
+using LangChain.Providers.OpenAI;
+using System.Runtime.Serialization;
+using static LangChain.Chains.Chain;
 
-var inMemoryHistory = new ChatMessageHistory();
+internal class Program
+{
+    private static async Task Main(string[] args)
+    {
+        // Pull the API key from the environment, so it's never checked in with source
+        var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ??
+            throw new InvalidOperationException("OPENAI_API_KEY environment variable is not found.");
 
-await inMemoryHistory.AddUserMessage("hi!");
+        // Use a common, general-purpose LLM
+        var model = new OpenAiModel(apiKey, "gpt-3.5-turbo");
 
-await inMemoryHistory.AddAiMessage("whats up?");
+        // Create a simple prompt template for the conversation to help the AI
+        var template = @"
+The following is a friendly conversation between a human and an AI.
 
-foreach (var message in inMemoryHistory.Messages)
-{
-    Console.WriteLine(message.GetType().Name + ":" + message.Content);
-}
+{history}
+Human: {input}
+AI: ";
+
+        // To have a conversation that remembers previous messages we need to use memory.
+        // Here we pick one of a number of different strategies for implementing memory.
+        var memory = PickMemoryStrategy(model);
+
+        // Build the chain that will be used for each turn in our conversation.
+        // This is just declaring the chain.  Actual execution of the chain happens
+        // in the conversation loop below.  On every pass through the loop, the user's
+        // input is added to the beginning of this chain to make a new chain.
+        var chain =
+            LoadMemory(memory, outputKey: "history")
+            | Template(template)
+            | LLM(model)
+            | UpdateMemory(memory, requestKey: "input", responseKey: "text");
+
+        Console.WriteLine();
+        Console.WriteLine("Start a conversation with the friendly AI!");
+        Console.WriteLine("(Enter 'exit' or hit Ctrl-C to end the conversation)");
+
+        // Run an endless loop of conversation
+        while (true)
+        {
+            Console.WriteLine();
+
+            Console.Write("Human: ");
+            var input = Console.ReadLine();
+            if (input == "exit")
+            {
+                break;
+            }
+
+            // Build a new chain by prepending the user's input to the original chain
+            var currentChain = Set(input, "input")
+                | chain;
+
+            // Get a response from the AI
+            var response = await currentChain.Run("text");
+
+            Console.Write("AI: ");
+            Console.WriteLine(response);
+        }
+    }
+
+    private static BaseChatMemory PickMemoryStrategy(IChatModel model)
+    {
+        // The memory will add prefixes to messages to indicate where they came from
+        // The prefixes specified here should match those used in our prompt template
+        MessageFormatter messageFormatter = new MessageFormatter
+        {
+            AiPrefix = "AI",
+            HumanPrefix = "Human"
+        };
+
+        BaseChatMessageHistory chatHistory = GetChatMessageHistory();
+
+        string memoryClassName = PromptForChoice(new[]
+        {
+            nameof(ConversationBufferMemory),
+            nameof(ConversationWindowBufferMemory),
+            nameof(ConversationSummaryMemory),
+            nameof(ConversationSummaryBufferMemory)
+        });
+
+        switch (memoryClassName)
+        {
+            case nameof(ConversationBufferMemory):
+                return GetConversationBufferMemory(chatHistory, messageFormatter);
 
+            case nameof(ConversationWindowBufferMemory):
+                return GetConversationWindowBufferMemory(chatHistory, messageFormatter);
+
+            case nameof(ConversationSummaryMemory):
+                return GetConversationSummaryMemory(chatHistory, messageFormatter, model);
+
+            case nameof(ConversationSummaryBufferMemory):
+                return GetConversationSummaryBufferMemory(chatHistory, messageFormatter, (IChatModelWithTokenCounting)model);
+
+            default:
+                throw new InvalidOperationException($"Unexpected memory class name: '{memoryClassName}'");
+        }
+    }
+
+    private static string PromptForChoice(string[] choiceTexts)
+    {
+        while (true)
+        {
+            Console.Clear();
+            Console.WriteLine("Select from the following options:");
+
+            int choiceNumber = 1;
+
+            foreach (string choiceText in choiceTexts)
+            {
+                Console.WriteLine($"    {choiceNumber}: {choiceText}");
+                choiceNumber++;
+            }
+
+            Console.WriteLine();
+            Console.Write("Enter choice: ");
+
+            string choiceEntry = Console.ReadLine();
+            if (int.TryParse(choiceEntry, out int choiceIndex))
+            {
+                string choiceText = choiceTexts[choiceIndex];
+
+                Console.WriteLine();
+                Console.WriteLine($"You selected '{choiceText}'");
+
+                return choiceText;
+            }
+        }
+    }
+
+    private static BaseChatMessageHistory GetChatMessageHistory()
+    {
+        // Other types of chat history work, too!
+        return new ChatMessageHistory();
+    }
+
+    private static BaseChatMemory GetConversationBufferMemory(BaseChatMessageHistory chatHistory, MessageFormatter messageFormatter)
+    {
+        return new ConversationBufferMemory(chatHistory)
+        {
+            Formatter = messageFormatter
+        };
+    }
+
+    private static BaseChatMemory GetConversationWindowBufferMemory(BaseChatMessageHistory chatHistory, MessageFormatter messageFormatter)
+    {
+        return new ConversationWindowBufferMemory(chatHistory)
+        {
+            WindowSize = 3,
+            Formatter = messageFormatter
+        };
+    }
+
+    private static BaseChatMemory GetConversationSummaryMemory(BaseChatMessageHistory chatHistory, MessageFormatter messageFormatter, IChatModel model)
+    {
+        return new ConversationSummaryMemory(model, chatHistory)
+        {
+            Formatter = messageFormatter
+        };
+    }
+    private static BaseChatMemory GetConversationSummaryBufferMemory(BaseChatMessageHistory chatHistory, MessageFormatter messageFormatter, IChatModelWithTokenCounting model)
+    {
+        return new ConversationSummaryBufferMemory(model, chatHistory)
+        {
+            MaxTokenCount = 25,
+            Formatter = messageFormatter
+        };
+    }
+}

src/libs/LangChain.Core/Chains/Chain.cs

@@ -149,15 +149,15 @@ public static StuffDocumentsChain CombineDocuments(
     /// <param name="responseKey"></param>
     /// <returns></returns>
     public static UpdateMemoryChain UpdateMemory(
-        ConversationBufferMemory memory,
+        BaseChatMemory memory,
         string requestKey = "text",
         string responseKey = "text")
     {
         return new UpdateMemoryChain(memory, requestKey, responseKey);
     }
 
     public static LoadMemoryChain LoadMemory(
-        ConversationBufferMemory memory,
+        BaseChatMemory memory,
         string outputKey = "text")
     {
         return new LoadMemoryChain(memory, outputKey);

src/libs/LangChain.Core/Chains/StackableChains/Agents/GroupChat.cs

@@ -18,7 +18,8 @@ public class GroupChat : BaseStackableChain
     private readonly string _outputKey;
 
     int _currentAgentId;
-    private readonly ConversationBufferMemory _conversationBufferMemory;
+    private readonly MessageFormatter _messageFormatter;
+    private readonly ChatMessageHistory _chatMessageHistory;
 
     /// <summary>
     /// 
@@ -46,7 +47,20 @@ public GroupChat(
         _messagesLimit = messagesLimit;
         _inputKey = inputKey;
         _outputKey = outputKey;
-        _conversationBufferMemory = new ConversationBufferMemory(new ChatMessageHistory()) { AiPrefix = "", HumanPrefix = "", SystemPrefix = "", SaveHumanMessages = false };
+
+        _messageFormatter = new MessageFormatter
+        {
+            AiPrefix = "",
+            HumanPrefix = "",
+            SystemPrefix = ""
+        };
+
+        _chatMessageHistory = new ChatMessageHistory()
+        {
+            // Do not save human messages
+            IsMessageAccepted = x => (x.Role != MessageRole.Human)
+        };
+
         InputKeys = new[] { inputKey };
         OutputKeys = new[] { outputKey };
     }
@@ -55,27 +69,28 @@ public GroupChat(
     /// 
     /// </summary>
     /// <returns></returns>
-    public IReadOnlyList<Message> History => _conversationBufferMemory.ChatHistory.Messages;
+    public IReadOnlyList<Message> History => _chatMessageHistory.Messages;
 
     /// <inheritdoc />
     protected override async Task<IChainValues> InternalCall(IChainValues values)
     {
         values = values ?? throw new ArgumentNullException(nameof(values));
 
-        await _conversationBufferMemory.Clear().ConfigureAwait(false);
+        await _chatMessageHistory.Clear().ConfigureAwait(false);
         foreach (var agent in _agents)
         {
             agent.SetHistory("");
         }
         var firstAgent = _agents[0];
         var firstAgentMessage = (string)values.Value[_inputKey];
-        await _conversationBufferMemory.ChatHistory.AddMessage(new Message($"{firstAgent.Name}: {firstAgentMessage}",
+        await _chatMessageHistory.AddMessage(new Message($"{firstAgent.Name}: {firstAgentMessage}",
             MessageRole.System)).ConfigureAwait(false);
         int messagesCount = 1;
         while (messagesCount<_messagesLimit)
         {
             var agent = GetNextAgent();
-            agent.SetHistory(_conversationBufferMemory.BufferAsString+"\n"+$"{agent.Name}:");
+            string bufferText = _messageFormatter.Format(_chatMessageHistory.Messages);
+            agent.SetHistory(bufferText + "\n" + $"{agent.Name}:");
             var res = await agent.CallAsync(values).ConfigureAwait(false);
             var message = (string)res.Value[agent.OutputKeys[0]];
             if (message.Contains(_stopPhrase))
@@ -85,13 +100,13 @@ await _conversationBufferMemory.ChatHistory.AddMessage(new Message($"{firstAgent
 
             if (!agent.IsObserver)
             {
-                await _conversationBufferMemory.ChatHistory.AddMessage(new Message($"{agent.Name}: {message}",
+                await _chatMessageHistory.AddMessage(new Message($"{agent.Name}: {message}",
                                        MessageRole.System)).ConfigureAwait(false);
             }
         }
 
-        var result = _conversationBufferMemory.ChatHistory.Messages[^1];
-        messagesCount = _conversationBufferMemory.ChatHistory.Messages.Count;
+        var result = _chatMessageHistory.Messages[^1];
+        messagesCount = _chatMessageHistory.Messages.Count;
         if (ThrowOnLimit && messagesCount >= _messagesLimit)
         {
             throw new InvalidOperationException($"Message limit reached:{_messagesLimit}");