feat(community): add FileChatMessageHistory

docs/core_docs/docs/integrations/memory/file.mdx

@@ -0,0 +1,31 @@
+---
+hide_table_of_contents: true
+---
+
+import CodeBlock from "@theme/CodeBlock";
+
+# File Chat Message History
+
+The `FileChatMessageHistory` uses a JSON file to store chat message history. For longer-term persistence across chat sessions, you can swap out the default in-memory `chatHistory` that backs chat memory classes like `BufferMemory`.
+
+## Setup
+
+You'll first need to install the [`@langchain/community`](https://www.npmjs.com/package/@langchain/community) package:
+
+```bash npm2yarn
+npm install @langchain/community @langchain/core
+```
+
+import IntegrationInstallTooltip from "@mdx_components/integration_install_tooltip.mdx";
+
+<IntegrationInstallTooltip></IntegrationInstallTooltip>
+
+```bash npm2yarn
+npm install @langchain/openai @langchain/community @langchain/core
+```
+
+## Usage
+
+import Example from "@examples/memory/file.ts";
+
+<CodeBlock language="typescript">{Example}</CodeBlock>

examples/src/memory/file.ts

@@ -0,0 +1,71 @@
+import { ChatOpenAI } from "@langchain/openai";
+import { FileSystemChatMessageHistory } from "@langchain/community/stores/message/file_system";
+import { RunnableWithMessageHistory } from "@langchain/core/runnables";
+import { StringOutputParser } from "@langchain/core/output_parsers";
+import {
+  ChatPromptTemplate,
+  MessagesPlaceholder,
+} from "@langchain/core/prompts";
+
+const model = new ChatOpenAI({
+  model: "gpt-3.5-turbo",
+  temperature: 0,
+});
+
+const prompt = ChatPromptTemplate.fromMessages([
+  [
+    "system",
+    "You are a helpful assistant. Answer all questions to the best of your ability.",
+  ],
+  new MessagesPlaceholder("chat_history"),
+  ["human", "{input}"],
+]);
+
+const chain = prompt.pipe(model).pipe(new StringOutputParser());
+
+const chainWithHistory = new RunnableWithMessageHistory({
+  runnable: chain,
+  inputMessagesKey: "input",
+  historyMessagesKey: "chat_history",
+  getMessageHistory: async (sessionId) => {
+    const chatHistory = new FileSystemChatMessageHistory({
+      sessionId,
+      userId: "user-id",
+    });
+    return chatHistory;
+  },
+});
+
+const res1 = await chainWithHistory.invoke(
+  { input: "Hi! I'm Jim." },
+  { configurable: { sessionId: "langchain-test-session" } }
+);
+console.log({ res1 });
+/*
+ { res1: 'Hi Jim! How can I assist you today?' }
+ */
+
+const res2 = await chainWithHistory.invoke(
+  { input: "What did I just say my name was?" },
+  { configurable: { sessionId: "langchain-test-session" } }
+);
+console.log({ res2 });
+/*
+ { res2: { response: 'You said your name was Jim.' } 
+ */
+
+// Give this session a title
+const chatHistory = (await chainWithHistory.getMessageHistory(
+  "langchain-test-session"
+)) as FileSystemChatMessageHistory;
+
+await chatHistory.setContext({ title: "Introducing Jim" });
+
+// List all session for the user
+const sessions = await chatHistory.getAllSessions();
+console.log(sessions);
+/*
+ [
+  { sessionId: 'langchain-test-session', context: { title: "Introducing Jim"  } }
+ ]
+ */

libs/langchain-community/.gitignore

@@ -770,6 +770,10 @@ stores/message/firestore.cjs
 stores/message/firestore.js
 stores/message/firestore.d.ts
 stores/message/firestore.d.cts
+stores/message/file_system.cjs
+stores/message/file_system.js
+stores/message/file_system.d.ts
+stores/message/file_system.d.cts
 stores/message/in_memory.cjs
 stores/message/in_memory.js
 stores/message/in_memory.d.ts

libs/langchain-community/langchain.config.js

@@ -242,6 +242,7 @@ export const config = {
     "stores/message/convex": "stores/message/convex",
     "stores/message/dynamodb": "stores/message/dynamodb",
     "stores/message/firestore": "stores/message/firestore",
+    "stores/message/file_system": "stores/message/file_system",
     "stores/message/in_memory": "stores/message/in_memory",
     "stores/message/ipfs_datastore": "stores/message/ipfs_datastore",
     "stores/message/ioredis": "stores/message/ioredis",

libs/langchain-community/package.json

@@ -2449,6 +2449,15 @@
       "import": "./stores/message/firestore.js",
       "require": "./stores/message/firestore.cjs"
     },
+    "./stores/message/file_system": {
+      "types": {
+        "import": "./stores/message/file_system.d.ts",
+        "require": "./stores/message/file_system.d.cts",
+        "default": "./stores/message/file_system.d.ts"
+      },
+      "import": "./stores/message/file_system.js",
+      "require": "./stores/message/file_system.cjs"
+    },
     "./stores/message/in_memory": {
       "types": {
         "import": "./stores/message/in_memory.d.ts",
@@ -3873,6 +3882,10 @@
     "stores/message/firestore.js",
     "stores/message/firestore.d.ts",
     "stores/message/firestore.d.cts",
+    "stores/message/file_system.cjs",
+    "stores/message/file_system.js",
+    "stores/message/file_system.d.ts",
+    "stores/message/file_system.d.cts",
     "stores/message/in_memory.cjs",
     "stores/message/in_memory.js",
     "stores/message/in_memory.d.ts",

libs/langchain-community/src/load/import_map.ts

@@ -67,6 +67,7 @@ export * as caches__upstash_redis from "../caches/upstash_redis.js";
 export * as stores__doc__base from "../stores/doc/base.js";
 export * as stores__doc__gcs from "../stores/doc/gcs.js";
 export * as stores__doc__in_memory from "../stores/doc/in_memory.js";
+export * as stores__message__file_system from "../stores/message/file_system.js";
 export * as stores__message__in_memory from "../stores/message/in_memory.js";
 export * as memory__chat_memory from "../memory/chat_memory.js";
 export * as indexes__base from "../indexes/base.js";

libs/langchain-community/src/stores/message/file_system.ts

@@ -0,0 +1,199 @@
+import { promises as fs } from "node:fs";
+import { dirname } from "node:path";
+
+import { BaseListChatMessageHistory } from "@langchain/core/chat_history";
+import {
+  BaseMessage,
+  StoredMessage,
+  mapChatMessagesToStoredMessages,
+  mapStoredMessagesToChatMessages,
+} from "@langchain/core/messages";
+
+export const FILE_HISTORY_DEFAULT_FILE_PATH = ".history/history.json";
+
+/**
+ * Represents a lightweight file chat session.
+ */
+export type FileChatSession = {
+  id: string;
+  context: Record<string, unknown>;
+};
+
+/**
+ * Represents a stored chat session.
+ */
+export type StoredFileChatSession = FileChatSession & {
+  messages: StoredMessage[];
+};
+
+/**
+ * Type for the store of chat sessions.
+ */
+export type FileChatStore = {
+  [userId: string]: Record<string, StoredFileChatSession>;
+};
+
+/**
+ * Type for the input to the `FileSystemChatMessageHistory` constructor.
+ */
+export interface FileSystemChatMessageHistoryInput {
+  sessionId: string;
+  userId?: string;
+  filePath?: string;
+}
+
+let store: FileChatStore;
+
+/**
+ * Store chat message history using a local JSON file.
+ * For demo and development purposes only.
+ *
+ * @example
+ * ```typescript
+ *  const model = new ChatOpenAI({
+ *   model: "gpt-3.5-turbo",
+ *   temperature: 0,
+ * });
+ * const prompt = ChatPromptTemplate.fromMessages([
+ *   [
+ *     "system",
+ *     "You are a helpful assistant. Answer all questions to the best of your ability.",
+ *   ],
+ *   ["placeholder", "chat_history"],
+ *   ["human", "{input}"],
+ * ]);
+ *
+ * const chain = prompt.pipe(model).pipe(new StringOutputParser());
+ * const chainWithHistory = new RunnableWithMessageHistory({
+ *   runnable: chain,
+ *  inputMessagesKey: "input",
+ *  historyMessagesKey: "chat_history",
+ *   getMessageHistory: async (sessionId) => {
+ *     const chatHistory = new FileSystemChatMessageHistory({
+ *       sessionId: sessionId,
+ *       userId: "userId",  // Optional
+ *     })
+ *     return chatHistory;
+ *   },
+ * });
+ * await chainWithHistory.invoke(
+ *   { input: "What did I just say my name was?" },
+ *   { configurable: { sessionId: "session-id" } }
+ * );
+ * ```
+ */
+export class FileSystemChatMessageHistory extends BaseListChatMessageHistory {
+  lc_namespace = ["langchain", "stores", "message", "file"];
+
+  private sessionId: string;
+
+  private userId: string;
+
+  private filePath: string;
+
+  constructor(chatHistoryInput: FileSystemChatMessageHistoryInput) {
+    super();
+
+    this.sessionId = chatHistoryInput.sessionId;
+    this.userId = chatHistoryInput.userId ?? "";
+    this.filePath = chatHistoryInput.filePath ?? FILE_HISTORY_DEFAULT_FILE_PATH;
+  }
+
+  private async init(): Promise<void> {
+    if (store) {
+      return;
+    }
+    try {
+      store = await this.loadStore();
+    } catch (error) {
+      console.error("Error initializing FileSystemChatMessageHistory:", error);
+      throw error;
+    }
+  }
+
+  protected async loadStore(): Promise<FileChatStore> {
+    try {
+      await fs.access(this.filePath, fs.constants.F_OK);
+      const store = await fs.readFile(this.filePath, "utf-8");
+      return JSON.parse(store) as FileChatStore;
+    } catch (_error) {
+      const error = _error as NodeJS.ErrnoException;
+      if (error.code === "ENOENT") {
+        return {};
+      }
+      throw new Error(
+        `Error loading FileSystemChatMessageHistory store: ${error}`
+      );
+    }
+  }
+
+  protected async saveStore(): Promise<void> {
+    try {
+      await fs.mkdir(dirname(this.filePath), { recursive: true });
+      await fs.writeFile(this.filePath, JSON.stringify(store));
+    } catch (error) {
+      throw new Error(
+        `Error saving FileSystemChatMessageHistory store: ${error}`
+      );
+    }
+  }
+
+  async getMessages(): Promise<BaseMessage[]> {
+    await this.init();
+    const messages = store[this.userId]?.[this.sessionId]?.messages ?? [];
+    return mapStoredMessagesToChatMessages(messages);
+  }
+
+  async addMessage(message: BaseMessage): Promise<void> {
+    await this.init();
+    const messages = await this.getMessages();
+    messages.push(message);
+    const storedMessages = mapChatMessagesToStoredMessages(messages);
+    store[this.userId] ??= {};
+    store[this.userId][this.sessionId] = {
+      ...store[this.userId][this.sessionId],
+      messages: storedMessages,
+    };
+    await this.saveStore();
+  }
+
+  async clear(): Promise<void> {
+    await this.init();
+    if (store[this.userId]) {
+      delete store[this.userId][this.sessionId];
+    }
+    await this.saveStore();
+  }
+
+  async getContext(): Promise<Record<string, unknown>> {
+    await this.init();
+    return store[this.userId]?.[this.sessionId]?.context ?? {};
+  }
+
+  async setContext(context: Record<string, unknown>): Promise<void> {
+    await this.init();
+    store[this.userId] ??= {};
+    store[this.userId][this.sessionId] = {
+      ...store[this.userId][this.sessionId],
+      context,
+    };
+    await this.saveStore();
+  }
+
+  async clearAllSessions() {
+    await this.init();
+    delete store[this.userId];
+    await this.saveStore();
+  }
+
+  async getAllSessions(): Promise<FileChatSession[]> {
+    await this.init();
+    const userSessions = store[this.userId]
+      ? Object.values(store[this.userId]).map((session) => ({
+          id: session.id,
+          context: session.context,
+        }))
+      : [];
+    return userSessions;
+  }
+}