chat_memory.ts

import { BaseChatMessageHistory } from "@langchain/core/chat_history";
import {
  BaseMemory,
  InputValues,
  OutputValues,
  getInputValue,
  getOutputValue,
} from "@langchain/core/memory";
import { ChatMessageHistory } from "../stores/message/in_memory.js";

/**
 * Interface for the input parameters of the BaseChatMemory class.
 */
export interface BaseChatMemoryInput {
  chatHistory?: BaseChatMessageHistory;
  returnMessages?: boolean;
  inputKey?: string;
  outputKey?: string;
}

/**
 * Abstract class that provides a base for implementing different types of
 * memory systems. It is designed to maintain the state of an application,
 * specifically the history of a conversation. This class is typically
 * extended by other classes to create specific types of memory systems.
 */
export abstract class BaseChatMemory extends BaseMemory {
  chatHistory: BaseChatMessageHistory;

  returnMessages = false;

  inputKey?: string;

  outputKey?: string;

  constructor(fields?: BaseChatMemoryInput) {
    super();
    this.chatHistory = fields?.chatHistory ?? new ChatMessageHistory();
    this.returnMessages = fields?.returnMessages ?? this.returnMessages;
    this.inputKey = fields?.inputKey ?? this.inputKey;
    this.outputKey = fields?.outputKey ?? this.outputKey;
  }

  /**
   * Method to add user and AI messages to the chat history in sequence.
   * @param inputValues The input values from the user.
   * @param outputValues The output values from the AI.
   * @returns Promise that resolves when the context has been saved.
   */
  async saveContext(
    inputValues: InputValues,
    outputValues: OutputValues
  ): Promise<void> {
    // this is purposefully done in sequence so they're saved in order
    await this.chatHistory.addUserMessage(
      getInputValue(inputValues, this.inputKey)
    );
    await this.chatHistory.addAIChatMessage(
      getOutputValue(outputValues, this.outputKey)
    );
  }

  /**
   * Method to clear the chat history.
   * @returns Promise that resolves when the chat history has been cleared.
   */
  async clear(): Promise<void> {
    await this.chatHistory.clear();
  }
}