07_chat.js

import { config } from "dotenv";
config();

import { ConversationChain } from "langchain/chains";
import { ChatOpenAI } from "langchain/chat_models/openai";
import {
  ChatPromptTemplate,
  HumanMessagePromptTemplate,
  SystemMessagePromptTemplate,
  MessagesPlaceholder,
} from "langchain/prompts";
import { BufferMemory } from "langchain/memory";

const chat = new ChatOpenAI({ temperature: 0 });

const chatPrompt = ChatPromptTemplate.fromPromptMessages([
  SystemMessagePromptTemplate.fromTemplate(
    "The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know."
  ),
  new MessagesPlaceholder("history"),
  HumanMessagePromptTemplate.fromTemplate("{input}"),
]);

const chain = new ConversationChain({
  memory: new BufferMemory({ returnMessages: true, memoryKey: "history" }),
  prompt: chatPrompt,
  llm: chat,
});

const response = await chain.call({
  input: "What is the capital of France?",
});
const response2 = await chain.call({
  input: "What is a great place to see there?",
});

console.log(response2);