firestore.ts

import { BufferMemory } from "langchain/memory";
import { FirestoreChatMessageHistory } from "@langchain/community/stores/message/firestore";
import { ChatOpenAI } from "@langchain/openai";
import { ConversationChain } from "langchain/chains";
import admin from "firebase-admin";

const memory = new BufferMemory({
  chatHistory: new FirestoreChatMessageHistory({
    collections: ["langchain"],
    docs: ["lc-example"],
    sessionId: "lc-example-id",
    userId: "a@example.com",
    config: {
      projectId: "YOUR-PROJECT-ID",
      credential: admin.credential.cert({
        projectId: "YOUR-PROJECT-ID",
        privateKey:
          "-----BEGIN PRIVATE KEY-----\nnCHANGE-ME\n-----END PRIVATE KEY-----\n",
        clientEmail: "CHANGE-ME@CHANGE-ME-TOO.iam.gserviceaccount.com",
      }),
    },
  }),
});

const model = new ChatOpenAI();
const chain = new ConversationChain({ llm: model, memory });

const res1 = await chain.call({ input: "Hi! I'm Jim." });
console.log({ res1 });
/*
{ res1: { text: "Hello Jim! It's nice to meet you. My name is AI. How may I assist you today?" } }
*/

const res2 = await chain.call({ input: "What did I just say my name was?" });
console.log({ res2 });

/*
{ res1: { text: "You said your name was Jim." } }
*/