app.py

import chainlit as cl
from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.document_loaders import BSHTMLLoader
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain.vectorstores import FAISS
from langchain.chains import RetrievalQA
from langchain.chat_models import ChatOpenAI
from langchain.prompts import ChatPromptTemplate
import chainlit as cl

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=100)


@cl.author_rename
def rename(orig_author: str):
    rename_dict = {"RetrievalQA": "Coho Blogs", "Chatbot": "Coho Assistant"}
    return rename_dict.get(orig_author, orig_author)


@cl.on_chat_start
async def init():
    msg = cl.Message(content=f"Building Index...")
    await msg.send()

    core_embeddings_model = OpenAIEmbeddings()

    new_db = FAISS.load_local("faiss_index", core_embeddings_model)

    chain = RetrievalQA.from_chain_type(
        ChatOpenAI(model="gpt-3.5-turbo", temperature=0, streaming=True),
        chain_type="stuff",
        return_source_documents=True,
        retriever=new_db.as_retriever(),
    )

    msg.content = f"Index built!"
    await msg.send()

    cl.user_session.set("chain", chain)


@cl.on_message
async def main(message):
    chain = cl.user_session.get("chain")
    cb = cl.AsyncLangchainCallbackHandler(
        stream_final_answer=True, answer_prefix_tokens=["FINAL", "ANSWER"]
    )
    cb.answer_reached = True
    res = await chain.acall(message, callbacks=[cb])

    answer = res["result"]

    if cb.has_streamed_final_answer:
        await cb.final_stream.update()
    else:
        await cl.Message(content=answer).send()