app.py

import os
from typing import List

from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain.vectorstores import Chroma
from langchain.chains import (
    ConversationalRetrievalChain,
)
from langchain.document_loaders import PyPDFLoader
from langchain.chat_models import ChatOpenAI
from langchain.prompts.chat import (
    ChatPromptTemplate,
    SystemMessagePromptTemplate,
    HumanMessagePromptTemplate,
)
from langchain.docstore.document import Document
from langchain.memory import ChatMessageHistory, ConversationBufferMemory


import chainlit as cl

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

system_template = """Use the following pieces of context to answer the users question.
If you don't know the answer, just say that you don't know, don't try to make up an answer.
ALWAYS return a "SOURCES" part in your answer.
The "SOURCES" part should be a reference to the source of the document from which you got your answer.

And if the user greets with greetings like Hi, hello, How are you, etc reply accordingly as well.

Example of your response should be:

The answer is foo
SOURCES: xyz


Begin!
----------------
{summaries}"""
messages = [
    SystemMessagePromptTemplate.from_template(system_template),
    HumanMessagePromptTemplate.from_template("{question}"),
]
prompt = ChatPromptTemplate.from_messages(messages)
chain_type_kwargs = {"prompt": prompt}


def process_file(file: cl.AskFileMessage):
    import tempfile

    with tempfile.NamedTemporaryFile(mode="w", delete=False) as tempfile:
        with open(tempfile.name, "wb") as f:
            f.write(file.content)

    pypdf_loader = PyPDFLoader(tempfile.name)
    texts = pypdf_loader.load_and_split()
    texts = [text.page_content for text in texts]
    return texts



@cl.on_chat_start
async def on_chat_start():
    files = None

    # Wait for the user to upload a file
    while files is None:
        # Note: This now accepts both text/plain and application/pdf files
        files = await cl.AskFileMessage(
            content="Please upload a text or PDF file to begin!",
            accept=["text/plain", "application/pdf"],
            max_size_mb=20,  # Assuming PDFs might be larger
            timeout=180,
        ).send()

    file = files[0]

    # Notify the user that their file is being processed
    msg = cl.Message(content=f"Processing `{file.name}`...")
    await msg.send()

    # Initialize an empty list for texts, this will be populated based on file type
    texts = []

    # Check the file type and process accordingly
    if file.content_type == "text/plain":
        # Handle text file
        with open(file.path, "r", encoding="utf-8") as f:
            text = f.read()
        texts.append(text)  # Add the text to the texts list

        # Update the user about the text file
        await cl.Message(
            content=f"`{file.name}` uploaded, it contains {len(text)} characters!"
        ).send()
        
    elif file.content_type == "application/pdf":
        # Handle PDF file
        texts = process_file(file)  # Assuming process_file() is a function you've defined to extract text from PDF

        # Create metadata for each chunk
        metadatas = [{"source": f"{i}-pl"} for i in range(len(texts))]

        # Create a Chroma vector store
        embeddings = OpenAIEmbeddings()
        docsearch = await cl.make_async(Chroma.from_texts)(
            texts, embeddings, metadatas=metadatas
        )

    # The rest of your setup, like creating the chain, goes here
    # This part is unchanged from your second snippet
    message_history = ChatMessageHistory()

    memory = ConversationBufferMemory(
        memory_key="chat_history",
        output_key="answer",
        chat_memory=message_history,
        return_messages=True,
    )

    chain = ConversationalRetrievalChain.from_llm(
        ChatOpenAI(model_name="gpt-3.5-turbo", temperature=0, streaming=True),
        chain_type="stuff",
        retriever=docsearch.as_retriever(),
        memory=memory,
        return_source_documents=True,
    )

    # Let the user know that the system is ready
    msg.content = f"Processing `{file.name}` done. You can now ask questions!"
    await msg.update()

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


@cl.on_message
async def main(message):
    chain = cl.user_session.get("chain")  # type: ConversationalRetrievalChain
    cb = cl.AsyncLangchainCallbackHandler()

    res = await chain.acall(message.content, callbacks=[cb])
    answer = res["answer"]
    source_documents = res["source_documents"]  # type: List[Document]

    text_elements = []  # type: List[cl.Text]

    if source_documents:
        for source_idx, source_doc in enumerate(source_documents):
            source_name = f"source_{source_idx}"
            # Create the text element referenced in the message
            text_elements.append(
                cl.Text(content=source_doc.page_content, name=source_name)
            )
        source_names = [text_el.name for text_el in text_elements]

        if source_names:
            answer += f"\nSources: {', '.join(source_names)}"
        else:
            answer += "\nNo sources found"

    await cl.Message(content=answer, elements=text_elements).send()