app.py

import json
import os
from langchain.chains.combine_documents import create_stuff_documents_chain
from langchain.chains.history_aware_retriever import create_history_aware_retriever
from langchain.chains.retrieval import create_retrieval_chain
from langchain_community.vectorstores import FAISS
from langchain_community.chat_message_histories import ChatMessageHistory
from langchain_core.chat_history import BaseChatMessageHistory
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_groq import ChatGroq
from langchain_huggingface import HuggingFaceEmbeddings
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langchain_community.document_loaders import PyPDFLoader
import streamlit as st
from dotenv import load_dotenv
from langchain_core.runnables.history import RunnableWithMessageHistory

load_dotenv()

# Langsmith Tracking
os.environ['LANGCHAIN_API_KEY'] = os.getenv('LANGCHAIN_API_KEY')
os.environ['LANGCHAIN_TRACING_V2'] = 'true'
os.environ['LANGCHAIN_PROJECT'] = "Rag with chat history"
os.environ['GROQ_API_KEY'] = os.getenv('GROQ_API_KEY')
os.environ["HF_TOKEN"] = os.getenv('HF_TOKEN')
os.environ["TOKENIZERS_PARALLELISM"] = "false"

# Initialize embeddings
embeddings = HuggingFaceEmbeddings(model_name="all-MiniLM-L6-v2")

# Load or initialize sessions.json
session_file = 'sessions.json'
if not os.path.exists(session_file):
    with open(session_file, 'w') as f:
        json.dump({"current_session_id": 1}, f)

def get_new_session_id():
    with open(session_file, 'r+') as f:
        data = json.load(f)
        session_id = data['current_session_id']
        data['current_session_id'] += 1
        f.seek(0)
        json.dump(data, f)
        f.truncate()
    return session_id

# Set up Streamlit App
st.title("Rag with chat history")

llm = ChatGroq(model="llama-3.1-70b-Versatile")

# Get or create session ID
if 'session_id' not in st.session_state:
    st.session_state.session_id = get_new_session_id()
session_id = st.session_state.session_id
st.write(f"Session ID: {session_id}")

# Statefully manage chat history
if 'store' not in st.session_state:
    st.session_state.store = {}

uploaded_files = st.file_uploader("Choose a PDF file", type="pdf", accept_multiple_files=True)

# Process Uploaded Files:
if uploaded_files:
    documents = []
    for uploaded_file in uploaded_files:
        temppdf = f"./temp.pdf"
        with open(temppdf, "wb") as file:
            file.write(uploaded_file.getvalue())
        
        loader = PyPDFLoader(temppdf)
        docs = loader.load()
        documents.extend(docs)

    # Split and create embedding documents
    text_splitter = RecursiveCharacterTextSplitter(chunk_size=5000, chunk_overlap=500)
    splits = text_splitter.split_documents(documents)
    vector_store = FAISS.from_documents(documents=splits, embedding=embeddings)
    retriever = vector_store.as_retriever()

    contextualize_q_systemprompt = (
        "Given a chat history and the latest user question "
        "which might reference context in the chat history, "
        "formulate a standalone question which can be understood "
        "without the chat history. Do not answer the question, "
        "just reformulate it if needed and otherwise return it as it is."
    )

    contextualize_q_prompt = ChatPromptTemplate.from_messages(
        [
            ("system", contextualize_q_systemprompt),
            MessagesPlaceholder("chat_history"),
            ("human", "{input}")
        ]
    )

    history_aware_retriever = create_history_aware_retriever(llm, retriever, contextualize_q_prompt)

    # Answer question prompt
    system_prompt = (
        "You are an assistant for question-answering tasks. "
        "Use the following pieces of retrieved context to answer the question. "
        "If you don't have enough context, you can say that you "
        "don't know. Use three sentences maximum and keep the "
        "answer concise."
        "\n\n"
        "{context}"
    )

    qa_prompt = ChatPromptTemplate.from_messages(
        [
            ("system", system_prompt),
            MessagesPlaceholder("chat_history"),
            ("human", "{input}")
        ]
    )

    question_answer_chain = create_stuff_documents_chain(llm, qa_prompt)
    rag_chain = create_retrieval_chain(history_aware_retriever, question_answer_chain)

    def get_session_history(session: str) -> BaseChatMessageHistory:
        if session_id not in st.session_state.store:
            st.session_state.store[session_id] = ChatMessageHistory()
        return st.session_state.store[session_id]

    conversational_rag_chain = RunnableWithMessageHistory(
        rag_chain, get_session_history,
        input_messages_key="input",
        history_messages_key="chat_history",
        output_messages_key="answer"
    )

    user_input = st.text_input("Ask a question")
    if user_input:
        session_history = get_session_history(session_id)
        response = conversational_rag_chain.invoke(
            {"input": user_input},
            config={"configurable": {"session_id": session_id}},
        )
        st.session_state.store[session_id] = session_history
        st.write(st.session_state.store)
        st.write("Assistant:", response["answer"])
        st.write("Chat History:", session_history.messages)

else:
    st.write("Please upload a file")