app.py

import streamlit as st
import replicate
import os
import PyPDF2

from langchain_community.vectorstores import FAISS
from langchain_community.document_loaders import PyPDFLoader
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain.chains import ConversationalRetrievalChain, RetrievalQA
from langchain_community.embeddings import HuggingFaceEmbeddings 
from langchain.memory import ConversationBufferMemory
from langchain_community.llms import HuggingFaceEndpoint

from dotenv import load_dotenv

# Load environment variables
load_dotenv()

st.set_page_config(page_title="💬 Chatbot")

# Get Hugging Face API token from environment variables
replicate_api = os.getenv("REPLICATE_API_TOKEN")
hf_api_token = os.getenv("HF_AUTH_TOKEN")

def load_doc(list_file_path):    
    loaders = [PyPDFLoader(x) for x in list_file_path]
    pages = []
    for loader in loaders:
        pages.extend(loader.load())
    text_splitter = RecursiveCharacterTextSplitter(
        chunk_size=1024, 
        chunk_overlap=64 
    )  
    doc_splits = text_splitter.split_documents(pages)
    return doc_splits

def read_pdf(uploaded_file):
    pdf_reader = PyPDF2.PdfReader(uploaded_file)
    text = ""
    for page in pdf_reader.pages:
        text += page.extract_text()
    return text

def split_chunks(docs):
    text_splitter = RecursiveCharacterTextSplitter(
        chunk_size=1000,
        chunk_overlap=100,
    )
    return text_splitter.split_text(docs)

def create_db(splits):
    embeddings_model = HuggingFaceEmbeddings(model_name='sentence-transformers/all-MiniLM-L6-v2')
    vectordb = FAISS.from_texts(splits, embeddings_model)
    return vectordb

def initialize_llmchain(llm_model, temperature, max_tokens, top_k, vector_db):
    llm = HuggingFaceEndpoint(
        repo_id=llm_model,
        huggingfacehub_api_token=hf_api_token,
        temperature=temperature,
        max_new_tokens=max_tokens,
        top_k=top_k,
    )    
    
    memory = ConversationBufferMemory(
        memory_key="chat_history",
        output_key='response',
        return_messages=True
    )

    retriever = vector_db.as_retriever()
    #qa_chain = ConversationalRetrievalChain.from_llm(
        #llm,
        #retriever=retriever,
        #chain_type="stuff", 
        ##memory=memory,
        #return_source_documents=True,
        #verbose=False,
   # )

    qa_chain=RetrievalQA.from_chain_type(
    llm=llm, 
    chain_type="stuff", 
    retriever=retriever,
    return_source_documents=True, 
    #chain_type_kwargs=chain_type_kwargs
    )

    return qa_chain      

def format_chat_history(chat_history):
    formatted_chat_history = []
    for message in chat_history:
        formatted_chat_history.append((message['role'], message['content']))
    #st.write(formatted_chat_history)
    return formatted_chat_history

def generate_llama2_response(prompt_input):
    string_dialogue = "You are a helpful assistant. You do not respond as 'User' or pretend to be 'User'. You only respond once as 'Assistant'."
    for dict_message in st.session_state.messages:
        if dict_message["role"] == "user":
            string_dialogue += "User: " + dict_message["content"] + "\n\n"
        else:
            string_dialogue += "Assistant: " + dict_message["content"] + "\n\n"
    #st.write(llm_model)

    qa_chain = initialize_llmchain(llm_model, temperature, max_tokens, top_k, st.session_state.vector_db)
    #st.write(llm_model, temperature, max_tokens, top_k)
    #formatted_chat_history = format_chat_history(st.session_state.messages)
    #response = qa_chain.invoke({"question": message, "chat_history": formatted_chat_history})
   
    response=qa_chain({"query": prompt_input})
    
    #st.write(response["result"])
    #st.write(response["answer"])
    return response["result"]

def clear_chat_history():
    st.session_state.messages = [{"role": "assistant", "content": "How may I assist you today?"}]

# Store LLM generated responses
if "messages" not in st.session_state.keys():
    st.session_state.messages = [{"role": "assistant", "content": "How may I assist you today?"}]
    
if "vector_db" not in st.session_state:
    st.session_state.vector_db = None

if "uploaded_file" not in st.session_state:
    st.session_state.uploaded_file = None

# Main app layout
st.title("QA Chatbot with PDF Upload")
st.markdown("---")

# Sidebar for model selection and parameters
with st.sidebar:

    uploaded_file = st.sidebar.file_uploader("Upload a PDF", type="pdf") 

    # Check if a new file has been uploaded or the file has been removed
    if uploaded_file != st.session_state.uploaded_file:
        st.session_state.uploaded_file = uploaded_file
        clear_chat_history()
        st.session_state.vector_db = None

    if uploaded_file is not None and st.session_state.vector_db is None:    
        with st.spinner("Converting to Vectors..."):
            text = read_pdf(uploaded_file)
            chunks = split_chunks(docs=text)
            st.session_state.vector_db = create_db(chunks)
        
            #st.sidebar.write("PDF processed and vector database created!")
            st.sidebar.markdown('<p style="color:green;">PDF processed and vector database created!</p>', unsafe_allow_html=True)

    st.sidebar.title("Model Settings")
    selected_model = st.sidebar.selectbox('Choose a LLM model', ['Llama-3-8B', 'Mistral-7B'], key='selected_model')
    llm_model = 'meta-llama/Meta-Llama-3-8B-Instruct' if selected_model == 'Llama-3-8B' else 'mistralai/Mistral-7B-Instruct-v0.2'
    temperature = st.sidebar.slider('Temperature', 0.1, 1.0, 0.1)
    top_k = st.sidebar.slider('Top_k', 1, 10, 3)
    max_tokens = st.sidebar.slider('Max Tokens', 1, 512, 256)

    #st.sidebar.button('Clear Chat History', on_click=clear_chat_history)
    
show_clear_button = len(st.session_state.messages) > 1

if st.session_state.vector_db is not None:
    for message in st.session_state.messages:
        with st.chat_message(message["role"]):
            st.write(message["content"])

    # User-provided prompt
    if prompt := st.chat_input(disabled=not replicate_api):
    #if button_clicked and prompt:
        st.session_state.messages.append({"role": "user", "content": prompt})
        with st.chat_message("user"):
            st.write(prompt)

    # Generate a new response if last message is not from assistant
    if st.session_state.messages[-1]["role"] != "assistant":
        with st.chat_message("assistant"):
            with st.spinner("Thinking..."):
                response = generate_llama2_response(prompt)
                #st.write(response)
                placeholder = st.empty()
                full_response = ''
                for item in response:
                    full_response += item
                    #placeholder.markdown(full_response)
                placeholder.markdown(full_response)
        message = {"role": "assistant", "content": full_response}
        #st.write("-------")
        #st.write(message)
        st.session_state.messages.append(message)
        show_clear_button = len(st.session_state.messages) > 1

else:
    st.write("Please upload a PDF file to initialize the database.")

if show_clear_button and st.button('Clear Chat History'):
        clear_chat_history()
        st.experimental_rerun()  # This line ensures the page reruns to reflect the changes