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import subprocess
import sys

# Function to install a package
def install_package(package):
    subprocess.check_call([sys.executable, "-m", "pip", "install", package])

# Install required packages if they are not already installed
required_packages = [
    "PyPDF2", "streamlit", "langchain", "faiss-cpu", 
    "sentence-transformers", "python-dotenv"
]
for package in required_packages:
    try:
        __import__(package)
    except ImportError:
        install_package(package)

import os
import streamlit as st
from dotenv import load_dotenv
from PyPDF2 import PdfReader
from langchain.text_splitter import CharacterTextSplitter
from langchain.vectorstores import FAISS
from langchain.memory import ConversationBufferMemory
from langchain.chains import ConversationalRetrievalChain
from langchain.llms import HuggingFaceHub
from langchain.embeddings import HuggingFaceEmbeddings

def get_pdf_text(pdf_docs):
    text = ""
    for pdf in pdf_docs:
        try:
            pdf_reader = PdfReader(pdf)
            for page in pdf_reader.pages:
                text += page.extract_text()
        except Exception as e:
            st.error(f"Error reading {pdf.name}: {e}. Skipping this file.")
    return text

def get_text_chunks(text):
    text_splitter = CharacterTextSplitter(
        separator="\n",
        chunk_size=1000,
        chunk_overlap=200,
        length_function=len
    )
    chunks = text_splitter.split_text(text)
    return chunks

def get_vectorstore(text_chunks):
    try:
        embedding = HuggingFaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
        vectorstore = FAISS.from_texts(texts=text_chunks, embedding=embedding)
        return vectorstore
    except Exception as e:
        st.error(f"Error creating vector store: {e}")
        return None

def get_conversation_chain(vectorstore):
    # Fetch the HuggingFace API token from environment variable
    api_token = os.getenv("HUGGINGFACE_API_TOKEN")
    if not api_token:
        st.error("HuggingFace API token not found. Please ensure it is set in the environment variables.")
        return None

    llm = HuggingFaceHub(repo_id="google/flan-t5-xxl", model_kwargs={"temperature": 0.5, "max_length": 512}, huggingfacehub_api_token=api_token)

    memory = ConversationBufferMemory(
        memory_key='chat_history', return_messages=True)
    conversation_chain = ConversationalRetrievalChain.from_llm(
        llm=llm,
        retriever=vectorstore.as_retriever(),
        memory=memory
    )
    return conversation_chain

def handle_userinput(user_question):
    response = st.session_state.conversation({'question': user_question})
    st.session_state.chat_history = response['chat_history']

def main():
    load_dotenv()
    st.set_page_config(page_title="Chat with multiple PDFs", page_icon=":books:")

    if "conversation" not in st.session_state:
        st.session_state.conversation = None
    if "chat_history" not in st.session_state:
        st.session_state.chat_history = None

    st.header("Chat with multiple PDFs :books:")
    user_question = st.text_input("Ask a question about your documents:")
    if user_question:
        handle_userinput(user_question)

    with st.sidebar:
        st.subheader("Your documents")
        pdf_docs = st.file_uploader(
            "Upload your PDFs here and click on 'Process'", accept_multiple_files=True)
        if st.button("Process"):
            with st.spinner("Processing"):
                # get pdf text
                raw_text = get_pdf_text(pdf_docs)

                if raw_text:  # Proceed only if there is valid text
                    # get the text chunks
                    text_chunks = get_text_chunks(raw_text)

                    # create vector store
                    vectorstore = get_vectorstore(text_chunks)

                    if vectorstore:  # Check if vectorstore is valid
                        # create conversation chain
                        st.session_state.conversation = get_conversation_chain(vectorstore)

if __name__ == '__main__':
    main()