app.py

import streamlit as st
import os
from huggingface_hub import InferenceApi
from PyPDF2 import PdfReader
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain_community.embeddings import HuggingFaceEmbeddings
from langchain.vectorstores import FAISS
from langdetect import detect

# Load the Hugging Face token from environment variables (secrets)
token = os.environ.get("KEY2")  # Replace "KEY2" with your secret key name

# Initialize the Hugging Face Inference API
def load_llm():
    model_name = "HuggingFaceH4/zephyr-7b-alpha"  # Replace with your preferred model
    api = InferenceApi(repo_id=model_name, token=token)
    return api

# Extract text from PDF
def extract_text_from_pdf(file):
    reader = PdfReader(file)
    text = ""
    for page in reader.pages:
        text += page.extract_text()
    return text

# Split text into chunks
def split_text(text, chunk_size=1000, chunk_overlap=200):
    splitter = RecursiveCharacterTextSplitter(chunk_size=chunk_size, chunk_overlap=chunk_overlap)
    chunks = splitter.split_text(text)
    return chunks

# Create embeddings and vector store
def create_vector_store(chunks, indexing_method="multi-representation", **kwargs):
    embeddings = HuggingFaceEmbeddings(model_name="all-MiniLM-L6-v2")
    if indexing_method == "multi-representation":
        vector_store = FAISS.from_texts(chunks, embeddings)
    elif indexing_method == "raptors":
        # Implement RAPTORS logic here (e.g., hierarchical chunking)
        vector_store = FAISS.from_texts(chunks, embeddings)
    elif indexing_method == "colbert":
        # Implement ColBERT logic here (e.g., contextualized embeddings)
        vector_store = FAISS.from_texts(chunks, embeddings)
    return vector_store

# Query the PDF using the Hugging Face API
def query_pdf(vector_store, query, api, query_method="multi-query", max_new_tokens=200, temperature=0.7, top_k=50):
    # Retrieve relevant chunks from the vector store
    docs = vector_store.similarity_search(query)
    context = " ".join([doc.page_content for doc in docs])

    # Create a prompt for the LLM
    prompt = f"Context: {context}\n\nQuestion: {query}\n\nAnswer:"

    # Query the Hugging Face API
    response = api(
        inputs=prompt,
        parameters={
            "max_new_tokens": max_new_tokens,
            "temperature": temperature,
            "top_k": top_k,
        },
    )
    return response[0]["generated_text"], docs

# Detect language of the text
def detect_language(text):
    try:
        return detect(text)
    except:
        return "en"  # Default to English if detection fails

# Streamlit App
def main():
    st.title("Chat with PDF")
    st.write("Upload a PDF and ask questions about it!")

    # File uploader
    uploaded_file = st.file_uploader("Upload a PDF", type="pdf")
    if uploaded_file is None:
        st.info("Using default PDF.")
        uploaded_file = "default.pdf"  # Add a default PDF

    # Step 1: Extract text and split into chunks
    if "text" not in st.session_state:
        st.session_state.text = None
    if "chunks" not in st.session_state:
        st.session_state.chunks = None

    if st.button("Extract Text and Split into Chunks"):
        st.session_state.text = extract_text_from_pdf(uploaded_file)
        st.session_state.chunks = split_text(st.session_state.text)
        st.success("Text extracted and split into chunks!")

    # Step 2: Create vector store
    if "vector_store" not in st.session_state:
        st.session_state.vector_store = None

    if st.session_state.chunks:
        st.subheader("Indexing Options")
        indexing_method = st.selectbox(
            "Indexing Method",
            ["multi-representation", "raptors", "colbert"],
            help="Choose how to index the PDF text."
        )
        if st.button("Create Vector Store"):
            st.session_state.vector_store = create_vector_store(st.session_state.chunks, indexing_method=indexing_method)
            st.success("Vector store created!")

    # Step 3: Load LLM (Hugging Face API)
    if "api" not in st.session_state:
        st.session_state.api = None

    if st.session_state.vector_store:
        st.subheader("LLM Parameters")
        temperature = st.slider("Temperature", 0.1, 1.0, 0.7, help="Controls randomness in the output.")
        top_k = st.slider("Top-k", 1, 100, 50, help="Limits sampling to the top-k tokens.")
        max_new_tokens = st.slider("Max New Tokens", 50, 500, 200, help="Maximum number of tokens to generate.")
        if st.button("Load LLM"):
            api = load_llm()
            st.session_state.api = api
            st.success("LLM loaded!")

    # Step 4: Query the PDF
    if st.session_state.api:
        st.subheader("Query Translation Options")
        query_method = st.selectbox(
            "Query Translation Method",
            ["multi-query", "rag-fusion", "decomposition", "step-back", "hyde"],
            help="Choose a method to improve query retrieval."
        )
        query = st.text_input("Ask a question about the PDF:")
        if query:
            answer, source_docs = query_pdf(
                st.session_state.vector_store,
                query,
                st.session_state.api,
                query_method=query_method,
                max_new_tokens=max_new_tokens,
                temperature=temperature,
                top_k=top_k,
            )
            st.write("**Answer:**", answer)
            st.write("**Source Text:**")
            for doc in source_docs:
                st.write(doc.page_content)

if __name__ == "__main__":
    main()