app.py

import gradio as gr
import json
import os
import pdfplumber
import together
from sentence_transformers import SentenceTransformer
import faiss
import numpy as np
import re
import unicodedata
from dotenv import load_dotenv

load_dotenv()

# Set up Together.AI API Key (Replace with your actual key)
assert os.getenv("TOGETHER_API_KEY"), "api key missing"

# Use a sentence transformer for embeddings
#'BAAI/bge-base-en-v1.5'
# embedding_model = SentenceTransformer("BAAI/bge-base-en-v1.5")  

# 'togethercomputer/m2-bert-80M-8k-retrieval'
embedding_model = SentenceTransformer(
    "togethercomputer/m2-bert-80M-8k-retrieval", 
    trust_remote_code=True  # Allow remote code execution
)
embedding_dim = 768  # Adjust according to model

# Initialize FAISS index
index = faiss.IndexFlatL2(embedding_dim)
documents = []  # Store raw text for reference

# Initialize paths
DOCUMENT_DIR = os.path.join(os.path.dirname(__file__), "documents")
INDEX_FILE = "faiss_index.bin"  # FAISS index file (binary format)
METADATA_FILE = "metadata.json"  # Document metadata

# Create the documents directory if it doesn’t exist
os.makedirs(DOCUMENT_DIR, exist_ok=True)

# Load FAISS index if it exists
if os.path.exists(INDEX_FILE):
    index = faiss.read_index(INDEX_FILE)

# Load metadata
if os.path.exists(METADATA_FILE):
    with open(METADATA_FILE, "r") as f:
        metadata = json.load(f)
else:
    metadata = {}

def store_document(text):
    print(" Storing document...")

    # Generate a unique filename
    doc_id = len(metadata) + 1
    filename = os.path.join(DOCUMENT_DIR, f"doc_{doc_id}.txt")
    print(f"Saving document at: {filename}")

    # Save document to file
    with open(filename, "w", encoding="utf-8") as f:
        f.write(text)
    print(" Document saved")

    # Generate and store embedding
    embedding = embedding_model.encode([text]).astype(np.float32)
    index.add(embedding)  # Add to FAISS index
    print(" Embeddings generated")

    # Get FAISS index for the new document
    doc_index = index.ntotal - 1

    # Update metadata with FAISS index
    metadata[str(doc_index)] = filename
    with open(METADATA_FILE, "w") as f:
        json.dump(metadata, f)

    # Save FAISS index properly
    faiss.write_index(index, INDEX_FILE)

    print(f" Document stored successfully at: {filename}")
    return "Document stored!"

def retrieve_document(query):
    print(f"retrieving doc based on: \n{query}")

    query_embedding = embedding_model.encode([query]).astype(np.float32)
    _, closest_idx = index.search(query_embedding, 1)

    if not closest_idx or closest_idx[0][0] not in metadata:
        return "No relevant document found."

    
    if closest_idx[0][0] in metadata:  # Ensure a valid match
        filename = metadata[str(closest_idx[0][0])]
        with open(filename, "r") as f:
            return f.read()
    else:
        return None


def clean_text(text):
    """Cleans extracted text for better processing by the model."""
    print("cleaning")
    text = unicodedata.normalize("NFKC", text)  # Normalize Unicode characters
    text = re.sub(r'\s+', ' ', text).strip()  # Remove extra spaces and newlines
    text = re.sub(r'[^a-zA-Z0-9.,!?;:\'\"()\-]', ' ', text)  # Keep basic punctuation
    text = re.sub(r'(?i)(page\s*\d+)', '', text)  # Remove page numbers
    return text

def extract_text_from_pdf(pdf_file):
    """Extract and clean text from the uploaded PDF."""
    print("extracting")
    try:
        with pdfplumber.open(pdf_file) as pdf:
            text = " ".join(clean_text(text) for page in pdf.pages if (text := page.extract_text()))
        store_document(text)
        return text
    except Exception as e:
        print(f"Error extracting text: {e}")
        return None

def split_text(text, chunk_size=500):
    """Splits text into smaller chunks for better processing."""
    print("splitting")
    return [text[i:i+chunk_size] for i in range(0, len(text), chunk_size)]

def chatbot(pdf_file, user_question):
    """Processes the PDF and answers the user's question."""
    print("chatbot start")

    if pdf_file:
        # Extract text from the PDF
        text = extract_text_from_pdf(pdf_file)
        if not text:
            return "Could not extract any text from the PDF."

    # retrieve the document relevant to the query
    doc = retrieve_document(user_question)           
    
    if doc:
        print("found doc")
        # Split into smaller chunks
        chunks = split_text(doc)
      
        # Use only the first chunk (to optimize token usage)
        prompt = f"Based on this document, answer the question:\n\nDocument:\n{chunks[0]}\n\nQuestion: {user_question}"
        print(f"prompt: \n{prompt}")
    else:
              prompt=user_question

    try:
            print("asking")
            response = together.Completion.create(
                model="mistralai/Mistral-7B-Instruct-v0.1",
                prompt=prompt,
                max_tokens=200,
                temperature=0.7,
            )
        
            # Return chatbot's response
            return response.choices[0].text
    except  Exception as e:
        return f"Error generating response: {e}"
        
    # Send to Together.AI (Mistral-7B)



# Gradio Interface
iface = gr.Interface(
    fn=chatbot,
    inputs=[gr.File(label="Upload PDF"), gr.Textbox(label="Ask a Question")],
    outputs=gr.Textbox(label="Answer"),
    title="PDF Q&A Chatbot (Powered by Together.AI)"
)

# Launch Gradio app
iface.launch()