app.py

import numpy as np
from sentence_transformers import SentenceTransformer
import faiss
import re
import gradio as gr
import PyPDF2
import tempfile
import os

def extract_text_from_pdf(pdf_file):
    """
    Extract text from a PDF file for Hugging Face Spaces
    """
    if pdf_file is None:
        return "Please upload a PDF file."
    
    pdf_text = ""
    try:
        # In Hugging Face Spaces, pdf_file is already a file path
        with open(pdf_file.name, 'rb') as f:
            pdf_reader = PyPDF2.PdfReader(f)
            for page_num in range(len(pdf_reader.pages)):
                page = pdf_reader.pages[page_num]
                pdf_text += page.extract_text() + "\n"
        
    except Exception as e:
        return f"Error processing PDF: {str(e)}"
    
    return pdf_text

def preprocess_text(text):
    """
    Preprocess the text into structured question-answer pairs
    """
    # Split text into sections by questions
    sections = []
    current_section = []
    
    for line in text.split('\n'):
        line = line.strip()
        if line.startswith('Question'):
            if current_section:
                sections.append(' '.join(current_section))
            current_section = [line]
        elif line:
            current_section.append(line)
    
    if current_section:
        sections.append(' '.join(current_section))
    
    # Create a structured format
    structured_sections = []
    for section in sections:
        # Remove page numbers and other irrelevant text
        section = re.sub(r'\d+\s*$', '', section)
        section = re.sub(r'TRAPS:|BEST ANSWER:|PASSABLE ANSWER:', ' ', section)
        structured_sections.append(section.strip())
    
    return structured_sections

def create_qa_system(pdf_text, model_name="all-MiniLM-L6-v2"):
    """
    Create and return a QA system with the processed text
    """
    # Process text into structured sections
    text_chunks = preprocess_text(pdf_text)
    
    # Create embeddings
    model = SentenceTransformer(model_name)
    embeddings = model.encode(text_chunks)
    
    # Create FAISS index with cosine similarity
    dimension = embeddings.shape[1]
    
    # Normalize vectors for cosine similarity
    faiss.normalize_L2(embeddings)
    index = faiss.IndexFlatIP(dimension)  # Inner product for cosine similarity
    index.add(embeddings)
    
    return model, index, text_chunks

def query_qa_system(question, model, index, text_chunks, similarity_threshold=0.3):
    """
    Query the QA system with improved matching
    """
    # Encode and normalize the question
    question_embedding = model.encode([question])
    faiss.normalize_L2(question_embedding)
    
    # Search for the most similar chunks
    k = 1  # Get only the best match
    similarities, indices = index.search(question_embedding, k)
    
    best_idx = indices[0][0]
    similarity_score = similarities[0][0]  # Cosine similarity score
    
    if similarity_score >= similarity_threshold:
        matched_text = text_chunks[best_idx]
        # Extract just the question number for reference
        question_num = re.search(r'Question \d+:', matched_text)
        question_num = question_num.group(0) if question_num else "Matching section"
        
        return {
            'question': question_num,
            'full_text': matched_text,
            'confidence': float(similarity_score),
            'found_answer': True
        }
    else:
        return {
            'question': None,
            'full_text': "I couldn't find a sufficiently relevant answer to your question in the provided document.",
            'confidence': float(similarity_score),
            'found_answer': False
        }

# Global variables to store model, index, and text chunks
global_model = None
global_index = None
global_text_chunks = None

def upload_file(file):
    global global_model, global_index, global_text_chunks
    if file is not None:
        try:
            # Extract text from PDF
            pdf_text = extract_text_from_pdf(file)
            
            if isinstance(pdf_text, str) and pdf_text.startswith("Error"):
                return pdf_text
            
            # Initialize QA system
            global_model, global_index, global_text_chunks = create_qa_system(pdf_text)
            
            return "✅ Document processed successfully! You can now ask questions."
        except Exception as e:
            return f"❌ Error processing document: {str(e)}"
    else:
        return "❌ Please upload a PDF file."

def answer_question(question):
    global global_model, global_index, global_text_chunks
    
    if global_model is None or global_index is None or global_text_chunks is None:
        return "Please upload and process a document first."
    
    if not question.strip():
        return "Please enter a question."
    
    result = query_qa_system(question, global_model, global_index, global_text_chunks)
    
    if result['found_answer']:
        response = f"Found matching section (confidence: {result['confidence']:.2f}):\n\n{result['full_text']}"
    else:
        response = f"{result['full_text']}\nBest match confidence: {result['confidence']:.2f}"
    
    return response

# Custom CSS for professional styling
custom_css = """
.gradio-container {
    max-width: 1200px !important;
    margin: auto !important;
    padding: 20px !important;
    background-color: #f8f9fa !important;
}

.main-header {
    text-align: center;
    margin-bottom: 2rem;
    padding: 2rem;
    background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
    color: white;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.main-header h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

.main-header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

.upload-section {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
}

.qa-section {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.status-box {
    margin-top: 1rem;
    padding: 1rem;
    border-radius: 8px;
    background: #f0f9ff;
    border: 1px solid #bae6fd;
}

.custom-button {
    background: #2563eb !important;
    color: white !important;
    border-radius: 8px !important;
    padding: 0.75rem 1.5rem !important;
    font-weight: 500 !important;
}

.custom-button:hover {
    background: #1d4ed8 !important;
}

.answer-box {
    background: #f8fafc !important;
    border: 1px solid #e2e8f0 !important;
    border-radius: 8px !important;
    font-family: 'Source Code Pro', monospace !important;
}

.section-title {
    color: #1e293b;
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

/* Responsive design */
@media (max-width: 768px) {
    .gradio-container {
        padding: 10px !important;
    }
    
    .main-header {
        padding: 1.5rem;
    }
    
    .main-header h1 {
        font-size: 2rem;
    }
}
"""

# Create the enhanced Gradio interface
with gr.Blocks(title="Q&A Assistant", css=custom_css) as demo:
    # Header Section
    with gr.Row(elem_classes=["main-header"]):
        with gr.Column():
            gr.Markdown("# Q&A Assistant")
            gr.Markdown("AI-powered interview preparation companion. Upload your PDF and get instant, relevant answers to your queries.")
    
    # Upload Section
    with gr.Row():
        with gr.Column(elem_classes=["upload-section"]):
            gr.Markdown("### 📁 Document Upload", elem_classes=["section-title"])
            with gr.Row():
                pdf_upload = gr.File(
                    label="Upload your interview questions PDF",
                    file_types=[".pdf"],
                    elem_classes=["file-upload"]
                )
            with gr.Row():
                upload_button = gr.Button("Initialize Q&A System", elem_classes=["custom-button"])
            with gr.Row():
                status_text = gr.Textbox(
                    label="System Status",
                    value="Upload a PDF to begin",
                    elem_classes=["status-box"]
                )
    
    # Q&A Section
    with gr.Row():
        with gr.Column(elem_classes=["qa-section"]):
            gr.Markdown("### 💡 Ask Questions", elem_classes=["section-title"])
            with gr.Row():
                question_input = gr.Textbox(
                    label="What would you like to know ?",
                    placeholder="e.g., What are the common behavioral questions?",
                    lines=2
                )
            with gr.Row():
                submit_button = gr.Button("Get Answer", elem_classes=["custom-button"])
            with gr.Row():
                answer_output = gr.Textbox(
                    label="Answer",
                    lines=10,
                    elem_classes=["answer-box"]
                )
    
    # Information Section
    with gr.Row():
        gr.Markdown("""
        <div style="text-align: center; padding: 2rem; color: #64748b; font-size: 0.9rem;">
            Made with ❤️ for interview preparation success
        </div>
        """)
    
    # Set up events
    upload_button.click(upload_file, inputs=pdf_upload, outputs=status_text)
    submit_button.click(answer_question, inputs=question_input, outputs=answer_output)

# Launch the app
if __name__ == "__main__":
    demo.launch()