import gradio as gr
from langchain_community.document_loaders import PyPDFLoader
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langchain_huggingface import HuggingFaceEmbeddings
from langchain_community.vectorstores import FAISS
from huggingface_hub import InferenceClient

embedding_model = HuggingFaceEmbeddings(
    model_name="sentence-transformers/all-MiniLM-L6-v2",
    model_kwargs={'device': 'cpu'}
)

client = InferenceClient(model="HuggingFaceH4/zephyr-7b-beta")
vectorstore = None

def process_pdf(pdf_file):
    global vectorstore
    if pdf_file is None:
        return "Please upload a PDF file."
    try:
        loader = PyPDFLoader(pdf_file.name)
        documents = loader.load()
        text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=200)
        chunks = text_splitter.split_documents(documents)
        vectorstore = FAISS.from_documents(documents=chunks, embedding=embedding_model)
        return f"✅ Processed {len(documents)} pages into {len(chunks)} chunks."
    except Exception as e:
        return f"❌ Error: {str(e)}"

def answer_question(question):
    global vectorstore
    if vectorstore is None:
        return "Upload a PDF first.", ""
    if not question.strip():
        return "Enter a question.", ""
    try:
        docs = vectorstore.similarity_search(question, k=3)
        context = "\n\n".join([doc.page_content for doc in docs])
        prompt = f"<|system|>\nAnswer based on context only.\n</s>\n<|user|>\nContext:\n{context}\n\nQuestion: {question}\n</s>\n<|assistant|>\n"
        response = client.text_generation(prompt, max_new_tokens=512, temperature=0.7)
        sources = [f"{i}. Page {doc.metadata.get('page', 'N/A')}" for i, doc in enumerate(docs, 1)]
        return response, "\n".join(sources)
    except Exception as e:
        return f"Error: {str(e)}", ""

with gr.Blocks() as demo:
    gr.Markdown("# 📚 RAG Document Q&A")
    with gr.Row():
        with gr.Column():
            pdf = gr.File(label="Upload PDF", file_types=[".pdf"])
            btn1 = gr.Button("Process PDF")
            status = gr.Textbox(label="Status")
        with gr.Column():
            question = gr.Textbox(label="Question")
            btn2 = gr.Button("Ask")
            answer = gr.Textbox(label="Answer", lines=5)
            sources = gr.Textbox(label="Sources")
    btn1.click(process_pdf, pdf, status)
    btn2.click(answer_question, question, [answer, sources])

demo.launch(server_name="0.0.0.0", server_port=7860)