app.py

import gradio as gr
import spaces
import os
import logging
from langchain.document_loaders import PyPDFLoader
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain.embeddings import HuggingFaceEmbeddings
from langchain.vectorstores import Chroma
from huggingface_hub import InferenceClient, get_token

# Set up logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Set HF_HOME for caching Hugging Face assets in persistent storage
os.environ["HF_HOME"] = "/data/.huggingface"
os.makedirs(os.environ["HF_HOME"], exist_ok=True)

# Define persistent storage directories
DATA_DIR = "/data"  # Root persistent storage directory
DOCS_DIR = os.path.join(DATA_DIR, "documents")  # Subdirectory for uploaded PDFs
CHROMA_DIR = os.path.join(DATA_DIR, "chroma_db")  # Subdirectory for Chroma vector store

# Create directories if they don't exist
os.makedirs(DOCS_DIR, exist_ok=True)
os.makedirs(CHROMA_DIR, exist_ok=True)

# Initialize Cerebras InferenceClient
try:
    client = InferenceClient(
        model="meta-llama/Llama-4-Scout-17B-16E-Instruct",
        provider="cerebras",
        token=get_token()  # PRO account token with $2 monthly credits
    )
except Exception as e:
    logger.error(f"Failed to initialize InferenceClient: {str(e)}")
    client = None

# Global variables for vector store
vectorstore = None
retriever = None

@spaces.GPU(duration=120)  # Use ZeroGPU (H200) for embedding generation, 120s timeout
def initialize_rag(file):
    global vectorstore, retriever
    try:
        # Save uploaded file to persistent storage
        file_name = os.path.basename(file.name)
        file_path = os.path.join(DOCS_DIR, file_name)
        if os.path.exists(file_path):
            logger.info(f"File {file_name} already exists in {DOCS_DIR}, skipping save.")
        else:
            with open(file_path, "wb") as f:
                f.write(file.read())
            logger.info(f"Saved {file_name} to {file_path}")

        # Load and split document
        loader = PyPDFLoader(file_path)
        documents = loader.load()
        text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=200)
        texts = text_splitter.split_documents(documents)

        # Create or update embeddings and vector store
        embeddings = HuggingFaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
        vectorstore = Chroma.from_documents(
            texts, embeddings, persist_directory=CHROMA_DIR
        )
        vectorstore.persist()  # Save to persistent storage
        retriever = vectorstore.as_retriever(search_kwargs={"k": 3})
        return f"Document '{file_name}' processed and saved to {DOCS_DIR}!"
    except Exception as e:
        logger.error(f"Error processing document: {str(e)}")
        return f"Error processing document: {str(e)}"

def query_documents(query, history, system_prompt, max_tokens, temperature):
    global retriever, client
    try:
        if client is None:
            return history, "Error: InferenceClient not initialized."
        if retriever is None:
            return history, "Error: No documents loaded. Please upload a document first."

        # Retrieve relevant documents
        docs = retriever.get_relevant_documents(query)
        context = "\n".join([doc.page_content for doc in docs])

        # Call Cerebras inference
        response = client.chat_completion(
            messages=[
                {"role": "system", "content": system_prompt},
                {"role": "user", "content": f"Context: {context}\n\nQuery: {query}"}
            ],
            max_tokens=int(max_tokens),
            temperature=float(temperature),
            stream=False
        )
        answer = response.choices[0].message.content

        # Update chat history
        history.append((query, answer))
        return history, history
    except Exception as e:
        logger.error(f"Error querying documents: {str(e)}")
        return history, f"Error querying documents: {str(e)}"

# Load existing vector store on startup
try:
    if os.path.exists(CHROMA_DIR):
        embeddings = HuggingFaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
        vectorstore = Chroma(persist_directory=CHROMA_DIR, embedding_function=embeddings)
        retriever = vectorstore.as_retriever(search_kwargs={"k": 3})
        logger.info(f"Loaded existing vector store from {CHROMA_DIR}")
except Exception as e:
    logger.error(f"Error loading vector store: {str(e)}")

with gr.Blocks() as demo:
    gr.Markdown("# RAG Chatbot with Persistent Storage and Cerebras Inference")

    # File upload
    file_input = gr.File(label="Upload Document (PDF)", file_types=[".pdf"])
    file_output = gr.Textbox(label="Upload Status")
    file_input.upload(initialize_rag, file_input, file_output)

    # Chat interface
    chatbot = gr.Chatbot(label="Conversation")

    # Query and parameters
    with gr.Row():
        query_input = gr.Textbox(label="Query", placeholder="Ask about the document...")
        system_prompt = gr.Textbox(
            label="System Prompt",
            value="You are a helpful assistant answering questions based on the provided document context."
        )
        max_tokens = gr.Slider(label="Max Tokens", minimum=50, maximum=2000, value=500, step=50)
        temperature = gr.Slider(label="Temperature", minimum=0.1, maximum=1.0, value=0.7, step=0.1)

    # Submit button
    submit_btn = gr.Button("Send")
    submit_btn.click(
        query_documents,
        inputs=[query_input, chatbot, system_prompt, max_tokens, temperature],
        outputs=[chatbot, chatbot]
    )

if __name__ == "__main__":
    demo.launch()