app/main.py

import os, asyncio, logging
import gradio as gr
from huggingface_hub import InferenceClient
from .prompt import build_prompt

# ---------------------------------------------------------------------
# model / client initialisation
# ---------------------------------------------------------------------
HF_TOKEN  = os.getenv("HF_TOKEN")
MODEL_ID  = os.getenv("MODEL_ID", "meta-llama/Meta-Llama-3-8B-Instruct")
MAX_TOKENS = int(os.getenv("MAX_NEW_TOKENS", "512"))
TEMPERATURE = float(os.getenv("TEMPERATURE", "0.2"))

if not HF_TOKEN:
    raise RuntimeError(
        "HF_TOKEN env-var missing. "
    )

client = InferenceClient(model=MODEL_ID, token=HF_TOKEN)

# ---------------------------------------------------------------------
# Core generation function for both Gradio UI and MCP
# ---------------------------------------------------------------------
async def _call_llm(prompt: str) -> str:
    """
    Try text_generation first (for models/providers that still support it);
    fall back to chat_completion when the provider is chat-only (Novita, etc.).
    """
    try:
        # hf-inference
        return await asyncio.to_thread(
            client.text_generation,
            prompt,
            max_new_tokens=MAX_TOKENS,
            temperature=TEMPERATURE,
        )
    except ValueError as e:
        if "Supported task: conversational" not in str(e):
            raise                              # genuine error → bubble up

        # fallback for Novita
        messages = [{"role": "user", "content": prompt}]
        completion = await asyncio.to_thread(
            client.chat_completion,
            messages=messages,
            model=MODEL_ID,
            max_tokens=MAX_TOKENS,
            temperature=TEMPERATURE,
        )
        return completion.choices[0].message.content.strip()

async def rag_generate(query: str, context: str) -> str:
    """
    Generate an answer to a query using provided context through RAG.
    
    This function takes a user query and relevant context, then uses a language model
    to generate a comprehensive answer based on the provided information.
    
    Args:
        query (str): The user's question or query
        context (str): The relevant context/documents to use for answering
        
    Returns:
        str: The generated answer based on the query and context
    """
    if not query.strip():
        return "Error: Query cannot be empty"
    
    if not context.strip():
        return "Error: Context cannot be empty"
    
    prompt = build_prompt(query, context)
    try:
        answer = await _call_llm(prompt)
        return answer
    except Exception as e:
        logging.exception("Generation failed")
        return f"Error: {str(e)}"

# ---------------------------------------------------------------------
# Gradio Interface with MCP support
# ---------------------------------------------------------------------
ui = gr.Interface(
    fn=rag_generate,
    inputs=[
        gr.Textbox(
            label="Query", 
            lines=2, 
            placeholder="What would you like to know?",
            info="Enter your question here"
        ),
        gr.Textbox(
            label="Context", 
            lines=8, 
            placeholder="Paste relevant documents or context here...",
            info="Provide the context/documents to use for answering"
        ),
    ],
    outputs=gr.Textbox(
        label="Generated Answer",
        lines=6,
        show_copy_button=True
    ),
    title="RAG Generation Service",
    description="Ask questions and get answers based on your provided context. This service is also available as an MCP server for integration with AI applications.",
    examples=[
        [
            "What is the main benefit mentioned?",
            "Machine learning has revolutionized many industries. The main benefit is increased efficiency and accuracy in data processing."
        ],
        [
            "Who is the CEO?",
            "Company ABC was founded in 2020. The current CEO is Jane Smith, who has led the company to significant growth."
        ]
    ]
)

# Launch with MCP server enabled
if __name__ == "__main__":
    ui.launch(
        server_name="0.0.0.0",
        server_port=7860,
        mcp_server=True,
        show_error=True
    )