app.py

from fastapi import FastAPI,Query
from transformers import AutoTokenizer, AutoModelForCausalLM
import torch
import os
from pydantic import BaseModel
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles


# ✅ Force Hugging Face cache to /tmp (writable in Spaces)
os.environ["HF_HOME"] = "/tmp"
os.environ["TRANSFORMERS_CACHE"] = "/tmp"


model_id = "rabiyulfahim/qa_python_gpt2"

tokenizer = AutoTokenizer.from_pretrained(model_id, cache_dir="/tmp")
model = AutoModelForCausalLM.from_pretrained(model_id, cache_dir="/tmp")


app = FastAPI(title="QA GPT2 API UI", description="Serving HuggingFace model with FastAPI")

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)
# Request schema
class QueryRequest(BaseModel):
    question: str
    max_new_tokens: int = 50
    temperature: float = 0.7
    top_p: float = 0.9


@app.get("/")
def home():
    return {"message": "Welcome to QA GPT2 API 🚀"}

@app.get("/ask")
def ask(question: str, max_new_tokens: int = 50):
    inputs = tokenizer(question, return_tensors="pt")
    outputs = model.generate(**inputs, max_new_tokens=max_new_tokens)
    answer = tokenizer.decode(outputs[0], skip_special_tokens=True)
    return {"question": question, "answer": answer}


# Mount static folder
app.mount("/static", StaticFiles(directory="static"), name="static")

@app.get("/ui", response_class=HTMLResponse)
def serve_ui():
    html_path = os.path.join("static", "index.html")
    with open(html_path, "r", encoding="utf-8") as f:
        return HTMLResponse(f.read())


# Health check endpoint
@app.get("/health")
def health():
    return {"status": "ok"}

# Inference endpoint
@app.post("/predict")
def predict(request: QueryRequest):
    inputs = tokenizer(request.question, return_tensors="pt")
    outputs = model.generate(
        **inputs,
        max_new_tokens=request.max_new_tokens,
        do_sample=True,
        temperature=0.7,
        top_p=0.9,
        pad_token_id=tokenizer.eos_token_id,
        return_dict_in_generate=True
    )

    answer = tokenizer.decode(outputs.sequences[0], skip_special_tokens=True)
    return {
        "question": request.question,
        "answer": answer
    }




@app.get("/answers")
def predict(question: str = Query(..., description="The question to ask"), max_new_tokens: int = Query(50, description="Max new tokens to generate")):
    # Tokenize the input question
    inputs = tokenizer(question, return_tensors="pt")

    # Generate output from model
    outputs = model.generate(
        **inputs,
        max_new_tokens=max_new_tokens,
        do_sample=True,
        temperature=0.7,
        top_p=0.9,
        pad_token_id=tokenizer.eos_token_id,
        return_dict_in_generate=True
    )

    # Decode output
    answer = tokenizer.decode(outputs.sequences[0], skip_special_tokens=True)

    return {
        "question": question,
        "answer": answer
    }