import asyncio
from fastapi import FastAPI, File, UploadFile
from fastapi.responses import StreamingResponse
from io import BytesIO

app = FastAPI()

@app.post("/tex2pdf")
async def convert_to_pdf(file: UploadFile = File(...)):
    input_file = BytesIO(await file.read())

    process = await asyncio.create_subprocess_exec(
        'pdflatex', '-f', 'pdf',
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE
    )

    output_pdf, error = await process.communicate(input=input_file.getvalue())

    if process.returncode == 0:
        return StreamingResponse(BytesIO(output_pdf), media_type='application/pdf')
    else:
        return {"error": "Conversion failed.", "details": error.decode()}