from fastapi import FastAPI, UploadFile, File, HTTPException
from fastapi.responses import JSONResponse
import shutil
import os
from uuid import uuid4
from marker.converters.pdf import PdfConverter
from marker.models import create_model_dict
from marker.output import text_from_rendered
from threading import Lock

app = FastAPI()

# Singleton class for PdfConverter
class PdfConverterSingleton:
    _instance = None
    _lock = Lock()

    def __new__(cls):
        if cls._instance is None:
            with cls._lock:
                if cls._instance is None:
                    instance = super().__new__(cls)
                    instance._initialize()
                    cls._instance = instance
        return cls._instance

    def _initialize(self):
        self.converter = PdfConverter(artifact_dict=create_model_dict())

    def get_text(self, pdf_path: str) -> str:
        rendered = self.converter(pdf_path)
        text, _, _ = text_from_rendered(rendered)
        return str(text)

# API function to call converter
def extract_text_from_pdf(pdf_path: str) -> str:
    return PdfConverterSingleton().get_text(pdf_path)

# Endpoint to upload a file and extract markdown text
@app.post("/extract-pdf-text")
async def extract_pdf_text(file: UploadFile = File(...)):
    if file.content_type != "application/pdf":
        raise HTTPException(status_code=400, detail="Only PDF files are supported.")

    temp_filename = f"/tmp/{uuid4().hex}.pdf"
    try:
        with open(temp_filename, "wb") as buffer:
            shutil.copyfileobj(file.file, buffer)

        text = extract_text_from_pdf(temp_filename)
        return JSONResponse(content={"markdown_text": text})

    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))

    finally:
        if os.path.exists(temp_filename):
            os.remove(temp_filename)