from pathlib import Path

import requests


DATA_DIR = Path(__file__).parent / 'data'


def get_file(url, filename, etag: str = None):
    if not DATA_DIR.is_dir():
        DATA_DIR.mkdir()

    head_response = requests.head(url, allow_redirects=True)
    headers = head_response.headers
    if not etag:
        etag = headers.get('ETag').split('/')[-1].replace('"', '')

    file = DATA_DIR / filename.format(etag=etag)
    if file.exists():
        return file

    response = requests.get(url, allow_redirects=True)
    with file.open('wb') as f:
        f.write(response.content)

    return file