import os

from django.conf import settings
from django.core import checks

@checks.register('directories')
def check_cdn_directory_exists(app_configs, **kwargs):
    """This checks that the path from which the CDN will serve static files for
       this version of the datatracker actually exists.  In development and test
       mode STATIC_ROOT will normally be just static/, but in production it will be
       set to a different part of the file system which is served via CDN, and the
       path will contain the datatracker release version.
    """
    errors = []
    if settings.SERVER_MODE == 'production' and not os.path.exists(settings.STATIC_ROOT):
        errors.append(checks.Error(
            "The static files directory has not been set up.",
            hint="Please run 'ietf/manage.py collectstatic'.",
            obj=None,
            id='datatracker.E001',
        ))
    return errors