import logging
from django.apps import apps
from django.contrib.auth import get_user_model
from django.contrib.auth.models import Group

app_config = apps.get_containing_app_config(__package__)
logger = logging.getLogger(__name__)


def get_system_user():
    return get_user_model().objects.get_or_create(username='-system-')[0]


def get_ghost_user():
    return get_user_model().objects.get_or_create(username='-deleted-')[0]


def get_group_members(group_name, ignore_missing=False):
    users = []
    try:
        group = Group.objects.get(name=group_name)
        users.extend(group.user_set.all())
    except Group.DoesNotExist:
        if not ignore_missing:
            raise
    return users


def get_group_name_by_role(role):
    group_name_var = 'group_{}'.format(role)
    return getattr(app_config.settings, group_name_var, None)


def get_users_by_role(role):
    users = []
    group_name = get_group_name_by_role(role)
    if group_name:
        users = get_group_members(group_name, ignore_missing=True)
    return users


def has_role(user, role):
    group_name = get_group_name_by_role(role)
    if group_name and user.groups.filter(name=group_name).count():
        return True
    return False