import importlib
from django.conf import settings
from rosetta.conf import settings as rosetta_settings
from django.core.exceptions import ImproperlyConfigured


def can_translate(user):
    return get_access_control_function()(user)


def get_access_control_function():
    """
    Return a predicate for determining if a user can access the Rosetta views
    """
    fn_path = getattr(settings, 'ROSETTA_ACCESS_CONTROL_FUNCTION', None)
    if fn_path is None:
        return is_superuser_staff_or_in_translators_group
    # Dynamically load a permissions function
    perm_module, perm_func = fn_path.rsplit('.', 1)
    perm_module = importlib.import_module(perm_module)
    return getattr(perm_module, perm_func)


# Default access control test
def is_superuser_staff_or_in_translators_group(user):
    if not getattr(settings, 'ROSETTA_REQUIRES_AUTH', True):
        return True
    try:
        if not user.is_authenticated:
            return False
        elif user.is_superuser and user.is_staff:
            return True
        else:
            return user.groups.filter(name='translators').exists()
    except AttributeError:
        if not hasattr(user, 'is_authenticated') or not hasattr(user, 'is_superuser') or not hasattr(user, 'groups'):
            raise ImproperlyConfigured('If you are using custom User Models you must implement a custom authentication method for Rosetta. See ROSETTA_ACCESS_CONTROL_FUNCTION here: https://django-rosetta.readthedocs.org/en/latest/settings.html')
        raise


def can_translate_language(user, langid):
    try:
        if not rosetta_settings.ROSETTA_LANGUAGE_GROUPS:
            return can_translate(user)
        elif not user.is_authenticated:
            return False
        elif user.is_superuser and user.is_staff:
            return True
        else:
            return user.groups.filter(name='translators-%s' % langid).exists()

    except AttributeError:
        if not hasattr(user, 'is_authenticated') or not hasattr(user, 'is_superuser') or not hasattr(user, 'groups'):
            raise ImproperlyConfigured('If you are using custom User Models you must implement a custom authentication method for Rosetta. See ROSETTA_ACCESS_CONTROL_FUNCTION here: https://django-rosetta.readthedocs.org/en/latest/settings.html')
        raise