# -*- coding: utf-8 -*-

import django
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured


def check_installed_app(app, max_dj_version=None):
    dj_version = django.VERSION
    installed_apps = settings.INSTALLED_APPS
    if max_dj_version is None:
        if app not in installed_apps:
            raise ImproperlyConfigured(
                '\'{}\' is required, '
                'add it to settings.INSTALLED_APPS.'.format(
                    app))
    elif dj_version < max_dj_version:
        if app not in installed_apps:
            raise ImproperlyConfigured(
                '\'{}\' is required before django {}.{}, '
                'add it to settings.INSTALLED_APPS.'.format(
                    app, *max_dj_version))
    else:
        if app in installed_apps:
            raise ImproperlyConfigured(
                '\'{}\' is no more required since django {}.{}, '
                'remove it from settings.INSTALLED_APPS.'.format(
                    app, *max_dj_version))


def check_installed_apps():
    check_installed_app('colorfield')
    check_installed_app('flat', max_dj_version=(1, 9))
    check_installed_app('flat_responsive', max_dj_version=(2, 0))