"""Utilities to assist with commerce tasks."""
from urlparse import urljoin

from django.conf import settings

from commerce.models import CommerceConfiguration
from openedx.core.djangoapps.site_configuration import helpers as configuration_helpers


class EcommerceService(object):
    """ Helper class for ecommerce service integration. """
    def __init__(self):
        self.config = CommerceConfiguration.current()

    def is_enabled(self, user):
        """
        Determines the availability of the EcommerceService based on user activation and service configuration.
        Note: If the user is anonymous we bypass the user activation gate and only look at the service config.

        Returns:
            Boolean
        """
        allow_user = user.is_active or user.is_anonymous()
        return allow_user and self.config.checkout_on_ecommerce_service

    def payment_page_url(self):
        """ Return the URL for the checkout page.

        Example:
            http://localhost:8002/basket/single_item/
        """
        ecommerce_url_root = configuration_helpers.get_value(
            'ECOMMERCE_PUBLIC_URL_ROOT',
            settings.ECOMMERCE_PUBLIC_URL_ROOT,
        )
        return urljoin(ecommerce_url_root, self.config.single_course_checkout_page)

    def checkout_page_url(self, sku):
        """ Construct the URL to the ecommerce checkout page and include a product.

        Example:
            http://localhost:8002/basket/single_item/?sku=5H3HG5
        """
        return "{}?sku={}".format(self.payment_page_url(), sku)