"""
This is the shoppingcart context_processor module.
Currently the only context_processor detects whether request.user has a cart that should be displayed in the
navigation.  We want to do this in the context_processor to
1) keep database accesses out of templates (this led to a transaction bug with user email changes)
2) because navigation.html is "called" by being included in other templates, there's no "views.py" to put this.
"""

from .models import CourseRegCodeItem, Order, PaidCourseRegistration
from .utils import is_shopping_cart_enabled


def user_has_cart_context_processor(request):
    """
    Checks if request has an authenticated user.  If so, checks if request.user has a cart that should
    be displayed.  Anonymous users don't.
    Adds `display_shopping_cart` to the context
    """
    def should_display_shopping_cart():
        """
        Returns a boolean if the user has an items in a cart whereby the shopping cart should be
        displayed to the logged in user
        """
        return (
            # user is logged in and
            request.user.is_authenticated() and
            # do we have the feature turned on
            is_shopping_cart_enabled() and
            # does the user actually have a cart (optimized query to prevent creation of a cart when not needed)
            Order.does_user_have_cart(request.user) and
            # user's cart has PaidCourseRegistrations or CourseRegCodeItem
            Order.user_cart_has_items(
                request.user,
                [PaidCourseRegistration, CourseRegCodeItem]
            )
        )

    return {'should_display_shopping_cart_func': should_display_shopping_cart}
