middleware.py

"""
dj-stripe middleware

Refer to SubscriptionPaymentMiddleware docstring for more info.
"""
import fnmatch

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.shortcuts import redirect
from django.urls import resolve
from django.utils.deprecation import MiddlewareMixin

from .utils import subscriber_has_active_subscription


class SubscriptionPaymentMiddleware(MiddlewareMixin):
    """
    Used to redirect users from subcription-locked request destinations.

    Rules:

    - "(app_name)" means everything from this app is exempt
    - "[namespace]" means everything with this name is exempt
    - "namespace:name" means this namespaced URL is exempt
    - "name" means this URL is exempt
    - The entire djstripe namespace is exempt
    - If settings.DEBUG is True, then django-debug-toolbar is exempt
    - A 'fn:' prefix means the rest of the URL is fnmatch'd.

    Example:

    ```py
    DJSTRIPE_SUBSCRIPTION_REQUIRED_EXCEPTION_URLS = (
        "[blogs]",  # Anything in the blogs namespace
        "products:detail",  # A ProductDetail view you want shown to non-payers
        "home",  # Site homepage
        "fn:/accounts*",  # anything in the accounts/ URL path
    )
    ```
    """

    def process_request(self, request):
        """Check the subscriber's subscription status.

        Returns early if request does not outlined in this middleware's docstring.
        """
        if self.is_matching_rule(request):
            return

        return self.check_subscription(request)

    def is_matching_rule(self, request):
        """Check according to the rules defined in the class docstring."""
        # First, if in DEBUG mode and with django-debug-toolbar, we skip
        #   this entire process.
        from .settings import SUBSCRIPTION_REQUIRED_EXCEPTION_URLS

        if settings.DEBUG and request.path.startswith("/__debug__"):
            return True

        exempt_urls = list(SUBSCRIPTION_REQUIRED_EXCEPTION_URLS) + ["[djstripe]"]

        # Second we check against matches
        match = resolve(
            request.path, getattr(request, "urlconf", settings.ROOT_URLCONF)
        )
        if "({0})".format(match.app_name) in exempt_urls:
            return True

        if "[{0}]".format(match.namespace) in exempt_urls:
            return True

        if "{0}:{1}".format(match.namespace, match.url_name) in exempt_urls:
            return True

        if match.url_name in exempt_urls:
            return True

        # Third, we check wildcards:
        for exempt in [x for x in exempt_urls if x.startswith("fn:")]:
            exempt = exempt.replace("fn:", "")
            if fnmatch.fnmatch(request.path, exempt):
                return True

        return False

    def check_subscription(self, request):
        """Redirect to the subscribe page if the user lacks an active subscription."""
        from .settings import SUBSCRIPTION_REDIRECT, subscriber_request_callback

        subscriber = subscriber_request_callback(request)

        if not subscriber_has_active_subscription(subscriber):
            if not SUBSCRIPTION_REDIRECT:
                raise ImproperlyConfigured("DJSTRIPE_SUBSCRIPTION_REDIRECT is not set.")
            return redirect(SUBSCRIPTION_REDIRECT)