# Django 5.2 documentation

# Source code for django.contrib.redirects.middleware

    from django.apps import apps
    from django.conf import settings
    from django.contrib.redirects.models import Redirect
    from django.contrib.sites.shortcuts import get_current_site
    from django.core.exceptions import ImproperlyConfigured
    from django.http import HttpResponseGone, HttpResponsePermanentRedirect
    from django.utils.deprecation import MiddlewareMixin

    class RedirectFallbackMiddleware(MiddlewareMixin):
        # Defined as class-level attributes to be subclassing-friendly.
        response_gone_class = HttpResponseGone
        response_redirect_class = HttpResponsePermanentRedirect

        def __init__(self, get_response):
            if not apps.is_installed("django.contrib.sites"):
                raise ImproperlyConfigured(
                    "You cannot use RedirectFallbackMiddleware when "
                    "django.contrib.sites is not installed."
                )
            super().__init__(get_response)

        def process_response(self, request, response):
            # No need to check for a redirect for non-404 responses.
            if response.status_code != 404:
                return response

            full_path = request.get_full_path()
            current_site = get_current_site(request)

            r = None
            try:
                r = Redirect.objects.get(site=current_site, old_path=full_path)
            except Redirect.DoesNotExist:
                pass
            if r is None and settings.APPEND_SLASH and not request.path.endswith("/"):
                try:
                    r = Redirect.objects.get(
                        site=current_site,
                        old_path=request.get_full_path(force_append_slash=True),
                    )
                except Redirect.DoesNotExist:
                    pass
            if r is not None:
                if r.new_path == "":
                    return self.response_gone_class()
                return self.response_redirect_class(r.new_path)

            # No redirect was found. Return the response.
            return response