import re

from django import http
from django.conf import settings
from django.urls import is_valid_path
from django.core.exceptions import ImproperlyConfigured
from django.utils.deprecation import MiddlewareMixin


class RemoveSlashMiddleware(MiddlewareMixin):
    def process_request(self, request):
        if getattr(settings, "APPEND_SLASH") and getattr(settings, "REMOVE_SLASH"):
            raise ImproperlyConfigured("APPEND_SLASH and REMOVE_SLASH may not both be True.")

        old_url = request.path_info # path_info only includes path, query information
        if getattr(settings, "REMOVE_SLASH", False) and old_url[-1] == "/":
            urlconf = getattr(request, "urlconf", None)

            new_url = old_url[:-1]

            # If the url with a / would 404 and without a slash wouldn't
            if (not is_valid_path(old_url, urlconf)) and is_valid_path(new_url, urlconf):
                if settings.DEBUG and request.method == "POST":
                    if old_url.startswith("/api/"):
                        return api.error("You made a POST request to a URL ending with a slash. Please repeat your request without the slash.")

                    raise RuntimeError(""
                        "You called this URL via POST, but the URL ends in a "
                        "slash and you have REMOVE_SLASH set. Django can't "
                        "redirect to the non-slash URL while maintaining POST "
                        f"data. Change your form to point to {new_url} (without a "
                        "trailing slash), or set REMOVE_SLASH=False in your "
                        "Django settings.")

                # The ? and everything after
                query_data = re.match(r"^[^?]*(\?.*)?$", request.build_absolute_uri()).group(1) or ""

                return http.HttpResponsePermanentRedirect(new_url + query_data)