text: "This is the locale selecting middleware that will look at accept headers"
  
  from django.conf import settings
  from django.conf.urls.i18n import is_language_prefix_patterns_used
  from django.http import HttpResponseRedirect
  from django.urls import get_script_prefix, is_valid_path
  from django.utils import translation
  from django.utils.cache import patch_vary_headers
  from django.utils.deprecation import MiddlewareMixin
  
  
  class LocaleMiddleware(MiddlewareMixin):
      """
      This is a very simple middleware that parses a request
      and decides what translation object to install in the current
      thread context. This allows pages to be dynamically
      translated to the language the user desires (if the language
      is available, of course).
      """
      response_redirect_class = HttpResponseRedirect
  
      def process_request(self, request):
          urlconf = getattr(request, 'urlconf', settings.ROOT_URLCONF)
          i18n_patterns_used, prefixed_default_language = is_language_prefix_patterns_used(urlconf)
          language = translation.get_language_from_request(request, check_path=i18n_patterns_used)
          language_from_path = translation.get_language_from_path(request.path_info)
          if not language_from_path and i18n_patterns_used and not prefixed_default_language:
              language = settings.LANGUAGE_CODE
          translation.activate(language)
          request.LANGUAGE_CODE = translation.get_language()
  
      def process_response(self, request, response):
          language = translation.get_language()
          language_from_path = translation.get_language_from_path(request.path_info)
          urlconf = getattr(request, 'urlconf', settings.ROOT_URLCONF)
          i18n_patterns_used, prefixed_default_language = is_language_prefix_patterns_used(urlconf)
  
          if (response.status_code == 404 and not language_from_path and
                  i18n_patterns_used and prefixed_default_language):
              # Maybe the language code is missing in the URL? Try adding the
              # language prefix and redirecting to that URL.
              language_path = '/%s%s' % (language, request.path_info)
              path_valid = is_valid_path(language_path, urlconf)
              path_needs_slash = (
                  not path_valid and (
                      settings.APPEND_SLASH and not language_path.endswith('/') and
                      is_valid_path('%s/' % language_path, urlconf)
                  )
              )
  
              if path_valid or path_needs_slash:
                  script_prefix = get_script_prefix()
                  # Insert language after the script prefix and before the
                  # rest of the URL
                  language_url = request.get_full_path(force_append_slash=path_needs_slash).replace(
                      script_prefix,
                      '%s%s/' % (script_prefix, language),
                      1
                  )
                  return self.response_redirect_class(language_url)
  
          if not (i18n_patterns_used and language_from_path):
              patch_vary_headers(response, ('Accept-Language',))
          if 'Content-Language' not in response:
              response['Content-Language'] = language
          return response
  