from django.conf import settings
from django.http import Http404, HttpResponsePermanentRedirect
from django.utils import translation
from django.utils.cache import patch_vary_headers
       
class RedirectLanguage(Exception):
    pass

class LocaleURLMiddleware:
    def get_language_from_request(self, request):
        supported = dict(settings.LANGUAGES)
        lang = settings.LANGUAGE_CODE[:2]
        check = re.match(r"^/(\w\w)/.*", request.path)
        changed = False
        redir = False
        if check is not None:
            url_list = request.path.split('/')
            t = check.group(1)
            if t in url_list and url_list.index(t) == 1:
                del url_list[1]
                request.path = u'/'.join(url_list)
            if t in supported:
                lang = t
                if hasattr(request, 'session'):
                    request.session['django_language'] = lang
                else:
                    response.set_cookie('django_language', lang)
                changed = True
        else:
            redir = True
        if not changed:
            if hasattr(request, 'session'):
                lang = request.session.get('django_language', None)
                if lang in supported and lang is not None:
                    return lang, redir
            else:
                lang = request.COOKIES.get('django_language', None)
                if lang in supported and lang is not None:
                    return lang, redir
        return lang, redir

    def process_request(self, request):
        language, redir = self.get_language_from_request(request)
        if language is None:
            language = settings.LANGUAGE_CODE[:2]
        translation.activate(language)
        request.LANGUAGE_CODE = translation.get_language()
        if redir:
            redir_url = '/%s%s' % (language, request.path)
            return HttpResponsePermanentRedirect(redir_url)

    def process_response(self, request, response):
        patch_vary_headers(response, ('Accept-Language',))
        translation.deactivate()
        return response