from django.utils import translation
from django.utils.cache import patch_vary_headers

from . import preferences


class PreferencesMiddleware:
    """Read the preference cookies and activate the language for this request (AD-15)."""

    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        prefs = preferences.from_request(request)
        request.preferences = prefs
        request.LANGUAGE_CODE = prefs.language_code
        translation.activate(prefs.language_code)
        try:
            response = self.get_response(request)
        finally:
            translation.deactivate()
        response.headers.setdefault("Content-Language", prefs.language)
        patch_vary_headers(response, ("Cookie", "Accept-Language"))
        return response