from django.conf import settings
from django.contrib.sessions.middleware import SessionMiddleware
from rest_framework.authentication import get_authorization_header
from rest_framework.reverse import reverse_lazy


class AppSessionToTokenAuthConversionMiddleware(SessionMiddleware):
    """
    Apps SessionMiddleware to insert the session cookie id to the request body. This is used as a token
    by the app FE to send requests. Also this takes the session cookie id from the Authorization header
    and inserts it into request cookies.
    """

    authorization_keyword = settings.SESSION_COOKIE_NAME
    session_cookie_name = settings.SESSION_COOKIE_NAME

    def process_response(self, request, response):
        """Pass the sessionid from response cookies to the response body."""

        response = super(AppSessionToTokenAuthConversionMiddleware, self).process_response(
            request, response
        )

        if (
            request.path == reverse_lazy("authentication:login")
            and self.session_cookie_name in response.cookies.keys()
        ):
            # update session id in response body
            session_id = response.cookies[self.session_cookie_name].value
            response.data[self.session_cookie_name] = session_id
            response._is_rendered = False
            response.render()

        return response

    def process_request(self, request):
        """Get the sessionid from the request Authorization header and pass it to the request."""

        sessionid = self.get_sessionid_from_authorization_header(request)
        if sessionid:
            request.COOKIES[self.session_cookie_name] = sessionid

        return super(AppSessionToTokenAuthConversionMiddleware, self).process_request(request)

    def get_sessionid_from_authorization_header(self, request):
        """
        Gets the session-id from the Authorization header in the request. Passed 
        as `{self.authorization_keyword} <token>`. Valid length is 2.
        """

        auth = get_authorization_header(request).split()

        if (
            not auth
            or auth[0].lower() != self.authorization_keyword.lower().encode()
            or len(auth) != 2
        ):
            return None

        try:
            return auth[1].decode()
        except UnicodeError:
            pass

        return None