from django.db.models import Q
from django.contrib.auth.models import User
from django.contrib.auth.backends import ModelBackend
from piston.authentication import (OAuthAuthentication as
                                   PistonOAuthAuthentication, send_oauth_error)
from piston import oauth
from model_cache import ModelCache


user_cache = ModelCache(User)


class OAuthAuthentication(PistonOAuthAuthentication):
    """
    Replacement for piston.authentication.OAuthAuthentication that utilizes
    the cache for it's lookups
    """
    def is_authenticated(self, request):
        """
        piston.authentication.OAuthAuthentication sets request.user,
        request.consumer and request.throttle_extra from token.consumer.id.
        This little hack alleviates having to fetch `token.consumer` and
        `token.user` if the request does not need it.
        """

        if self.is_valid_request(request):
            try:
                consumer, token, params = self.validate_token(request)
            except oauth.OAuthError, err:
                print send_oauth_error(err)
                return False
            if consumer and token:
                #import pdb; pdb.set_trace()

                request.user = user_cache(Q(pk=token.user_id))
                request.consumer = consumer
                request.token = token
                request.throttle_extra = consumer.id
                return True
        return False


class CachedUserBackend(ModelBackend):
    """
    A django.contrib.auth.backends.ModelBackend that gets it's user from the
    cache if possible
    """
    def authenticate(self, username=None, password=None):
        try:
            user = user_cache(Q(username=username))
            if user.check_password(password):
                return user
        except User.DoesNotExist:
            return None