from django.db import models
from django.contrib.auth.models import Group
from django.contrib.auth import get_user_model
from django.contrib.contenttypes.fields import (
    GenericForeignKey, GenericRelation
)
from django.contrib.contenttypes.models import ContentType
from django.utils.translation import ugettext_lazy as _

User = get_user_model()


class Subscription(models.Model):
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')

    class Meta:
        abstract = True


class UserSubscription(Subscription):
    user = models.ForeignKey(User)
    is_unsub = models.BooleanField(
        _("désinscription"),
        default=False
    )

    class Meta:
        verbose_name = _("souscription utilisateur")
        unique_together = ("user", "content_type", "object_id")


class GroupSubscription(Subscription):
    group = models.ForeignKey(Group)

    class Meta:
        verbose_name = _("souscription en groupe")
        unique_together = ("group", "content_type", "object_id")


class SubscriptionMixin(models.Model):
    user_subscriptions = GenericRelation(UserSubscription)
    group_subscriptions = GenericRelation(GroupSubscription)

    def get_all_subscribers(self):
        subscribed_users = User.objects.filter(
            usersubscription__in=self.user_subscriptions.filter(is_unsub=False)
        )
        subscribed_groups = Group.objects.filter(
            groupsubscription__in=self.group_subscriptions.all()
        )
        subscribers_from_groups = User.objects.filter(
                groups__in=subscribed_groups,
            ).exclude(
                usersubscription__in=self.user_subscriptions.filter(
                    is_unsub=True
                )
            )

        return subscribed_users.union(subscribers_from_groups)

    class Meta:
        abstract = True