from django.dispatch import receiver
from django.db.models.signals import post_save, post_migrate
from django.apps import apps
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import Permission
from event.models import Event, EventGroup
from guardian.shortcuts import assign_perm


@receiver(post_save, sender=Event)
def create_groups_for_event(sender, **kwargs):
    event, created = kwargs["instance"], kwargs["created"]
    if created:
        orgas = EventGroup.objects.create(
            name="{}_orgas".format(event.slug),
            event=event
        )

        for perm in Permission.objects.filter(
                content_type=ContentType.objects.get_for_model(Event),
                codename__contains="event_"):
            assign_perm(perm.codename, orgas, event)

        EventGroup.objects.create(
            name="{}_participants".format(event.slug),
            event=event,
        )


@receiver(post_migrate)
def create_event_permissions(sender, **kwargs):

    def event_specific_permissions():
        opes = ['Add', 'Change', 'Delete']
        models = [model.__name__.lower() for model in apps.get_models()
                  if getattr(model, 'needs_event_permissions', False)]

        return [
            ('event_{}_{}'.format(op.lower(), model),
                '{} {} for event'.format(op, model))
            for op in opes
            for model in models
        ]

    content_type = ContentType.objects.get_for_model(Event)
    for (code, verbose) in event_specific_permissions():
        Permission.objects.get_or_create(
            name=verbose,
            content_type=content_type,
            codename=code
        )