from django.contrib.auth.tokens import default_token_generator
from django.contrib.contenttypes.models import ContentType
from django.contrib.sites.models import Site
from django.core.mail import send_mail
from django.dispatch import Signal
from django.utils.encoding import force_bytes
from django.utils.http import urlsafe_base64_encode

user_confirmed = Signal(providing_args=["user", "instance", "key"])


class AlreadyConfirmed(Exception):
    """The given resource has already been confirmed."""
    pass


def encode_pk(obj):
    return urlsafe_base64_encode(force_bytes(obj.pk))


def request_confirmation(user, instance, key=None):
    site = Site.objects.first()
    uid = encode_pk(user)
    token = default_token_generator.make_token(user)
    obj_type = ContentType.objects.get_for_model(instance)
    type_id = encode_pk(obj_type)
    obj_id = encode_pk(instance)
    confirmation_url = f"https://{site.domain}/confirm/{uid}/{token}/{type_id}/{obj_id}"
    send_mail(
        f"{site.name}: Bestätigung der Anfrage",
        f"Bitte bestätige, dass du deine E-Mail-Adresse auf der Seite {site.name} ({site.domain}) eingegeben hast. "
        f"Kopiere dazu folgende URL in deinen Webbrowser:\n\n{confirmation_url}",
        None, [user.email]
    )