from django.db import models
from django.utils.translation import gettext_lazy as _


class NotificationSetting(models.Model):
    """
    Stores that a user wants to get notifications of a certain type via a certain
    method for a certain event. If event is None, the notification shall be sent
    for all events the user has access to.

    :param user: The user to nofify.
    :type user: User
    :param action_type: The type of action to notify for.
    :type action_type: str
    :param event: The event to notify for.
    :type event: Event
    :param method: The method to notify with.
    :type method: str
    :param enabled: Indicates whether the specified notification is enabled. If no
                    event is set, this must always be true. If no event is set, setting
                    this to false is equivalent to deleting the object.
    :type enabled: bool
    """
    CHANNELS = (
        ('mail', _('E-mail')),
    )
    user = models.ForeignKey('User', on_delete=models.CASCADE,
                             related_name='notification_settings')
    action_type = models.CharField(max_length=255)
    event = models.ForeignKey('Event', null=True, blank=True, on_delete=models.CASCADE,
                              related_name='notification_settings')
    method = models.CharField(max_length=255, choices=CHANNELS)
    enabled = models.BooleanField(default=True)

    class Meta:
        unique_together = ('user', 'action_type', 'event', 'method')