from pytask.profile.models import Notification

def get_notification(nid, user):

    """ if notification exists, and belongs to the current user, return it.

    else return None.

    """

    user_notifications = user.notification_sent_to.filter(is_deleted=False).order_by('sent_date')

    current_notifications = user_notifications.filter(uniq_key=nid)

    if user_notifications:

        current_notification = current_notifications[0]

        try:

            newer_notification = current_notification.get_next_by_sent_date(sent_to=user, is_deleted=False)

            newest_notification = user_notifications.reverse()[0]

            if newest_notification == newer_notification:

                newest_notification = None

        except Notification.DoesNotExist:

            newest_notification, newer_notification = None, None

        try:

            older_notification = current_notification.get_previous_by_sent_date(sent_to=user, is_deleted=False)

            oldest_notification = user_notifications[0]

            if oldest_notification == older_notification:

                oldest_notification = None

        except:

            oldest_notification, older_notification = None, None

        return newest_notification, newer_notification, current_notification, older_notification, oldest_notification

    else:

        return None, None, None, None, None