81 lines
No EOL
2.8 KiB
Python
81 lines
No EOL
2.8 KiB
Python
from itertools import chain
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from random import sample
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from django.db import IntegrityError
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from django.db.models.signals import post_save, pre_save, pre_delete, post_init
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from django.dispatch import receiver
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from pinaxcon.raffle.models import DrawnTicket, Raffle, Draw, Prize
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# Much of the following could be handled by directly overriding the
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# relevant model methods. However, since `.objects.delete()` bypasses
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# a model's delete() method but not its pre_ and post_delete signals,
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# using signals gives us slightly better coverage of edge cases.
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#
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# In order to avoid mixing the two approaches we make extensive use of
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# signals.
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@receiver(post_save, sender=Draw)
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def draw_raffle_tickets(sender, instance, created, **kwargs):
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"""
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Draws tickets once a :model:`pinaxcon_raffle.Draw` instance
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has been created and prizes are still available.
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"""
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if not created:
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return
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raffle = instance.raffle
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prizes = raffle.prizes.filter(winning_ticket__isnull=True)
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tickets = list(chain(*(ticket[1] for ticket in raffle.get_tickets())))
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if not tickets:
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return
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drawn_tickets = sample(tickets, len(prizes))
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for prize, ticket in zip(prizes, drawn_tickets):
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item_id = int(ticket.split('-')[0])
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drawn_ticket = DrawnTicket.objects.create(
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draw=instance,
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prize=prize,
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ticket=ticket,
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lineitem_id=item_id,
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)
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prize.winning_ticket = drawn_ticket
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prize.save(update_fields=('winning_ticket',))
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@receiver(post_init, sender=Prize)
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def set_prize_lock(sender, instance, **kwargs):
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"""Locks :model:`pinaxcon_raffle.Prize` if a winner exists."""
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instance._locked = instance.winning_ticket is not None
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@receiver(pre_save, sender=Prize)
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def enforce_prize_lock(sender, instance, **kwargs):
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"""Denies updates to :model:`pinaxcon_raffle.Prize` if lock is in place."""
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if instance.locked:
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raise IntegrityError("Updating a locked prize is not allowed.")
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@receiver(pre_delete, sender=Prize)
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def prevent_locked_prize_deletion(sender, instance, **kwargs):
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"""Denies deletion of :model:`pinaxcon_raffle.Prize` if lock is in place."""
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if instance.locked:
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raise IntegrityError("Deleting a locked prize is not allowed.")
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@receiver(pre_delete, sender=DrawnTicket)
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def prevent_drawn_ticket_deletion(sender, instance, **kwargs):
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"""Protects :model:`pinaxcon_raffle.DrawnTicket` from deletion if lock is in place."""
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if instance.locked:
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raise IntegrityError("Deleting a drawn ticket is not allowed.")
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@receiver(pre_save, sender=DrawnTicket)
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def prevent_drawn_ticket_update(sender, instance, **kwargs):
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"""Protects :model:`pinaxcon_raffle.DrawnTicket` from updates."""
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if getattr(instance, 'pk', None):
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raise IntegrityError("Updating a drawn ticket is not allowed.") |