Refator payment provider, deal with cancellations

src/pretix/base/models/orders.py

@@ -458,11 +458,15 @@ class Order(LockModel, LoggedModel):
         positions = list(
             self.positions.all().annotate(
                 has_checkin=Exists(Checkin.objects.filter(position_id=OuterRef('pk')))
-            ).select_related('item')
+            ).select_related('item').prefetch_related('issued_gift_cards')
         )
         cancelable = all([op.item.allow_cancel and not op.has_checkin for op in positions])
         if not cancelable or not positions:
             return False
+        for op in positions:
+            for gc in op.issued_gift_cards.all():
+                if gc.value != op.price:
+                    return False
         if self.user_cancel_deadline and now() > self.user_cancel_deadline:
             return False
         if self.status == Order.STATUS_PENDING:

src/pretix/base/payment.py

@@ -7,6 +7,7 @@ from typing import Any, Dict, Union
 import pytz
 from django import forms
 from django.conf import settings
+from django.contrib import messages
 from django.core.exceptions import ImproperlyConfigured
 from django.db import transaction
 from django.dispatch import receiver
@@ -21,8 +22,8 @@ from i18nfield.strings import LazyI18nString
 
 from pretix.base.forms import PlaceholderValidator
 from pretix.base.models import (
-    CartPosition, Event, InvoiceAddress, Order, OrderPayment, OrderRefund,
-    Quota,
+    CartPosition, Event, GiftCard, InvoiceAddress, Order, OrderPayment,
+    OrderRefund, Quota,
 )
 from pretix.base.reldate import RelativeDateField, RelativeDateWrapper
 from pretix.base.settings import SettingsSandbox
@@ -30,6 +31,7 @@ from pretix.base.signals import register_payment_providers
 from pretix.base.templatetags.money import money_filter
 from pretix.base.templatetags.rich_text import rich_text
 from pretix.helpers.money import DecimalTextInput
+from pretix.multidomain.urlreverse import eventreverse
 from pretix.presale.views import get_cart_total
 from pretix.presale.views.cart import cart_session, get_or_create_cart_id
 
@@ -890,12 +892,11 @@ class OffsettingProvider(BasePaymentProvider):
 
 
 class GiftCardPayment(BasePaymentProvider):
-    is_enabled = True
     identifier = "giftcard"
     verbose_name = _("Gift card")
 
     def is_allowed(self, request: HttpRequest, total: Decimal=None) -> bool:
-        return False
+        return super().is_allowed(request, total) and self.event.organizer.has_gift_cards
 
     def order_change_allowed(self, order: Order) -> bool:
         return False
@@ -903,6 +904,9 @@ class GiftCardPayment(BasePaymentProvider):
     def execute_payment(self, request: HttpRequest, payment: OrderPayment) -> str:
         raise PaymentException("Invalid state, should never occur.")
 
+    def payment_form_render(self, request: HttpRequest, total: Decimal) -> str:
+        return get_template('pretixcontrol/giftcards/checkout.html').render({})
+
     def payment_control_render(self, request, payment) -> str:
         from .models import GiftCard
 
@@ -933,6 +937,42 @@ class GiftCardPayment(BasePaymentProvider):
     def payment_refund_supported(self, payment: OrderPayment) -> bool:
         return True
 
+    def checkout_prepare(self, request: HttpRequest, cart: Dict[str, Any]) -> Union[bool, str, None]:
+        cs = cart_session(request)
+        try:
+            gc = self.event.organizer.accepted_gift_cards.get(
+                secret=request.POST.get("giftcard")
+            )
+            if gc.currency != self.event.currency:
+                messages.error(request, _("This gift card does not support this currency."))
+                return
+            if gc.value <= Decimal("0.00"):
+                messages.error(request, _("All credit on this gift card has been used."))
+                return
+            if 'gift_cards' not in cs:
+                cs['gift_cards'] = []
+            elif gc.pk in cs['gift_cards']:
+                messages.error(request, _("This gift card is already used for your payment."))
+                return
+            cs['gift_cards'] = cs['gift_cards'] + [gc.pk]
+
+            remainder = cart['total'] - gc.value
+            if remainder >= Decimal('0.00'):
+                messages.success(request, _("Your gift card has been applied, but {} still need to be paid. Please select a payment method.").format(
+                    money_filter(remainder, self.event.currency)
+                ))
+            else:
+                messages.success(request, _("Your gift card has been applied."))
+
+            kwargs = {'step': 'payment'}
+            if request.resolver_match and 'cart_namespace' in request.resolver_match.kwargs:
+                kwargs['cart_namespace'] = request.resolver_match.kwargs['cart_namespace']
+            return eventreverse(self.event, 'presale:event.checkout', kwargs=kwargs)
+        except GiftCard.DoesNotExist:
+            messages.error(request, _("This gift card is not known."))
+        except GiftCard.MultipleObjectsReturned:
+            messages.error(request, _("This gift card can not be redeemed since its code is not unique. Please contact the organizer of this event."))
+
     @transaction.atomic()
     def execute_refund(self, refund: OrderRefund):
         from .models import GiftCard

src/pretix/base/services/orders.py

@@ -329,6 +329,15 @@ def _cancel_order(order, user=None, send_mail: bool=True, api_token=None, device
                 if position.voucher:
                     Voucher.objects.filter(pk=position.voucher.pk).update(redeemed=Greatest(0, F('redeemed') - 1))
 
+        for position in order.positions.all():
+            for gc in position.issued_gift_cards.all():
+                if gc.value < position.price:
+                    raise OrderError(_('This order can not be canceled since the gift card {card} purchased in this order has already been redeemed.').format(
+                        card=gc.secret
+                    ))
+                else:
+                    gc.transactions.create(value=-position.price, order=order)
+
         order.log_action('pretix.event.order.canceled', user=user, auth=api_token or oauth_application or device,
                          data={'cancellation_fee': cancellation_fee})
 
@@ -1659,9 +1668,16 @@ def change_payment_provider(order: Order, payment_provider, amount=None, new_pay
 @receiver(order_paid, dispatch_uid="pretixbase_order_paid_giftcards")
 @transaction.atomic()
 def signal_listener_issue_giftcards(sender: Event, order: Order, **kwargs):
+    any_giftcards = False
     for p in order.positions.all():
         if p.item.issue_giftcard:
             gc = sender.organizer.issued_gift_cards.create(
                 currency=sender.currency, issued_in=p
             )
             gc.transactions.create(value=p.price, order=order)
+            any_giftcards = True
+            p.secret = gc.secret
+            p.save(update_fields=['secret'])
+
+    if any_giftcards:
+        tickets.invalidate_cache.apply_async(kwargs={'event': sender.pk, 'order': order.pk})

src/pretix/base/settings.py

@@ -133,6 +133,10 @@ DEFAULTS = {
         'default': 'True',
         'type': bool
     },
+    'payment_giftcard__enabled': {
+        'default': 'True',
+        'type': bool
+    },
     'payment_term_accept_late': {
         'default': 'True',
         'type': bool