Proof of concept

src/pretix/base/migrations/0135_auto_20190910_2020.py

@@ -1,7 +1,8 @@
 # Generated by Django 2.2.1 on 2019-09-10 20:20
 
-from django.db import migrations, models
 import django.db.models.deletion
+from django.db import migrations, models
+
 import pretix.base.models.fields
 import pretix.base.models.giftcards
 

src/pretix/base/payment.py

@@ -888,6 +888,21 @@ class OffsettingProvider(BasePaymentProvider):
         return _('Balanced against orders: %s' % ', '.join(payment.info_data['orders']))
 
 
+class GiftCardPayment(BasePaymentProvider):
+    is_enabled = True
+    identifier = "giftcard"
+    verbose_name = _("Gift card")
+    is_implicit = True
+
+    def is_allowed(self, request: HttpRequest, total: Decimal=None) -> bool:
+        return False
+
+    def order_change_allowed(self, order: Order) -> bool:
+        return False
+
+    # TODO: execute, refund, api, control render
+
+
 @receiver(register_payment_providers, dispatch_uid="payment_free")
 def register_payment_provider(sender, **kwargs):
-    return [FreeOrderProvider, BoxOfficeProvider, OffsettingProvider, ManualPayment]
+    return [FreeOrderProvider, BoxOfficeProvider, OffsettingProvider, ManualPayment, GiftCardPayment]

src/pretix/base/services/cart.py

@@ -14,8 +14,8 @@ from django_scopes import scopes_disabled
 
 from pretix.base.i18n import language
 from pretix.base.models import (
-    CartPosition, Event, InvoiceAddress, Item, ItemBundle, ItemVariation, Seat,
+    CartPosition, Event, GiftCard, InvoiceAddress, Item, ItemBundle,
-    SeatCategoryMapping, Voucher,
+    ItemVariation, Seat, SeatCategoryMapping, Voucher,
 )
 from pretix.base.models.event import SubEvent
 from pretix.base.models.orders import OrderFee
@@ -958,14 +958,36 @@ def update_tax_rates(event: Event, cart_id: str, invoice_address: InvoiceAddress
 
 
 def get_fees(event, request, total, invoice_address, provider):
-    fees = []
+    from pretix.presale.views.cart import cart_session
 
+    fees = []
     for recv, resp in fee_calculation_for_cart.send(sender=event, request=request, invoice_address=invoice_address,
                                                     total=total):
         if resp:
             fees += resp
 
     total = total + sum(f.value for f in fees)
+
+    cs = cart_session(request)
+    if cs.get('gift_cards'):
+        gc_qs = GiftCard.objects.filter(pk__in=cs.get('gift_cards'))
+        summed = 0
+        for gc in gc_qs:
+            fval = Decimal(gc.value)  # TODO: don't require an extra query
+            fval = min(fval, total - summed)
+            if fval > 0:
+                total -= fval
+                summed += fval
+                fees.append(OrderFee(
+                    fee_type=OrderFee.FEE_TYPE_GIFTCARD,
+                    internal_type='giftcard',
+                    description=gc.secret,
+                    value=-1 * fval,
+                    tax_rate=Decimal('0.00'),
+                    tax_value=Decimal('0.00'),
+                    tax_rule=TaxRule.zero()
+                ))
+
     if provider and total != 0:
         provider = event.get_payment_providers().get(provider)
         if provider:

src/pretix/base/services/orders.py

@@ -20,8 +20,9 @@ from pretix.api.models import OAuthApplication
 from pretix.base.email import get_email_context
 from pretix.base.i18n import LazyLocaleException, language
 from pretix.base.models import (
-    CartPosition, Device, Event, Item, ItemVariation, Order, OrderPayment,
+    CartPosition, Device, Event, GiftCard, Item, ItemVariation, Order,
-    OrderPosition, Quota, Seat, SeatCategoryMapping, User, Voucher,
+    OrderPayment, OrderPosition, Quota, Seat, SeatCategoryMapping, User,
+    Voucher,
 )
 from pretix.base.models.event import SubEvent
 from pretix.base.models.items import ItemBundle
@@ -545,7 +546,7 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
 
 
 def _get_fees(positions: List[CartPosition], payment_provider: BasePaymentProvider, address: InvoiceAddress,
-              meta_info: dict, event: Event):
+              meta_info: dict, event: Event, gift_cards: List[GiftCard]):
     fees = []
     total = sum([c.price for c in positions])
 
@@ -553,8 +554,18 @@ def _get_fees(positions: List[CartPosition], payment_provider: BasePaymentProvid
                                                  meta_info=meta_info, positions=positions):
         if resp:
             fees += resp
-
     total += sum(f.value for f in fees)
+
+    summed = 0
+    gift_card_values = {}
+    for gc in gift_cards:
+        fval = Decimal(gc.value)  # TODO: don't require an extra query
+        fval = min(fval, total - summed)
+        if fval > 0:
+            total -= fval
+            summed += fval
+            gift_card_values[gc] = fval
+
     if payment_provider:
         payment_fee = payment_provider.calculate_fee(total)
     else:
@@ -565,17 +576,24 @@ def _get_fees(positions: List[CartPosition], payment_provider: BasePaymentProvid
                       internal_type=payment_provider.identifier)
         fees.append(pf)
 
-    return fees, pf
+    return fees, pf, gift_card_values
 
 
 def _create_order(event: Event, email: str, positions: List[CartPosition], now_dt: datetime,
                   payment_provider: BasePaymentProvider, locale: str=None, address: InvoiceAddress=None,
-                  meta_info: dict=None, sales_channel: str='web'):
+                  meta_info: dict=None, sales_channel: str='web', gift_cards: list=None):
-    fees, pf = _get_fees(positions, payment_provider, address, meta_info, event)
-    total = sum([c.price for c in positions]) + sum([c.value for c in fees])
     p = None
-
     with transaction.atomic():
+        checked_gift_cards = []
+        if gift_cards:
+            gc_qs = GiftCard.objects.select_for_update().filter(pk__in=gift_cards)  # TODO: Make sure to prevent race conditions
+            for gc in gc_qs:
+                # TODO: Re-check acceptance
+                checked_gift_cards.append(gc)
+
+        fees, pf, gift_card_values = _get_fees(positions, payment_provider, address, meta_info, event, checked_gift_cards)
+        total = pending_sum = sum([c.price for c in positions]) + sum([c.value for c in fees])
+
         order = Order(
             status=Order.STATUS_PENDING,
             event=event,
@@ -606,11 +624,30 @@ def _create_order(event: Event, email: str, positions: List[CartPosition], now_d
                 fee.tax_rule = None  # TODO: deprecate
             fee.save()
 
+        for gc, val in gift_card_values.items():
+            p = order.payments.create(
+                state=OrderPayment.PAYMENT_STATE_CONFIRMED,
+                provider='giftcard',
+                amount=val,
+                fee=pf
+            )
+            trans = gc.transactions.create(
+                value=-1 * val,
+                order=order,
+                payment=p
+            )
+            p.info_data = {
+                'gift_card': gc.pk,
+                'transaction_id': trans.pk,
+            }
+            p.save()
+            pending_sum -= val
+
         if payment_provider and not order.require_approval:
             p = order.payments.create(
                 state=OrderPayment.PAYMENT_STATE_CREATED,
                 provider=payment_provider.identifier,
-                amount=total,
+                amount=pending_sum,
                 fee=pf
             )
 
@@ -658,7 +695,8 @@ def _order_placed_email_attendee(event: Event, order: Order, position: OrderPosi
 
 
 def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
-                   email: str, locale: str, address: int, meta_info: dict=None, sales_channel: str='web'):
+                   email: str, locale: str, address: int, meta_info: dict=None, sales_channel: str='web',
+                   gift_cards: list=None):
     if payment_provider:
         pprov = event.get_payment_providers().get(payment_provider)
         if not pprov:
@@ -707,9 +745,10 @@ def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
             raise OrderError(error_messages['internal'])
         _check_positions(event, now_dt, positions, address=addr)
         order, payment = _create_order(event, email, positions, now_dt, pprov,
-                                       locale=locale, address=addr, meta_info=meta_info, sales_channel=sales_channel)
+                                       locale=locale, address=addr, meta_info=meta_info, sales_channel=sales_channel,
+                                       gift_cards=gift_cards)
 
-        free_order_flow = payment and payment_provider == 'free' and order.total == Decimal('0.00') and not order.require_approval
+        free_order_flow = payment and payment_provider == 'free' and order.pending_sum == Decimal('0.00') and not order.require_approval
         if free_order_flow:
             try:
                 payment.confirm(send_mail=False, lock=not locked)
@@ -1466,12 +1505,12 @@ class OrderChangeManager:
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(OrderError,))
 def perform_order(self, event: Event, payment_provider: str, positions: List[str],
                   email: str=None, locale: str=None, address: int=None, meta_info: dict=None,
-                  sales_channel: str='web'):
+                  sales_channel: str='web', gift_cards: list=None):
     with language(locale):
         try:
             try:
                 return _perform_order(event, payment_provider, positions, email, locale, address, meta_info,
-                                      sales_channel)
+                                      sales_channel, gift_cards)
             except LockTimeoutException:
                 self.retry()
         except (MaxRetriesExceededError, LockTimeoutException):

src/pretix/presale/checkoutflow.py

@@ -15,7 +15,7 @@ from django.utils.translation import (
 from django.views.generic.base import TemplateResponseMixin
 from django_scopes import scopes_disabled
 
-from pretix.base.models import Order
+from pretix.base.models import GiftCard, Order
 from pretix.base.models.orders import InvoiceAddress, OrderPayment
 from pretix.base.services.cart import (
     get_fees, set_cart_addons, update_tax_rates,
@@ -530,6 +530,24 @@ class PaymentStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
 
     def post(self, request):
         self.request = request
+        if request.POST.get("giftcard"):
+            # TODO: cross-organizer acceptance, check for valid money, …
+            try:
+                gc = GiftCard.objects.get(
+                    issuer=request.organizer,
+                    secret=request.POST.get("giftcard")
+                )
+                if gc.currency != request.event.currency:
+                    messages.error(self.request, _("This gift card does not support this currency."))
+                    return self.render()
+                if 'gift_cards' not in self.cart_session:
+                    self.cart_session['gift_cards'] = []
+                self.cart_session['gift_cards'] = self.cart_session['gift_cards'] + [gc.pk]
+                return self.render()
+            except GiftCard.DoesNotExist:
+                messages.error(self.request, _("This gift card is not known."))
+                return self.render()
+
         for p in self.provider_forms:
             if p['provider'].identifier == request.POST.get('payment', ''):
                 self.cart_session['payment'] = p['provider'].identifier
@@ -709,7 +727,7 @@ class ConfirmStep(CartMixin, AsyncAction, TemplateFlowStep):
         return self.do(self.request.event.id, self.payment_provider.identifier if self.payment_provider else None,
                        [p.id for p in self.positions], self.cart_session.get('email'),
                        translation.get_language(), self.invoice_address.pk, meta_info,
-                       request.sales_channel)
+                       request.sales_channel, self.cart_session.get('gift_cards'))
 
     def get_success_message(self, value):
         create_empty_cart_id(self.request)

src/pretix/presale/templates/pretixpresale/event/checkout_payment.html

@@ -11,6 +11,8 @@
     <form method="post">
         {% csrf_token %}
         <div class="panel-group" id="payment_accordion">
+            {# TODO: make this proper #}
+            <input type="text" class="form-control" placeholder="Add gift card" name="giftcard">
             {% for p in providers %}
                 <div class="panel panel-default" data-total="{{ p.total|floatformat:2 }}">
                     <label class="accordion-radio">