Merge pull request #1396 from pretix/giftcard

Support for gift cards

src/pretix/base/migrations/0138_auto_20191017_1151.py

@@ -0,0 +1,107 @@
+# Generated by Django 2.2.4 on 2019-10-17 11:51
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+import pretix.base.models.base
+import pretix.base.models.fields
+import pretix.base.models.giftcards
+
+
+def fwd(app, schema_editor):
+    Team = app.get_model('pretixbase', 'Team')
+    Team.objects.filter(can_change_organizer_settings=True).update(can_manage_gift_cards=True)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('pretixbase', '0137_auto_20191015_1141'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='GiftCard',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False)),
+                ('issuance', models.DateTimeField(auto_now_add=True)),
+                ('secret', models.CharField(db_index=True, default=pretix.base.models.giftcards.gen_giftcard_secret,
+                                            max_length=190)),
+                ('currency', models.CharField(max_length=10)),
+                ('issued_in', models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT,
+                                                related_name='issued_gift_cards', to='pretixbase.OrderPosition')),
+                ('issuer',
+                 models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, related_name='issued_gift_cards',
+                                   to='pretixbase.Organizer')),
+                ('testmode', django.db.models.BooleanField(default=False)),
+            ],
+            options={
+                'unique_together': {('secret', 'issuer')},
+            },
+            bases=(models.Model, pretix.base.models.base.LoggingMixin),
+        ),
+        migrations.AddField(
+            model_name='item',
+            name='issue_giftcard',
+            field=models.BooleanField(default=False),
+        ),
+        migrations.AddField(
+            model_name='team',
+            name='can_manage_gift_cards',
+            field=models.BooleanField(default=False),
+        ),
+        migrations.AlterField(
+            model_name='question',
+            name='dependency_values',
+            field=pretix.base.models.fields.MultiStringField(default=[]),
+        ),
+        migrations.AlterField(
+            model_name='voucher',
+            name='item',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='vouchers',
+                                    to='pretixbase.Item'),
+        ),
+        migrations.AlterField(
+            model_name='voucher',
+            name='quota',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='vouchers',
+                                    to='pretixbase.Quota'),
+        ),
+        migrations.AlterField(
+            model_name='voucher',
+            name='variation',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='vouchers',
+                                    to='pretixbase.ItemVariation'),
+        ),
+        migrations.CreateModel(
+            name='GiftCardTransaction',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False)),
+                ('datetime', models.DateTimeField(auto_now_add=True)),
+                ('value', models.DecimalField(decimal_places=2, max_digits=10)),
+                ('card', models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, related_name='transactions',
+                                           to='pretixbase.GiftCard')),
+                ('order', models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT,
+                                            related_name='gift_card_transactions', to='pretixbase.Order')),
+                ('payment', models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT,
+                                              related_name='gift_card_transactions', to='pretixbase.OrderPayment')),
+                ('refund', models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT,
+                                             related_name='gift_card_transactions', to='pretixbase.OrderRefund')),
+            ],
+            options={
+                'ordering': ('datetime',),
+            },
+        ),
+        migrations.CreateModel(
+            name='GiftCardAcceptance',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False)),
+                ('collector', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE,
+                                                related_name='gift_card_issuer_acceptance', to='pretixbase.Organizer')),
+                ('issuer', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE,
+                                             related_name='gift_card_collector_acceptance', to='pretixbase.Organizer')),
+            ],
+        ),
+        migrations.RunPython(
+            fwd, migrations.RunPython.noop
+        ),
+    ]

src/pretix/base/models/__init__.py

@@ -7,6 +7,7 @@ from .event import (
     Event, Event_SettingsStore, EventLock, EventMetaProperty, EventMetaValue,
     RequiredAction, SubEvent, SubEventMetaValue, generate_invite_token,
 )
+from .giftcards import GiftCard, GiftCardAcceptance, GiftCardTransaction
 from .invoices import Invoice, InvoiceLine, invoice_filename
 from .items import (
     Item, ItemAddOn, ItemBundle, ItemCategory, ItemVariation, Question,

src/pretix/base/models/auth.py

@@ -335,6 +335,25 @@ class User(AbstractBaseUser, PermissionsMixin, LoggingMixin):
             | Q(id__in=self.teams.filter(**kwargs).values_list('limit_events__id', flat=True))
         )
 
+    @scopes_disabled()
+    def get_organizers_with_permission(self, permission, request=None):
+        """
+        Returns a queryset of organizers the user has a specific permissions to.
+
+        :param request: The current request (optional). Required to detect staff sessions properly.
+        :return: Iterable of Organizers
+        """
+        from .event import Organizer
+
+        if request and self.has_active_staff_session(request.session.session_key):
+            return Organizer.objects.all()
+
+        kwargs = {permission: True}
+
+        return Organizer.objects.filter(
+            id__in=self.teams.filter(**kwargs).values_list('organizer', flat=True)
+        )
+
     def has_active_staff_session(self, session_key=None):
         """
         Returns whether or not a user has an active staff session (formerly known as superuser session)

src/pretix/base/models/event.py

@@ -730,7 +730,7 @@ class Event(EventMixin, LoggedModel):
     def has_payment_provider(self):
         result = False
         for provider in self.get_payment_providers().values():
-            if provider.is_enabled and provider.identifier not in ('free', 'boxoffice', 'offsetting'):
+            if provider.is_enabled and provider.identifier not in ('free', 'boxoffice', 'offsetting', 'giftcard'):
                 result = True
                 break
         return result

src/pretix/base/models/giftcards.py

@@ -0,0 +1,112 @@
+from decimal import Decimal
+
+from django.conf import settings
+from django.db import models
+from django.db.models import Sum
+from django.utils.crypto import get_random_string
+from django.utils.translation import ugettext_lazy as _
+
+from pretix.base.banlist import banned
+from pretix.base.models import LoggedModel
+
+
+def gen_giftcard_secret():
+    charset = list('ABCDEFGHJKLMNPQRSTUVWXYZ3789')
+    while True:
+        code = get_random_string(length=settings.ENTROPY['giftcard_secret'], allowed_chars=charset)
+        if not banned(code) and not GiftCard.objects.filter(secret=code).exists():
+            return code
+
+
+class GiftCardAcceptance(models.Model):
+    issuer = models.ForeignKey(
+        'Organizer',
+        related_name='gift_card_collector_acceptance',
+        on_delete=models.CASCADE
+    )
+    collector = models.ForeignKey(
+        'Organizer',
+        related_name='gift_card_issuer_acceptance',
+        on_delete=models.CASCADE
+    )
+
+
+class GiftCard(LoggedModel):
+    issuer = models.ForeignKey(
+        'Organizer',
+        related_name='issued_gift_cards',
+        on_delete=models.PROTECT,
+    )
+    issued_in = models.ForeignKey(
+        'OrderPosition',
+        related_name='issued_gift_cards',
+        on_delete=models.PROTECT,
+        null=True, blank=True
+    )
+    issuance = models.DateTimeField(
+        auto_now_add=True,
+    )
+    secret = models.CharField(
+        max_length=190,
+        default=gen_giftcard_secret,
+        db_index=True,
+        verbose_name=_('Gift card code'),
+    )
+    testmode = models.BooleanField(
+        verbose_name=_('Test mode card'),
+        default=False
+    )
+    CURRENCY_CHOICES = [(c.alpha_3, c.alpha_3 + " - " + c.name) for c in settings.CURRENCIES]
+    currency = models.CharField(max_length=10, choices=CURRENCY_CHOICES)
+
+    def __str__(self):
+        return self.secret
+
+    @property
+    def value(self):
+        return self.transactions.aggregate(s=Sum('value'))['s'] or Decimal('0.00')
+
+    def accepted_by(self, organizer):
+        return self.issuer == organizer or GiftCardAcceptance.objects.filter(issuer=self.issuer, collector=organizer).exists()
+
+    class Meta:
+        unique_together = (('secret', 'issuer'),)
+
+
+class GiftCardTransaction(models.Model):
+    card = models.ForeignKey(
+        'GiftCard',
+        related_name='transactions',
+        on_delete=models.PROTECT
+    )
+    datetime = models.DateTimeField(
+        auto_now_add=True
+    )
+    value = models.DecimalField(
+        decimal_places=2,
+        max_digits=10
+    )
+    order = models.ForeignKey(
+        'Order',
+        related_name='gift_card_transactions',
+        null=True,
+        blank=True,
+        on_delete=models.PROTECT
+    )
+    payment = models.ForeignKey(
+        'OrderPayment',
+        related_name='gift_card_transactions',
+        null=True,
+        blank=True,
+        on_delete=models.PROTECT
+    )
+    refund = models.ForeignKey(
+        'OrderRefund',
+        related_name='gift_card_transactions',
+        null=True,
+        blank=True,
+        on_delete=models.PROTECT
+    )
+
+    class Meta:
+        ordering = ("datetime",)

src/pretix/base/models/items.py

@@ -242,6 +242,8 @@ class Item(LoggedModel):
     :type require_approval: bool
     :param sales_channels: Sales channels this item is available on.
     :type sales_channels: bool
+    :param issue_giftcard: If ``True``, buying this product will give you a gift card with the value of the product's price
+    :type issue_giftcard: bool
     """
 
     objects = ItemQuerySetManager()
@@ -413,6 +415,12 @@ class Item(LoggedModel):
         verbose_name=_('Sales channels'),
         default=['web']
     )
+    issue_giftcard = models.BooleanField(
+        verbose_name=_('This product is a gift card'),
+        help_text=_('When a customer buys this product, they will get a gift card with a value corresponding to the '
+                    'product price.'),
+        default=False
+    )
     # !!! Attention: If you add new fields here, also add them to the copying code in
     # pretix/control/forms/item.py if applicable.
 

src/pretix/base/models/orders.py

@@ -202,7 +202,7 @@ class Order(LockModel, LoggedModel):
         return self.full_code
 
     def gracefully_delete(self, user=None, auth=None):
-        from . import Voucher
+        from . import Voucher, GiftCard, GiftCardTransaction
 
         if not self.testmode:
             raise TypeError("Only test mode orders can be deleted.")
@@ -218,6 +218,10 @@ class Order(LockModel, LoggedModel):
                 if position.voucher:
                     Voucher.objects.filter(pk=position.voucher.pk).update(redeemed=Greatest(0, F('redeemed') - 1))
 
+        GiftCardTransaction.objects.filter(payment__in=self.payments.all()).update(payment=None)
+        GiftCardTransaction.objects.filter(refund__in=self.refunds.all()).update(refund=None)
+        GiftCardTransaction.objects.filter(order=self).update(order=None)
+        GiftCard.objects.filter(issued_in__in=self.positions.all()).update(issued_in=None)
         OrderPosition.all.filter(order=self, addon_to__isnull=False).delete()
         OrderPosition.all.filter(order=self).delete()
         OrderFee.all.filter(order=self).delete()
@@ -460,11 +464,15 @@ 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/models/organizer.py

@@ -2,6 +2,7 @@ import string
 
 from django.core.validators import RegexValidator
 from django.db import models
+from django.db.models import Exists, OuterRef, Q
 from django.utils.crypto import get_random_string
 from django.utils.functional import cached_property
 from django.utils.translation import ugettext_lazy as _
@@ -82,6 +83,24 @@ class Organizer(LoggedModel):
 
         return ObjectRelatedCache(self)
 
+    @property
+    def has_gift_cards(self):
+        return self.cache.get_or_set(
+            key='has_gift_cards',
+            timeout=15,
+            default=lambda: self.issued_gift_cards.exists() or self.gift_card_issuer_acceptance.exists()
+        )
+
+    @property
+    def accepted_gift_cards(self):
+        from .giftcards import GiftCard, GiftCardAcceptance
+
+        return GiftCard.objects.annotate(
+            accepted=Exists(GiftCardAcceptance.objects.filter(issuer=OuterRef('issuer'), collector=self))
+        ).filter(
+            Q(issuer=self) | Q(accepted=True)
+        )
+
     def allow_delete(self):
         from . import Order, Invoice
         return (
@@ -156,6 +175,10 @@ class Team(LoggedModel):
         help_text=_('Someone with this setting can get access to most data of all of your events, i.e. via privacy '
                     'reports, so be careful who you add to this team!')
     )
+    can_manage_gift_cards = models.BooleanField(
+        default=False,
+        verbose_name=_("Can manage gift cards")
+    )
 
     can_change_event_settings = models.BooleanField(
         default=False,

src/pretix/base/payment.py

@@ -7,7 +7,9 @@ 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
 from django.forms import Form
 from django.http import HttpRequest
@@ -20,8 +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
@@ -29,7 +31,8 @@ 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.presale.views import get_cart_total
+from pretix.multidomain.urlreverse import eventreverse
+from pretix.presale.views import get_cart, get_cart_total
 from pretix.presale.views.cart import cart_session, get_or_create_cart_id
 
 logger = logging.getLogger(__name__)
@@ -888,6 +891,206 @@ class OffsettingProvider(BasePaymentProvider):
         return _('Balanced against orders: %s' % ', '.join(payment.info_data['orders']))
 
 
+class GiftCardPayment(BasePaymentProvider):
+    identifier = "giftcard"
+    verbose_name = _("Gift card")
+
+    @property
+    def settings_form_fields(self):
+        f = super().settings_form_fields
+        del f['_fee_abs']
+        del f['_fee_percent']
+        del f['_fee_reverse_calc']
+        del f['_total_min']
+        del f['_total_max']
+        del f['_invoice_text']
+        return f
+
+    @property
+    def test_mode_message(self) -> str:
+        return _("In test mode, only test cards will work.")
+
+    def is_allowed(self, request: HttpRequest, total: Decimal=None) -> bool:
+        return super().is_allowed(request, total) and self.event.organizer.has_gift_cards
+
+    def order_change_allowed(self, order: Order) -> bool:
+        return super().order_change_allowed(order) and self.event.organizer.has_gift_cards
+
+    def payment_form_render(self, request: HttpRequest, total: Decimal) -> str:
+        return get_template('pretixcontrol/giftcards/checkout.html').render({})
+
+    def checkout_confirm_render(self, request) -> str:
+        return get_template('pretixcontrol/giftcards/checkout_confirm.html').render({})
+
+    def payment_control_render(self, request, payment) -> str:
+        from .models import GiftCard
+
+        if 'gift_card' in payment.info_data:
+            gc = GiftCard.objects.get(pk=payment.info_data.get('gift_card'))
+            template = get_template('pretixcontrol/giftcards/payment.html')
+
+            ctx = {
+                'request': request,
+                'event': self.event,
+                'gc': gc,
+            }
+            return template.render(ctx)
+
+    def api_payment_details(self, payment: OrderPayment):
+        from .models import GiftCard
+        gc = GiftCard.objects.get(pk=payment.info_data.get('gift_card'))
+        return {
+            'gift_card': {
+                'id': gc.pk,
+                'secret': gc.secret,
+                'organizer': gc.issuer.slug
+            }
+        }
+
+    def payment_partial_refund_supported(self, payment: OrderPayment) -> bool:
+        return True
+
+    def payment_refund_supported(self, payment: OrderPayment) -> bool:
+        return True
+
+    def checkout_prepare(self, request: HttpRequest, cart: Dict[str, Any]) -> Union[bool, str, None]:
+        for p in get_cart(request):
+            if p.item.issue_giftcard:
+                messages.error(request, _("You cannot pay with gift cards when buying a gift card."))
+                return
+
+        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.testmode and not self.event.testmode:
+                messages.error(request, _("This gift card can only be used in test mode."))
+                return
+            if not gc.testmode and self.event.testmode:
+                messages.error(request, _("Only test gift cards can be used in test mode."))
+                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:
+            if self.event.vouchers.filter(code__iexact=request.POST.get("giftcard")).exists():
+                messages.warning(request, _("You entered a voucher instead of a gift card. Vouchers can only be entered on the first page of the shop below "
+                                            "the product selection."))
+            else:
+                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."))
+
+    def payment_prepare(self, request: HttpRequest, payment: OrderPayment) -> Union[bool, str, None]:
+        for p in payment.order.positions.all():
+            if p.item.issue_giftcard:
+                messages.error(request, _("You cannot pay with gift cards when buying a gift card."))
+                return
+
+        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.testmode and not payment.order.testmode:
+                messages.error(request, _("This gift card can only be used in test mode."))
+                return
+            if not gc.testmode and payment.order.testmode:
+                messages.error(request, _("Only test gift cards can be used in test mode."))
+                return
+            if gc.value <= Decimal("0.00"):
+                messages.error(request, _("All credit on this gift card has been used."))
+                return
+            payment.info_data = {
+                'gift_card': gc.pk,
+                'retry': True
+            }
+            payment.amount = min(payment.amount, gc.value)
+            payment.save()
+
+            return True
+        except GiftCard.DoesNotExist:
+            if self.event.vouchers.filter(code__iexact=request.POST.get("giftcard")).exists():
+                messages.warning(request, _("You entered a voucher instead of a gift card. Vouchers can only be entered on the first page of the shop below "
+                                            "the product selection."))
+            else:
+                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."))
+
+    def execute_payment(self, request: HttpRequest, payment: OrderPayment) -> str:
+        # This method will only be called when retrying payments, e.g. after a payment_prepare call. It is not called
+        # during the order creation phase because this payment provider is a special case.
+        for p in payment.order.positions.all():  # noqa - just a safeguard
+            if p.item.issue_giftcard:
+                raise PaymentException(_("You cannot pay with gift cards when buying a gift card."))
+
+        gcpk = payment.info_data.get('gift_card')
+        if not gcpk or not payment.info_data.get('retry'):
+            raise PaymentException("Invalid state, should never occur.")
+        with transaction.atomic():
+            gc = GiftCard.objects.select_for_update().get(pk=gcpk)
+            if gc.currency != self.event.currency:  # noqa - just a safeguard
+                raise PaymentException(_("This gift card does not support this currency."))
+            if not gc.accepted_by(self.event.organizer):  # noqa - just a safeguard
+                raise PaymentException(_("This gift card is not accepted by this event organizer."))
+            if payment.amount > gc.value:  # noqa - just a safeguard
+                raise PaymentException(_("This gift card was used in the meantime. Please try again"))
+            trans = gc.transactions.create(
+                value=-1 * payment.amount,
+                order=payment.order,
+                payment=payment
+            )
+            payment.info_data = {
+                'gift_card': gc.pk,
+                'transaction_id': trans.pk,
+            }
+            payment.confirm()
+
+    def payment_is_valid_session(self, request: HttpRequest) -> bool:
+        return True
+
+    @transaction.atomic()
+    def execute_refund(self, refund: OrderRefund):
+        from .models import GiftCard
+        gc = GiftCard.objects.get(pk=refund.payment.info_data.get('gift_card'))
+        trans = gc.transactions.create(
+            value=refund.amount,
+            order=refund.order,
+            refund=refund
+        )
+        refund.info_data = {
+            'gift_card': gc.pk,
+            'transaction_id': trans.pk,
+        }
+        refund.done()
+
+
 @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

@@ -97,6 +97,7 @@ error_messages = {
     'seat_forbidden': _('You can not select a seat for this position.'),
     'seat_unavailable': _('The seat you selected has already been taken. Please select a different seat.'),
     'seat_multiple': _('You can not select the same seat multiple times.'),
+    'gift_card': _("You entered a gift card instead of a voucher. Gift cards can be entered later on when you're asked for your payment details."),
 }
 
 
@@ -958,14 +959,41 @@ 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'):
+        gcs = cs['gift_cards']
+        gc_qs = event.organizer.accepted_gift_cards.filter(pk__in=cs.get('gift_cards'), currency=event.currency)
+        summed = 0
+        for gc in gc_qs:
+            if gc.testmode != event.testmode:
+                gcs.remove(gc.pk)
+                continue
+            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()
+                ))
+        cs['gift_cards'] = gcs
+
     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,
-    OrderPosition, Quota, Seat, SeatCategoryMapping, User, Voucher,
+    CartPosition, Device, Event, GiftCard, Item, ItemVariation, Order,
+    OrderPayment, OrderPosition, Quota, Seat, SeatCategoryMapping, User,
+    Voucher,
 )
 from pretix.base.models.event import SubEvent
 from pretix.base.models.items import ItemBundle
@@ -43,8 +44,8 @@ from pretix.base.services.pricing import get_price
 from pretix.base.services.tasks import ProfiledEventTask, ProfiledTask
 from pretix.base.signals import (
     allow_ticket_download, order_approved, order_canceled, order_changed,
-    order_denied, order_expired, order_fee_calculation, order_placed,
-    order_split, periodic_task, validate_order,
+    order_denied, order_expired, order_fee_calculation, order_paid,
+    order_placed, order_split, periodic_task, validate_order,
 )
 from pretix.celery_app import app
 from pretix.helpers.models import modelcopy
@@ -291,6 +292,19 @@ def _cancel_order(order, user=None, send_mail: bool=True, api_token=None, device
         if i:
             generate_cancellation(i)
 
+        for position in order.positions.all():
+            for gc in position.issued_gift_cards.all():
+                gc = GiftCard.objects.select_for_update().get(pk=gc.pk)
+                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)
+
         if cancellation_fee:
             with order.event.lock():
                 for position in order.positions.all():
@@ -545,7 +559,7 @@ 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 +567,16 @@ 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)
+
+    gift_card_values = {}
+    for gc in gift_cards:
+        fval = Decimal(gc.value)  # TODO: don't require an extra query
+        fval = min(fval, total)
+        if fval > 0:
+            total -= fval
+            gift_card_values[gc] = fval
+
     if payment_provider:
         payment_fee = payment_provider.calculate_fee(total)
     else:
@@ -565,17 +587,34 @@ 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'):
-    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])
+                  meta_info: dict=None, sales_channel: str='web', gift_cards: list=None,
+                  shown_total=None):
     p = None
-
     with transaction.atomic():
+        checked_gift_cards = []
+        if gift_cards:
+            gc_qs = GiftCard.objects.select_for_update().filter(pk__in=gift_cards)
+            for gc in gc_qs:
+                if gc.currency != event.currency:
+                    raise OrderError(_("This gift card does not support this currency."))
+                if gc.testmode and not event.testmode:
+                    raise OrderError(_("This gift card can only be used in test mode."))
+                if not gc.testmode and event.testmode:
+                    raise OrderError(_("Only test gift cards can be used in test mode."))
+                if not gc.accepted_by(event.organizer):
+                    raise OrderError(_("This gift card is not accepted by this event organizer."))
+                checked_gift_cards.append(gc)
+        if checked_gift_cards and any(c.item.issue_giftcard for c in positions):
+            raise OrderError(_("You cannot pay with gift cards when buying a gift card."))
+
+        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 +645,41 @@ 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
+
+        # Safety check: Is the amount we're now going to charge the same amount the user has been shown when they
+        # pressed "Confirm purchase"? If not, we should better warn the user and show the confirmation page again.
+        # The only *known* case where this happens is if a gift card is used in two concurrent sessions.
+        if shown_total is not None:
+            if Decimal(shown_total) != pending_sum:
+                raise OrderError(
+                    _('While trying to place your order, we noticed that the order total has changed. Either one of '
+                      'the prices changed just now, or a gift card you used has been used in the meantime. Please '
+                      'check the prices below and try again.')
+                )
+
         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 +727,8 @@ 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, shown_total=None):
     if payment_provider:
         pprov = event.get_payment_providers().get(payment_provider)
         if not pprov:
@@ -707,9 +777,10 @@ 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, shown_total=shown_total)
 
-        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)
@@ -894,6 +965,7 @@ class OrderChangeManager:
         'seat_subevent_mismatch': _('You selected seat "{seat}" for a date that does not match the selected ticket date. Please choose a seat again.'),
         'seat_required': _('The selected product requires you to select a seat.'),
         'seat_forbidden': _('The selected product does not allow to select a seat.'),
+        'gift_card_change': _('You cannot change the price of a position that has been used to issue a gift card.'),
     }
     ItemOperation = namedtuple('ItemOperation', ('position', 'item', 'variation'))
     SubeventOperation = namedtuple('SubeventOperation', ('position', 'subevent'))
@@ -961,6 +1033,9 @@ class OrderChangeManager:
     def change_price(self, position: OrderPosition, price: Decimal):
         price = position.item.tax(price, base_price_is='gross')
 
+        if position.issued_gift_cards.exists():
+            raise OrderError(self.error_messages['gift_card_change'])
+
         self._totaldiff += price.gross - position.price
 
         if self.order.event.settings.invoice_include_free or price.gross != Decimal('0.00') or position.price != Decimal('0.00'):
@@ -1188,6 +1263,17 @@ class OrderChangeManager:
                 op.position._calculate_tax()
                 op.position.save()
             elif isinstance(op, self.CancelOperation):
+                for gc in op.position.issued_gift_cards.all():
+                    gc = GiftCard.objects.select_for_update().get(pk=gc.pk)
+                    if gc.value < op.position.price:
+                        raise OrderError(_(
+                            'A position 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=-op.position.price, order=self.order)
+
                 for opa in op.position.addons.all():
                     self.order.log_action('pretix.event.order.changed.cancel', user=self.user, auth=self.auth, data={
                         'position': opa.pk,
@@ -1466,12 +1552,12 @@ 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, shown_total=None):
     with language(locale):
         try:
             try:
                 return _perform_order(event, payment_provider, positions, email, locale, address, meta_info,
-                                      sales_channel)
+                                      sales_channel, gift_cards, shown_total)
             except LockTimeoutException:
                 self.retry()
         except (MaxRetriesExceededError, LockTimeoutException):
@@ -1615,3 +1701,25 @@ def change_payment_provider(order: Order, payment_provider, amount=None, new_pay
             generate_invoice(order)
 
     return old_fee, new_fee, fee, new_payment
+
+
+@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:
+            issued = Decimal('0.00')
+            for gc in p.issued_gift_cards.all():
+                issued += gc.transactions.first().value
+            if p.price - issued > 0:
+                gc = sender.organizer.issued_gift_cards.create(
+                    currency=sender.currency, issued_in=p, testmode=order.testmode
+                )
+                gc.transactions.create(value=p.price - issued, 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