Support for external gift cards (#2912)

src/pretix/base/email.py

@@ -320,13 +320,16 @@ def get_email_context(**kwargs):
     return ctx
 
 
-def _placeholder_payment(order, payment):
-    if not payment:
-        return None
-    if 'payment' in inspect.signature(payment.payment_provider.order_pending_mail_render).parameters:
-        return str(payment.payment_provider.order_pending_mail_render(order, payment))
-    else:
-        return str(payment.payment_provider.order_pending_mail_render(order))
+def _placeholder_payments(order, payments):
+    d = []
+    for payment in payments:
+        if 'payment' in inspect.signature(payment.payment_provider.order_pending_mail_render).parameters:
+            d.append(str(payment.payment_provider.order_pending_mail_render(order, payment)))
+        else:
+            d.append(str(payment.payment_provider.order_pending_mail_render(order)))
+    d = [line for line in d if line.strip()]
+    if d:
+        return '\n\n'.join(d)
 
 
 def get_best_name(position_or_address, parts=False):
@@ -617,7 +620,7 @@ def base_placeholders(sender, **kwargs):
             _('An individual text with a reason can be inserted here.'),
         ),
         SimpleFunctionalMailTextPlaceholder(
-            'payment_info', ['order', 'payment'], _placeholder_payment,
+            'payment_info', ['order', 'payments'], _placeholder_payments,
             _('The amount has been charged to your card.'),
         ),
         SimpleFunctionalMailTextPlaceholder(

src/pretix/base/migrations/0225_orderpayment_process_initiated.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.16 on 2022-11-17 15:27
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0224_eventmetaproperty_filter_allowed'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='orderpayment',
+            name='process_initiated',
+            field=models.BooleanField(null=True),
+        ),
+    ]

src/pretix/base/models/orders.py

@@ -1509,6 +1509,9 @@ class OrderPayment(models.Model):
     :type info: str
     :param fee: The ``OrderFee`` object used to track the fee for this order.
     :type fee: pretix.base.models.OrderFee
+    :param process_initiated: Only for internal use inside pretix.presale to check which payments have started
+                              the execution process.
+    :type process_initiated: bool
     """
     PAYMENT_STATE_CREATED = 'created'
     PAYMENT_STATE_PENDING = 'pending'
@@ -1559,6 +1562,9 @@ class OrderPayment(models.Model):
         null=True, blank=True, related_name='payments', on_delete=models.SET_NULL
     )
     migrated = models.BooleanField(default=False)
+    process_initiated = models.BooleanField(
+        null=True  # null = created before this field was introduced
+    )
 
     objects = ScopedManager(organizer='order__event__organizer')
 

src/pretix/base/payment.py

@@ -63,14 +63,13 @@ from pretix.base.models import (
     OrderRefund, Quota,
 )
 from pretix.base.reldate import RelativeDateField, RelativeDateWrapper
-from pretix.base.services.cart import get_fees
 from pretix.base.settings import SettingsSandbox
 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.countries import CachedCountries
 from pretix.helpers.money import DecimalTextInput
-from pretix.multidomain.urlreverse import build_absolute_uri, eventreverse
+from pretix.multidomain.urlreverse import build_absolute_uri
 from pretix.presale.views import get_cart, get_cart_total
 from pretix.presale.views.cart import cart_session, get_or_create_cart_id
 
@@ -138,6 +137,48 @@ class BasePaymentProvider:
         """
         return self.settings.get('_enabled', as_type=bool)
 
+    @property
+    def multi_use_supported(self) -> bool:
+        """
+        Returns whether or whether not this payment provider supports being used multiple times in the same
+        checkout, or in addition to a different payment provider. This is usually only useful for payment providers
+        that represent gift cards, i.e. payment methods with an upper limit per payment instrument that can usually
+        be combined with other instruments.
+
+        If you set this property to ``True``, the behavior of how pretix interacts with your payment provider changes
+        and you will need to respect the following rules:
+
+        - ``payment_form_render`` must not depend on session state, it must always allow a user to add a new payment.
+           Editing a payment is not possible, but pretix will give users an option to delete it.
+
+        - Returning ``True`` from ``checkout_prepare`` is no longer enough. Instead, you must *also* call
+          ``pretix.base.services.cart.add_payment_to_cart(request, provider, min_value, max_value, info_data)``
+          to add the payment to the session. You are still allowed to do a redirect from ``checkout_prepare`` and then
+          call this function upon return.
+
+        - Unlike in the general case, when ``checkout_prepare`` is called, the ``cart['total']`` parameter will _not yet_
+          include payment fees charged by your provider as we don't yet know the amount of the charge, so you need to
+          take care of that yourself when setting your maximum amount.
+
+        - ``payment_is_valid_session`` will not be called during checkout, don't rely on it. If you called
+          ``add_payment_to_cart``, we'll trust the payment is okay and your next chance to change that will be
+          ``execute_payment``.
+
+        The changed behavior currently only affects the behavior during initial checkout (i.e. ``checkout_prepare``),
+        for ``payment_prepare`` the regular behavior applies and you are expected to just modify the amount of the
+        ``OrderPayment`` object if you need to.
+        """
+        return False
+
+    @property
+    def execute_payment_needs_user(self) -> bool:
+        """
+        Set this to ``True`` if your ``execute_payment`` function needs to be triggered by a user request, i.e. either
+        needs the ``request`` object or might require a browser redirect. If this is ``False``, you will not receive
+        a ``request`` and may not redirect since execute_payment might be called server-side.
+        """
+        return True
+
     @property
     def test_mode_message(self) -> str:
         """
@@ -574,7 +615,7 @@ class BasePaymentProvider:
         ctx = {'request': request, 'form': form}
         return template.render(ctx)
 
-    def checkout_confirm_render(self, request, order: Order=None) -> str:
+    def checkout_confirm_render(self, request, order: Order=None, info_data: dict=None) -> str:
         """
         If the user has successfully filled in their payment data, they will be redirected
         to a confirmation page which lists all details of their order for a final review.
@@ -584,7 +625,9 @@ class BasePaymentProvider:
         In most cases, this should include a short summary of the user's input and
         a short explanation on how the payment process will continue.
 
+        :param request: The current HTTP request.
         :param order: Only set when this is a change to a new payment method for an existing order.
+        :param info_data: The ``info_data`` dictionary you set during ``add_payment_to_cart`` (only filled if ``multi_use_supported`` is set)
         """
         raise NotImplementedError()  # NOQA
 
@@ -618,6 +661,10 @@ class BasePaymentProvider:
         .. IMPORTANT:: If this is called, the user has not yet confirmed their order.
            You may NOT do anything which actually moves money.
 
+        Note: The behavior of this method changes significantly when you set
+              ``multi_use_supported``. Please refer to the ``multi_use_supported`` documentation
+              for more information.
+
         :param cart: This dictionary contains at least the following keys:
 
             positions:
@@ -657,9 +704,9 @@ class BasePaymentProvider:
         You will be passed an :py:class:`pretix.base.models.OrderPayment` object that contains
         the amount of money that should be paid.
 
-        If you need any special behavior, you can return a string
-        containing the URL the user will be redirected to. If you are done with your process
-        you should return the user to the order's detail page.
+        If you need any special behavior, you can return a string containing the URL the user will be redirected to.
+        If you are done with your process you should return the user to the order's detail page. Redirection is not
+        allowed if you set ``execute_payment_needs_user`` to ``True``.
 
         If the payment is completed, you should call ``payment.confirm()``. Please note that this might
         raise a ``Quota.QuotaExceededException`` if (and only if) the payment term of this order is over and
@@ -671,7 +718,7 @@ class BasePaymentProvider:
 
         On errors, you should raise a ``PaymentException``.
 
-        :param order: The order object
+        :param request: A HTTP request, except if ``execute_payment_needs_user`` is ``False``
         :param payment: An ``OrderPayment`` instance
         """
         return None
@@ -905,6 +952,7 @@ class FreeOrderProvider(BasePaymentProvider):
     is_implicit = True
     is_enabled = True
     identifier = "free"
+    execute_payment_needs_user = False
 
     def checkout_confirm_render(self, request: HttpRequest) -> str:
         return _("No payment is required as this order only includes products which are free of charge.")
@@ -991,6 +1039,7 @@ class BoxOfficeProvider(BasePaymentProvider):
 class ManualPayment(BasePaymentProvider):
     identifier = 'manual'
     verbose_name = _('Manual payment')
+    execute_payment_needs_user = False
 
     @property
     def test_mode_message(self):
@@ -1133,6 +1182,8 @@ class GiftCardPayment(BasePaymentProvider):
     identifier = "giftcard"
     verbose_name = _("Gift card")
     priority = 10
+    multi_use_supported = True
+    execute_payment_needs_user = False
 
     @property
     def settings_form_fields(self):
@@ -1158,8 +1209,10 @@ class GiftCardPayment(BasePaymentProvider):
     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 checkout_confirm_render(self, request, order=None, info_data=None) -> str:
+        return get_template('pretixcontrol/giftcards/checkout_confirm.html').render({
+            'info_data': info_data,
+        })
 
     def refund_control_render(self, request, refund) -> str:
         from .models import GiftCard
@@ -1213,6 +1266,8 @@ class GiftCardPayment(BasePaymentProvider):
         return True
 
     def checkout_prepare(self, request: HttpRequest, cart: Dict[str, Any]) -> Union[bool, str, None]:
+        from pretix.base.services.cart import add_payment_to_cart
+
         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."))
@@ -1221,7 +1276,7 @@ class GiftCardPayment(BasePaymentProvider):
         cs = cart_session(request)
         try:
             gc = self.event.organizer.accepted_gift_cards.get(
-                secret=request.POST.get("giftcard")
+                secret=request.POST.get("giftcard").strip()
             )
             if gc.currency != self.event.currency:
                 messages.error(request, _("This gift card does not support this currency."))
@@ -1238,34 +1293,22 @@ class GiftCardPayment(BasePaymentProvider):
             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]
 
-            total = sum(p.total for p in cart['positions'])
-            # Recompute fees. Some plugins, e.g. pretix-servicefees, change their fee schedule if a gift card is
-            # applied.
-            fees = get_fees(
-                self.event, request, total, cart['invoice_address'], cs.get('payment'),
-                cart['raw']
+            for p in cs.get('payments', []):
+                if p['provider'] == self.identifier and p['info_data']['gift_card'] == gc.pk:
+                    messages.error(request, _("This gift card is already used for your payment."))
+                    return
+
+            add_payment_to_cart(
+                request,
+                self,
+                max_value=gc.value,
+                info_data={
+                    'gift_card': gc.pk,
+                    'gift_card_secret': gc.secret,
+                }
             )
-            total += sum([f.value for f in fees])
-            remainder = total
-            if remainder > Decimal('0.00'):
-                del cs['payment']
-                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)
+            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 "
@@ -1283,7 +1326,7 @@ class GiftCardPayment(BasePaymentProvider):
 
         try:
             gc = self.event.organizer.accepted_gift_cards.get(
-                secret=request.POST.get("giftcard")
+                secret=request.POST.get("giftcard").strip()
             )
             if gc.currency != self.event.currency:
                 messages.error(request, _("This gift card does not support this currency."))
@@ -1302,6 +1345,7 @@ class GiftCardPayment(BasePaymentProvider):
                 return
             payment.info_data = {
                 'gift_card': gc.pk,
+                'gift_card_secret': gc.secret,
                 'retry': True
             }
             payment.amount = min(payment.amount, gc.value)
@@ -1309,7 +1353,7 @@ class GiftCardPayment(BasePaymentProvider):
 
             return True
         except GiftCard.DoesNotExist:
-            if self.event.vouchers.filter(code__iexact=request.POST.get("giftcard")).exists():
+            if self.event.vouchers.filter(code__iexact=request.POST.get("giftcard").strip()).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:
@@ -1318,36 +1362,45 @@ class GiftCardPayment(BasePaymentProvider):
             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
+        for p in payment.order.positions.all():
             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'):
+        if not gcpk:
             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."))
-            if gc.expires and gc.expires < now():  # noqa - just a safeguard
-                messages.error(request, _("This gift card is no longer valid."))
-                return
-            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()
+        try:
+            with transaction.atomic():
+                try:
+                    gc = GiftCard.objects.select_for_update().get(pk=gcpk)
+                except GiftCard.DoesNotExist:
+                    raise PaymentException(_("This gift card does not support this currency."))
+                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):
+                    raise PaymentException(_("This gift card is not accepted by this event organizer."))
+                if payment.amount > gc.value:
+                    raise PaymentException(_("This gift card was used in the meantime. Please try again."))
+                if gc.testmode and not payment.order.testmode:
+                    raise PaymentException(_("This gift card can only be used in test mode."))
+                if not gc.testmode and payment.order.testmode:
+                    raise PaymentException(_("Only test gift cards can be used in test mode."))
+                if gc.expires and gc.expires < now():
+                    raise PaymentException(_("This gift card is no longer valid."))
+
+                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()
+        except PaymentException as e:
+            payment.fail(info={'error': str(e)})
+            raise e
 
     def payment_is_valid_session(self, request: HttpRequest) -> bool:
         return True

src/pretix/base/services/cart.py

@@ -31,7 +31,7 @@
 # Unless required by applicable law or agreed to in writing, software distributed under the Apache License 2.0 is
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
-
+import uuid
 from collections import Counter, defaultdict, namedtuple
 from datetime import datetime, time, timedelta
 from decimal import Decimal
@@ -1265,44 +1265,71 @@ class CartManager:
                 raise CartError(err)
 
 
-def get_fees(event, request, total, invoice_address, provider, positions):
+def add_payment_to_cart(request, provider, min_value: Decimal=None, max_value: Decimal=None, info_data: dict=None):
+    """
+    :param request: The current HTTP request context.
+    :param provider: The instance of your payment provider.
+    :param min_value: The minimum value this payment instrument supports, or ``None`` for unlimited.
+    :param max_value: The maximum value this payment instrument supports, or ``None`` for unlimited. Highly discouraged
+                      to use for payment providers which charge a payment fee, as this can be very user-unfriendly if
+                      users need a second payment method just for the payment fee of the first method.
+    :param info_data: A dictionary of information that will be passed through to the ``OrderPayment.info_data`` attribute.
+    :return:
+    """
     from pretix.presale.views.cart import cart_session
 
+    cs = cart_session(request)
+    cs.setdefault('payments', [])
+
+    cs['payments'].append({
+        'id': str(uuid.uuid4()),
+        'provider': provider.identifier,
+        'multi_use_supported': provider.multi_use_supported,
+        'min_value': str(min_value) if min_value is not None else None,
+        'max_value': str(max_value) if max_value is not None else None,
+        'info_data': info_data or {},
+    })
+
+
+def get_fees(event, request, total, invoice_address, payments, positions):
+    if payments and not isinstance(payments, list):
+        raise TypeError("payments must now be a list")
+
     fees = []
     for recv, resp in fee_calculation_for_cart.send(sender=event, request=request, invoice_address=invoice_address,
-                                                    total=total, positions=positions):
+                                                    total=total, positions=positions, payment_requests=payments):
         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)
-        for gc in gc_qs:
-            if gc.testmode != event.testmode:
-                gcs.remove(gc.pk)
+    if total != 0 and payments:
+        total_remaining = total
+        for p in payments:
+            # This algorithm of treating min/max values and fees needs to stay in sync between the following
+            # places in the code base:
+            # - pretix.base.services.cart.get_fees
+            # - pretix.base.services.orders._get_fees
+            # - pretix.presale.views.CartMixin.current_selected_payments
+            if p.get('min_value') and total_remaining < Decimal(p['min_value']):
                 continue
-            fval = Decimal(gc.value)  # TODO: don't require an extra query
-            fval = min(fval, total)
-            if fval > 0:
-                total -= 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:
-            payment_fee = provider.calculate_fee(total)
+            to_pay = total_remaining
+            if p.get('max_value') and to_pay > Decimal(p['max_value']):
+                to_pay = min(to_pay, Decimal(p['max_value']))
+
+            pprov = event.get_payment_providers(cached=True).get(p['provider'])
+            if not pprov:
+                continue
+
+            payment_fee = pprov.calculate_fee(to_pay)
+            total_remaining += payment_fee
+            to_pay += payment_fee
+
+            if p.get('max_value') and to_pay > Decimal(p['max_value']):
+                to_pay = min(to_pay, Decimal(p['max_value']))
+
+            total_remaining -= to_pay
 
             if payment_fee:
                 payment_fee_tax_rule = event.settings.tax_rate_default or TaxRule.zero()

src/pretix/base/services/orders.py

@@ -74,7 +74,7 @@ from pretix.base.models.orders import (
 )
 from pretix.base.models.organizer import TeamAPIToken
 from pretix.base.models.tax import TAXED_ZERO, TaxedPrice, TaxRule
-from pretix.base.payment import BasePaymentProvider, PaymentException
+from pretix.base.payment import PaymentException
 from pretix.base.reldate import RelativeDateWrapper
 from pretix.base.secrets import assign_ticket_secret
 from pretix.base.services import tickets
@@ -793,68 +793,75 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
         raise OrderError(err, errargs)
 
 
-def _get_fees(positions: List[CartPosition], payment_provider: BasePaymentProvider, address: InvoiceAddress,
-              meta_info: dict, event: Event, gift_cards: List[GiftCard]):
+def _get_fees(positions: List[CartPosition], payment_requests: List[dict], address: InvoiceAddress,
+              meta_info: dict, event: Event, require_approval=False):
     fees = []
     total = sum([c.price for c in positions])
 
-    for recv, resp in order_fee_calculation.send(sender=event, invoice_address=address, total=total,
+    gift_cards = []  # for backwards compatibility
+    for p in payment_requests:
+        if p['provider'] == 'giftcard':
+            gift_cards.append(GiftCard.objects.get(pk=p['info_data']['gift_card']))
+
+    for recv, resp in order_fee_calculation.send(sender=event, invoice_address=address, total=total, payment_requests=payment_requests,
                                                  meta_info=meta_info, positions=positions, gift_cards=gift_cards):
         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
+    total_remaining = total
+    for p in payment_requests:
+        # This algorithm of treating min/max values and fees needs to stay in sync between the following
+        # places in the code base:
+        # - pretix.base.services.cart.get_fees
+        # - pretix.base.services.orders._get_fees
+        # - pretix.presale.views.CartMixin.current_selected_payments
+        if p.get('min_value') and total_remaining < Decimal(p['min_value']):
+            p['payment_amount'] = Decimal('0.00')
+            continue
 
-    if payment_provider:
-        payment_fee = payment_provider.calculate_fee(total)
-    else:
-        payment_fee = 0
-    pf = None
-    if payment_fee:
-        pf = OrderFee(fee_type=OrderFee.FEE_TYPE_PAYMENT, value=payment_fee,
-                      internal_type=payment_provider.identifier)
-        fees.append(pf)
+        to_pay = total_remaining
+        if p.get('max_value') and to_pay > Decimal(p['max_value']):
+            to_pay = min(to_pay, Decimal(p['max_value']))
 
-    return fees, pf, gift_card_values
+        payment_fee = p['pprov'].calculate_fee(to_pay)
+        total_remaining += payment_fee
+        to_pay += payment_fee
+
+        if p.get('max_value') and to_pay > Decimal(p['max_value']):
+            to_pay = min(to_pay, Decimal(p['max_value']))
+
+        total_remaining -= to_pay
+
+        p['payment_amount'] = to_pay
+        if payment_fee:
+            pf = OrderFee(fee_type=OrderFee.FEE_TYPE_PAYMENT, value=payment_fee,
+                          internal_type=p['pprov'].identifier)
+            fees.append(pf)
+            p['fee'] = pf
+
+    if total_remaining != Decimal('0.00') and not require_approval:
+        raise OrderError(_("The selected payment methods do not cover the total balance."))
+
+    return fees
 
 
 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', gift_cards: list=None, shown_total=None,
+                  payment_requests: List[dict], locale: str=None, address: InvoiceAddress=None,
+                  meta_info: dict=None, sales_channel: str='web', shown_total=None,
                   customer=None):
-    p = None
+    payments = []
     sales_channel = get_all_sales_channels()[sales_channel]
 
     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."))
 
         try:
             validate_memberships_in_order(customer, positions, event, lock=True, testmode=event.testmode)
         except ValidationError as e:
             raise OrderError(e.message)
 
-        fees, pf, gift_card_values = _get_fees(positions, payment_provider, address, meta_info, event, checked_gift_cards)
+        require_approval = any(p.requires_approval(invoice_address=address) for p in positions)
+        fees = _get_fees(positions, payment_requests, address, meta_info, event, require_approval=require_approval)
         total = pending_sum = sum([c.price for c in positions]) + sum([c.value for c in fees])
 
         order = Order(
@@ -867,7 +874,7 @@ def _create_order(event: Event, email: str, positions: List[CartPosition], now_d
             total=total,
             testmode=True if sales_channel.testmode_supported and event.testmode else False,
             meta_info=json.dumps(meta_info or {}),
-            require_approval=any(p.requires_approval(invoice_address=address) for p in positions),
+            require_approval=require_approval,
             sales_channel=sales_channel.identifier,
             customer=customer,
         )
@@ -891,28 +898,11 @@ 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.
+        # We used to have a *known* case where this happened is if a gift card is used in two concurrent sessions,
+        # but this is now a payment error instead. So currently this code branch is usually only triggered by bugs
+        # in other places (e.g. tax calculation).
         if shown_total is not None:
             if Decimal(shown_total) != pending_sum:
                 raise OrderError(
@@ -921,13 +911,17 @@ def _create_order(event: Event, email: str, positions: List[CartPosition], now_d
                       '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=pending_sum,
-                fee=pf
-            )
+        if payment_requests and not order.require_approval:
+            for p in payment_requests:
+                if not p.get('multi_use_supported') or p['payment_amount'] > Decimal('0.00'):
+                    payments.append(order.payments.create(
+                        state=OrderPayment.PAYMENT_STATE_CREATED,
+                        provider=p['provider'],
+                        amount=p['payment_amount'],
+                        fee=p.get('fee'),
+                        info=json.dumps(p['info_data']),
+                        process_initiated=False,
+                    ))
 
         orderpositions = OrderPosition.transform_cart_positions(positions, order)
         order.create_transactions(positions=orderpositions, fees=fees, is_new=True)
@@ -939,12 +933,12 @@ def _create_order(event: Event, email: str, positions: List[CartPosition], now_d
                 order.log_action('pretix.event.order.consent', data={'msg': msg})
 
     order_placed.send(event, order=order)
-    return order, p
+    return order, payments
 
 
-def _order_placed_email(event: Event, order: Order, pprov: BasePaymentProvider, email_template, subject_template,
-                        log_entry: str, invoice, payment: OrderPayment, is_free=False):
-    email_context = get_email_context(event=event, order=order, payment=payment if pprov else None)
+def _order_placed_email(event: Event, order: Order, email_template, subject_template,
+                        log_entry: str, invoice, payments: List[OrderPayment], is_free=False):
+    email_context = get_email_context(event=event, order=order, payments=payments)
     try:
         order.send_mail(
             subject_template, email_template, email_context,
@@ -979,15 +973,13 @@ def _order_placed_email_attendee(event: Event, order: Order, position: OrderPosi
         logger.exception('Order received email could not be sent to attendee')
 
 
-def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
+def _perform_order(event: Event, payment_requests: List[dict], position_ids: List[str],
                    email: str, locale: str, address: int, meta_info: dict=None, sales_channel: str='web',
-                   gift_cards: list=None, shown_total=None, customer=None):
-    if payment_provider:
-        pprov = event.get_payment_providers().get(payment_provider)
-        if not pprov:
+                   shown_total=None, customer=None):
+    for p in payment_requests:
+        p['pprov'] = event.get_payment_providers(cached=True)[p['provider']]
+        if not p['pprov']:
             raise OrderError(error_messages['internal'])
-    else:
-        pprov = None
 
     if customer:
         customer = event.organizer.customers.get(pk=customer)
@@ -1017,8 +1009,17 @@ def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
         id__in=position_ids, event=event
     )
 
-    validate_order.send(event, payment_provider=pprov, email=email, positions=positions, locale=locale,
-                        invoice_address=addr, meta_info=meta_info, customer=customer)
+    validate_order.send(
+        event,
+        payment_provider=payment_requests[0]['provider'] if payment_requests else None,  # only for backwards compatibility
+        payments=payment_requests,
+        email=email,
+        positions=positions,
+        locale=locale,
+        invoice_address=addr,
+        meta_info=meta_info,
+        customer=customer,
+    )
 
     lockfn = NoLockManager
     locked = False
@@ -1038,21 +1039,28 @@ def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
         if len(position_ids) != len(positions):
             raise OrderError(error_messages['internal'])
         _check_positions(event, now_dt, positions, address=addr, sales_channel=sales_channel, customer=customer)
-        order, payment = _create_order(event, email, positions, now_dt, pprov,
-                                       locale=locale, address=addr, meta_info=meta_info, sales_channel=sales_channel,
-                                       gift_cards=gift_cards, shown_total=shown_total, customer=customer)
+        order, payment_objs = _create_order(event, email, positions, now_dt, payment_requests,
+                                            locale=locale, address=addr, meta_info=meta_info, sales_channel=sales_channel,
+                                            shown_total=shown_total, customer=customer)
 
-        free_order_flow = payment and payment_provider == 'free' and order.pending_sum == Decimal('0.00') and not order.require_approval
+        free_order_flow = (
+            payment_objs and
+            any(p['provider'] == 'free' for p in payment_requests) 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)
+                for p in payment_objs:
+                    if p.provider == 'free':
+                        p.confirm(send_mail=False, lock=not locked)
             except Quota.QuotaExceededException:
                 pass
 
     invoice = order.invoices.last()  # Might be generated by plugin already
     if not invoice and invoice_qualified(order):
         if event.settings.get('invoice_generate') == 'True' or (
-                event.settings.get('invoice_generate') == 'paid' and payment.payment_provider.requires_invoice_immediately):
+                event.settings.get('invoice_generate') == 'paid' and any(p['pprov'].requires_invoice_immediately for p in payment_requests)):
             invoice = generate_invoice(
                 order,
                 trigger_pdf=not event.settings.invoice_email_attachment or not order.email
@@ -1084,7 +1092,7 @@ def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
             subject_attendees_template = event.settings.mail_subject_order_placed_attendee
 
         if sales_channel in event.settings.mail_sales_channel_placed_paid:
-            _order_placed_email(event, order, pprov, email_template, subject_template, log_entry, invoice, payment,
+            _order_placed_email(event, order, email_template, subject_template, log_entry, invoice, payment_objs,
                                 is_free=free_order_flow)
             if email_attendees:
                 for p in order.positions.all():
@@ -1092,7 +1100,33 @@ def _perform_order(event: Event, payment_provider: str, position_ids: List[str],
                         _order_placed_email_attendee(event, order, p, email_attendees_template, subject_attendees_template, log_entry,
                                                      is_free=free_order_flow)
 
-    return order.id
+    warnings = []
+    any_failed = False
+    for p in payment_objs:
+        if not p.payment_provider.execute_payment_needs_user:
+            try:
+                p.process_initiated = True
+                p.save(update_fields=['process_initiated'])
+                resp = p.payment_provider.execute_payment(None, p)
+                if isinstance(resp, str):
+                    logger.warning('Payment provider returned URL from execute_payment even though execute_payment_needs_user is not set')
+            except PaymentException as e:
+                warnings.append(str(e))
+                any_failed = True
+            except Exception:
+                logger.exception('Error during payment attempt')
+
+    if any_failed:
+        # Cancel all other payments because their amount might be wrong now.
+        for p in payment_objs:
+            if p.state == OrderPayment.PAYMENT_STATE_CREATED:
+                p.state = OrderPayment.PAYMENT_STATE_CANCELED
+                p.save(update_fields=['state'])
+
+    return {
+        'order_id': order.id,
+        'warnings': warnings,
+    }
 
 
 @receiver(signal=periodic_task)
@@ -2394,14 +2428,14 @@ 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],
+def perform_order(self, event: Event, payments: List[dict], positions: List[str],
                   email: str=None, locale: str=None, address: int=None, meta_info: dict=None,
-                  sales_channel: str='web', gift_cards: list=None, shown_total=None, customer=None):
+                  sales_channel: str='web', shown_total=None, customer=None):
     with language(locale):
         try:
             try:
-                return _perform_order(event, payment_provider, positions, email, locale, address, meta_info,
-                                      sales_channel, gift_cards, shown_total, customer)
+                return _perform_order(event, payments, positions, email, locale, address, meta_info,
+                                      sales_channel, shown_total, customer)
             except LockTimeoutException:
                 self.retry()
         except (MaxRetriesExceededError, LockTimeoutException):

src/pretix/base/signals.py

@@ -307,7 +307,7 @@ The ``sender`` keyword argument will contain an organizer.
 validate_order = EventPluginSignal(
 )
 """
-Arguments: ``payment_provider``, ``positions``, ``email``, ``locale``, ``invoice_address``,
+Arguments: ``payments``, ``positions``, ``email``, ``locale``, ``invoice_address``,
 ``meta_info``, ``customer``
 
 This signal is sent out when the user tries to confirm the order, before we actually create
@@ -316,6 +316,9 @@ but you can raise an OrderError with an appropriate exception message if you lik
 the order. We strongly discourage making changes to the order here.
 
 As with all event-plugin signals, the ``sender`` keyword argument will contain the event.
+
+**DEPRECTATION:** Stop listening to the ``payment_provider`` attribute, it will be removed
+in the future, as the ``payments`` attribute gives more information.
 """
 
 validate_cart = EventPluginSignal()
@@ -564,7 +567,7 @@ an OrderedDict of (setting name, form field).
 
 order_fee_calculation = EventPluginSignal()
 """
-Arguments: ``positions``, ``invoice_address``, ``meta_info``, ``total``, ``gift_cards``
+Arguments: ``positions``, ``invoice_address``, ``meta_info``, ``total``, ``gift_cards``, ``payment_requests``
 
 This signals allows you to add fees to an order while it is being created. You are expected to
 return a list of ``OrderFee`` objects that are not yet saved to the database
@@ -574,8 +577,10 @@ As with all plugin signals, the ``sender`` keyword argument will contain the eve
 argument will contain the cart positions and ``invoice_address`` the invoice address (useful for
 tax calculation). The argument ``meta_info`` contains the order's meta dictionary. The ``total``
 keyword argument will contain the total cart sum without any fees. You should not rely on this
-``total`` value for fee calculations as other fees might interfere. The ``gift_cards`` argument lists
-the gift cards in use.
+``total`` value for fee calculations as other fees might interfere. The ``gift_cards`` argument
+lists the gift cards in use.
+
+**DEPRECTATION:** Stop listening to the ``gift_cards`` attribute, it will be removed in the future.
 """
 
 order_fee_type_name = EventPluginSignal()