Seat-specific vouchers (#1486)

* Basic functionality

* API

* Do not delete seats with vouchers

* Show seat in list of seats

* Validate availability of seats

* Fix invalid logic in Seat.is_available

* Show voucher name in edit form

src/pretix/base/models/event.py

@@ -12,7 +12,7 @@ from django.core.files.storage import default_storage
 from django.core.mail import get_connection
 from django.core.validators import RegexValidator
 from django.db import models
-from django.db.models import Exists, OuterRef, Prefetch, Q, Subquery
+from django.db.models import Exists, F, OuterRef, Prefetch, Q, Subquery
 from django.template.defaultfilters import date as _date
 from django.utils.crypto import get_random_string
 from django.utils.functional import cached_property
@@ -377,9 +377,18 @@ class Event(EventMixin, LoggedModel):
         if img:
             return urljoin(build_absolute_uri(self, 'presale:event.index'), img)
 
-    @property
-    def free_seats(self):
+    def free_seats(self, ignore_voucher=None):
         from .orders import CartPosition, Order, OrderPosition
+        from .vouchers import Voucher
+        vqs = Voucher.objects.filter(
+            event=self,
+            seat_id=OuterRef('pk'),
+            redeemed__lt=F('max_usages'),
+        ).filter(
+            Q(valid_until__isnull=True) | Q(valid_until__gte=now())
+        )
+        if ignore_voucher:
+            vqs = vqs.exclude(pk=ignore_voucher.pk)
         return self.seats.annotate(
             has_order=Exists(
                 OrderPosition.objects.filter(
@@ -394,8 +403,11 @@ class Event(EventMixin, LoggedModel):
                     seat_id=OuterRef('pk'),
                     expires__gte=now()
                 )
+            ),
+            has_voucher=Exists(
+                vqs
             )
-        ).filter(has_order=False, has_cart=False, blocked=False)
+        ).filter(has_order=False, has_cart=False, has_voucher=False, blocked=False)
 
     @property
     def presale_has_ended(self):
@@ -986,9 +998,19 @@ class SubEvent(EventMixin, LoggedModel):
     def __str__(self):
         return '{} - {}'.format(self.name, self.get_date_range_display())
 
-    @property
-    def free_seats(self):
+    def free_seats(self, ignore_voucher=None):
         from .orders import CartPosition, Order, OrderPosition
+        from .vouchers import Voucher
+        vqs = Voucher.objects.filter(
+            event_id=self.event_id,
+            subevent=self,
+            seat_id=OuterRef('pk'),
+            redeemed__lt=F('max_usages'),
+        ).filter(
+            Q(valid_until__isnull=True) | Q(valid_until__gte=now())
+        )
+        if ignore_voucher:
+            vqs = vqs.exclude(pk=ignore_voucher.pk)
         return self.seats.annotate(
             has_order=Exists(
                 OrderPosition.objects.filter(
@@ -1005,8 +1027,11 @@ class SubEvent(EventMixin, LoggedModel):
                     seat_id=OuterRef('pk'),
                     expires__gte=now()
                 )
+            ),
+            has_voucher=Exists(
+                vqs
             )
-        ).filter(has_order=False, has_cart=False, blocked=False)
+        ).filter(has_order=False, has_cart=False, blocked=False, has_voucher=False)
 
     @cached_property
     def settings(self):

src/pretix/base/models/seating.py

@@ -5,6 +5,7 @@ import jsonschema
 from django.contrib.staticfiles import finders
 from django.core.exceptions import ValidationError
 from django.db import models
+from django.db.models import F, Q
 from django.utils.deconstruct import deconstructible
 from django.utils.timezone import now
 from django.utils.translation import gettext, ugettext_lazy as _
@@ -110,15 +111,21 @@ class Seat(models.Model):
             return self.name
         return ', '.join(parts)
 
-    def is_available(self, ignore_cart=None, ignore_orderpos=None):
+    def is_available(self, ignore_cart=None, ignore_orderpos=None, ignore_voucher_id=None):
         from .orders import Order
 
         if self.blocked:
             return False
         opqs = self.orderposition_set.filter(order__status__in=[Order.STATUS_PENDING, Order.STATUS_PAID])
         cpqs = self.cartposition_set.filter(expires__gte=now())
-        if ignore_cart:
+        vqs = self.vouchers.filter(
+            Q(Q(valid_until__isnull=True) | Q(valid_until__gte=now())) &
+            Q(redeemed__lt=F('max_usages'))
+        )
+        if ignore_cart and ignore_cart is not True:
             cpqs = cpqs.exclude(pk=ignore_cart.pk)
         if ignore_orderpos:
             opqs = opqs.exclude(pk=ignore_orderpos.pk)
-        return not opqs.exists() and not cpqs.exists()
+        if ignore_voucher_id:
+            vqs = vqs.exclude(pk=ignore_voucher_id)
+        return not opqs.exists() and (ignore_cart is True or not cpqs.exists()) and not vqs.exists()

src/pretix/base/models/vouchers.py

@@ -11,7 +11,7 @@ from django.utils.translation import pgettext_lazy, ugettext_lazy as _
 from django_scopes import ScopedManager, scopes_disabled
 
 from pretix.base.banlist import banned
-from pretix.base.models import SeatCategoryMapping
+from pretix.base.models import Seat, SeatCategoryMapping
 
 from ..decimal import round_decimal
 from .base import LoggedModel
@@ -171,6 +171,12 @@ class Voucher(LoggedModel):
             "If enabled, the voucher is valid for any product affected by this quota."
         )
     )
+    seat = models.ForeignKey(
+        Seat, related_name='vouchers',
+        null=True, blank=True,
+        on_delete=models.PROTECT,
+        verbose_name=_("Specific seat"),
+    )
     tag = models.CharField(
         max_length=255,
         verbose_name=_("Tag"),
@@ -335,6 +341,38 @@ class Voucher(LoggedModel):
         if 'code' in data and Voucher.objects.filter(Q(code__iexact=data['code']) & Q(event=event) & ~Q(pk=pk)).exists():
             raise ValidationError(_('A voucher with this code already exists.'))
 
+    @staticmethod
+    def clean_seat_id(data, item, event, pk):
+        try:
+            if event.has_subevents:
+                if not data.get('subevent'):
+                    raise ValidationError(_('You need to choose a date if you select a seat.'))
+                seat = event.seats.get(seat_guid=data.get('seat'), subevent=data.get('subevent'))
+            else:
+                seat = event.seats.get(seat_guid=data.get('seat'))
+        except Seat.DoesNotExist:
+            raise ValidationError(_('The specified seat ID "{id}" does not exist for this event.').format(
+                id=data.get('seat')))
+
+        if not seat.is_available(ignore_voucher_id=pk, ignore_cart=True):
+            raise ValidationError(_('The seat "{id}" is currently unavailable (blocked, already sold or a '
+                                    'different voucher).').format(
+                id=seat.seat_guid))
+
+        if not item:
+            raise ValidationError(_('You need to choose a specific product if you select a seat.'))
+
+        if data.get('max_usages', 1) > 1:
+            raise ValidationError(_('Seat-specific vouchers can only be used once.'))
+
+        if seat.product != item:
+            raise ValidationError(_('You need to choose the product "{prod}" for this seat.').format(prod=seat.product))
+
+        if not seat.is_available(ignore_voucher_id=pk):
+            raise ValidationError(_('The seat "{id}" is already sold or currently blocked.').format(id=seat.seat_guid))
+
+        return seat
+
     def save(self, *args, **kwargs):
         self.code = self.code.upper()
         super().save(*args, **kwargs)