Fix test failure

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

doc/api/resources/checkin.rst

@@ -46,12 +46,14 @@ Checking a ticket in
                         this request twice with the same nonce, the second request will also succeed but will always
                         create only one check-in object even when the previous request was successful as well. This
                         allows for a certain level of idempotency and enables you to re-try after a connection failure.
+   :<json string exchange_medium_type: To perform an exchange to a reusable medium, pass the type of the new reusable medium
+   :<json string exchange_medium_identifier: To perform an exchange to a reusable media, pass the identifier of the new medium
    :<json boolean use_order_locale: Specifies that pretix should use the customer's language (``locale`` field from the
                                     order) when building texts (currently only the ``reason_explanation`` response field).
                                     Defaults to ``false`` in which case the server will determine the language (currently
                                     the event default language, might change in the future with support for the
                                     ``Accept-Language`` header).
-   :>json string status: ``"ok"``, ``"incomplete"``, or ``"error"``
+   :>json string status: ``"ok"``, ``"incomplete"``, ``"exchange"``, or ``"error"``
    :>json string reason: Reason code, only set on status ``"error"``, see below for possible values.
    :>json string reason_explanation: Human-readable explanation, only set on status ``"error"`` and reason ``"rules"``, can be null.
    :>json object position: Copy of the matching order position (if any was found). The contents are the same as the
@@ -67,6 +69,8 @@ Checking a ticket in
    :>json object list: Excerpt of information about the matching :ref:`check-in list <rest-checkinlists>` (if any was found),
                        including the attributes ``id``, ``name``, ``event``, ``subevent``, and ``include_pending``.
    :>json object questions: List of questions to be answered for check-in, only set on status ``"incomplete"``.
+   :>json object media_policy: Reusable media policy (see documentation on items), only set on status ``"exchange"``.
+   :>json object media_type: Reusable media type (see documentation on items), only set on status ``"exchange"``.
 
    **Example request**:
 
@@ -224,6 +228,9 @@ Checking a ticket in
    * ``ambiguous`` - Multiple tickets match scan, rejected.
    * ``revoked`` - Ticket code has been revoked.
    * ``unapproved`` - Order has not yet been approved.
+   * ``already_exchanged`` - Ticket already has been exchanged for a reusable medium that must now be used for check-in.
+   * ``medium_invalid`` - Reusable medium identifier given was not found or is not valid.
+   * ``medium_exists`` - Reusable medium identifier already exists, but expected to be new.
    * ``error`` - Internal error.
 
    In case of reason ``rules`` and ``invalid_time``, there might be an additional response field ``reason_explanation``

doc/api/resources/checkinlists.rst

@@ -602,7 +602,8 @@ Order position endpoints
 
       We no longer recommend using this API if you're building a ticket scanning application, as it has a few design
       flaws that can lead to `security issues`_ or compatibility issues due to barcode content characters that are not
-      URL-safe. We recommend to use our new :ref:`check-in API <rest-checkin>` instead.
+      URL-safe. We recommend to use our new :ref:`check-in API <rest-checkin>` instead. Advanced features like medium
+      exchange are only supported on the new API.
 
    :query boolean untrusted_input: If set to true, the lookup parameter is **always** interpreted as a ``secret``, never
                                    as an ``id``. This should be always set if you are passing through untrusted, scanned
@@ -741,6 +742,9 @@ Order position endpoints
    * ``ambiguous`` - Multiple tickets match scan, rejected.
    * ``revoked`` - Ticket code has been revoked.
    * ``unapproved`` - Order has not yet been approved.
+   * ``already_exchanged`` - Ticket already has been exchanged for a reusable medium that must now be used for check-in.
+   * ``medium_invalid`` - Reusable medium identifier given was not found and could not be automatically created.
+   * ``medium_exists`` - Reusable medium identifier already exists, but expected to be new.
 
    In case of reason ``rules`` or ``invalid_time``, there might be an additional response field ``reason_explanation``
    with a human-readable description of the violated rules. However, that field can also be missing or be ``null``.

doc/api/resources/items.rst

@@ -131,7 +131,7 @@ allow_waitinglist                       boolean                    If ``false``,
                                                                    product when it is sold out.
 issue_giftcard                          boolean                    If ``true``, buying this product will yield a gift card.
 media_policy                            string                     Policy on how to handle reusable media (experimental feature).
-                                                                   Possible values are ``null``, ``"new"``, ``"reuse"``, and ``"reuse_or_new"``.
+                                                                   Possible values are ``null``, ``"new"``, ``"reuse"``, ``"reuse_or_new"``, ``"append"``, and ``"append_or_new"``.
 media_type                              string                     Type of reusable media to work on (experimental feature). See :ref:`rest-reusablemedia` for possible choices.
 show_quota_left                         boolean                    Publicly show how many tickets are still available.
                                                                    If this is ``null``, the event default is used.

doc/api/resources/orders.rst

@@ -1069,8 +1069,7 @@ Creating orders
       * ``valid_from`` (optional, if both ``valid_from`` and ``valid_until`` are **missing** (not ``null``) the availability will be computed from the given product)
       * ``valid_until`` (optional, if both ``valid_from`` and ``valid_until`` are **missing** (not ``null``) the availability will be computed from the given product)
       * ``requested_valid_from`` (optional, can be set **instead** of ``valid_from`` and ``valid_until`` to signal a user choice for the start time that may or may not be respected)
-      * ``use_reusable_medium`` (optional, causes the new ticket to take over the given reusable medium, identified by its ID)
-      * ``add_to_reusable_medium`` (optional, causes the new ticket to be added to the given reusable medium, identified by its ID)
+      * ``use_reusable_medium`` (optional, causes the new ticket to be connected to the given reusable medium, identified by its ID)
       * ``discount`` (optional, only possible if ``price`` is set; attention: if this is set to not-``null`` on any position, automatic calculation of discounts will not run)
       * ``answers``
 

src/pretix/api/auth/devicesecurity.py

@@ -110,6 +110,8 @@ class PretixScanSecurityProfile(AllowListSecurityProfile):
         ('POST', 'api-v1:checkinrpc.redeem'),
         ('GET', 'api-v1:checkinrpc.search'),
         ('GET', 'api-v1:reusablemedium-list'),
+        ('POST', 'api-v1:reusablemedium-lookup'),
+        ('PATCH', 'api-v1:reusablemedium-detail')
     )
 
 

src/pretix/api/serializers/checkin.py

@@ -88,11 +88,19 @@ class CheckinRPCRedeemInputSerializer(serializers.Serializer):
     nonce = serializers.CharField(required=False, allow_null=True)
     datetime = serializers.DateTimeField(required=False, allow_null=True)
     answers = serializers.JSONField(required=False, allow_null=True)
+    exchange_medium_type = serializers.ChoiceField(required=False, choices=MEDIA_TYPES)
+    exchange_medium_identifier = serializers.CharField(required=False)
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.fields['lists'].child_relation.queryset = CheckinList.objects.filter(event__in=self.context['events']).select_related('event')
 
+    def validate(self, attrs):
+        exchange_fields = ["exchange_medium_type", "exchange_medium_identifier"]
+        if any(attrs.get(k) is None for k in exchange_fields) and not all(attrs.get(k) is None for k in exchange_fields):
+            raise ValidationError("If you set any of exchange_medium_type or exchange_medium_identifier, you need to set both of them.")
+        return attrs
+
 
 class MiniCheckinListSerializer(I18nAwareModelSerializer):
     event = serializers.SlugRelatedField(slug_field='slug', read_only=True)

src/pretix/api/serializers/event.py

@@ -871,6 +871,7 @@ class EventSettingsSerializer(SettingsSerializer):
         'og_image',
         'name_scheme',
         'reusable_media_active',
+        'reusable_media_usage_enforced',
         'reusable_media_type_barcode',
         'reusable_media_type_barcode_identifier_length',
         'reusable_media_type_nfc_uid',
@@ -885,6 +886,7 @@ class EventSettingsSerializer(SettingsSerializer):
     readonly_fields = [
         # These are read-only since they are currently only settable on organizers, not events
         'reusable_media_active',
+        'reusable_media_usage_enforced',
         'reusable_media_type_barcode',
         'reusable_media_type_barcode_identifier_length',
         'reusable_media_type_nfc_uid',

src/pretix/api/serializers/order.py

@@ -1043,15 +1043,13 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
     requested_valid_from = serializers.DateTimeField(required=False, allow_null=True)
     use_reusable_medium = serializers.PrimaryKeyRelatedField(queryset=ReusableMedium.objects.none(),
                                                              required=False, allow_null=True)
-    add_to_reusable_medium = serializers.PrimaryKeyRelatedField(queryset=ReusableMedium.objects.none(),
-                                                                required=False, allow_null=True)
 
     class Meta:
         model = OrderPosition
         fields = ('positionid', 'item', 'variation', 'price', 'attendee_name', 'attendee_name_parts', 'attendee_email',
                   'company', 'street', 'zipcode', 'city', 'country', 'state', 'is_bundled',
                   'secret', 'addon_to', 'subevent', 'answers', 'seat', 'voucher', 'valid_from', 'valid_until',
-                  'requested_valid_from', 'use_reusable_medium', 'add_to_reusable_medium', 'discount')
+                  'requested_valid_from', 'use_reusable_medium', 'discount')
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -1063,8 +1061,6 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
         with scopes_disabled():
             if 'use_reusable_medium' in self.fields:
                 self.fields['use_reusable_medium'].queryset = ReusableMedium.objects.all()
-            if 'add_to_reusable_medium' in self.fields:
-                self.fields['add_to_reusable_medium'].queryset = ReusableMedium.objects.all()
 
     def validate_secret(self, secret):
         if secret and OrderPosition.all.filter(order__event=self.context['event'], secret=secret).exists():
@@ -1080,9 +1076,6 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
             )
         return m
 
-    def validate_add_to_reusable_medium(self, m):
-        return self.validate_use_reusable_medium(m)
-
     def validate_item(self, item):
         if item.event != self.context['event']:
             raise ValidationError(
@@ -1157,12 +1150,6 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
                 {'discount': ['You can only specify a discount if you do the price computation, but price is not set.']}
             )
 
-        if 'use_reusable_medium' in data and 'add_to_reusable_medium' in data:
-            raise ValidationError({
-                'use_reusable_medium': ['You can only specify either use_reusable_medium or add_to_reusable_medium.'],
-                'add_to_reusable_medium': ['You can only specify either use_reusable_medium or add_to_reusable_medium.'],
-            })
-
         return data
 
 
@@ -1602,7 +1589,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 pos_data['attendee_name_parts'] = {
                     '_legacy': attendee_name
                 }
-            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k not in ('answers', '_quotas', 'use_reusable_medium', 'add_to_reusable_medium')})
+            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k not in ('answers', '_quotas', 'use_reusable_medium')})
             if simulate:
                 pos.order = order._wrapped
             else:
@@ -1676,7 +1663,6 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         for pos_data in positions_data:
             answers_data = pos_data.pop('answers', [])
             use_reusable_medium = pos_data.pop('use_reusable_medium', None)
-            add_to_reusable_medium = pos_data.pop('add_to_reusable_medium', None)
             pos = pos_data['__instance']
             pos._calculate_tax(invoice_address=ia)
 
@@ -1718,14 +1704,17 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                         answ.options.add(*options)
 
                 if use_reusable_medium:
-                    for op_pk in use_reusable_medium.linked_orderpositions.values_list('pk', flat=True):
-                        use_reusable_medium.log_action(
-                            'pretix.reusable_medium.linked_orderposition.removed',
-                            data={
-                                'linked_orderposition': op_pk,
-                            }
-                        )
-                    use_reusable_medium.linked_orderpositions.set([pos])
+                    if pos.item.media_policy not in (Item.MEDIA_POLICY_APPEND, Item.MEDIA_POLICY_APPEND_OR_NEW):
+                        for op_pk in use_reusable_medium.linked_orderpositions.values_list('pk', flat=True):
+                            use_reusable_medium.log_action(
+                                'pretix.reusable_medium.linked_orderposition.removed',
+                                data={
+                                    'linked_orderposition': op_pk,
+                                }
+                            )
+                        use_reusable_medium.linked_orderpositions.set([pos])
+                    else:
+                        use_reusable_medium.linked_orderpositions.add(pos)
                     use_reusable_medium.log_action(
                         'pretix.reusable_medium.linked_orderposition.added',
                         data={
@@ -1733,15 +1722,6 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                             'linked_orderposition': pos.pk,
                         }
                     )
-                elif add_to_reusable_medium:
-                    add_to_reusable_medium.linked_orderpositions.add(pos)
-                    add_to_reusable_medium.log_action(
-                        'pretix.reusable_medium.linked_orderposition.added',
-                        data={
-                            'by_order': order.code,
-                            'linked_orderposition': pos.pk,
-                        }
-                    )
 
         if not simulate:
             for cp in delete_cps:

src/pretix/api/serializers/organizer.py

@@ -605,6 +605,7 @@ class OrganizerSettingsSerializer(SettingsSerializer):
         'cookie_consent_dialog_button_yes',
         'cookie_consent_dialog_button_no',
         'reusable_media_active',
+        'reusable_media_usage_enforced',
         'reusable_media_type_barcode',
         'reusable_media_type_barcode_identifier_length',
         'reusable_media_type_nfc_uid',

src/pretix/api/views/checkin.py

@@ -69,8 +69,10 @@ from pretix.base.models import (
 from pretix.base.models.orders import PrintLog
 from pretix.base.permissions import AnyPermissionOf
 from pretix.base.services.checkin import (
-    CheckInError, RequiredQuestionsError, SQLLogic, perform_checkin,
+    CheckInError, RequiredMediaExchangeError, RequiredQuestionsError, SQLLogic,
+    perform_checkin,
 )
+from pretix.base.services.media import perform_media_exchange
 from pretix.base.signals import checkin_annulled
 from pretix.helpers import OF_SELF
 
@@ -454,7 +456,8 @@ def _checkin_list_position_queryset(checkinlists, ignore_status=False, ignore_pr
 
 def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force, checkin_type, ignore_unpaid, nonce,
                     untrusted_input, user, auth, expand, pdf_data, request, questions_supported, canceled_supported,
-                    source_type='barcode', legacy_url_support=False, simulate=False, gate=None, use_order_locale=False):
+                    source_type='barcode', legacy_url_support=False, simulate=False, gate=None, use_order_locale=False,
+                    exchange_medium_type=None, exchange_medium_identifier=None):
     if not checkinlists:
         raise ValidationError('No check-in list passed.')
 
@@ -463,6 +466,7 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
 
     device = auth if isinstance(auth, Device) else None
     gate = gate or (auth.gate if isinstance(auth, Device) else None)
+    medium = None
 
     context = {
         'request': request,
@@ -522,7 +526,7 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
     #    with respecting the force option), or it's a reusable medium (-> proceed with that)
     if not op_candidates:
         try:
-            media = ReusableMedium.objects.active().filter(
+            medium = ReusableMedium.objects.active().filter(
                 Exists(ReusableMedium.linked_orderpositions.through.objects.filter(reusablemedium_id=OuterRef('pk')))
             ).get(
                 organizer_id=checkinlists[0].event.organizer_id,
@@ -630,7 +634,7 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
                     'list': MiniCheckinListSerializer(list_by_event[revoked_matches[0].event_id]).data,
                 }, status=400)
         else:
-            linked_ops = media.linked_orderpositions.all().select_related("order").prefetch_related("addons")
+            linked_ops = medium.linked_orderpositions.all().select_related("order").prefetch_related("addons")
             linked_event_ids = {op.order.event_id for op in linked_ops}
             if not any(event_id in list_by_event for event_id in linked_event_ids):
                 # Medium exists but connected ticket is for the wrong event
@@ -661,7 +665,7 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
             op_candidates = []
             for op in linked_ops:
                 if op.order.event_id in list_by_event:
-                    reusable_medium_used = media
+                    reusable_medium_used = medium
                     op_candidates.append(op)
                     if list_by_event[op.order.event_id].addon_match:
                         op_candidates += list(op.addons.all())
@@ -801,7 +805,14 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
         locale = op.order.event.settings.locale
     with language(locale):
         try:
-            perform_checkin(
+            if exchange_medium_identifier and medium:
+                # Cannot scan a medium and then request to exchange it
+                raise CheckInError(
+                    gettext('You cannot exchange a medium for a medium.'),
+                    'error'
+                )
+
+            checkin_args = dict(
                 op=op,
                 clist=list_by_event[op.order.event_id],
                 given_answers=given_answers,
@@ -819,7 +830,25 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
                 from_revoked_secret=from_revoked_secret,
                 simulate=simulate,
                 gate=gate,
+                reusable_medium=medium,
             )
+
+            if exchange_medium_identifier:  # other fields are filled, see CheckinRPCRedeemInputSerializer.validate
+                with transaction.atomic():
+                    # Do exchange and check-in atomically, i.e. both succeed or both fail
+                    medium = perform_media_exchange(
+                        organizer=request.organizer,
+                        media_type=exchange_medium_type,
+                        identifier=exchange_medium_identifier,
+                        link_orderposition=op,
+                        user=user,
+                        auth=auth,
+                    )
+                    source_type = medium.media_type.identifier
+                    checkin_args['reusable_medium'] = medium
+                    perform_checkin(**checkin_args)
+            else:
+                perform_checkin(**checkin_args)
         except RequiredQuestionsError as e:
             return Response({
                 'status': 'incomplete',
@@ -831,6 +860,17 @@ def _redeem_process(*, checkinlists, raw_barcode, answers_data, datetime, force,
                 ],
                 'list': MiniCheckinListSerializer(list_by_event[op.order.event_id]).data,
             }, status=400)
+        except RequiredMediaExchangeError as e:
+            return Response({
+                'status': 'exchange',
+                'require_attention': op.require_checkin_attention,
+                'checkin_texts': op.checkin_texts,
+                'position': CheckinListOrderPositionSerializer(op, context=_make_context(context, op.order.event)).data,
+                'media_policy': e.media_policy,
+                'media_type': e.media_type,
+                'list': MiniCheckinListSerializer(list_by_event[op.order.event_id]).data,
+                'reason_explanation': e.msg,
+            }, status=400)
         except CheckInError as e:
             if not simulate:
                 op.order.log_action('pretix.event.checkin.denied', data={
@@ -1018,6 +1058,8 @@ class CheckinRPCRedeemView(views.APIView):
             canceled_supported=True,
             request=self.request,  # this is not clean, but we need it in the serializers for URL generation
             legacy_url_support=False,
+            exchange_medium_type=s.validated_data.get('exchange_medium_type'),
+            exchange_medium_identifier=s.validated_data.get('exchange_medium_identifier'),
         )
 
 

src/pretix/api/views/media.py

@@ -196,7 +196,7 @@ class ReusableMediaViewSet(viewsets.ModelViewSet):
 
             return Response({"result": None})
 
-    @scopes_disabled()  # we are sure enough that get_queryset() is correct, so we save some perforamnce
+    @scopes_disabled()  # we are sure enough that get_queryset() is correct, so we save some performance
     def list(self, request, **kwargs):
         date = serializers.DateTimeField().to_representation(now())
         queryset = self.filter_queryset(self.get_queryset())

src/pretix/base/media.py

@@ -26,6 +26,7 @@ from django.utils.translation import gettext_lazy as _
 
 class BaseMediaType:
     medium_created_by_server = False
+    medium_created_from_unknown_supported = False
     supports_orderposition = False
     supports_giftcard = False
 
@@ -56,7 +57,7 @@ class BaseMediaType:
     def is_active(self, organizer):
         return organizer.settings.get(f'reusable_media_type_{self.identifier}', as_type=bool, default=False)
 
-    def handle_unknown(self, organizer, identifier, user, auth):
+    def handle_unknown(self, organizer, identifier, user, auth, force_create=False):
         pass
 
     def handle_new(self, organizer, medium, user, auth):
@@ -88,23 +89,32 @@ class NfcUidMediaType(BaseMediaType):
     verbose_name = _('NFC UID-based')
     icon = 'pretixbase/img/media/nfc_uid.svg'
     medium_created_by_server = False
+    medium_created_from_unknown_supported = True
     supports_giftcard = True
-    supports_orderposition = False
+    supports_orderposition = True
 
-    def handle_unknown(self, organizer, identifier, user, auth):
+    def handle_unknown(self, organizer, identifier, user, auth, force_create=False):
         from pretix.base.models import GiftCard, ReusableMedium
 
-        if organizer.settings.get(f'reusable_media_type_{self.identifier}_autocreate_giftcard', as_type=bool):
+        create_giftcard = organizer.settings.get(f'reusable_media_type_{self.identifier}_autocreate_giftcard', as_type=bool)
+        if create_giftcard or force_create:
             if identifier.startswith("08"):
                 # Don't create gift cards for NFC UIDs that start with 08, which represents NFC cards that issue random
                 # UIDs on every read, so they won't be useful.
                 return
             with transaction.atomic():
-                gc = GiftCard.objects.create(
-                    issuer=organizer,
-                    expires=organizer.default_gift_card_expiry,
-                    currency=organizer.settings.get(f'reusable_media_type_{self.identifier}_autocreate_giftcard_currency'),
-                )
+                if create_giftcard:
+                    gc = GiftCard.objects.create(
+                        issuer=organizer,
+                        expires=organizer.default_gift_card_expiry,
+                        currency=organizer.settings.get(f'reusable_media_type_{self.identifier}_autocreate_giftcard_currency'),
+                    )
+                    gc.log_action(
+                        'pretix.giftcards.created',
+                        user=user, auth=auth,
+                    )
+                else:
+                    gc = None
                 m = ReusableMedium.objects.create(
                     type=self.identifier,
                     identifier=identifier,
@@ -116,10 +126,6 @@ class NfcUidMediaType(BaseMediaType):
                     'pretix.reusable_medium.created.auto',
                     user=user, auth=auth,
                 )
-                gc.log_action(
-                    'pretix.giftcards.created',
-                    user=user, auth=auth,
-                )
                 return m
 
 
@@ -129,7 +135,7 @@ class NfcMf0aesMediaType(BaseMediaType):
     icon = 'pretixbase/img/media/nfc_secure.svg'
     medium_created_by_server = False
     supports_giftcard = True
-    supports_orderposition = False
+    supports_orderposition = True
 
     def handle_new(self, organizer, medium, user, auth):
         from pretix.base.models import GiftCard

src/pretix/base/models/checkin.py

@@ -346,11 +346,14 @@ class Checkin(models.Model):
     REASON_INCOMPLETE = 'incomplete'
     REASON_ALREADY_REDEEMED = 'already_redeemed'
     REASON_AMBIGUOUS = 'ambiguous'
+    REASON_MEDIUM_INVALID = 'medium_invalid'
+    REASON_MEDIUM_EXISTS = 'medium_exists'
     REASON_ERROR = 'error'
     REASON_BLOCKED = 'blocked'
     REASON_UNAPPROVED = 'unapproved'
     REASON_INVALID_TIME = 'invalid_time'
     REASON_ANNULLED = 'annulled'
+    REASON_ALREADY_EXCHANGED = 'already_exchanged'
     REASONS = (
         (REASON_CANCELED, _('Order canceled')),
         (REASON_INVALID, _('Unknown ticket')),
@@ -366,6 +369,9 @@ class Checkin(models.Model):
         (REASON_UNAPPROVED, _('Order not approved')),
         (REASON_INVALID_TIME, _('Ticket not valid at this time')),
         (REASON_ANNULLED, _('Check-in annulled')),
+        (REASON_ALREADY_EXCHANGED, _('Ticket already exchanged')),
+        (REASON_MEDIUM_INVALID, _('Reusable medium invalid')),
+        (REASON_MEDIUM_EXISTS, _('Reusable medium already exists')),
     )
 
     successful = models.BooleanField(

src/pretix/base/models/items.py

@@ -452,11 +452,16 @@ class Item(LoggedModel):
     MEDIA_POLICY_REUSE = 'reuse'
     MEDIA_POLICY_NEW = 'new'
     MEDIA_POLICY_REUSE_OR_NEW = 'reuse_or_new'
+    MEDIA_POLICY_APPEND = 'append'
+    MEDIA_POLICY_APPEND_OR_NEW = 'append_or_new'
     MEDIA_POLICIES = (
-        (None, _("Don't use re-usable media, use regular one-off tickets")),
-        (MEDIA_POLICY_REUSE, _('Require an existing medium to be re-used')),
+        (None, _("Don't use reusable media, use regular one-off tickets")),
         (MEDIA_POLICY_NEW, _('Require a previously unknown medium to be newly added')),
-        (MEDIA_POLICY_REUSE_OR_NEW, _('Require either an existing or a new medium to be used')),
+        (MEDIA_POLICY_REUSE, _('Require an existing medium to be reused, replacing any previous tickets')),
+        (MEDIA_POLICY_REUSE_OR_NEW, _('Require either an existing or a new medium to be used, replacing any previous tickets')),
+        (MEDIA_POLICY_APPEND, _('Require an existing medium to be reused, adding to any previous tickets')),
+        (MEDIA_POLICY_APPEND_OR_NEW,
+         _('Require either an existing or a new medium to be used, adding to any previous tickets')),
     )
 
     objects = ItemQuerySetManager()
@@ -769,7 +774,7 @@ class Item(LoggedModel):
         null=True, blank=True, max_length=16,
         verbose_name=_('Reusable media policy'),
         help_text=_(
-            'If this product should be stored on a re-usable physical medium, you can attach a physical media policy. '
+            'If this product should be stored on a reusable physical medium, you can attach a physical media policy. '
             'This is not required for regular tickets, which just use a one-time barcode, but only for products like '
             'renewable season tickets or re-chargeable gift card wristbands. '
             'This is an advanced feature that also requires specific configuration of ticketing and printing settings.'
@@ -778,7 +783,7 @@ class Item(LoggedModel):
     media_type = models.CharField(
         max_length=100,
         null=True, blank=True,
-        choices=[(None, _("Don't use re-usable media, use regular one-off tickets"))] + [(k, v) for k, v in MEDIA_TYPES.items()],
+        choices=[(None, _("Don't use reusable media, use regular one-off tickets"))] + [(k, v) for k, v in MEDIA_TYPES.items()],
         verbose_name=_('Reusable media type'),
         help_text=_(
             'Select the type of physical medium that should be used for this product. Note that not all media types '
@@ -995,6 +1000,11 @@ class Item(LoggedModel):
                 raise ValidationError(_('The selected media type does not support usage for tickets currently.'))
             if not mt.supports_giftcard and issue_giftcard:
                 raise ValidationError(_('The selected media type does not support usage for gift cards currently.'))
+            if media_policy in (Item.MEDIA_POLICY_NEW, Item.MEDIA_POLICY_APPEND_OR_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW):
+                if not mt.medium_created_by_server and not mt.medium_created_from_unknown_supported:
+                    raise ValidationError(_('The selected media type requires all media to be registered in the system '
+                                            'prior to their usage. Therefore, the selected media policy does not make '
+                                            'sense for this media type.'))
             if issue_giftcard:
                 raise ValidationError(_('You currently cannot create gift cards with a reusable media policy. Instead, '
                                         'gift cards for some reusable media types can be created or re-charged directly '
@@ -2220,7 +2230,7 @@ class Quota(LoggedModel):
 class ItemMetaProperty(LoggedModel):
     """
     An event can have ItemMetaProperty objects attached to define meta information fields
-    for its items. This information can be re-used for example in ticket layouts.
+    for its items. This information can be reused for example in ticket layouts.
 
     :param event: The event this property is defined for.
     :type event: Event

src/pretix/base/models/media.py

@@ -129,7 +129,7 @@ class ReusableMedium(LoggedModel):
 
     @property
     def is_expired(self):
-        return self.expires and self.expires > now()
+        return self.expires and self.expires < now()
 
     class Meta:
         unique_together = (("identifier", "type", "organizer"),)

src/pretix/base/services/cart.py

@@ -287,11 +287,11 @@ def _check_position_constraints(
         raise CartPositionError(error_messages['unavailable'])
 
     # Invalid media policy for online sale
-    if item.media_policy in (Item.MEDIA_POLICY_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW):
+    if item.media_policy in (Item.MEDIA_POLICY_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW, Item.MEDIA_POLICY_APPEND_OR_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW):
         mt = MEDIA_TYPES[item.media_type]
         if not mt.medium_created_by_server:
             raise CartPositionError(error_messages['media_usage_not_implemented'])
-    elif item.media_policy == Item.MEDIA_POLICY_REUSE:
+    elif item.media_policy in (Item.MEDIA_POLICY_REUSE, Item.MEDIA_POLICY_APPEND):
         raise CartPositionError(error_messages['media_usage_not_implemented'])
 
     # Item removed from sales channel

src/pretix/base/services/checkin.py

@@ -867,6 +867,15 @@ class RequiredQuestionsError(Exception):
         super().__init__(msg)
 
 
+class RequiredMediaExchangeError(Exception):
+    def __init__(self, msg, code, media_policy, media_type):
+        self.msg = msg
+        self.code = code
+        self.media_policy = media_policy
+        self.media_type = media_type
+        super().__init__(msg)
+
+
 def _save_answers(op, answers, given_answers):
     def _create_answer(question, answer):
         try:
@@ -939,7 +948,7 @@ def perform_checkin(op: OrderPosition, clist: CheckinList, given_answers: dict,
                     ignore_unpaid=False, nonce=None, datetime=None, questions_supported=True,
                     user=None, auth=None, canceled_supported=False, type=Checkin.TYPE_ENTRY,
                     raw_barcode=None, raw_source_type=None, from_revoked_secret=False, simulate=False,
-                    gate=None):
+                    gate=None, reusable_medium=None):
     """
     Create a checkin for this particular order position and check-in list. Fails with CheckInError if the check in is
     not valid at this time.
@@ -955,6 +964,7 @@ def perform_checkin(op: OrderPosition, clist: CheckinList, given_answers: dict,
     :param datetime: The datetime of the checkin, defaults to now.
     :param simulate: If true, the check-in is not saved.
     :param gate: The gate the check-in was performed at.
+    :param reusable_medium: The medium that is available for an exchange
     """
 
     # !!!!!!!!!
@@ -1035,7 +1045,7 @@ def perform_checkin(op: OrderPosition, clist: CheckinList, given_answers: dict,
 
     with transaction.atomic():
         # Lock order positions, if it is an entry. We don't need it for exits, as a race condition wouldn't be problematic
-        opqs = OrderPosition.all
+        opqs = OrderPosition.all.select_related("order", "item")
         if type != Checkin.TYPE_EXIT:
             opqs = opqs.select_for_update(of=OF_SELF)
         op = opqs.get(pk=op.pk)
@@ -1101,6 +1111,24 @@ def perform_checkin(op: OrderPosition, clist: CheckinList, given_answers: dict,
                 require_answers
             )
 
+        required_media_policy = op.item.media_policy
+        required_media_type = op.item.media_type
+        require_a_medium = required_media_policy and required_media_type
+        linked_media = op.linked_media
+        if require_a_medium and not reusable_medium and not force:
+            if not linked_media.exists():
+                raise RequiredMediaExchangeError(
+                    _('Ticket needs to be exchanged to a suitable medium.'),
+                    'exchange',
+                    required_media_policy,
+                    required_media_type
+                )
+            elif op.organizer.settings.reusable_media_usage_enforced:
+                raise CheckInError(
+                    _('This ticket has already been exchanged for a reusable medium that now needs to be used instead.'),
+                    'already_exchanged',
+                )
+
         device = None
         if isinstance(auth, Device):
             device = auth

src/pretix/base/services/media.py

@@ -23,10 +23,13 @@ import secrets
 
 from django.db import IntegrityError
 from django.db.models import Q
+from django.utils.translation import gettext as _
 from django_scopes import scopes_disabled
 
-from pretix.base.models import GiftCardAcceptance
-from pretix.base.models.media import MediumKeySet
+from pretix.base.media import MEDIA_TYPES
+from pretix.base.models import Checkin, GiftCardAcceptance, Item
+from pretix.base.models.media import MediumKeySet, ReusableMedium
+from pretix.base.services.checkin import CheckInError
 
 
 def create_nfc_mf0aes_keyset(organizer):
@@ -70,3 +73,173 @@ def get_keysets_for_organizer(organizer):
         if new_set:
             sets.append(new_set)
     return sets
+
+
+def perform_media_exchange(organizer, media_type, identifier, link_orderposition, user, auth):
+    """
+    Create or retrieve a medium, then link the order position to it. Expected to be called in a transaction.
+
+    :param organizer: Organizer to operate in
+    :param media_type: Type of medium to operate with
+    :param identifier: Identifier of the medium
+    :param link_orderposition: Position to link to the medium
+    :return: ReusableMedium
+    """
+    medium = None
+    media_policy = link_orderposition.item.media_policy
+
+    if media_type not in MEDIA_TYPES:  # should be caught by serializer already
+        raise CheckInError(
+            _('Invalid medium type.'),
+            Checkin.REASON_ERROR,
+            reason=_('Invalid medium type.'),
+        )
+
+    if not MEDIA_TYPES[media_type].is_active(organizer):
+        raise CheckInError(
+            _('Medium type is not enabled for organizer.'),
+            Checkin.REASON_ERROR,
+            reason=_('Medium type is not enabled for organizer.'),
+        )
+
+    if link_orderposition.item.media_type != media_type:
+        raise CheckInError(
+            _('Incorrect medium type for product.'),
+            Checkin.REASON_PRODUCT,
+            reason=_('Incorrect medium type for product.'),
+        )
+
+    if link_orderposition.linked_media.exists():
+        raise CheckInError(
+            _('Ticket is already exchanged for reusable medium.'),
+            Checkin.REASON_ALREADY_EXCHANGED,
+            reason=_('Ticket is already exchanged for reusable medium.'),
+        )
+
+    if media_policy in (Item.MEDIA_POLICY_APPEND, Item.MEDIA_POLICY_APPEND_OR_NEW, Item.MEDIA_POLICY_NEW):
+        link_action = "append"
+    else:
+        link_action = "replace"
+
+    if media_policy in (Item.MEDIA_POLICY_REUSE, Item.MEDIA_POLICY_APPEND):
+        try:
+            medium = ReusableMedium.objects.get(
+                type=media_type,
+                identifier=identifier,
+                organizer=organizer,
+            )
+        except ReusableMedium.DoesNotExist:
+            raise CheckInError(
+                _('Reusable medium not found.'),
+                Checkin.REASON_MEDIUM_INVALID,
+                reason=_('Reusable medium not found.'),
+            )
+        else:
+            if medium.is_expired or not medium.active:
+                raise CheckInError(
+                    _('Reusable medium is inactive or expired.'),
+                    Checkin.REASON_MEDIUM_INVALID,
+                    reason=_('Reusable medium is inactive or expired.'),
+                )
+
+    elif media_policy in (Item.MEDIA_POLICY_REUSE_OR_NEW, Item.MEDIA_POLICY_APPEND_OR_NEW):
+        try:
+            medium = ReusableMedium.objects.get(
+                type=media_type,
+                identifier=identifier,
+                organizer=organizer,
+            )
+        except ReusableMedium.DoesNotExist:
+            if not MEDIA_TYPES[media_type].medium_created_from_unknown_supported:
+                raise CheckInError(
+                    _('Reusable medium not found and could not be created.'),
+                    Checkin.REASON_MEDIUM_INVALID,
+                )
+
+            medium = MEDIA_TYPES[media_type].handle_unknown(organizer, identifier, user, auth, force_create=True)
+            if not medium:
+                raise CheckInError(
+                    _('Reusable medium not found and could not be created.'),
+                    Checkin.REASON_MEDIUM_INVALID,
+                )
+
+        if medium.is_expired or not medium.active:
+            raise CheckInError(
+                _('Reusable medium is inactive or expired.'),
+                Checkin.REASON_MEDIUM_INVALID,
+                reason=_('Reusable medium is inactive or expired.'),
+            )
+
+    elif media_policy == Item.MEDIA_POLICY_NEW:
+        if not MEDIA_TYPES[media_type].medium_created_from_unknown_supported:
+            raise CheckInError(
+                _('Reusable medium not found and could not be created.'),
+                Checkin.REASON_MEDIUM_INVALID,
+            )
+        try:
+            medium = MEDIA_TYPES[media_type].handle_unknown(organizer, identifier, user, auth, force_create=True)
+        except IntegrityError:
+            raise CheckInError(
+                _('Reusable medium already exists.'),
+                Checkin.REASON_MEDIUM_EXISTS,
+            )
+        else:
+            if not medium:
+                raise CheckInError(
+                    _('Reusable medium could not be created.'),
+                    Checkin.REASON_MEDIUM_INVALID,
+                )
+
+    else:
+        raise CheckInError(
+            _('Product does not support medium exchange.'),
+            Checkin.REASON_PRODUCT,
+            reason=_('Product does not support medium exchange.'),
+        )
+
+    if link_action == 'append':
+        medium.linked_orderpositions.add(link_orderposition)
+        medium.log_action(
+            'pretix.reusable_medium.linked_orderposition.added',
+            user=user,
+            auth=auth,
+            data={
+                'linked_orderposition': link_orderposition,
+            }
+        )
+    elif link_action == 'replace':
+        already_found = False
+        for op_pk in medium.linked_orderpositions.values_list('pk', flat=True):
+            if op_pk == link_orderposition.pk:
+                already_found = True
+                continue
+            else:
+                medium.log_action(
+                    'pretix.reusable_medium.linked_orderposition.removed',
+                    data={
+                        'linked_orderposition': op_pk,
+                    }
+                )
+        if not already_found:
+            medium.linked_orderpositions.set([link_orderposition])
+            medium.log_action(
+                'pretix.reusable_medium.linked_orderposition.added',
+                user=user,
+                auth=auth,
+                data={
+                    'linked_orderposition': link_orderposition,
+                }
+            )
+
+    link_orderposition.order.log_action(
+        'pretix.reusable_medium.exchanged',
+        data={
+            'position': link_orderposition.pk,
+            'positionid': link_orderposition.positionid,
+            'medium': medium.pk,
+            'medium_identifier': medium.identifier,
+            'medium_type': medium.media_type.identifier,
+        }
+    )
+
+    return medium

src/pretix/base/services/orders.py

@@ -3506,7 +3506,7 @@ def signal_listener_issue_media(sender: Event, order: Order, **kwargs):
     from pretix.base.models import ReusableMedium
 
     for p in order.positions.all():
-        if p.item.media_policy in (Item.MEDIA_POLICY_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW):
+        if p.item.media_policy in (Item.MEDIA_POLICY_NEW, Item.MEDIA_POLICY_REUSE_OR_NEW, Item.MEDIA_POLICY_APPEND_OR_NEW):
             mt = MEDIA_TYPES[p.item.media_type]
             if mt.medium_created_by_server and not p.linked_media.exists():
                 rm = ReusableMedium.objects.create(

src/pretix/base/settings.py

@@ -211,12 +211,25 @@ DEFAULTS = {
         'form_class': forms.BooleanField,
         'serializer_class': serializers.BooleanField,
         'form_kwargs': dict(
-            label=_("Activate re-usable media"),
-            help_text=_("The re-usable media feature allows you to connect tickets and gift cards with physical media "
-                        "such as wristbands or chip cards that may be re-used for different tickets or gift cards "
+            label=_("Activate reusable media"),
+            help_text=_("The reusable media feature allows you to connect tickets and gift cards with physical media "
+                        "such as wristbands or chip cards that may be reused for different tickets or gift cards "
                         "later.")
         )
     },
+    'reusable_media_usage_enforced': {
+        'default': 'False',
+        'type': bool,
+        'form_class': forms.BooleanField,
+        'serializer_class': serializers.BooleanField,
+        'form_kwargs': dict(
+            label=_("Enforce the usage of issued reusable media for check-in"),
+            help_text=_("If enabled, a ticket barcode will not be accepted anymore, if a reusable medium has been "
+                        "created and linked to a ticket. Keeping this option turned off will treat the reusable "
+                        "medium and ticket as equals."),
+            widget=forms.CheckboxInput(attrs={'data-display-dependency': '#id_settings-reusable_media_active'}),
+        )
+    },
     'reusable_media_type_barcode': {
         'default': 'False',
         'type': bool,

src/pretix/control/forms/organizer.py

@@ -636,6 +636,7 @@ class OrganizerSettingsForm(SettingsForm):
         'cookie_consent_dialog_button_yes',
         'cookie_consent_dialog_button_no',
         'reusable_media_active',
+        'reusable_media_usage_enforced',
         'reusable_media_type_barcode',
         'reusable_media_type_barcode_identifier_length',
         'reusable_media_type_nfc_uid',

src/pretix/control/logdisplay.py

@@ -746,6 +746,7 @@ class CoreUserImpersonatedLogEntryType(UserImpersonatedLogEntryType):
     'pretix.reusable_medium.linked_orderposition.added': _('A new ticket has been added to the medium.'),
     'pretix.reusable_medium.linked_orderposition.removed': _('A ticket has been removed from the medium.'),
     'pretix.reusable_medium.linked_orderposition.changed': _('The medium has been connected to a new ticket.'),
+    'pretix.reusable_medium.exchanged': _('The ticket #{positionid} was exchanged for reusable medium {medium_identifier}.'),
     'pretix.reusable_medium.linked_giftcard.changed': _('The medium has been connected to a new gift card.'),
     'pretix.email.error': _('Sending of an email has failed.'),
     'pretix.event.comment': _('The event\'s internal comment has been updated.'),

src/pretix/control/templates/pretixcontrol/checkin/simulator.html

@@ -54,6 +54,8 @@
                     <span class="fa fa-check-circle"></span>
                 {% elif result.status == "incomplete" %}
                     <span class="fa fa-question-circle"></span>
+                {% elif result.status == "exchange" %}
+                    <span class="fa fa-recycle"></span>
                 {% elif result.status == "error" %}
                     {% if result.reason == "already_redeemed" %}
                         <span class="fa fa-warning"></span>
@@ -79,6 +81,14 @@
                             </li>
                         {% endfor %}
                     </ul>
+                {% elif result.status == "exchange" %}
+                    <h3 class="nomargin-top">{% trans "Media exchange required" %}</h3>
+                    <p>
+                        {% blocktrans trimmed with media_policy=media_policies|getitem:result.media_policy media_type=media_types|getitem:result.media_type %}
+                            This ticket needs to be exchanged into a <strong>{{ media_type }}</strong> reusable medium.
+                            <strong>{{ media_policy }}</strong>.
+                        {% endblocktrans %}
+                    </p>
                 {% elif result.status == "error" %}
                     <h3 class="nomargin-top">{{ reason_labels|getitem:result.reason }}</h3>
                     {% if result.reason_explanation %}

src/pretix/control/templates/pretixcontrol/organizers/edit.html

@@ -222,6 +222,7 @@
                     <fieldset>
                         <legend>{% trans "Reusable media" %}</legend>
                         {% bootstrap_field sform.reusable_media_active layout="control" %}
+                        {% bootstrap_field sform.reusable_media_usage_enforced layout="control" %}
                         <div data-display-dependency="#{{ sform.reusable_media_active.id_for_label }}">
 
                             <div class="panel panel-default">

src/pretix/control/views/checkin.py

@@ -50,7 +50,7 @@ from i18nfield.strings import LazyI18nString
 
 from pretix.api.views.checkin import _redeem_process
 from pretix.base.media import MEDIA_TYPES
-from pretix.base.models import Checkin, LogEntry, Order, OrderPosition
+from pretix.base.models import Checkin, Item, LogEntry, Order, OrderPosition
 from pretix.base.models.checkin import CheckinList
 from pretix.base.models.orders import PrintLog
 from pretix.base.permissions import AnyPermissionOf
@@ -532,6 +532,8 @@ class CheckInListSimulator(EventPermissionRequiredMixin, FormView):
             checkinlist=self.list,
             result=self.result,
             reason_labels=dict(Checkin.REASONS),
+            media_policies=dict(Item.MEDIA_POLICIES),
+            media_types=dict(MEDIA_TYPES),
         )
 
     def form_valid(self, form):

src/pretix/static/jsi18n/en/djangojs.js

@@ -1,5 +1,4 @@
 
-
 'use strict';
 {
   const globals = this;

src/pretix/static/pretixcontrol/scss/main.scss

@@ -864,6 +864,9 @@ tbody th {
 .checkin-sim-result-status-incomplete {
     background: $brand-primary;
 }
+.checkin-sim-result-status-exchange {
+    background: $brand-primary;
+}
 .checkin-sim-result-status-error {
     background: $brand-danger;
 }

src/tests/api/test_checkinrpc.py

@@ -34,7 +34,7 @@ from tests.const import SAMPLE_PNG
 
 from pretix.api.serializers.item import QuestionSerializer
 from pretix.base.models import (
-    Checkin, InvoiceAddress, Order, OrderPosition, ReusableMedium,
+    Checkin, InvoiceAddress, Item, Order, OrderPosition, ReusableMedium,
 )
 
 # Lots of this code is overlapping with test_checkin.py, and some of it is arguably redundant since it's triggering
@@ -1253,3 +1253,489 @@ def test_annul_failures(device_client, team, organizer, clist, clist_event2, eve
     with scopes_disabled():
         ci = p.all_checkins.get()
         assert ci.successful
+
+
+@pytest.mark.django_db
+def test_exchange_incomplete_body(token_client, organizer, clist, event, order):
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid"
+    })
+    assert resp.status_code == 400
+    assert resp.data == {
+        'non_field_errors': ['If you set any of exchange_medium_type or exchange_medium_identifier, you need to set both of them.']
+    }
+
+
+@pytest.mark.django_db
+def test_exchange_medium_for_medium(token_client, organizer, clist, event, order):
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="barcode",
+            identifier="abcdef",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "abcdef", {
+        "source_type": "barcode",
+        "exchange_medium_type": "barcode",
+        "exchange_medium_identifier": "hijkl",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'error'
+
+
+@pytest.mark.django_db
+def test_exchange_unknown_media_type(token_client, organizer, clist, event, order):
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "unknown",
+        "exchange_medium_identifier": "hijkl",
+    })
+    assert resp.status_code == 400
+    assert resp.data == {"exchange_medium_type": ["\"unknown\" is not a valid choice."]}
+
+
+@pytest.mark.django_db
+def test_exchange_disabled_media_type(token_client, organizer, clist, event, order):
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "hijkl",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'error'
+    assert resp.data['reason_explanation'] == 'Medium type is not enabled for organizer.'
+
+
+@pytest.mark.django_db
+def test_exchange_mismatch_media_type(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "barcode"
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'product'
+    assert resp.data['reason_explanation'] == 'Incorrect medium type for product.'
+
+
+@pytest.mark.django_db
+def test_exchange_no_item_policy(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'product'
+    assert resp.data['reason_explanation'] == 'Product does not support medium exchange.'
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_or_new_new(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_REUSE_OR_NEW
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    with scopes_disabled():
+        rm = ReusableMedium.objects.get(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        assert rm.linked_orderpositions.get().secret == "z3fsn8jyufm5kpk768q69gkbyr5f4h6w"
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_or_new_reuse_replace(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_REUSE_OR_NEW
+    item.save()
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.last())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    rm.refresh_from_db()
+    with scopes_disabled():
+        assert rm.linked_orderpositions.get().secret == "z3fsn8jyufm5kpk768q69gkbyr5f4h6w"
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_or_new_reuse_append(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_APPEND_OR_NEW
+    item.save()
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.last())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    rm.refresh_from_db()
+    with scopes_disabled():
+        assert rm.linked_orderpositions.count() == 2
+        assert rm.linked_orderpositions.filter(secret="z3fsn8jyufm5kpk768q69gkbyr5f4h6w").exists()
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_exists_append(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_APPEND_OR_NEW
+    item.save()
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.last())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    rm.refresh_from_db()
+    with scopes_disabled():
+        assert rm.linked_orderpositions.count() == 2
+        assert rm.linked_orderpositions.filter(secret="z3fsn8jyufm5kpk768q69gkbyr5f4h6w").exists()
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_expired(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_REUSE
+    item.save()
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+            expires=now() - datetime.timedelta(hours=2),
+        )
+        rm.linked_orderpositions.add(order.positions.last())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'medium_invalid'
+
+
+@pytest.mark.django_db
+def test_exchange_reuse_not_exists(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_REUSE
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'medium_invalid'
+
+
+@pytest.mark.django_db
+def test_exchange_new_exists(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.last())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+        "exchange_link_action": "append",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'medium_exists'
+
+
+@pytest.mark.django_db
+def test_exchange_new_not_exists(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "12345678",
+        "exchange_link_action": "replace",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    with scopes_disabled():
+        rm = ReusableMedium.objects.get(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        assert rm.linked_orderpositions.get().secret == "z3fsn8jyufm5kpk768q69gkbyr5f4h6w"
+
+
+@pytest.mark.django_db
+def test_exchange_required(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'exchange'
+    assert resp.data['media_policy'] == 'new'
+    assert resp.data['media_type'] == 'nfc_uid'
+
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+    # Force works
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "force": True,
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+
+
+@pytest.mark.django_db
+def test_exchanged_original_barcode_ok(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+
+
+@pytest.mark.django_db
+def test_exchanged_original_barcode_not_ok(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    organizer.settings.reusable_media_usage_enforced = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'already_exchanged'
+    # Force works
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "force": True,
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+
+
+@pytest.mark.django_db
+def test_exchanged_scan_medium_ok(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    organizer.settings.reusable_media_usage_enforced = True
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "12345678", {
+        "source_type": "nfc_uid",
+    })
+    assert resp.status_code == 201
+    assert resp.data['status'] == 'ok'
+
+
+@pytest.mark.django_db
+def test_exchanged_double_exchange(token_client, organizer, clist, event, order, item):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    organizer.settings.reusable_media_usage_enforced = False
+    item.media_type = "nfc_uid"
+    item.media_policy = Item.MEDIA_POLICY_NEW
+    item.save()
+
+    with scopes_disabled():
+        rm = ReusableMedium.objects.create(
+            type="nfc_uid",
+            identifier="12345678",
+            organizer=organizer,
+        )
+        rm.linked_orderpositions.add(order.positions.first())
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "87654321",
+        "exchange_link_action": "replace",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'already_exchanged'
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    "media_policy,media_type",
+    [
+        (Item.MEDIA_POLICY_NEW, "nfc_mf0aes"),
+        (Item.MEDIA_POLICY_REUSE_OR_NEW, "nfc_mf0aes"),
+        (Item.MEDIA_POLICY_APPEND_OR_NEW, "nfc_mf0aes"),
+        (Item.MEDIA_POLICY_NEW, "barcode"),
+        (Item.MEDIA_POLICY_REUSE_OR_NEW, "barcode"),
+        (Item.MEDIA_POLICY_APPEND_OR_NEW, "barcode"),
+    ]
+)
+def test_exchange_unsupported_media_type_for_new(token_client, organizer, clist, event, order, item, media_policy, media_type):
+    organizer.settings.set(f'reusable_media_type_{media_type}', True)
+    # Shouldn't be configurable, but test that the logic is solid anyway
+    item.media_type = media_type
+    item.media_policy = media_policy
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": media_type,
+        "exchange_medium_identifier": "12345678",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'medium_invalid'
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    "media_policy",
+    [
+        Item.MEDIA_POLICY_NEW,
+        Item.MEDIA_POLICY_REUSE_OR_NEW,
+        Item.MEDIA_POLICY_APPEND_OR_NEW,
+    ]
+)
+def test_exchange_rejected_media_identifier(token_client, organizer, clist, event, order, item, media_policy):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    item.media_type = "nfc_uid"
+    item.media_policy = media_policy
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "08RANDOM",
+    })
+    assert resp.status_code == 400
+    assert resp.data['status'] == 'error'
+    assert resp.data['reason'] == 'medium_invalid'
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    "media_policy",
+    [
+        Item.MEDIA_POLICY_NEW,
+        Item.MEDIA_POLICY_REUSE_OR_NEW,
+        Item.MEDIA_POLICY_APPEND_OR_NEW,
+    ]
+)
+def test_exchange_create_gift_card(token_client, organizer, clist, event, order, item, media_policy):
+    organizer.settings.reusable_media_type_nfc_uid = True
+    organizer.settings.reusable_media_type_nfc_uid_autocreate_giftcard = True
+    organizer.settings.reusable_media_type_nfc_uid_autocreate_giftcard_currency = "EUR"
+    item.media_type = "nfc_uid"
+    item.media_policy = media_policy
+    item.save()
+    resp = _redeem(token_client, organizer, clist, "z3fsn8jyufm5kpk768q69gkbyr5f4h6w", {
+        "source_type": "barcode",
+        "exchange_medium_type": "nfc_uid",
+        "exchange_medium_identifier": "0412345",
+    })
+    assert resp.status_code == 201
+    with scopes_disabled():
+        rm = ReusableMedium.objects.get(identifier="0412345")
+        assert rm.linked_giftcard.currency == "EUR"

src/tests/api/test_order_create.py

@@ -3141,24 +3141,13 @@ def test_order_create_use_medium(token_client, organizer, event, item, quota, qu
 @pytest.mark.django_db
 def test_order_create_add_to_medium(token_client, organizer, event, item, quota, question, medium):
     item.media_type = medium.type
-    item.media_policy = Item.MEDIA_POLICY_REUSE_OR_NEW
+    item.media_policy = Item.MEDIA_POLICY_APPEND_OR_NEW
     item.save()
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
     res['positions'][0]['item'] = item.pk
     res['positions'][0]['use_reusable_medium'] = medium.pk
-    res['positions'][0]['add_to_reusable_medium'] = medium.pk
     res['positions'][0]['answers'][0]['question'] = question.pk
 
-    # do not use use_reusable_medium and add_to_reusable_medium
-    resp = token_client.post(
-        '/api/v1/organizers/{}/events/{}/orders/?pdf_data=true'.format(
-            organizer.slug, event.slug
-        ), format='json', data=res
-    )
-    assert resp.status_code == 400
-
-    del res['positions'][0]['use_reusable_medium']
-
     resp = token_client.post(
         '/api/v1/organizers/{}/events/{}/orders/?pdf_data=true'.format(
             organizer.slug, event.slug
@@ -3179,8 +3168,9 @@ def test_order_create_add_to_medium(token_client, organizer, event, item, quota,
         medium.refresh_from_db()
         assert medium.linked_orderpositions.count() == 2
 
+    item.media_policy = Item.MEDIA_POLICY_REUSE_OR_NEW
+    item.save()
     res['positions'][0]['use_reusable_medium'] = medium.pk
-    del res['positions'][0]['add_to_reusable_medium']
     resp = token_client.post(
         '/api/v1/organizers/{}/events/{}/orders/?pdf_data=true'.format(
             organizer.slug, event.slug

src/tests/base/test_checkin.py

@@ -1186,7 +1186,7 @@ def test_rules_reasoning_prefer_number_over_date(event, position, clist):
 
 @pytest.mark.django_db(transaction=True)
 def test_position_queries(django_assert_max_num_queries, position, clist):
-    with django_assert_max_num_queries(13) as captured:
+    with django_assert_max_num_queries(12) as captured:
         perform_checkin(position, clist, {})
     if 'sqlite' not in settings.DATABASES['default']['ENGINE']:
         assert any('FOR UPDATE' in s['sql'] for s in captured)