Payment step: Allow to postpone payment choice on some sales channels (#6516)

* Payment step: Allow to postpone payment choice on some sales channels

* Add tests

* handle payment provider (de-)selection and partial payments (#6526)

---------

Co-authored-by: Lukas Bockstaller <bockstaller@pretix.eu>

src/pretix/base/services/cart.py

@@ -1605,6 +1605,7 @@ def add_payment_to_cart_session(cart_session, provider, min_value: Decimal=None,
         'max_value': str(max_value) if max_value is not None else None,
         'info_data': info_data or {},
     })
+    cart_session['payments_postpone'] = False
 
 
 def add_payment_to_cart(request, provider, min_value: Decimal=None, max_value: Decimal=None, info_data: dict=None):

src/pretix/base/services/orders.py

@@ -961,7 +961,7 @@ def _check_positions(event: Event, now_dt: datetime, time_machine_now_dt: dateti
 
 
 def _apply_rounding_and_fees(positions: List[CartPosition], payment_requests: List[dict], address: InvoiceAddress,
-                             meta_info: dict, event: Event, require_approval=False):
+                             meta_info: dict, event: Event, sales_channel: SalesChannel, require_approval=False):
     fees = []
     # Pre-rounding, pre-fee total is used for fee calculation
     total = sum([c.gross_price_before_rounding for c in positions])
@@ -1021,7 +1021,14 @@ def _apply_rounding_and_fees(positions: List[CartPosition], payment_requests: Li
         payments_assigned += to_pay
         p['payment_amount'] = to_pay
 
-    if total != payments_assigned and not require_approval:
+    allow_postponed_payment = (
+        require_approval or
+        (
+            sales_channel.identifier in event.settings.payment_choice_postpone_allowed_channels and not payment_requests
+        )
+    )
+
+    if total != payments_assigned and not allow_postponed_payment:
         raise OrderError(_("The selected payment methods do not cover the total balance."))
 
     return fees
@@ -1043,7 +1050,15 @@ def _create_order(event: Event, *, email: str, positions: List[CartPosition], no
 
     # Final calculation of fees, also performs final rounding
     try:
-        fees = _apply_rounding_and_fees(positions, payment_requests, address, meta_info, event, require_approval=require_approval)
+        fees = _apply_rounding_and_fees(
+            positions,
+            payment_requests,
+            address,
+            meta_info,
+            event,
+            sales_channel=sales_channel,
+            require_approval=require_approval
+        )
     except TaxRule.SaleNotAllowed:
         raise OrderError(error_messages['country_blocked'])
 

src/pretix/base/services/payment.py

@@ -0,0 +1,76 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020  Raphael Michel and contributors
+# Copyright (C) 2020-today pretix GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+from datetime import datetime, time, timedelta
+from zoneinfo import ZoneInfo
+
+from django.utils.timezone import make_aware, now
+
+from pretix.base.models import Event, SalesChannel
+from pretix.base.reldate import RelativeDateWrapper
+
+
+def compute_payment_deadline(event: Event, sales_channel: SalesChannel, now_dt=None, subevents=None) -> datetime:
+    now_dt = now_dt or now()
+    tz = ZoneInfo(event.settings.timezone)
+
+    sales_channel_suffix = "_" + sales_channel.identifier.replace(".", "_")
+    if not (mode := event.settings.get(f'payment_term_mode{sales_channel_suffix}')):
+        mode = event.settings.get('payment_term_mode')
+        sales_channel_suffix = ""
+
+    if mode == 'days':
+        exp_by_date = now_dt.astimezone(tz) + timedelta(
+            days=event.settings.get(f'payment_term_days{sales_channel_suffix}', as_type=int))
+        exp_by_date = exp_by_date.astimezone(tz).replace(hour=23, minute=59, second=59, microsecond=0)
+        if event.settings.get('payment_term_weekdays'):
+            if exp_by_date.weekday() == 5:
+                exp_by_date += timedelta(days=2)
+            elif exp_by_date.weekday() == 6:
+                exp_by_date += timedelta(days=1)
+    elif mode == 'minutes':
+        exp_by_date = now_dt.astimezone(tz) + timedelta(
+            minutes=event.settings.get(f'payment_term_minutes{sales_channel_suffix}', as_type=int))
+    else:
+        raise ValueError("'payment_term_mode' has an invalid value '{}'.".format(mode))
+
+    expires = exp_by_date
+
+    term_last = event.settings.get('payment_term_last', as_type=RelativeDateWrapper)
+    if term_last:
+        if event.has_subevents and subevents:
+            terms = [
+                term_last.datetime(se).date()
+                for se in subevents
+            ]
+            if not terms:
+                return expires
+            term_last = min(terms)
+        else:
+            term_last = term_last.datetime(event).date()
+        term_last = make_aware(datetime.combine(
+            term_last,
+            time(hour=23, minute=59, second=59)
+        ), tz)
+        if term_last < expires:
+            return term_last
+
+    return expires