From 17c2b40d1f9821d24b5716b7b80cb25e2b40c1d6 Mon Sep 17 00:00:00 2001
From: Richard Schreiber <wiffbi@gmail.com>
Date: Mon, 19 Sep 2022 17:33:27 +0200
Subject: [PATCH] add option to split taxes

---
 pretix_servicefees/signals.py                 | 48 ++++++++++++++++++-
 .../pretix_servicefees/settings.html          |  1 +
 pretix_servicefees/views.py                   |  5 ++
 3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/pretix_servicefees/signals.py b/pretix_servicefees/signals.py
index 2645534..c81aa61 100644
--- a/pretix_servicefees/signals.py
+++ b/pretix_servicefees/signals.py
@@ -1,3 +1,4 @@
+from collections import defaultdict
 from decimal import Decimal
 
 from django.urls import resolve, reverse
@@ -5,7 +6,7 @@ from django.dispatch import receiver
 from django.http import HttpRequest
 from django.utils.translation import gettext_lazy as _, gettext, get_language
 from pretix.base.decimal import round_decimal
-from pretix.base.models import Event, Order, TaxRule
+from pretix.base.models import CartPosition, Event, Order, TaxRule
 from pretix.base.models.orders import OrderFee
 from pretix.base.settings import settings_hierarkey
 from pretix.base.signals import order_fee_calculation
@@ -76,7 +77,52 @@ def get_fees(event, total, invoice_address, mod='', request=None, positions=[],
                 summed += fval
 
     if (fee_per_ticket or fee_abs or fee_percent) and total != Decimal('0.00'):
+        tax_rule_zero = TaxRule.zero()
         fee = round_decimal(fee_abs + total * (fee_percent / 100) + len(positions) * fee_per_ticket, event.currency)
+        split_taxes = event.settings.get('service_fee_split_taxes', as_type=bool)
+        if split_taxes:
+            # split taxes based on products ordered
+            d = defaultdict(lambda: Decimal('0.00'))
+            for p in positions:
+                if isinstance(p, CartPosition):
+                    tr = p.item.tax_rule
+                else:
+                    tr = p.tax_rule
+                d[tr] += p.price - p.tax_value
+
+            base_values = sorted([tuple(t) for t in d.items()], key=lambda t: t[0].rate)
+            sum_base = sum(t[1] for t in base_values)
+            if sum_base:
+                fee_values = [(t[0], round_decimal(fee * t[1] / sum_base, event.currency))
+                              for t in base_values]
+                sum_fee = sum(t[1] for t in fee_values)
+
+                # If there are rounding differences, we fix them up, but always leaning to the benefit of the tax
+                # authorities
+                if sum_fee > fee:
+                    fee_values[0] = (fee_values[0][0], fee_values[0][1] + (fee - sum_fee))
+                elif sum_fee < fee:
+                    fee_values[-1] = (fee_values[-1][0], fee_values[-1][1] + (fee - sum_fee))
+            else:
+                fee_values = [(event.settings.tax_rate_default or tax_rule_zero, fee)]
+
+        else:
+            fee_values = [(event.settings.tax_rate_default or tax_rule_zero, fee)]
+
+        fees = []
+        for tax_rule, price in fee_values:
+            tax_rule = tax_rule or tax_rule_zero
+            tax = tax_rule.tax(price, invoice_address=invoice_address, base_price_is='gross')
+            fees.append(OrderFee(
+                fee_type=OrderFee.FEE_TYPE_SERVICE,
+                internal_type='',
+                value=price,
+                tax_rate=tax.rate,
+                tax_value=tax.tax,
+                tax_rule=tax_rule
+            ))
+        return fees
+
         tax_rule = event.settings.tax_rate_default or TaxRule.zero()
         tax = tax_rule.tax(fee, invoice_address=invoice_address, base_price_is='gross')
         return [OrderFee(
diff --git a/pretix_servicefees/templates/pretix_servicefees/settings.html b/pretix_servicefees/templates/pretix_servicefees/settings.html
index 642e6be..1160621 100644
--- a/pretix_servicefees/templates/pretix_servicefees/settings.html
+++ b/pretix_servicefees/templates/pretix_servicefees/settings.html
@@ -14,6 +14,7 @@
             {% bootstrap_field form.service_fee_skip_free layout="control" %}
             {% bootstrap_field form.service_fee_abs addon_after=request.event.currency layout="control" %}
             {% bootstrap_field form.service_fee_percent addon_after="%" layout="control" %}
+            {% bootstrap_field form.service_fee_split_taxes layout="control" %}
             {% bootstrap_field form.service_fee_skip_if_gift_card layout="control" %}
         </fieldset>
         <fieldset>
diff --git a/pretix_servicefees/views.py b/pretix_servicefees/views.py
index 1afbc4d..41f67fb 100644
--- a/pretix_servicefees/views.py
+++ b/pretix_servicefees/views.py
@@ -46,6 +46,11 @@ class ServiceFeeSettingsForm(SettingsForm):
         help_text=_('Note that regardless of this setting, a per-ticket fee will not be charged if the entire order is free.'),
         required=False
     )
+    service_fee_split_taxes = forms.BooleanField(
+        label=_('Split taxes proportionate to the tax rates and net values of the ordered products.'),
+        help_text=_('If not split based on ordered products, the tax rate falls back to the event’s base tax rate or no tax, if none is given.'),
+        required=False
+    )
 
     service_fee_abs_resellers = forms.DecimalField(
         label=_('Fixed fee per order'),