Add support for custom taxation rules

src/pretix/control/forms/event.py

@@ -4,8 +4,11 @@ from django.contrib.auth.hashers import check_password
 from django.core.exceptions import ValidationError
 from django.core.validators import RegexValidator
 from django.db.models import Q
+from django.forms import formset_factory
 from django.utils.timezone import get_current_timezone_name
 from django.utils.translation import pgettext_lazy, ugettext_lazy as _
+from django_countries import Countries
+from django_countries.fields import LazyTypedChoiceField
 from i18nfield.forms import I18nFormField, I18nTextarea
 from pytz import common_timezones, timezone
 
@@ -907,6 +910,43 @@ class CommentForm(I18nModelForm):
         }
 
 
+class CountriesAndEU(Countries):
+    override = {
+        'ZZ': _('Any country'),
+        'EU': _('European Union')
+    }
+    first = ['ZZ', 'EU']
+
+
+class TaxRuleLineForm(forms.Form):
+    country = LazyTypedChoiceField(
+        choices=CountriesAndEU(),
+        required=False
+    )
+    address_type = forms.ChoiceField(
+        choices=[
+            ('', _('Any customer')),
+            ('individual', _('Individual')),
+            ('business', _('Business')),
+            ('business_vat_id', _('Business with valid VAT ID')),
+        ],
+        required=False
+    )
+    action = forms.ChoiceField(
+        choices=[
+            ('vat', _('Charge VAT')),
+            ('reverse', _('Reverse charge')),
+            ('no', _('No VAT')),
+        ],
+    )
+
+
+TaxRuleLineFormSet = formset_factory(
+    TaxRuleLineForm,
+    can_order=False, can_delete=True, extra=0
+)
+
+
 class TaxRuleForm(I18nModelForm):
     class Meta:
         model = TaxRule

src/pretix/control/templates/pretixcontrol/event/tax_edit.html

@@ -1,5 +1,6 @@
 {% extends "pretixcontrol/event/settings_base.html" %}
 {% load i18n %}
+{% load formset_tags %}
 {% load bootstrap3 %}
 {% block title %}
     {% if rule %}
@@ -21,7 +22,7 @@
         {% bootstrap_field form.rate addon_after="%" layout="control" %}
         <legend>{% trans "Advanced settings" %}</legend>
         <div class="alert alert-warning">
-            <span class="fa fa-w fa-legal fa-4x pull-left"></span>
+            <span class="fa fa-fw fa-legal fa-4x pull-left"></span>
             {% blocktrans trimmed with docs="https://docs.pretix.eu/en/latest/user/events/taxes.html" %}
                 These settings are intended for advanced users. See the <a href="{{ docs }}">documentation</a>
                 for more information. Note that we are not responsible for the correct handling
@@ -32,6 +33,75 @@
         {% bootstrap_field form.price_includes_tax layout="control" %}
         {% bootstrap_field form.eu_reverse_charge layout="control" %}
         {% bootstrap_field form.home_country layout="control" %}
+        <legend>{% trans "Custom taxation rules" %}</legend>
+        <div class="alert alert-warning">
+            <span class="fa fa-fw fa-exclamation-circle fa-4x pull-left"></span>
+            {% blocktrans trimmed %}
+                These settings are intended for professional users with very specific taxation situations.
+                If you create any rule here, the reverse charge settings above will be ignored. The rules will be
+                checked in order and once the first rule matches the order, it will be used and all further rules will
+                be ignored. If no rule matches, tax will be charged.
+            {% endblocktrans %}
+            <div class="clearfix"></div>
+        </div>
+
+        <div class="formset" data-formset data-formset-prefix="{{ formset.prefix }}">
+            {{ formset.management_form }}
+            {% bootstrap_formset_errors formset %}
+            <div data-formset-body>
+                {% for form in formset %}
+                    {% bootstrap_form_errors form %}
+                    <div class="row" data-formset-form>
+                        <div class="sr-only">
+                            {{ form.id }}
+                            {% bootstrap_field form.DELETE form_group_class="" layout="inline" %}
+                        </div>
+                        <div class="col-sm-4">
+                            {% bootstrap_field form.country layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-3">
+                            {% bootstrap_field form.address_type layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-3">
+                            {% bootstrap_field form.action layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-2 text-right">
+                            <button type="button" class="btn btn-danger" data-formset-delete-button>
+                                <i class="fa fa-trash"></i></button>
+                        </div>
+                    </div>
+                {% endfor %}
+            </div>
+            <script type="form-template" data-formset-empty-form>
+                {% escapescript %}
+                    <div class="row" data-formset-form>
+                        <div class="sr-only">
+                            {{ form.id }}
+                            {% bootstrap_field formset.empty_form.DELETE form_group_class="" layout="inline" %}
+                        </div>
+                        <div class="col-sm-4">
+                            {% bootstrap_field formset.empty_form.country layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-3">
+                            {% bootstrap_field formset.empty_form.address_type layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-3">
+                            {% bootstrap_field formset.empty_form.action layout='inline' form_group_class="" %}
+                        </div>
+                        <div class="col-sm-2 text-right">
+                            <button type="button" class="btn btn-danger" data-formset-delete-button>
+                                <i class="fa fa-trash"></i></button>
+                        </div>
+                    </div>
+                {% endescapescript %}
+            </script>
+            <p>
+                <button type="button" class="btn btn-default" data-formset-add>
+                    <i class="fa fa-plus"></i> {% trans "Add a new rule" %}</button>
+            </p>
+        </div>
+
+
         <div class="form-group submit-group">
             <button type="submit" class="btn btn-primary btn-save">
                 {% trans "Save" %}

src/pretix/control/views/event.py

@@ -1,3 +1,4 @@
+import json
 import re
 from collections import OrderedDict
 from datetime import timedelta
@@ -40,8 +41,8 @@ from pretix.base.templatetags.money import money_filter
 from pretix.control.forms.event import (
     CommentForm, DisplaySettingsForm, EventDeleteForm, EventMetaValueForm,
     EventSettingsForm, EventUpdateForm, InvoiceSettingsForm, MailSettingsForm,
-    PaymentSettingsForm, ProviderForm, TaxRuleForm, TicketSettingsForm,
-    WidgetCodeForm,
+    PaymentSettingsForm, ProviderForm, TaxRuleForm, TaxRuleLineFormSet,
+    TicketSettingsForm, WidgetCodeForm,
 )
 from pretix.control.permissions import EventPermissionRequiredMixin
 from pretix.control.signals import nav_event_settings
@@ -952,9 +953,30 @@ class TaxCreate(EventSettingsViewMixin, EventPermissionRequiredMixin, CreateView
             'name': LazyI18nString.from_gettext(ugettext('VAT'))
         }
 
+    def post(self, request, *args, **kwargs):
+        form = self.get_form()
+        if form.is_valid() and self.formset.is_valid():
+            return self.form_valid(form)
+        else:
+            return self.form_invalid(form)
+
+    @cached_property
+    def formset(self):
+        return TaxRuleLineFormSet(
+            data=self.request.POST if self.request.method == "POST" else None,
+        )
+
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx['formset'] = self.formset
+        return ctx
+
     @transaction.atomic
     def form_valid(self, form):
         form.instance.event = self.request.event
+        form.instance.custom_rules = json.dumps([
+            f.cleaned_data for f in self.formset if f not in self.formset.deleted_forms
+        ])
         messages.success(self.request, _('The new tax rule has been created.'))
         ret = super().form_valid(form)
         form.instance.log_action('pretix.event.taxrule.added', user=self.request.user, data=dict(form.cleaned_data))
@@ -980,9 +1002,32 @@ class TaxUpdate(EventSettingsViewMixin, EventPermissionRequiredMixin, UpdateView
         except TaxRule.DoesNotExist:
             raise Http404(_("The requested tax rule does not exist."))
 
+    def post(self, request, *args, **kwargs):
+        self.object = self.get_object(self.get_queryset())
+        form = self.get_form()
+        if form.is_valid() and self.formset.is_valid():
+            return self.form_valid(form)
+        else:
+            return self.form_invalid(form)
+
+    @cached_property
+    def formset(self):
+        return TaxRuleLineFormSet(
+            data=self.request.POST if self.request.method == "POST" else None,
+            initial=json.loads(self.object.custom_rules) if self.object.custom_rules else []
+        )
+
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx['formset'] = self.formset
+        return ctx
+
     @transaction.atomic
     def form_valid(self, form):
         messages.success(self.request, _('Your changes have been saved.'))
+        form.instance.custom_rules = json.dumps([
+            f.cleaned_data for f in self.formset if f not in self.formset.deleted_forms
+        ])
         if form.has_changed():
             self.object.log_action(
                 'pretix.event.taxrule.changed', user=self.request.user, data={