Invoicing: Allow to show exchange rates based on sources/rules (#3122)

src/pretix/base/apps.py

@@ -46,7 +46,7 @@ class PretixBaseConfig(AppConfig):
         from . import invoice  # NOQA
         from . import notifications  # NOQA
         from . import email  # NOQA
-        from .services import auth, checkin, export, mail, tickets, cart, orderimport, orders, invoices, cleanup, update_check, quotas, notifications, vouchers  # NOQA
+        from .services import auth, checkin, currencies, export, mail, tickets, cart, orderimport, orders, invoices, cleanup, update_check, quotas, notifications, vouchers  # NOQA
         from .models import _transactions  # NOQA
         from django.conf import settings
 

src/pretix/base/invoice.py

@@ -50,6 +50,7 @@ from reportlab.platypus import (
 
 from pretix.base.decimal import round_decimal
 from pretix.base.models import Event, Invoice, Order, OrderPayment
+from pretix.base.services.currencies import SOURCE_NAMES
 from pretix.base.signals import register_invoice_renderers
 from pretix.base.templatetags.money import money_filter
 from pretix.helpers.reportlab import ThumbnailingImageReader
@@ -773,9 +774,10 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
                     Spacer(1, height=2 * mm),
                     Paragraph(
                         pgettext(
-                            'invoice', 'Using the conversion rate of 1:{rate} as published by the European Central Bank on '
+                            'invoice', 'Using the conversion rate of 1:{rate} as published by the {authority} on '
                                        '{date}, this corresponds to:'
                         ).format(rate=localize(self.invoice.foreign_currency_rate),
+                                 authority=SOURCE_NAMES.get(self.invoice.foreign_currency_source, "?"),
                                  date=date_format(self.invoice.foreign_currency_rate_date, "SHORT_DATE_FORMAT")),
                         self.stylesheet['Fineprint']
                     ),
@@ -787,10 +789,11 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
             story.append(Spacer(1, 5 * mm))
             story.append(Paragraph(
                 pgettext(
-                    'invoice', 'Using the conversion rate of 1:{rate} as published by the European Central Bank on '
+                    'invoice', 'Using the conversion rate of 1:{rate} as published by the {authority} on '
                                '{date}, the invoice total corresponds to {total}.'
                 ).format(rate=localize(self.invoice.foreign_currency_rate),
                          date=date_format(self.invoice.foreign_currency_rate_date, "SHORT_DATE_FORMAT"),
+                         authority=SOURCE_NAMES.get(self.invoice.foreign_currency_source, "?"),
                          total=fmt(foreign_total)),
                 self.stylesheet['Fineprint']
             ))

src/pretix/base/migrations/0232_exchangerate.py

@@ -0,0 +1,34 @@
+# Generated by Django 3.2.17 on 2023-02-14 15:34
+
+import django.core.serializers.json
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0231_auto_20230208_1546'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ExchangeRate',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False)),
+                ('source', models.CharField(max_length=100)),
+                ('source_date', models.DateField()),
+                ('updated', models.DateTimeField(auto_now=True)),
+                ('source_currency', models.CharField(max_length=3)),
+                ('other_currency', models.CharField(max_length=3)),
+                ('rate', models.DecimalField(decimal_places=6, max_digits=16)),
+            ],
+            options={
+                'unique_together': {('source', 'source_currency', 'other_currency')},
+            },
+        ),
+        migrations.AddField(
+            model_name='invoice',
+            name='foreign_currency_source',
+            field=models.CharField(max_length=100, null=True),
+        ),
+    ]

src/pretix/base/models/__init__.py

@@ -23,6 +23,7 @@ from ..settings import GlobalSettingsObject_SettingsStore
 from .auth import U2FDevice, User, WebAuthnDevice
 from .base import CachedFile, LoggedModel, cachedfile_name
 from .checkin import Checkin, CheckinList
+from .currencies import ExchangeRate
 from .customers import Customer
 from .devices import Device, Gate
 from .discount import Discount

src/pretix/base/models/currencies.py

@@ -0,0 +1,34 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io 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 django.db import models
+
+
+class ExchangeRate(models.Model):
+    source = models.CharField(max_length=100)
+    source_date = models.DateField()
+    updated = models.DateTimeField(auto_now=True)
+    source_currency = models.CharField(max_length=3)
+    other_currency = models.CharField(max_length=3)
+    rate = models.DecimalField(decimal_places=6, max_digits=16)
+
+    class Meta:
+        unique_together = (('source', 'source_currency', 'other_currency'))

src/pretix/base/models/invoices.py

@@ -105,6 +105,8 @@ class Invoice(models.Model):
     :type foreign_currency_rate: Decimal
     :param foreign_currency_rate_date: The date of the foreign currency exchange rates.
     :type foreign_currency_rate_date: date
+    :param foreign_currency_rate_source: The source of the foreign currency rate.
+    :type foreign_currency_rate_source: str
     :param file: The filename of the rendered invoice
     :type file: File
     """
@@ -152,6 +154,7 @@ class Invoice(models.Model):
     foreign_currency_display = models.CharField(max_length=50, null=True, blank=True)
     foreign_currency_rate = models.DecimalField(decimal_places=4, max_digits=10, null=True, blank=True)
     foreign_currency_rate_date = models.DateField(null=True, blank=True)
+    foreign_currency_source = models.CharField(max_length=100, null=True, blank=True)
 
     shredded = models.BooleanField(default=False)
 

src/pretix/base/services/currencies.py

@@ -0,0 +1,145 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io 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 date, datetime, timedelta
+from decimal import Decimal
+
+import requests
+from django.conf import settings
+from django.db.models import Max
+from django.dispatch import receiver
+from django.utils.translation import gettext_lazy as _
+from lxml import etree
+
+from pretix.base.models import ExchangeRate
+from pretix.base.signals import periodic_task
+from pretix.celery_app import app
+
+SOURCE_NAMES = {
+    None: _('European Central Bank'),  # backwards-compatibility
+    'eu:ecb:eurofxref-daily': _('European Central Bank'),
+    'cz:cnb:rate-fixing-daily': _('Czech National Bank'),
+}
+
+
+@receiver(signal=periodic_task)
+def fetch_rates(sender, **kwargs):
+    if not settings.FETCH_ECB_RATES:
+        return
+
+    source_tasks = {
+        'eu:ecb:eurofxref-daily': fetch_ecb_rates,
+        'cz:cnb:rate-fixing-daily': fetch_cnb_cz_rates,
+    }
+
+    for source_name, task in source_tasks.items():
+        last_source_date = ExchangeRate.objects.filter(source=source_name).aggregate(m=Max('source_date'))['m']
+        if last_source_date and last_source_date >= date.today():
+            # We assume that the rates we fetch are only updated daily
+            continue
+
+        last_fetch_date = ExchangeRate.objects.filter(source=source_name).aggregate(m=Max('updated'))['m']
+        if last_fetch_date and last_fetch_date >= datetime.utcnow() - timedelta(hours=1):
+            # Only try to fetch once per hour
+            continue
+
+        # Today's rate not yet published, let's try to fetch it
+        task.apply_async()
+
+
+@app.task()
+def fetch_ecb_rates():
+    """
+    Fetches currency rates from the European Central Bank.
+    """
+    d = 'https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml'
+    r = requests.get(d)
+    r.raise_for_status()
+
+    # File looks like this:
+    # <?xml version="1.0" encoding="UTF-8"?>
+    # <gesmes:Envelope xmlns:gesmes="http://www.gesmes.org/xml/2002-08-01"
+    #                  xmlns="http://www.ecb.int/vocabulary/2002-08-01/eurofxref">
+    #   <gesmes:subject>Reference rates</gesmes:subject>
+    #   <gesmes:Sender>
+    #       <gesmes:name>European Central Bank</gesmes:name>
+    #   </gesmes:Sender>
+    #   <Cube>
+    #       <Cube time="2023-02-14">
+    #           <Cube currency="USD" rate="1.0759"/>
+    #           ...
+    #       </Cube>
+    #   </Cube>
+    # </gesmes:Envelope>
+
+    root = etree.fromstring(r.content)
+    namespaces = {
+        'gesmes': 'http://www.gesmes.org/xml/2002-08-01',
+        'eurofxref': 'http://www.ecb.int/vocabulary/2002-08-01/eurofxref'
+    }
+    outercube = root.xpath('./eurofxref:Cube/eurofxref:Cube[@time]', namespaces=namespaces)[0]
+    source_date = date.fromisoformat(outercube.get("time"))
+
+    for cube in outercube.xpath('./eurofxref:Cube[@currency][@rate]', namespaces=namespaces):
+        currency = cube.get('currency')
+        rate = Decimal(cube.get('rate'))
+        ExchangeRate.objects.update_or_create(
+            source='eu:ecb:eurofxref-daily',
+            source_currency='EUR',
+            other_currency=currency,
+            defaults=dict(
+                source_date=source_date,
+                rate=rate,
+            )
+        )
+
+
+@app.task()
+def fetch_cnb_cz_rates():
+    """
+    Fetches currency rates from the Czech National Bank.
+    """
+    d = f'https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/' \
+        f'central-bank-exchange-rate-fixing/daily.txt?date={date.today().strftime("%d.%m.%Y")}'
+    r = requests.get(d)
+    r.raise_for_status()
+
+    lines = r.text.splitlines()
+
+    # File looks like this:
+    # 14 Feb 2023 #32
+    # Country|Currency|Amount|Code|Rate
+    # Australia|dollar|1|AUD|15.412
+
+    source_date = datetime.strptime(lines[0].split("#")[0].strip(), "%d %b %Y").date()
+
+    for line in lines[2:]:
+        country, currency, amount, code, rate = line.split("|")
+        rate = Decimal(rate).quantize(Decimal('0.000001')) / int(amount)
+        ExchangeRate.objects.update_or_create(
+            source='cz:cnb:rate-fixing-daily',
+            source_currency=code,
+            other_currency='CZK',
+            defaults=dict(
+                source_date=source_date,
+                rate=rate,
+            )
+        )

src/pretix/base/services/invoices.py

@@ -33,16 +33,12 @@
 # License for the specific language governing permissions and limitations under the License.
 
 import inspect
-import json
 import logging
-import urllib.error
-from datetime import date, timedelta
+from datetime import timedelta
 from decimal import ROUND_HALF_UP, Decimal
 
-import vat_moss.exchange_rates
 from django.conf import settings
 from django.core.files.base import ContentFile
-from django.core.serializers.json import DjangoJSONEncoder
 from django.db import connection, transaction
 from django.db.models import Count
 from django.dispatch import receiver
@@ -56,11 +52,10 @@ from i18nfield.strings import LazyI18nString
 
 from pretix.base.i18n import language
 from pretix.base.models import (
-    Invoice, InvoiceAddress, InvoiceLine, Order, OrderFee,
+    ExchangeRate, Invoice, InvoiceAddress, InvoiceLine, Order, OrderFee,
 )
 from pretix.base.models.tax import EU_CURRENCIES
 from pretix.base.services.tasks import TransactionAwareTask
-from pretix.base.settings import GlobalSettingsObject
 from pretix.base.signals import invoice_line_text, periodic_task
 from pretix.celery_app import app
 from pretix.helpers.database import OF_SELF, rolledback_transaction
@@ -144,27 +139,54 @@ def build_invoice(invoice: Invoice) -> Invoice:
                 invoice.invoice_to += "\n" + pgettext("invoice", "VAT-ID: %s") % ia.vat_id
                 invoice.invoice_to_vat_id = ia.vat_id
 
-            cc = str(ia.country)
-
-            if cc in EU_CURRENCIES and EU_CURRENCIES[cc] != invoice.event.currency and invoice.event.settings.invoice_eu_currencies:
-                invoice.foreign_currency_display = EU_CURRENCIES[cc]
+            if invoice.event.settings.invoice_eu_currencies == 'True':
+                cc = str(ia.country)
+                if cc in EU_CURRENCIES and EU_CURRENCIES[cc] != invoice.event.currency:
+                    invoice.foreign_currency_display = EU_CURRENCIES[cc]
 
+                    if settings.FETCH_ECB_RATES:
+                        rate = ExchangeRate.objects.filter(
+                            source='eu:ecb:eurofxref-daily',
+                            source_currency=invoice.event.currency,
+                            other_currency=invoice.foreign_currency_display,
+                            source_date__gt=now().date() - timedelta(days=7)
+                        ).first()
+                        if rate:
+                            invoice.foreign_currency_rate = rate.rate.quantize(Decimal('0.0001'), ROUND_HALF_UP)
+                            invoice.foreign_currency_rate_date = rate.source_date
+                            invoice.foreign_currency_source = 'eu:ecb:eurofxref-daily'
+                        else:
+                            rate_eur_to_event = ExchangeRate.objects.filter(
+                                source='eu:ecb:eurofxref-daily',
+                                source_currency='EUR',
+                                other_currency=invoice.event.currency,
+                                source_date__gt=now().date() - timedelta(days=7)
+                            ).first()
+                            rate_eur_to_wanted = ExchangeRate.objects.filter(
+                                source='eu:ecb:eurofxref-daily',
+                                source_currency='EUR',
+                                other_currency=invoice.foreign_currency_display,
+                                source_date__gt=now().date() - timedelta(days=7)
+                            ).first()
+                            if rate_eur_to_wanted and rate_eur_to_event:
+                                invoice.foreign_currency_rate = (
+                                    rate_eur_to_wanted.rate / rate_eur_to_event.rate
+                                ).quantize(Decimal('0.0001'), ROUND_HALF_UP)
+                                invoice.foreign_currency_rate_date = min(rate_eur_to_wanted.source_date, rate_eur_to_event.source_date)
+                                invoice.foreign_currency_source = 'eu:ecb:eurofxref-daily'
+            elif invoice.event.settings.invoice_eu_currencies == 'CZK' and invoice.event.currency != 'CZK':
+                invoice.foreign_currency_display = 'CZK'
                 if settings.FETCH_ECB_RATES:
-                    gs = GlobalSettingsObject()
-                    rates_date = gs.settings.get('ecb_rates_date', as_type=date)
-                    rates_dict = gs.settings.get('ecb_rates_dict', as_type=dict)
-                    convert = (
-                        rates_date and rates_dict and
-                        rates_date > (now() - timedelta(days=7)).date() and
-                        invoice.event.currency in rates_dict and
-                        invoice.foreign_currency_display in rates_dict
-                    )
-                    if convert:
-                        invoice.foreign_currency_rate = (
-                            Decimal(rates_dict[invoice.foreign_currency_display])
-                            / Decimal(rates_dict[invoice.event.currency])
-                        ).quantize(Decimal('0.0001'), ROUND_HALF_UP)
-                        invoice.foreign_currency_rate_date = rates_date
+                    rate = ExchangeRate.objects.filter(
+                        source='cz:cnb:rate-fixing-daily',
+                        source_currency=invoice.event.currency,
+                        other_currency=invoice.foreign_currency_display,
+                        source_date__gt=now().date() - timedelta(days=7)
+                    ).first()
+                    if rate:
+                        invoice.foreign_currency_rate = rate.rate.quantize(Decimal('0.0001'), ROUND_HALF_UP)
+                        invoice.foreign_currency_rate_date = rate.source_date
+                        invoice.foreign_currency_source = 'cz:cnb:rate-fixing-daily'
 
         except InvoiceAddress.DoesNotExist:
             ia = None
@@ -474,23 +496,6 @@ def build_preview_invoice_pdf(event):
         return event.invoice_renderer.generate(invoice)
 
 
-@receiver(signal=periodic_task)
-def fetch_ecb_rates(sender, **kwargs):
-    if not settings.FETCH_ECB_RATES:
-        return
-
-    gs = GlobalSettingsObject()
-    if gs.settings.ecb_rates_date == now().strftime("%Y-%m-%d"):
-        return
-
-    try:
-        date, rates = vat_moss.exchange_rates.fetch()
-        gs.settings.ecb_rates_date = date
-        gs.settings.ecb_rates_dict = json.dumps(rates, cls=DjangoJSONEncoder)
-    except urllib.error.URLError:
-        logger.exception('Could not retrieve rates from ECB')
-
-
 @receiver(signal=periodic_task)
 @scopes_disabled()
 def send_invoices_to_organizer(sender, **kwargs):

src/pretix/base/settings.py

@@ -377,13 +377,27 @@ DEFAULTS = {
     },
     'invoice_eu_currencies': {
         'default': 'True',
-        'type': bool,
-        'form_class': forms.BooleanField,
-        'serializer_class': serializers.BooleanField,
+        'type': str,
+        'form_class': forms.ChoiceField,
+        'serializer_class': serializers.ChoiceField,
         'form_kwargs': dict(
-            label=_("On invoices from one EU country into another EU country with a different currency, print the "
-                    "tax amounts in both currencies if possible"),
-        )
+            label=_("Show exchange rates"),
+            widget=forms.RadioSelect,
+            choices=(
+                ('False', _('Never')),
+                ('True', _('Based on European Central Bank daily rates, whenever the invoice recipient is in an EU '
+                           'country that uses a different currency.')),
+                ('CZK', _('Based on Czech National Bank daily rates, whenever the invoice amount is not in CZK.')),
+            ),
+        ),
+        'serializer_kwargs': dict(
+            choices=(
+                ('False', _('Never')),
+                ('True', _('Based on European Central Bank daily rates, whenever the invoice recipient is in an EU '
+                           'country that uses a different currency.')),
+                ('CZK', _('Based on Czech National Bank daily rates, whenever the invoice amount is not in CZK.')),
+            ),
+        ),
     },
     'invoice_address_required': {
         'default': 'False',