Client side currency conversion (#4293)

* Automatically update exchange rates when base currency is updated

* Adds API endpoint with currency exchange information

* Add unit testing for new endpoint

* Implement javascript code for client-side conversion

* Adds helper function for calculating total price of a dataset

* javascript cleanup

* Add functionality to sales order tables

* JS linting

* Update API version

* Prevent auto currency updates under certain conditions

InvenTree/common/api.py

@@ -9,6 +9,7 @@ from django.views.decorators.csrf import csrf_exempt
 
 from django_filters.rest_framework import DjangoFilterBackend
 from django_q.tasks import async_task
+from djmoney.contrib.exchange.models import Rate
 from rest_framework import filters, permissions, serializers
 from rest_framework.exceptions import NotAcceptable, NotFound
 from rest_framework.permissions import IsAdminUser
@@ -102,6 +103,36 @@ class WebhookView(CsrfExemptMixin, APIView):
             raise NotFound()
 
 
+class CurrencyExchangeView(APIView):
+    """API endpoint for displaying currency information
+
+    TODO: Add a POST hook to refresh / update the currency exchange data
+    """
+
+    permission_classes = [
+        permissions.IsAuthenticated,
+    ]
+
+    def get(self, request, format=None):
+        """Return information on available currency conversions"""
+
+        # Extract a list of all available rates
+        try:
+            rates = Rate.objects.all()
+        except Exception:
+            rates = []
+
+        response = {
+            'base_currency': common.models.InvenTreeSetting.get_setting('INVENTREE_DEFAULT_CURRENCY', 'USD'),
+            'exchange_rates': {}
+        }
+
+        for rate in rates:
+            response['exchange_rates'][rate.currency] = rate.value
+
+        return Response(response)
+
+
 class SettingsList(ListAPI):
     """Generic ListView for settings.
 
@@ -418,6 +449,11 @@ common_api_urls = [
     # Webhooks
     path('webhook/<slug:endpoint>/', WebhookView.as_view(), name='api-webhook'),
 
+    # Currencies
+    re_path(r'^currency/', include([
+        re_path(r'^exchange/', CurrencyExchangeView.as_view(), name='api-currency-exchange'),
+    ])),
+
     # Notifications
     re_path(r'^notifications/', include([
         # Individual purchase order detail URLs

InvenTree/common/models.py

@@ -43,6 +43,7 @@ import build.validators
 import InvenTree.fields
 import InvenTree.helpers
 import InvenTree.ready
+import InvenTree.tasks
 import InvenTree.validators
 import order.validators
 
@@ -821,6 +822,18 @@ def validate_email_domains(setting):
             raise ValidationError(_(f'Invalid domain name: {domain}'))
 
 
+def update_exchange_rates(setting):
+    """Update exchange rates when base currency is changed"""
+
+    if InvenTree.ready.isImportingData():
+        return
+
+    if not InvenTree.ready.canAppAccessDatabase():
+        return
+
+    InvenTree.tasks.update_exchange_rates()
+
+
 class InvenTreeSetting(BaseInvenTreeSetting):
     """An InvenTreeSetting object is a key:value pair used for storing single values (e.g. one-off settings values).
 
@@ -901,9 +914,10 @@ class InvenTreeSetting(BaseInvenTreeSetting):
 
         'INVENTREE_DEFAULT_CURRENCY': {
             'name': _('Default Currency'),
-            'description': _('Default currency'),
+            'description': _('Select base currency for pricing caluclations'),
             'default': 'USD',
             'choices': CURRENCY_CHOICES,
+            'after_save': update_exchange_rates,
         },
 
         'INVENTREE_DOWNLOAD_FROM_URL': {

InvenTree/common/tests.py

@@ -900,3 +900,15 @@ class ColorThemeTest(TestCase):
         # check valid theme
         self.assertFalse(ColorTheme.is_valid_choice(aa))
         self.assertTrue(ColorTheme.is_valid_choice(ab))
+
+
+class CurrencyAPITests(InvenTreeAPITestCase):
+    """Unit tests for the currency exchange API endpoints"""
+
+    def test_exchange_endpoint(self):
+        """Test that the currency exchange endpoint works as expected"""
+
+        response = self.get(reverse('api-currency-exchange'), expected_code=200)
+
+        self.assertIn('base_currency', response.data)
+        self.assertIn('exchange_rates', response.data)