Exchange rate plugin (#5667)

* Add plugin mixin class for supporting exchange rates

* Split some mixin classes out into their own files

- mixins.py is becoming quite bloated!

* Add some new settings for controlling currency updates

* Adds basic plugin implementation

* Refactor existing implementation

- Builtin plugin uses frankfurter.app API
- Better error / edge case handlign

* Add sample plugin for currency exchange

* Allow user to select which plugin to use for plugin updates

* Observe user-configured setting for how often exchange rates are updated

* Updates for some of the sample plugins

* Fix plugin slug

* Add doc page

* Document simple example

* Improve sample

* Add blank page for currency settings info

* More info in "config" page

* Update docs again

* Updated unit tests

* Fill out default settings values when InvenTree runs

* Add log messages

* Significant improvement in default settings speed

- Use bulk create
- Be efficient
- Dont' be inefficient

* More strict checks

* Refactor default values implementation

- Don't run at startup
- Run on list API
- Implement generic @classmethod

InvenTree/common/api.py

@@ -160,7 +160,7 @@ class CurrencyRefreshView(APIView):
 
         from InvenTree.tasks import update_exchange_rates
 
-        update_exchange_rates()
+        update_exchange_rates(force=True)
 
         return Response({
             'success': 'Exchange rates updated',
@@ -192,6 +192,12 @@ class GlobalSettingsList(SettingsList):
     queryset = common.models.InvenTreeSetting.objects.exclude(key__startswith="_")
     serializer_class = common.serializers.GlobalSettingsSerializer
 
+    def list(self, request, *args, **kwargs):
+        """Ensure all global settings are created"""
+
+        common.models.InvenTreeSetting.build_default_values()
+        return super().list(request, *args, **kwargs)
+
 
 class GlobalSettingsPermissions(permissions.BasePermission):
     """Special permission class to determine if the user is "staff"."""
@@ -245,6 +251,12 @@ class UserSettingsList(SettingsList):
     queryset = common.models.InvenTreeUserSetting.objects.all()
     serializer_class = common.serializers.UserSettingsSerializer
 
+    def list(self, request, *args, **kwargs):
+        """Ensure all user settings are created"""
+
+        common.models.InvenTreeUserSetting.build_default_values(user=request.user)
+        return super().list(request, *args, **kwargs)
+
     def filter_queryset(self, queryset):
         """Only list settings which apply to the current user."""
         try:

InvenTree/common/models.py

@@ -197,6 +197,32 @@ class BaseInvenTreeSetting(models.Model):
         # Execute after_save action
         self._call_settings_function('after_save', args, kwargs)
 
+    @classmethod
+    def build_default_values(cls, **kwargs):
+        """Ensure that all values defined in SETTINGS are present in the database
+
+        If a particular setting is not present, create it with the default value
+        """
+
+        try:
+            existing_keys = cls.objects.filter(**kwargs).values_list('key', flat=True)
+            settings_keys = cls.SETTINGS.keys()
+
+            missing_keys = set(settings_keys) - set(existing_keys)
+
+            if len(missing_keys) > 0:
+                logger.info("Building %s default values for %s", len(missing_keys), str(cls))
+                cls.objects.bulk_create([
+                    cls(
+                        key=key,
+                        value=cls.get_setting_default(key),
+                        **kwargs
+                    ) for key in missing_keys if not key.startswith('_')
+                ])
+        except Exception as exc:
+            logger.exception("Failed to build default values for %s (%s)", str(cls), str(type(exc)))
+            pass
+
     def _call_settings_function(self, reference: str, args, kwargs):
         """Call a function associated with a particular setting.
 
@@ -939,6 +965,20 @@ def validate_email_domains(setting):
             raise ValidationError(_(f'Invalid domain name: {domain}'))
 
 
+def currency_exchange_plugins():
+    """Return a set of plugin choices which can be used for currency exchange"""
+
+    try:
+        from plugin import registry
+        plugs = registry.with_mixin('currencyexchange', active=True)
+    except Exception:
+        plugs = []
+
+    return [
+        ('', _('No plugin')),
+    ] + [(plug.slug, plug.human_name) for plug in plugs]
+
+
 def update_exchange_rates(setting):
     """Update exchange rates when base currency is changed"""
 
@@ -948,7 +988,7 @@ def update_exchange_rates(setting):
     if not InvenTree.ready.canAppAccessDatabase():
         return
 
-    InvenTree.tasks.update_exchange_rates()
+    InvenTree.tasks.update_exchange_rates(force=True)
 
 
 def reload_plugin_registry(setting):
@@ -1053,6 +1093,24 @@ class InvenTreeSetting(BaseInvenTreeSetting):
             'after_save': update_exchange_rates,
         },
 
+        'CURRENCY_UPDATE_INTERVAL': {
+            'name': _('Currency Update Interval'),
+            'description': _('How often to update exchange rates (set to zero to disable)'),
+            'default': 1,
+            'units': _('days'),
+            'validator': [
+                int,
+                MinValueValidator(0),
+            ],
+        },
+
+        'CURRENCY_UPDATE_PLUGIN': {
+            'name': _('Currency Update Plugin'),
+            'description': _('Currency update plugin to use'),
+            'choices': currency_exchange_plugins,
+            'default': 'inventreecurrencyexchange'
+        },
+
         'INVENTREE_DOWNLOAD_FROM_URL': {
             'name': _('Download from URL'),
             'description': _('Allow download of remote images and files from external URL'),