Initial commit

netbox_services/signals.py

@@ -0,0 +1,37 @@
+from django.db.models.signals import pre_delete, pre_save
+from django.dispatch import receiver
+from django.utils.translation import gettext_lazy as _
+
+from .models import Service, ServiceTemplate
+
+
+class TemplateLockedError(Exception):
+    """Raised when attempting to modify a locked template."""
+
+    def __init__(self, obj, message=None):
+        self.obj = obj
+        self.message = message or _(
+            "Cannot modify {}: it is locked because one or more services "
+            "have been spawned from it."
+        ).format(obj)
+        super().__init__(self.message)
+
+
+@receiver(pre_save, sender=ServiceTemplate)
+def lock_service_template_save(sender, instance, **kwargs):
+    if not instance.pk:
+        return
+    if instance.services.exists():
+        try:
+            old = ServiceTemplate.objects.get(pk=instance.pk)
+        except ServiceTemplate.DoesNotExist:
+            return
+        for field in ("name", "tree"):
+            if getattr(instance, field) != getattr(old, field):
+                raise TemplateLockedError(instance)
+
+
+@receiver(pre_delete, sender=ServiceTemplate)
+def lock_service_template_delete(sender, instance, **kwargs):
+    if instance.services.exists():
+        raise TemplateLockedError(instance)