add notes managers

scipost_django/pins/managers.py

+__copyright__ = "Copyright © Stichting SciPost (SciPost Foundation)"
+__license__ = "AGPL v3"
+
+from typing import Optional
+from django.contrib.auth.models import User
+from django.contrib.contenttypes.models import ContentType
+from django.db import models
+
+
+class NotesQuerySet(models.QuerySet):
+
+    def visible_to(
+        self,
+        user: Optional[User] = None,
+        model: Optional[models.Model] = None,
+    ):
+        """
+        Filter out notes which are not visible to the given user.
+        """
+
+        if user is None:
+            # Without specifying a user, only public notes are visible
+            return self.filter(visibility=self.model.VISIBILITY_PUBLIC)
+        else:
+            # Filter non-author users from viewing private notes
+            self = self.exclude(
+                models.Q(visibility=self.model.VISIBILITY_PRIVATE)
+                & ~models.Q(author=user.contributor)
+            )
+
+        # Filter out internal notes unless the user has the default "manager"
+        # permission for the given object, e.g. "can_manage_subsidies"
+        # If no model is given, just filter out all of them
+        model_plural = str(model._meta.verbose_name_plural).lower() if model else ""
+        if model is None or not user.has_perm(f"pins.can_manage_{model_plural}"):
+            self = self.exclude(visibility=self.model.VISIBILITY_INTERNAL)
+
+        return self
+
+    def for_object(self, content_type, object_id):
+        """
+        Filter notes for a given object.
+        """
+        return self.filter(
+            regarding_content_type=content_type,
+            regarding_object_id=object_id,
+        )
+
+    def visible_for(self, user, content_type, object_id):
+        """
+        Filter notes for a given object, accessible to the given user.
+        """
+        model = ContentType.objects.get_for_id(content_type)
+        return self.for_object(content_type, object_id).visible_to(user, model)

scipost_django/pins/models.py

@@ -4,6 +4,8 @@ __license__ = "AGPL v3"
 from django.db import models
 from django.contrib.contenttypes.fields import GenericForeignKey
 
+from .managers import NotesQuerySet
+
 
 class Note(models.Model):
     """
@@ -46,6 +48,8 @@ class Note(models.Model):
     created = models.DateTimeField(auto_now_add=True)
     modified = models.DateTimeField(auto_now=True)
 
+    objects = NotesQuerySet.as_manager()
+
     def __str__(self):
         return self.title