models.py

from django.conf import settings
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.utils.translation import gettext_lazy as _


class Assignment(models.Model):
    user = models.ForeignKey("auth.User", on_delete=models.PROTECT)
    subject_ct = models.ForeignKey(ContentType, on_delete=models.PROTECT)
    subject_id = models.PositiveIntegerField()
    subject = GenericForeignKey('subject_ct', 'subject_id')

    class Meta:
        unique_together = [
            ("subject_ct", "subject_id"),
        ]

    @classmethod
    def assign(cls, user, subject):
        Assignment.objects.get_or_create(
            user=user,
            subject_ct=ContentType.objects.get_for_model(subject),
            subject_id=subject.pk,
        )

    @classmethod
    def delete(cls, subject_id):
        Assignment.objects.filter(
            subject_id=subject_id,
        ).delete()


class NoteQuerySet(models.QuerySet):
    def for_user(self, user):
        notes = (
            self.filter(author=user)
        )
        if user.has_perm('users.view_all_notes'):
            notes |= (
                self.exclude(author=user).annotate(owner_label=models.F('author__username'))
            )
        elif user.groups.filter(name=settings.SUPER_LEXICOGRAPHS_GROUP_NAME).exists():
            notes |= (
                self.exclude(author=user)
                    .filter(super=True)
            )
            # notes |= (
            #     self.exclude(author=user).filter(author__groups__name=settings.SUPER_LEXICOGRAPHS_GROUP_NAME)
            #     .annotate(owner_label=models.Value(_('Super'), output_field=models.CharField()))
            # )

        return notes


class Note(models.Model):
    author = models.ForeignKey("auth.User", on_delete=models.PROTECT)
    subject_ct = models.ForeignKey(ContentType, on_delete=models.PROTECT)
    subject_id = models.PositiveIntegerField()
    subject = GenericForeignKey('subject_ct', 'subject_id')
    title = models.CharField(max_length=100)
    note = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    type = models.CharField(max_length=100, default=None, blank=True, null=True)
    super = models.BooleanField(default=False)

    objects = models.Manager.from_queryset(NoteQuerySet)()