content: from django.contrib.contenttypes.fields import GenericForeignKey
  from django.core.exceptions import ValidationError
  from django.db import models
  from django.urls import reverse
  from django.utils.translation import gettext_lazy as _
  
  from netbox.models import ChangeLoggedModel, NestedGroupModel, OrganizationalModel, PrimaryModel
  from netbox.models.features import CustomFieldsMixin, ExportTemplatesMixin, TagsMixin, has_feature
  from tenancy.choices import *
  
  __all__ = (
      'ContactAssignment',
      'Contact',
      'ContactGroup',
      'ContactRole',
  )
  
  
  class ContactGroup(NestedGroupModel):
      """
      An arbitrary collection of Contacts.
      """
      class Meta:
          ordering = ['name']
          constraints = (
              models.UniqueConstraint(
                  fields=('parent', 'name'),
                  name='%(app_label)s_%(class)s_unique_parent_name'
              ),
          )
          verbose_name = _('contact group')
          verbose_name_plural = _('contact groups')
  
  
  class ContactRole(OrganizationalModel):
      """
      Functional role for a Contact assigned to an object.
      """
      class Meta:
          ordering = ('name',)
          verbose_name = _('contact role')
          verbose_name_plural = _('contact roles')
  
  
  class Contact(PrimaryModel):
      """
      Contact information for a particular object(s) in NetBox.
      """
      groups = models.ManyToManyField(
          to='tenancy.ContactGroup',
          related_name='contacts',
          related_query_name='contact',
          blank=True
      )
      name = models.CharField(
          verbose_name=_('name'),
          max_length=100,
          db_collation="natural_sort"
      )
      title = models.CharField(
          verbose_name=_('title'),
          max_length=100,
          blank=True
      )
      phone = models.CharField(
          verbose_name=_('phone'),
          max_length=50,
          blank=True
      )
      email = models.EmailField(
          verbose_name=_('email'),
          blank=True
      )
      address = models.CharField(
          verbose_name=_('address'),
          max_length=200,
          blank=True
      )
      link = models.URLField(
          verbose_name=_('link'),
          blank=True
      )
  
      clone_fields = (
          'groups', 'name', 'title', 'phone', 'email', 'address', 'link',
      )
  
      class Meta:
          ordering = ['name']
          verbose_name = _('contact')
          verbose_name_plural = _('contacts')
  
      def __str__(self):
          return self.name
  
  
  class ContactAssignment(CustomFieldsMixin, ExportTemplatesMixin, TagsMixin, ChangeLoggedModel):
      object_type = models.ForeignKey(
          to='contenttypes.ContentType',
          on_delete=models.CASCADE
      )
      object_id = models.PositiveBigIntegerField()
      object = GenericForeignKey(
          ct_field='object_type',
          fk_field='object_id'
      )
      contact = models.ForeignKey(
          to='tenancy.Contact',
          on_delete=models.PROTECT,
          related_name='assignments'
      )
      role = models.ForeignKey(
          to='tenancy.ContactRole',
          on_delete=models.PROTECT,
          related_name='assignments'
      )
      priority = models.CharField(
          verbose_name=_('priority'),
          max_length=50,
          choices=ContactPriorityChoices,
          blank=True,
          null=True
      )
  
      clone_fields = ('object_type', 'object_id', 'role', 'priority')
  
      class Meta:
          ordering = ('contact', 'priority', 'role', 'pk')
          indexes = (
              models.Index(fields=('object_type', 'object_id')),
          )
          constraints = (
              models.UniqueConstraint(
                  fields=('object_type', 'object_id', 'contact', 'role'),
                  name='%(app_label)s_%(class)s_unique_object_contact_role'
              ),
          )
          verbose_name = _('contact assignment')
          verbose_name_plural = _('contact assignments')
  
      def __str__(self):
          if self.priority:
              return f"{self.contact} ({self.get_priority_display()}) -> {self.object}"
          return str(f"{self.contact} -> {self.object}")
  
      def get_absolute_url(self):
          return reverse('tenancy:contact', args=[self.contact.pk])
  
      def clean(self):
          super().clean()
  
          # Validate the assigned object type
          if not has_feature(self.object_type, 'contacts'):
              raise ValidationError(
                  _("Contacts cannot be assigned to this object type ({type}).").format(type=self.object_type)
              )
  
      def to_objectchange(self, action):
          objectchange = super().to_objectchange(action)
          objectchange.related_object = self.object
          return objectchange
  