netbox/netbox/extras/models/change_logging.py

from django.contrib.auth.models import User
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.contrib.postgres.fields import JSONField
from django.db import models
from django.urls import reverse

from utilities.querysets import RestrictedQuerySet
from utilities.utils import serialize_object
from extras.choices import *


#
# Change logging
#

class ChangeLoggedModel(models.Model):
    """
    An abstract model which adds fields to store the creation and last-updated times for an object. Both fields can be
    null to facilitate adding these fields to existing instances via a database migration.
    """
    created = models.DateField(
        auto_now_add=True,
        blank=True,
        null=True
    )
    last_updated = models.DateTimeField(
        auto_now=True,
        blank=True,
        null=True
    )

    class Meta:
        abstract = True

    def to_objectchange(self, action):
        """
        Return a new ObjectChange representing a change made to this object. This will typically be called automatically
        by extras.middleware.ChangeLoggingMiddleware.
        """
        return ObjectChange(
            changed_object=self,
            object_repr=str(self),
            action=action,
            object_data=serialize_object(self)
        )


class ObjectChange(models.Model):
    """
    Record a change to an object and the user account associated with that change. A change record may optionally
    indicate an object related to the one being changed. For example, a change to an interface may also indicate the
    parent device. This will ensure changes made to component models appear in the parent model's changelog.
    """
    time = models.DateTimeField(
        auto_now_add=True,
        editable=False,
        db_index=True
    )
    user = models.ForeignKey(
        to=User,
        on_delete=models.SET_NULL,
        related_name='changes',
        blank=True,
        null=True
    )
    user_name = models.CharField(
        max_length=150,
        editable=False
    )
    request_id = models.UUIDField(
        editable=False
    )
    action = models.CharField(
        max_length=50,
        choices=ObjectChangeActionChoices
    )
    changed_object_type = models.ForeignKey(
        to=ContentType,
        on_delete=models.PROTECT,
        related_name='+'
    )
    changed_object_id = models.PositiveIntegerField()
    changed_object = GenericForeignKey(
        ct_field='changed_object_type',
        fk_field='changed_object_id'
    )
    related_object_type = models.ForeignKey(
        to=ContentType,
        on_delete=models.PROTECT,
        related_name='+',
        blank=True,
        null=True
    )
    related_object_id = models.PositiveIntegerField(
        blank=True,
        null=True
    )
    related_object = GenericForeignKey(
        ct_field='related_object_type',
        fk_field='related_object_id'
    )
    object_repr = models.CharField(
        max_length=200,
        editable=False
    )
    object_data = JSONField(
        editable=False
    )

    objects = RestrictedQuerySet.as_manager()

    csv_headers = [
        'time', 'user', 'user_name', 'request_id', 'action', 'changed_object_type', 'changed_object_id',
        'related_object_type', 'related_object_id', 'object_repr', 'object_data',
    ]

    class Meta:
        ordering = ['-time']

    def __str__(self):
        return '{} {} {} by {}'.format(
            self.changed_object_type,
            self.object_repr,
            self.get_action_display().lower(),
            self.user_name
        )

    def save(self, *args, **kwargs):

        # Record the user's name and the object's representation as static strings
        if not self.user_name:
            self.user_name = self.user.username
        if not self.object_repr:
            self.object_repr = str(self.changed_object)

        return super().save(*args, **kwargs)

    def get_absolute_url(self):
        return reverse('extras:objectchange', args=[self.pk])

    def to_csv(self):
        return (
            self.time,
            self.user,
            self.user_name,
            self.request_id,
            self.get_action_display(),
            self.changed_object_type,
            self.changed_object_id,
            self.related_object_type,
            self.related_object_id,
            self.object_repr,
            self.object_data,
        )