# coding=utf-8
from django.conf import settings
from django.db.models import signals, NOT_PROVIDED
from django.db.models.expressions import CombinedExpression
try:
from django.db.models.fields.related_descriptors import ForwardManyToOneDescriptor, ReverseOneToOneDescriptor
except ImportError:
pass
from django.dispatch import receiver
from django.utils.encoding import force_text
from .signals import audit_trail_app_ready
from .stringifier import ModelFieldStringifier
class AuditTrailWatcher(object):
"""
Watcher class that tracks post_save and post_delete signals and generates AuditTrail records.
Attributs:
tracked_models (set): set of already tracked models. Used to avoid duplicate signals handlers.
"""
tracked_models = set()
def __init__(self, fields=None, track_related=None, notify_related=None,
track_only_with_related=False, excluded_fields=None):
"""
Constructor
:param fields: list fields that should be tracked. If None — all fields will be tracked.
:param track_related: list of tracked relations. F.e. ['comment_set']
:param notify_related: list of fields to be notified as parent. Internal use only
:param track_only_with_related: boolean state should be AuditTrail object created or not if there is no parent
object. F.e. if we track Post's comment_set and we don't need to track comments separately.
:return:
"""
self.model_class = None
self.fields = fields
self.notify_related = notify_related
self.track_related = track_related
self.track_only_with_related = track_only_with_related
self.excluded_fields = ['id']
if excluded_fields:
self.excluded_fields += excluded_fields
def contribute_to_class(self, cls, name=None):
if cls in self.__class__.tracked_models:
return False
self.model_class = cls
self.__class__.tracked_models.add(cls)
setattr(cls, 'audit', self)
return True
def init_signals(self):
signals.post_save.connect(self.on_post_save_create, sender=self.model_class, weak=False)
signals.post_init.connect(self.on_post_init, sender=self.model_class, weak=False)
signals.post_save.connect(self.on_post_save_update, sender=self.model_class, weak=False)
signals.pre_delete.connect(self.on_pre_delete, sender=self.model_class, weak=False)
signals.post_delete.connect(self.on_post_delete, sender=self.model_class, weak=False)
self.init_related_signals()
def init_related_signals(self):
if not self.track_related:
return
for attr_name in self.track_related:
attribute = getattr(self.model_class, attr_name)
from django import VERSION
related_model = None
if VERSION > (1, 9):
if hasattr(attribute, 'related_manager_cls'): # related object is queryset
related_model = attribute.field.model
related_field_name = attribute.field.name
else: # related object is FK
if isinstance(attribute, ReverseOneToOneDescriptor):
related_model = attribute.related.related_model
related_field_name = attribute.related.name
elif isinstance(attribute, ForwardManyToOneDescriptor):
related_model = attribute.field.related_model
related_field_name = attribute.field.related_query_name()
# related_query_name() returns related_name if it was set
# but if it's not returns autogenerated related name without '_set' postfix!
# F.e. instead of 'post_set' it'll return 'post' so we have to handle it manually
if not hasattr(related_model, related_field_name):
related_field_name += '_set'
else:
if hasattr(attribute, 'related'): # related object is queryset
related = attribute.related
related_model = related.related_model
related_field_name = related.field.name
else: # related object is FK
related_model = attribute.field.related_field.model
related_field_name = attribute.field.related_query_name()
# related_query_name() returns related_name if it was set
# but if it's not returns autogenerated related name without '_set' postfix!
# F.e. instead of 'post_set' it'll return 'post' so we have to handle it manually
if not hasattr(related_model, related_field_name):
related_field_name += '_set'
if not hasattr(related_model, 'audit'):
related_watcher = AuditTrailWatcher(track_only_with_related=True)
related_watcher.contribute_to_class(related_model)
related_watcher.init_signals()
related_model.audit.notify_related = related_model.audit.notify_related or []
related_model.audit.notify_related += [related_field_name]
def serialize_object(self, instance):
""" Returns stringified values for tracked fields. """
data = {}
for field in instance._meta.fields:
# Skip untracked fields
not_tracked_field = (self.fields is not None and field.name not in self.fields)
if not_tracked_field or field.name in self.excluded_fields:
continue
value = field.value_from_object(instance)
# http://stackoverflow.com/questions/33672920/django-db-models-f-combined-expression
if isinstance(value, CombinedExpression):
instance.refresh_from_db()
return self.serialize_object(instance)
data[field.name] = value
return data
def get_changes(self, old_values, new_values):
""" Returns list of changed fields. """
diff = {}
old_values = old_values or {}
new_values = new_values or {}
fields = self.fields or [field_name.name for field_name in self.model_class._meta.fields]
for field_name in fields:
field = self.model_class._meta.get_field(field_name)
default = None
if field.default != NOT_PROVIDED:
default = field.default
old_value = old_values.get(field_name, default)
new_value = new_values.get(field_name, None)
old_value_string = ModelFieldStringifier.stringify(field, old_value)
new_value_string = ModelFieldStringifier.stringify(field, new_value)
if old_value is not None:
old_value = force_text(old_value)
if new_value is not None:
new_value = force_text(new_value)
if old_value != new_value:
diff[field_name] = {
'old_value': old_value,
'old_value_string': old_value_string,
'new_value': new_value,
'new_value_string': new_value_string
}
return diff
def on_post_init(self, instance, sender, **kwargs):
"""Stores original field values."""
instance._original_values = self.serialize_object(instance)
def on_post_save_create(self, instance, sender, created, **kwargs):
"""Saves object's data."""
if getattr(settings, 'DISABLE_AUDIT_TRAIL', False):
return
if not created:
return
if self.track_only_with_related and not self.is_parent_object_exists(instance):
return
from .models import AuditTrail
audit_trail = AuditTrail.objects.generate_trail_for_instance_created(instance)
audit_trail.changes = self.get_changes({}, self.serialize_object(instance))
audit_trail.save()
instance._original_values = self.serialize_object(instance)
self.create_related_audit_trail(audit_trail)
def on_post_save_update(self, instance, sender, created, **kwargs):
""" Checks for difference and saves, if it's present. """
if getattr(settings, 'DISABLE_AUDIT_TRAIL', False):
return
if created:
return
if self.track_only_with_related and not self.is_parent_object_exists(instance):
return
changes = self.get_changes(getattr(instance, '_original_values', {}), self.serialize_object(instance))
if not changes:
return
from .models import AuditTrail
audit_trail = AuditTrail.objects.generate_trail_for_instance_updated(instance)
audit_trail.changes = changes
audit_trail.save()
instance._original_values = self.serialize_object(instance)
self.create_related_audit_trail(audit_trail)
def on_pre_delete(self, instance, sender, **kwargs):
""" Check if there related query_set that track current objects saves ids. """
if getattr(settings, 'DISABLE_AUDIT_TRAIL', False):
return
if not self.notify_related:
return
instance._audit_ids_to_notify_related_deletion = {}
for field_name in self.notify_related:
parent_object = getattr(instance, field_name, None)
if parent_object is None or hasattr(parent_object, '_meta'):
continue
if parent_object.all().exists():
ids = list(parent_object.all().values_list('id', flat=True))
instance._audit_ids_to_notify_related_deletion[field_name] = ids
def on_post_delete(self, instance, sender, **kwargs):
""" Saves deleted object data. """
if getattr(settings, 'DISABLE_AUDIT_TRAIL', False):
return
if self.track_only_with_related and not self.is_parent_object_exists(instance):
return
from .models import AuditTrail
audit_trail = AuditTrail.objects.generate_trail_for_instance_deleted(instance)
audit_trail.changes = self.get_changes(self.serialize_object(instance), {})
audit_trail.save()
self.create_deleted_related_audit_trail(audit_trail, instance)
def is_parent_object_exists(self, instance):
if not self.notify_related:
return
for field_name in self.notify_related:
parent_object = getattr(instance, field_name, None)
if parent_object is None:
continue
if hasattr(parent_object, '_meta'):
return True
else:
if parent_object.all().exists():
return True
if field_name in getattr(instance, '_audit_ids_to_notify_related_deletion', {}):
return True
return False
def create_related_audit_trail(self, audit_trail):
if not self.notify_related:
return
for field_name in self.notify_related:
changed_related_object = audit_trail.content_object
attribute = getattr(changed_related_object, field_name)
if attribute is None:
continue
if hasattr(attribute, '_meta'):
# Related object
notified_objects = [attribute]
else:
# RelatedManager doesn't have _meta attribute
notified_objects = attribute.all()
from .models import AuditTrail
for notified_object in notified_objects:
parent_audit_trail = AuditTrail.objects.generate_trail_for_related_change(notified_object)
parent_audit_trail.related_trail = audit_trail
parent_audit_trail.save()
def create_deleted_related_audit_trail(self, audit_trail, instance):
if not self.notify_related:
return
from .models import AuditTrail
for field_name in self.notify_related:
attribute = getattr(instance, field_name)
if attribute is None:
continue
if hasattr(attribute, '_meta'):
# Related object
notified_objects = [attribute]
else:
# RelatedManager doesn't have _meta attribute
ids = instance._audit_ids_to_notify_related_deletion.get(field_name)
if not ids:
continue
# now parent object is being filtered by instance id
# f.e.
# class Post(models.Model):
# class Post(models.Model):
# author = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
# audit = AuditTrailWatcher(track_related=['comment_set', 'author'])
# will be filtered as {'author__exact': instance}
# but since posts's author was set to null after author deletion we need to get posts by ids
# so we stored ids before author deletion on pre_delete
attribute.core_filters = {'id__in': ids}
notified_objects = list(attribute.all())
for notified_object in notified_objects:
parent_audit_trail = AuditTrail.objects.generate_trail_for_related_change(notified_object)
parent_audit_trail.related_trail = audit_trail
parent_audit_trail.save()
@receiver(audit_trail_app_ready)
def init_audit_instances(*args, **kwargs):
tracked_models = AuditTrailWatcher.tracked_models.copy()
for model_class in tracked_models:
model_class.audit.init_signals()
