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from django.core.exceptions import ImproperlyConfigured
from django.db import models, router, transaction
from django.db.models.functions import Now
from django.db.models.signals import post_save, pre_save
from django.utils.translation import gettext_lazy as _
from model_utils.fields import (
AutoCreatedField,
AutoLastModifiedField,
MonitorField,
StatusField,
UUIDField,
)
from model_utils.managers import QueryManager, SoftDeletableManager
now = Now()
class TimeStampedModel(models.Model):
"""
An abstract base class model that provides self-updating
``created`` and ``modified`` fields.
"""
created = AutoCreatedField(_('created'))
modified = AutoLastModifiedField(_('modified'))
def save(self, *args, **kwargs):
"""
Overriding the save method in order to make sure that
modified field is updated even if it is not given as
a parameter to the update field argument.
"""
update_fields = kwargs.get('update_fields', None)
if update_fields:
kwargs['update_fields'] = set(update_fields).union({'modified'})
super().save(*args, **kwargs)
class Meta:
abstract = True
class TimeFramedModel(models.Model):
"""
An abstract base class model that provides ``start``
and ``end`` fields to record a timeframe.
"""
start = models.DateTimeField(_('start'), null=True, blank=True)
end = models.DateTimeField(_('end'), null=True, blank=True)
class Meta:
abstract = True
class StatusModel(models.Model):
"""
An abstract base class model with a ``status`` field that
automatically uses a ``STATUS`` class attribute of choices, a
``status_changed`` date-time field that records when ``status``
was last modified, and an automatically-added manager for each
status that returns objects with that status only.
"""
status = StatusField(_('status'))
status_changed = MonitorField(_('status changed'), monitor='status')
def save(self, *args, **kwargs):
"""
Overriding the save method in order to make sure that
status_changed field is updated even if it is not given as
a parameter to the update field argument.
"""
update_fields = kwargs.get('update_fields', None)
if update_fields and 'status' in update_fields:
kwargs['update_fields'] = set(update_fields).union({'status_changed'})
super().save(*args, **kwargs)
class Meta:
abstract = True
def add_status_query_managers(sender, **kwargs):
"""
Add a Querymanager for each status item dynamically.
"""
if not issubclass(sender, StatusModel):
return
default_manager = sender._meta.default_manager
for value, display in getattr(sender, 'STATUS', ()):
if _field_exists(sender, value):
raise ImproperlyConfigured(
"StatusModel: Model '%s' has a field named '%s' which "
"conflicts with a status of the same name."
% (sender.__name__, value)
)
sender.add_to_class(value, QueryManager(status=value))
sender._meta.default_manager_name = default_manager.name
def add_timeframed_query_manager(sender, **kwargs):
"""
Add a QueryManager for a specific timeframe.
"""
if not issubclass(sender, TimeFramedModel):
return
if _field_exists(sender, 'timeframed'):
raise ImproperlyConfigured(
"Model '%s' has a field named 'timeframed' "
"which conflicts with the TimeFramedModel manager."
% sender.__name__
)
sender.add_to_class('timeframed', QueryManager(
(models.Q(start__lte=now) | models.Q(start__isnull=True))
& (models.Q(end__gte=now) | models.Q(end__isnull=True))
))
models.signals.class_prepared.connect(add_status_query_managers)
models.signals.class_prepared.connect(add_timeframed_query_manager)
def _field_exists(model_class, field_name):
return field_name in [f.attname for f in model_class._meta.local_fields]
class SoftDeletableModel(models.Model):
"""
An abstract base class model with a ``is_removed`` field that
marks entries that are not going to be used anymore, but are
kept in db for any reason.
Default manager returns only not-removed entries.
"""
is_removed = models.BooleanField(default=False)
class Meta:
abstract = True
objects = SoftDeletableManager(_emit_deprecation_warnings=True)
available_objects = SoftDeletableManager()
all_objects = models.Manager()
def delete(self, using=None, soft=True, *args, **kwargs):
"""
Soft delete object (set its ``is_removed`` field to True).
Actually delete object if setting ``soft`` to False.
"""
if soft:
self.is_removed = True
self.save(using=using)
else:
return super().delete(using=using, *args, **kwargs)
class UUIDModel(models.Model):
"""
This abstract base class provides id field on any model that inherits from it
which will be the primary key.
"""
id = UUIDField(
primary_key=True,
version=4,
editable=False,
)
class Meta:
abstract = True
class SaveSignalHandlingModel(models.Model):
"""
An abstract base class model to pass a parameter ``signals_to_disable``
to ``save`` method in order to disable signals
"""
class Meta:
abstract = True
def save(self, signals_to_disable=None, *args, **kwargs):
"""
Add an extra parameters to hold which signals to disable
If empty, nothing will change
"""
self.signals_to_disable = signals_to_disable or []
super().save(*args, **kwargs)
def save_base(self, raw=False, force_insert=False,
force_update=False, using=None, update_fields=None):
"""
Copied from base class for a minor change.
This is an ugly overwriting but since Django's ``save_base`` method
does not differ between versions 1.8 and 1.10,
that way of implementing wouldn't harm the flow
"""
using = using or router.db_for_write(self.__class__, instance=self)
assert not (force_insert and (force_update or update_fields))
assert update_fields is None or len(update_fields) > 0
cls = origin = self.__class__
if cls._meta.proxy:
cls = cls._meta.concrete_model
meta = cls._meta
if not meta.auto_created and 'pre_save' not in self.signals_to_disable:
pre_save.send(
sender=origin, instance=self, raw=raw, using=using,
update_fields=update_fields,
)
with transaction.atomic(using=using, savepoint=False):
if not raw:
self._save_parents(cls, using, update_fields)
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
self._state.db = using
self._state.adding = False
if not meta.auto_created and 'post_save' not in self.signals_to_disable:
post_save.send(
sender=origin, instance=self, created=(not updated),
update_fields=update_fields, raw=raw, using=using,
)
# Empty the signals in case it might be used somewhere else in future
self.signals_to_disable = []
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