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from django.db import models
from django.utils import timezone
from django_fsm import FSMField, transition
class State(object):
'''
Constants to represent the `state`s of the PublishableModel
'''
DRAFT = 'draft' # Early stages of content editing
APPROVED = 'approved' # Ready to be published
PUBLISHED = 'published' # Visible on the website
EXPIRED = 'expired' # Period for which the model is set to display has passed
DELETED = 'deleted' # Soft delete state
CHOICES = (
(DRAFT, DRAFT),
(APPROVED, APPROVED),
(PUBLISHED, PUBLISHED),
(EXPIRED, EXPIRED),
(DELETED, DELETED),
)
class PublishableModel(models.Model):
name = models.CharField(max_length=42, blank=False)
# One state to rule them all
state = FSMField(
default=State.DRAFT,
verbose_name='Publication State',
choices=State.CHOICES,
protected=True,
)
# For scheduled publishing
display_from = models.DateTimeField(blank=True, null=True)
display_until = models.DateTimeField(blank=True, null=True)
class Meta:
verbose_name = 'Post'
verbose_name_plural = 'Posts'
def __unicode__(self):
return self.name
########################################################
# Transition Conditions
# These must be defined prior to the actual transitions
# to be refrenced.
def has_display_dates(self):
return self.display_from and self.display_until
has_display_dates.hint = 'Display dates are required to expire a page.'
def can_display(self):
'''
The display dates must be valid for the current date
'''
return self.check_displayable(timezone.now())
can_display.hint = 'The display dates may need to be adjusted.'
def is_expired(self):
return self.state == State.EXPIRED
def check_displayable(self, date):
'''
Check that the current date falls within this object's display dates,
if set, otherwise default to being displayable.
'''
if not self.has_display_dates():
return True
displayable = self.display_from < date and self.display_until > date
# Expired Pages should transition to the expired state
if not displayable and not self.is_expired:
self.expire() # Calling the expire transition
self.save()
return displayable
########################################################
# Workflow (state) Transitions
@transition(field=state, source=[State.APPROVED, State.EXPIRED],
target=State.PUBLISHED,
conditions=[can_display])
def publish(self):
'''
Publish the object.
'''
@transition(field=state, source=State.PUBLISHED, target=State.EXPIRED,
conditions=[has_display_dates])
def expire(self):
'''
Automatically called when a object is detected as being not
displayable. See `check_displayable`
'''
self.display_until = timezone.now()
@transition(field=state, source=State.PUBLISHED, target=State.APPROVED)
def unpublish(self):
'''
Revert to the approved state
'''
@transition(field=state, source=State.DRAFT, target=State.APPROVED)
def approve(self):
'''
After reviewed by stakeholders, the Page is approved.
'''
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