"""
Base class for entities, objects that are managed by the Abilian framwework
(unlike SQLAlchemy models which are considered lower-level).
"""
from __future__ import absolute_import
import re
from inspect import isclass
from datetime import datetime
import sqlalchemy as sa
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.orm import mapper, Session
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.types import Integer, String, UnicodeText
from sqlalchemy import event
from .extensions import db
from .util import memoized, friendly_fqcn, slugify
from .models import BaseMixin
from .models.base import Indexable, SYSTEM, SEARCHABLE, EDITABLE
__all__ = ['Entity', 'all_entity_classes', 'db', 'ValidationError']
#
# Manual validation
#
[docs]class ValidationError(Exception):
pass
def validation_listener(mapper, connection, target):
if hasattr(target, "_validate"):
target._validate()
event.listen(mapper, 'before_insert', validation_listener)
event.listen(mapper, 'before_update', validation_listener)
#
# CRUD events. TODO: connect to signals instead?
#
def before_insert_listener(mapper, connection, target):
if hasattr(target, "_before_insert"):
target._before_insert()
def before_update_listener(mapper, connection, target):
if hasattr(target, "_before_update"):
target._before_update()
def before_delete_listener(mapper, connection, target):
if hasattr(target, "_before_delete"):
target._before_delete()
event.listen(mapper, 'before_insert', before_insert_listener)
event.listen(mapper, 'before_update', before_update_listener)
event.listen(mapper, 'before_delete', before_delete_listener)
def auto_slug_on_insert(mapper, connection, target):
"""
Generates a slug from :prop:`Entity.auto_slug` for new entities, unless slug
is already set.
"""
if target.slug is None and target.name:
target.slug = target.auto_slug
def auto_slug_after_insert(mapper, connection, target):
"""
Generates a slug from entity_type and id, unless slug is already set.
"""
if target.slug is None:
target.slug = u'{name}{sep}{id}'.format(name=target.entity_class.lower(),
sep=target.SLUG_SEPARATOR,
id=target.id)
class _EntityInherit(object):
"""
Mixin for Entity subclasses. Entity meta-class takes care of inserting it in
base classes.
"""
__indexable__ = True
@declared_attr
def id(cls):
return Column(
Integer,
ForeignKey('entity.id', use_alter=True, name='fk_inherited_entity_id'),
primary_key=True,
info=SYSTEM | SEARCHABLE)
@declared_attr
def __mapper_args__(cls):
return {'polymorphic_identity': cls.entity_type,
'inherit_condition': cls.id == Entity.id}
BaseMeta = db.Model.__class__
class EntityMeta(BaseMeta):
"""
Metaclass for Entities. It properly sets-up subclasses by adding
_EntityInherit to `__bases__`.
`_EntityInherit` provides `id` attibute and `__mapper_args__`
"""
def __new__(mcs, classname, bases, d):
if (d['__module__'] != EntityMeta.__module__ or classname != 'Entity'):
if not any(issubclass(b, _EntityInherit) for b in bases):
bases = (_EntityInherit,) + bases
d['id'] = _EntityInherit.id
if d.get('entity_type') is None:
entity_type_base = d.get('ENTITY_TYPE_BASE')
if not entity_type_base:
for base in bases:
entity_type_base = getattr(base, 'ENTITY_TYPE_BASE', None)
if entity_type_base:
break
else:
# no break happened during loop: use default type base
entity_type_base = d['__module__']
d['entity_type'] = entity_type_base + '.' + classname
d['SLUG_SEPARATOR'] = unicode(d.get('SLUG_SEPARATOR',
Entity.SLUG_SEPARATOR))
cls = BaseMeta.__new__(mcs, classname, bases, d)
event.listen(cls, 'before_insert', auto_slug_on_insert)
event.listen(cls, 'after_insert', auto_slug_after_insert)
return cls
def __init__(cls, classname, bases, d):
bases = cls.__bases__
BaseMeta.__init__(cls, classname, bases, d)
[docs]class Entity(Indexable, BaseMixin, db.Model):
"""
Base class for Abilian entities.
From Sqlalchemy POV Entities use `Joined-Table inheritance
<http://docs.sqlalchemy.org/en/rel_0_8/orm/inheritance.html#joined-table-inheritance>`_,
thus entities subclasses cannot use inheritance themselves (as of 2013
Sqlalchemy does not support multi-level inheritance)
The name is a string that is shown to the user; it could be a title
for document, a folder name, etc.
The slug attribute may be used in URLs to reference the entity, but
uniqueness is not enforced, even within same entity type. For example
if an entity class represent folders, one could want uniqueness only
within same parent folder.
If slug is empty at first creation, its is derived from the name. When name
changes the slug is not updated. If name is also empty, the slug will be the
friendly entity_type with concatenated with entity's id.
"""
__metaclass__ = EntityMeta
__mapper_args__ = {'polymorphic_on': '_entity_type'}
__indexable__ = False
__indexation_args__ = {}
__indexation_args__.update(Indexable.__indexation_args__)
index_to = __indexation_args__.setdefault('index_to', ())
index_to += BaseMixin.__indexation_args__.setdefault('index_to', ())
__indexation_args__['index_to'] = index_to
del index_to
SLUG_SEPARATOR = u'-' # \x2d \u002d HYPHEN-MINUS
name = Column('name', UnicodeText())
name.info = (EDITABLE | SEARCHABLE
| dict(index_to=('name', 'name_prefix', 'text')))
slug = Column('slug', UnicodeText(), info=SEARCHABLE)
_entity_type = Column('entity_type', String(1000), nullable=False)
entity_type = None
@property
def object_type(self):
return unicode(self.entity_type)
@classmethod
def _object_type(cls):
# overriden from Indexable
return cls.entity_type
@property
def entity_class(self):
return self.entity_type and friendly_fqcn(self.entity_type)
# Default magic metadata, should not be necessary
# TODO: remove
__editable__ = frozenset()
__searchable__ = frozenset()
__auditable__ = frozenset()
def __init__(self, *args, **kwargs):
db.Model.__init__(self, *args, **kwargs)
BaseMixin.__init__(self)
@property
def auto_slug(self):
"""
This property is used to auto-generate a slug from the name attribute.
It can be customized by subclasses.
"""
slug = self.name
if slug is not None:
slug = slugify(slug, separator=self.SLUG_SEPARATOR)
session = sa.orm.object_session(self)
if not session:
return None
q = session.query(Entity.slug)\
.filter(Entity._entity_type == self.object_type)
if self.id is not None:
q = q.filter(Entity.id != self.id)
slug_re = re.compile(re.escape(slug) + r'-?(-\d+)?')
results = [int(m.group(1) or 0) # 0: for the unnumbered slug
for m in (slug_re.match(s.slug) for s in q.all()
if s.slug)
if m]
max_id = max(-1, -1, *results) + 1
if max_id:
slug = u'{}-{}'.format(slug, max_id)
return slug
# TODO: make this unecessary
@event.listens_for(Entity, 'class_instrument', propagate=True)
def register_metadata(cls):
cls.__editable__ = set()
# TODO: use SQLAlchemy 0.8 introspection
if hasattr(cls, '__table__'):
columns = cls.__table__.columns
else:
columns = [v for k, v in vars(cls).items() if isinstance(v, Column)]
for column in columns:
name = column.name
info = column.info
if info.get("editable", True):
cls.__editable__.add(name)
@event.listens_for(Session, 'before_flush')
def polymorphic_update_timestamp(session, flush_context, instances):
"""
This listeners ensure an update statement is emited for "entity" table
to update 'updated_at'.
With joined-table inheritance if the only modified attributes are
subclass's ones, then no update statement will be emitted.
"""
for obj in session.dirty:
if not isinstance(obj, Entity):
continue
state = sa.inspect(obj)
history = state.get_history('updated_at', state.dict)
if not any((history.added, history.deleted)):
obj.updated_at = datetime.utcnow()
@memoized
[docs]def all_entity_classes():
"""
Returns the list of all concrete persistent classes that are subclasses of
Entity.
"""
persistent_classes = Entity._decl_class_registry.values()
# with sqlalchemy 0.8 _decl_class_registry holds object that are not classes
return [cls for cls in persistent_classes
if isclass(cls) and issubclass(cls, Entity)]
def register_all_entity_classes():
for cls in all_entity_classes():
register_metadata(cls)