#!/usr/bin/python2.5
#
# Copyright 2008 the Melange authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Helpers functions for updating different kinds of models in datastore.
"""
__authors__ = [
'"Todd Larsen" <tlarsen@google.com>',
'"Sverre Rabbelier" <sverre@rabbelier.nl>',
'"Lennard de Rijk" <ljvderijk@gmail.com>',
'"Pawel Solyga" <pawel.solyga@gmail.com>',
]
import itertools
from google.appengine.ext import db
from django.utils.translation import ugettext
from soc.cache import sidebar
from soc.logic import dicts
from soc.views import out_of_band
class Error(Exception):
"""Base class for all exceptions raised by this module.
"""
pass
class Logic(object):
"""Base logic for entity classes.
The BaseLogic class functions specific to Entity classes by relying
on arguments passed to __init__.
"""
def __init__(self, model, base_model=None, scope_logic=None,
name=None, skip_properties=None):
"""Defines the name, key_name and model for this entity.
"""
self._model = model
self._base_model = base_model
self._scope_logic = scope_logic
if name:
self._name = name
else:
self._name = self._model.__name__
if skip_properties:
self._skip_properties = skip_properties
else:
self._skip_properties = []
def getModel(self):
"""Returns the model this logic class uses.
"""
return self._model
def getScopeLogic(self):
"""Returns the logic of the enclosing scope.
"""
return self._scope_logic
def getScopeDepth(self):
"""Returns the scope depth for this entity.
Returns None if any of the parent scopes return None.
"""
if not self._scope_logic:
return 0
depth = self._scope_logic.logic.getScopeDepth()
return None if (depth is None) else (depth + 1)
def _updateField(self, entity, name, value):
"""Hook called when a field is updated.
Base classes should override if any special actions need to be
taken when a field is updated. The field is not updated if the
method does not return a True value.
Args:
entity: the unaltered entity
name: the name of the field to be changed
value: the new value
"""
return True
def _onCreate(self, entity):
"""Called when an entity has been created.
Classes that override this can use it to do any post-creation operations.
"""
sidebar.flush()
def _onUpdate(self, entity):
"""Called when an entity has been updated.
Classes that override this can use it to do any post-update operations.
"""
pass
def _onDelete(self, entity):
"""Called when an entity has been deleted.
Classes that override this can use it to do any post-deletion operations.
"""
pass
def getKeyNameFromFields(self, fields):
"""Returns the KeyName constructed from fields dict for this type of entity.
The KeyName is in the following format:
<key_value1>/<key_value2>/.../<key_valueN>
"""
key_field_names = self.getKeyFieldNames()
# check if all key_field_names for this entity are present in fields
if not all(field in fields.keys() for field in key_field_names):
raise Error("Not all the required key fields are present")
if not all(fields.get(field) for field in key_field_names):
raise Error("Not all KeyValues are non-false")
# construct the KeyValues in the order given by getKeyFieldNames()
keyvalues = []
for key_field_name in key_field_names:
keyvalues.append(fields[key_field_name])
# construct the KeyName in the appropriate format
return '/'.join(keyvalues)
def getFullModelClassName(self):
"""Returns fully-qualified model module.class name string.
"""
return '%s.%s' % (self._model.__module__, self._model.__name__)
def getKeyValuesFromEntity(self, entity):
"""Extracts the key values from entity and returns them.
The default implementation uses the scope and link_id as key values.
Args:
entity: the entity from which to extract the key values
"""
return [entity.scope_path, entity.link_id]
def getKeyValuesFromFields(self, fields):
"""Extracts the key values from a dict and returns them.
The default implementation uses the scope and link_id as key values.
Args:
fields: the dict from which to extract the key values
"""
return [fields['scope_path'], fields['link_id']]
def getKeyFieldNames(self):
"""Returns an array with the names of the Key Fields.
The default implementation uses the scope and link_id as key values.
"""
return ['scope_path', 'link_id']
def getKeySuffix(self, entity):
"""Returns a suffix for the specified entity or None if no entity specified.
Args:
entity: the entity for which to get the suffix
"""
if not entity:
return None
key_values = self.getKeyValuesFromEntity(entity)
suffix = '/'.join(key_values)
return suffix
def getKeyFieldsFromFields(self, dictionary):
"""Does any required massaging and filtering of dictionary.
The resulting dictionary contains just the key names, and has any
required translations/modifications performed.
Args:
dictionary: The arguments to massage
"""
keys = self.getKeyFieldNames()
values = self.getKeyValuesFromFields(dictionary)
key_fields = dicts.zip(keys, values)
return key_fields
def getFromKeyName(self, key_name):
""""Returns entity for key_name or None if not found.
Args:
key_name: key name of entity
"""
return self._model.get_by_key_name(key_name)
def getFromKeyFields(self, fields):
"""Returns the entity for the specified key names, or None if not found.
Args:
fields: a dict containing the fields of the entity that
uniquely identifies it
"""
key_fields = self.getKeyFieldsFromFields(fields)
if all(key_fields.values()):
key_name = self.getKeyNameFromFields(key_fields)
entity = self.getFromKeyName(key_name)
else:
entity = None
return entity
def getFromKeyFieldsOr404(self, fields):
"""Like getFromKeyFields but expects to find an entity.
Raises:
out_of_band.Error if no entity is found
"""
key_fields = self.getKeyFieldsFromFields(fields)
entity = self.getFromKeyFields(key_fields)
if entity:
return entity
format_text = ugettext('"%(key)s" is "%(value)s"')
msg_pairs = [format_text % {'key': key, 'value': value}
for key, value in key_fields.iteritems()]
joined_pairs = ' and '.join(msg_pairs)
msg = ugettext(
'There is no "%(name)s" where %(pairs)s.') % {
'name': self._name, 'pairs': joined_pairs}
raise out_of_band.Error(msg, status=404)
def getForFields(self, filter=None, unique=False, limit=1000, offset=0):
"""Returns all entities that have the specified properties.
Args:
filter: a dict for the properties that the entities should have
unique: if set, only the first item from the resultset will be returned
limit: the amount of entities to fetch at most
offset: the position to start at
"""
if unique:
limit = 1
if filter:
format_eq = '%(key)s = :%(num)d'
format_in = '%(key)s IN (%(values)s)'
n = 1
conditionals = []
args = []
for key, value in filter.iteritems():
if isinstance(value, list):
count = len(value)
args.extend(value)
values = ', '.join([':%d' % i for i in range(n, n + count)])
sub = format_in % {'key': key, 'values': values}
n = n + count
else:
sub = format_eq % {'key': key, 'num': n}
args.append(value)
n = n + 1
conditionals.append(sub)
joined_pairs = ' AND '.join(conditionals)
condition = 'WHERE ' + joined_pairs
q = self._model.gql(condition, *args)
else:
q = self._model.all()
result = q.fetch(limit, offset)
if unique:
return result[0] if result else None
return result
def updateEntityProperties(self, entity, entity_properties):
"""Update existing entity using supplied properties.
Args:
model: a model entity
model_properties: keyword arguments that correspond to entity
properties and their values
Returns:
The original entity with any supplied properties changed.
"""
def update():
return self._unsafeUpdateEntityProperties(entity, entity_properties)
entity = db.run_in_transaction(update)
# call the _onUpdate method
self._onUpdate(entity)
return entity
def _silentUpdateEntityProperties(self, entity, entity_properties):
"""See _unsafeUpdateEntityProperties.
Does not call _onUpdate.
"""
def update():
return self._unsafeUpdateEntityProperties(entity, entity_properties)
return db.run_in_transaction(update)
def _unsafeUpdateEntityProperties(self, entity, entity_properties):
"""See updateEntityProperties.
Like updateEntityProperties(), but not run within a transaction.
"""
properties = entity.properties()
for prop in properties.values():
name = prop.name
if not name in self._skip_properties and name in entity_properties:
value = entity_properties[prop.name]
if self._updateField(entity, name, value):
prop.__set__(entity, value)
entity.put()
return entity
def updateOrCreateFromKeyName(self, properties, key_name):
"""Update existing entity, or create new one with supplied properties.
Args:
properties: dict with entity properties and their values
key_name: the key_name of the entity that uniquely identifies it
Returns:
the entity corresponding to the key_name, with any supplied
properties changed, or a new entity now associated with the
supplied key_name and properties.
"""
entity = self.getFromKeyName(key_name)
create_entity = not entity
if create_entity:
# entity did not exist, so create one in a transaction
entity = self._model.get_or_insert(key_name, **properties)
# there is no way to be sure if get_or_insert() returned a new entity or
# got an existing one due to a race, so update with properties anyway,
# in a transaction
entity = self._silentUpdateEntityProperties(entity, properties)
if create_entity:
# a new entity has been created call _onCreate
self._onCreate(entity)
else:
# the entity has been updated call _onUpdate
self._onUpdate(entity)
return entity
def updateOrCreateFromFields(self, properties, fields):
"""Like updateOrCreateFromKeyName, but resolves fields to a key_name first.
"""
# attempt to retrieve the existing entity
key_name = self.getKeyNameFromFields(fields)
return self.updateOrCreateFromKeyName(properties, key_name)
def isDeletable(self, entity):
"""Returns whether the specified entity can be deleted.
Args:
entity: an existing entity in datastore
"""
return True
def delete(self, entity):
"""Delete existing entity from datastore.
Args:
entity: an existing entity in datastore
"""
entity.delete()
# entity has been deleted call _onDelete
self._onDelete(entity)