+
−#!/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_lazy
+
−
+
−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, model, 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.
+
−    """
+
−
+
−    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.
+
−    """
+
−    
+
−    pass
+
−  
+
−  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 _keyName(self, **kwargs):
+
−    """Returns the KeyName constructed from kwargs for this type of entity.
+
−
+
−    The KeyName is in the following format:
+
−    <key_value1>:<key_value2>:...:<key_valueN>
+
−    """
+
−
+
−    # get the KeyFieldNames for this entity
+
−    key_field_names = self.getKeyFieldNames()
+
−
+
−    # check if all given KeyFieldNames are valid for this entity
+
−    if not all(key in key_field_names for key in kwargs.keys()):
+
−      raise Error("Some of the provided arguments are not key fields")
+
−
+
−    # check if all key_field_names for this entity are present in kwargs
+
−    if not all(field in kwargs.keys() for field in key_field_names):
+
−      raise Error("Not all the required key fields are present")
+
−
+
−    # check if all kwargs.values() are non-false
+
−    if not all(kwargs.values()):
+
−      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(kwargs[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 getKeyValues(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.getKeyValues(entity)
+
−    suffix = '/'.join(key_values)
+
−
+
−    return suffix
+
−
+
−  def getKeyFieldsFromDict(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 getFromFields(self, **kwargs):
+
−    """Returns the entity for the specified key names, or None if not found.
+
−
+
−    Args:
+
−      **kwargs: the fields of the entity that uniquely identifies it
+
−    """
+
−
+
−    key_name = self.getKeyNameForFields(kwargs)
+
−
+
−    if key_name:
+
−      entity = self.getFromKeyName(key_name)
+
−    else:
+
−      entity = None
+
−
+
−    return entity
+
−
+
−  def getFromFieldsOr404(self, **fields):
+
−    """Like getFromFields but expects to find an entity.
+
−
+
−    Raises:
+
−      out_of_band.Error if no User entity is found
+
−    """
+
−
+
−    entity = self.getFromFields(**fields)
+
−
+
−    if entity:
+
−      return entity
+
−
+
−    format_text = ugettext_lazy('"%(key)s" is "%(value)s"')
+
−
+
−    msg_pairs = [format_text % {'key': key, 'value': value}
+
−      for key, value in fields.iteritems()]
+
−
+
−    joined_pairs = ' and '.join(msg_pairs)
+
−
+
−    msg = ugettext_lazy(
+
−      'There is no "%(name)s" where %(pairs)s.') % {
+
−        'name': self._name, 'pairs': joined_pairs}
+
−
+
−    raise out_of_band.Error(msg, status=404)
+
−
+
−  def getIfFields(self, fields):
+
−    """Like getFromFieldsOr404 but returns None if not all fields are set.
+
−
+
−    Raises:
+
−      out_of_band.Error if no User entity is found and all fields were set
+
−    """
+
−
+
−    if not all(fields.values()):
+
−      return None
+
−
+
−    return self.getFromFieldsOr404(**fields)
+
−
+
−  def getKeyNameForFields(self, fields):
+
−    """Return a Datastore key_name for a Entity from the specified fields.
+
−
+
−    Args:
+
−      fields: the fields of the entity that uniquely identifies it
+
−    """
+
−
+
−    if not all(fields.values()):
+
−      return None
+
−
+
−    return self._keyName(**fields)
+
−
+
−  def getForLimitAndOffset(self, limit, offset=0):
+
−    """Returns entities for given offset and limit or None if not found.
+
−
+
−    Args:
+
−      limit: max amount of entities to return
+
−      offset: optional number of results to skip first; default zero.
+
−    """
+
−
+
−    query = self._model.all()
+
−    return query.fetch(limit, offset)
+
−
+
−  def getForFields(self, filter, unique=False):
+
−    """Returns all entities that have the specified properties.
+
−
+
−    Args:
+
−      properties: the properties that the entity should have
+
−      unique: if set, only the first item from the resultset will be returned
+
−    """
+
−
+
−    if not filter:
+
−      raise Error("Properties did not contain any values")
+
−
+
−    queries = dicts.split(filter)
+
−
+
−    def toQuery(filter):
+
−      q = db.Query(self._model)
+
−      for key, value in filter.iteritems():
+
−        q.filter(key, value)
+
−      return q
+
−
+
−    result = itertools.chain(*[toQuery(x) for x in queries])
+
−
+
−    if unique:
+
−      # Return the first item, we need the loop as itertools.chain
+
−      # returns an iterable rather than a list
+
−      for item in result:
+
−        return item
+
−
+
−      # In the case result is empty, return None
+
−      return None
+
−
+
−    return result
+
−
+
−  def updateModelProperties(self, model, model_properties):
+
−    """Update existing model entity using supplied model properties.
+
−
+
−    Args:
+
−      model: a model entity
+
−      model_properties: keyword arguments that correspond to model entity
+
−        properties and their values
+
−
+
−    Returns:
+
−      The original model entity with any supplied properties changed.
+
−    """
+
−
+
−    def update():
+
−      return self._unsafeUpdateModelProperties(model, model_properties)
+
−
+
−    entity =  db.run_in_transaction(update)
+
−    
+
−    # call the _onUpdate method
+
−    self._onUpdate(entity)
+
−    
+
−    return entity
+
−  
+
−  def _silentUpdateModelProperties(self, model, model_properties):
+
−    """Update existing model entity without calling _onUpdate.
+
−    
+
−    Args:
+
−      model: a model entity
+
−      model_properties: keyword arguments that correspond to model entity
+
−        properties and their values
+
−
+
−    Returns:
+
−      The original model entity with any supplied properties changed.
+
−    """
+
−    
+
−    def update():
+
−      return self._unsafeUpdateModelProperties(model, model_properties)
+
−
+
−    return db.run_in_transaction(update)
+
−
+
−  def _unsafeUpdateModelProperties(self, model, model_properties):
+
−    """See updateModelProperties.
+
−
+
−    Like updateModelProperties(), but not run within a transaction.
+
−    """
+
−
+
−    properties = model.properties()
+
−
+
−    for prop in properties.values():
+
−      name = prop.name
+
−
+
−      if not name in self._skip_properties and name in model_properties:
+
−        value = model_properties[prop.name]
+
−
+
−        if self._updateField(model, name, value):
+
−          prop.__set__(model, value)
+
−
+
−    model.put()
+
−    return model
+
−
+
−  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._silentUpdateModelProperties(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.getKeyNameForFields(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)