#!/usr/bin/python2.5

#

# Copyright 2009 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.

"""Module contains logic memcaching functions.

"""

__authors__ = [

    '"Sverre Rabbelier" <sverre@rabbelier.nl>',

  ]

from google.appengine.api import memcache

from google.appengine.ext import db

import soc.cache.base

def key(model, filter, order):

  """Returns the memcache key for this query.

  """

  new_filter = {}

  for filter_key, value in filter.iteritems():

    new_value = value.key().name() if isinstance(value, db.Model) else value

    new_filter[filter_key] = new_value

  return 'query_for_%(kind)s_%(filter)s_%(order)s' % {

      'kind': repr(model.kind()),

      'filter': repr(new_filter),

      'order': repr(order),

      }

def get(model, filter, order, *args, **kwargs):

  """Retrieves the data for the specified query from the memcache.

  """

  memcache_key = key(model, filter, order)

  return memcache.get(memcache_key), memcache_key

def put(data, memcache_key, *args, **kwargs):

  """Sets the data for the specified query in the memcache.

  Args:

    data: the data to be cached

  """

  # Store data for fifteen minutes to force a refresh every so often

  retention = 15*60

  memcache.add(memcache_key, data, retention)

def flush(model, filter):

  """Removes the data for the current user from the memcache.

  """

  memcache_key = key(model, filter)

  memcache.delete(memcache_key)

# define the cache function

cache = soc.cache.base.getCacher(get, put)