#!/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 homepage memcaching functions.

"""

__authors__ = [

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

  ]

import logging

from google.appengine.api import memcache

from soc.logic import accounts

from soc.logic import system

import soc.cache.base

def key(entity):

  """Returns the memcache key for an entities homepage.

  """

  host = system.getHostname()

  version = system.getAppVersion()

  kind = entity.kind()

  key = entity.key().id_or_name()

  return 'homepage_for_%s_%s_%s_%s' % (host, version, kind, key)

def get(self, *args, **kwargs):

  """Retrieves the homepage for the specified entity from the memcache.

  """

  # only cache the page for non-logged-in users

  # TODO: figure out how to cache everything but the sidebar

  # also, no need to normalize as we don't use it anyway

  if accounts.getCurrentAccount(normalize=False):

    return (None, None)

  entity = self._logic.getFromKeyFields(kwargs)

  # if we can't retrieve the entity, leave it to the actual method

  if not entity:

    return (None, None)

  memcache_key = key(entity)

  logging.info("Retrieving %s" % memcache_key)

  # pylint: disable-msg=E1101

  return memcache.get(memcache_key), memcache_key

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

  """Sets the homepage for the specified entity in the memcache.

  Args:

    result: the homepage to be cached

  """

  # no sense in storing anything if we won't query it later on

  # also, no need to normalize as we don't use it anyway

  if accounts.getCurrentAccount(normalize=False):

    return

  # Store homepage for just ten minutes to force a refresh every so often

  retention = 10*60

  logging.info("Setting %s" % memcache_key)

  # pylint: disable-msg=E1101

  memcache.add(memcache_key, result, retention)

def flush(entity):

  """Removes the homepage for the current entity from the memcache.

  Also calls soc.cache.rights.flush for the specified user.

  Args:

    id: defaults to the current account if not set

  """

  memcache_key = key(entity)

  logging.info("Flushing %s" % memcache_key)

  # pylint: disable-msg=E1101

  memcache.delete(memcache_key)

# define the cache function

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