# -*- coding: utf-8 -*-
##############################################################################
#
# Copyright (c) 2009 Nexedi SA and Contributors. All Rights Reserved.
#                     Nicolas Delaby <nicolas@nexedi.com>
#
# WARNING: This program as such is intended to be used by professional
# programmers who take the whole responsability of assessing all potential
# consequences resulting from its eventual inadequacies and bugs
# End users who are looking for a ready-to-use solution with commercial
# garantees and support are strongly adviced to contract a Free Software
# Service Company
#
# This program is Free Software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#
##############################################################################

"""
ZODB Based cache plugin.
"""
import time
from BaseCache import BaseCache, CacheEntry
from BTrees.OOBTree import OOBTree
from Products.ERP5Type import Interface
import zope.interface

PRIVATE_ATTRIBUTE_ZODB_CACHE_NAME = '_zodb_cache'

class ZODBCache(BaseCache):
  """ ZODB based cache plugin."""

  zope.interface.implements(
        Interface.ICachePlugin
    )

  cache_tool = None
  cache_expire_check_interval = 300

  def __init__(self, params={}):
    BaseCache.__init__(self)
    self.cache_tool = params.get('cache_tool')

  def initCacheStorage(self):
    """Init cache storage
    Btree is enough for less than 1 Million entries.
    For higher scalability, wee need to implement cache with hierarchical Btree
    with clever key generator
    """
    if getattr(self.cache_tool, PRIVATE_ATTRIBUTE_ZODB_CACHE_NAME, None) is None:
      self.cache_tool._zodb_cache = OOBTree()

  def getCacheStorage(self, **kw):
    return getattr(self.cache_tool, PRIVATE_ATTRIBUTE_ZODB_CACHE_NAME)

  def get(self, cache_id, scope, default=None):
    cache = self.getCacheStorage()
    try:
      cache_entry = cache[(scope, cache_id)]
      # Note: tracking down cache hit could be achieved by uncommenting
      # methods below. In production environment this is likely uneeded
      #cache_entry.markCacheHit()
      #self.markCacheHit()
      return cache_entry
    except KeyError:
      pass
    return default

  def set(self, cache_id, scope, value, cache_duration=None, calculation_time=0):
    cache = self.getCacheStorage()
    cache[(scope, cache_id)] = CacheEntry(value, cache_duration, calculation_time)
    #self.markCacheMiss()

  def expireOldCacheEntries(self, forceCheck = False):
    now = time.time()
    if forceCheck or (now > self._next_cache_expire_check_at):
      ## time to check for expired cache items
      self._next_cache_expire_check_at = now + self.cache_expire_check_interval
      cache = self.getCacheStorage()
      for key, value in cache.items():
        if value.isExpired():
          try:
            del cache[key]
          except KeyError:
            # The key might have disappeared, due to multi-threading.
            pass

  def delete(self, cache_id, scope):
    try:
      del self.getCacheStorage()[(scope, cache_id)]
    except KeyError:
      pass

  def has_key(self, cache_id, scope):
    cache = self.getCacheStorage()
    return cache.has_key((scope, cache_id))

  def getScopeList(self):
    scope_set = set()
    for scope, cache_id in self.getCacheStorage().iterkeys():
      scope_set.add(scope)
    return list(scope_set)

  def getScopeKeyList(self, scope):
    key_list = []
    for key in self.getCacheStorage().iterkeys():
      if scope == key[0]:
        key_list.append(key[1])
    return key_list

  def clearCache(self):
    BaseCache.clearCache(self)
    self.getCacheStorage().clear()

  def clearCacheForScope(self, scope):
    cache = self.getCacheStorage()
    for key in cache.keys():
      if key[0] == scope:
        try:
          del cache[key]
        except KeyError:
          # The key might have disappeared, due to multi-threading.
          pass

  def getCachePluginTotalMemorySize(self):
    """Not Implemented"""
    return 0
