text: # -*- coding: utf-8 -*-
  '''
  Loader mechanism for caching data, with data expirations, etc.
  
  .. versionadded:: carbon
  '''
  from __future__ import absolute_import
  import os
  import salt.loader
  import time
  from salt.payload import Serial
  
  
  class Cache(object):
      '''
      Base caching object providing access to the modular cache subsystem.
  
      Related configuration options:
  
      :param cache:
          The name of the cache driver to use. This is the name of the python
          module of the `salt.cache` package. Defult is `localfs`.
  
      :param serial:
          The module of `salt.serializers` package that should be used by the cache
          driver to store data.
          If a driver can't use a specific module or uses specific objects storage
          it can ignore this parameter.
  
      Terminology.
  
      Salt cache subsystem is organized as a tree with nodes and leafs like a
      filesystem. Cache consists of banks. Each bank can contain a number of
      keys. Each key can contain a dict or any other object serializable with
      `salt.payload.Serial`. I.e. any data object in the cache can be
      addressed by the path to the bank and the key name:
          bank: 'minions/alpha'
          key:  'data'
  
      Bank names should be formatted in a way that can be used as a
      directory structure. If slashes are included in the name, then they
      refer to a nested structure.
  
      Key name is a string identifier of a data container (like a file inside a
      directory) which will hold the data.
      '''
      def __init__(self, opts):
          self.opts = opts
          self.driver = opts['cache']
          self.serial = Serial(opts)
          self._modules = None
  
      @property
      def modules(self):
          if self._modules is None:
              self._modules = salt.loader.cache(self.opts, self.serial)
          return self._modules
  
      def cache(self, bank, key, fun, loop_fun=None, **kwargs):
          '''
          Check cache for the data. If it is there, check to see if it needs to
          be refreshed.
  
          If the data is not there, or it needs to be refreshed, then call the
          callback function (``fun``) with any given ``**kwargs``.
  
          In some cases, the callback function returns a list of objects which
          need to be processed by a second function. If that is the case, then
          the second function is passed in as ``loop_fun``. Each item in the
          return list from the first function will be the only argument for the
          second function.
          '''
          expire_seconds = kwargs.get('expire', 86400)  # 1 day
  
          updated = self.updated(bank, key)
          update_cache = False
          if updated is None:
              update_cache = True
          else:
              if int(time.time()) - updated > expire_seconds:
                  update_cache = True
  
          data = self.fetch(bank, key)
  
          if not data or update_cache is True:
              if loop_fun is not None:
                  data = []
                  items = fun(**kwargs)
                  for item in items:
                      data.append(loop_fun(item))
              else:
                  data = fun(**kwargs)
              self.store(bank, key, data)
  
          return data
  
      def store(self, bank, key, data):
          '''
          Store data using the specified module
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :param key:
              The name of the key (or file inside a directory) which will hold
              the data. File extensions should not be provided, as they will be
              added by the driver itself.
  
          :param data:
              The data which will be stored in the cache. This data should be
              in a format which can be serialized by msgpack/json/yaml/etc.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'store')
          return self.modules[fun](bank, key, data)
  
      def fetch(self, bank, key):
          '''
          Fetch data using the specified module
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :param key:
              The name of the key (or file inside a directory) which will hold
              the data. File extensions should not be provided, as they will be
              added by the driver itself.
  
          :return:
              Return a python object fetched from the cache or None if the given
              path or key not found.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'fetch')
          return self.modules[fun](bank, key)
  
      def updated(self, bank, key):
          '''
          Get the last updated epoch for the specified key
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :param key:
              The name of the key (or file inside a directory) which will hold
              the data. File extensions should not be provided, as they will be
              added by the driver itself.
  
          :return:
              Return an int epoch time in seconds or None if the object wasn't
              found in cache.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'updated')
          return self.modules[fun](bank, key)
  
      def flush(self, bank, key=None):
          '''
          Remove the key from the cache bank with all the key content. If no key is specified remove
          the entire bank with all keys and sub-banks inside.
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :param key:
              The name of the key (or file inside a directory) which will hold
              the data. File extensions should not be provided, as they will be
              added by the driver itself.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'flush')
          return self.modules[fun](bank)
  
      def list(self, bank):
          '''
          Lists entries stored in the specified bank.
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :return:
              An iterable object containing all bank entries. Returns an empty
              iterator if the bank doesn't exists.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'list')
          return self.modules[fun](bank)
  
      def contains(self, bank, key=None):
          '''
          Checks if the specified bank contains the specified key.
  
          :param bank:
              The name of the location inside the cache which will hold the key
              and its associated data.
  
          :param key:
              The name of the key (or file inside a directory) which will hold
              the data. File extensions should not be provided, as they will be
              added by the driver itself.
  
          :return:
              Returns True if the specified key exists in the given bank and False
              if not.
              If key is None checks for the bank existense.
  
          :raises SaltCacheError:
              Raises an exception if cache driver detected an error accessing data
              in the cache backend (auth, permissions, etc).
          '''
          fun = '{0}.{1}'.format(self.driver, 'contains')
          return self.modules[fun](bank, key)
  