#!/usr/bin/python

import functools

from threading import RLock

import logging

LOGGER = logging.getLogger(__name__)

class CacheNullValue(object):

    pass

_Null = CacheNullValue()

class Cache(object):

    def __init__(self, cache_limit=1000):

        self._cache = {}

        self._queue = []

        self.cache_limit = cache_limit

        self._lock = RLock()

    def __getitem__(self, name):

        with self._lock:

            return self._cache.get(name, _Null)

    get = __getitem__

    def __setitem__(self, name, value):

        with self._lock:

            if len(self._queue) >= self.cache_limit:

                del self._cache[self._queue.pop(0)]

            self._queue.append(name)

            self._cache[name] = value

    set = __setitem__

def cache(cache_limit):

    """A function decorator for method cache store

    """

    def cached(f):

        @functools.wraps(f)

        def _cached(*args, **kwargs):

            cid = repr((args, kwargs))

            data = _cached.cache.get(cid)

            if data != _Null:

                LOGGER.debug('hit cached `' + _cached.__name__ + '` for ' + cid)

                return data

            data = _cached.f(*args, **kwargs)

            _cached.cache.set(cid, data)

            return data

        _cached.f = f

        _cached.cache = Cache(cache_limit)

        return _cached

    return cached

def setup(cache_limit):

    """ A global thread safe key-value store

    """

    global _cache_object

    _cache_object = Cache(cache_limit)

def set(cid, data):

    _cache_object.set(cid, data)

def get(cid):

    return _cache_object.get(cid)

if __name__ == '__main__':

    logging.basicConfig(level=logging.DEBUG,

                        format='%(asctime)s %(levelname)-8s %(message)s',

                        datefmt='%Y-%m-%d %H:%M:%S', filemode='a+')

    class T(object):

        @cache(100)

        def c(self, t):

            return t

    @cache(100)

    def cc(t):

        return t

    t = T()

    print t.c('hello')

    print t.c('hello')

    print t.c('h')

    print t.c('hello')

    print cc('he')

    print cc('he')