#!/usr/bin/env python
#
# Source: https://github.com/slezica/python-frozendict
#
# Copyright (c) 2012 Santiago Lezica
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

import collections, operator

class frozendict(collections.Mapping):

    def __init__(self, *args, **kwargs):
        self.__dict = dict(*args, **kwargs)
        self.__hash = None

    def __getitem__(self, key):
        return self.__dict[key]

    def copy(self, **add_or_replace):
        new = frozendict(self)
        new.__dict.update(add_or_replace) # Feels like cheating
        return new

    def __iter__(self):
        return iter(self.__dict)

    def __len__(self):
        return len(self.__dict)

    def __repr__(self):
        return '<frozendict %s>' % repr(self.__dict)

    def __hash__(self):
        if self.__hash is None:
            self.__hash = reduce(operator.xor, map(hash, self.iteritems()), 0)

        return self.__hash