# Copyright (c) 2014 Rackspace, Inc.
#
# 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.


def lazy_property(write=False, delete=True):
    """Creates a lazy property.

    :param write: Whether this property is "writable"
    :param delete: Whether this property can be deleted.
    """

    def wrapper(fn):
        attr_name = '_lazy_' + fn.__name__

        def getter(self):
            if not hasattr(self, attr_name):
                setattr(self, attr_name, fn(self))
            return getattr(self, attr_name)

        def setter(self, value):
            setattr(self, attr_name, value)

        def deleter(self):
            delattr(self, attr_name)

        return property(fget=getter,
                        fset=write and setter,
                        fdel=delete and deleter,
                        doc=fn.__doc__)
    return wrapper