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# -*- coding: utf-8 -*-
# slip.util.hookable -- run hooks on changes in objects
#
# Copyright © 2008 Red Hat, Inc.
#
# 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, see <http://www.gnu.org/licenses/>.
#
# Authors:
# Nils Philippsen <nils@redhat.com>
"""This module contains variants of certain base types which call registered
hooks on changes."""
import collections
from six import with_metaclass
__all__ = ["Hookable", "HookableSet"]
class HookableType(type):
def __new__(cls, name, bases, dct):
if '_hookable_change_methods' in dct:
try:
base = dct["_hookable_base_class"]
except KeyError:
base = None
for base_candidate in (x for x in bases if x != Hookable):
if base:
raise TypeError(
"too many base classes: %s" % str(bases))
else:
base = base_candidate
for methodname in dct["_hookable_change_methods"]:
dct[methodname] = HookableType.wrap_method(base, methodname)
return type.__new__(cls, name, bases, dct)
@classmethod
def wrap_method(cls, base, methodname):
func = getattr(base, methodname)
def methodwrapper(self, *p, **k):
retval = func(self, *p, **k)
self._run_hooks()
return retval
methodwrapper.__name__ = methodname
return methodwrapper
class _HookEntry(object):
def __init__(self, hook, args, kwargs, hookable=None):
assert(isinstance(hook, collections.Callable))
assert(isinstance(hookable, Hookable))
for n, x in enumerate(args):
try:
hash(x)
except TypeError:
raise TypeError(
"Positional argument %d is not hashable: %r" %
(n, x))
for k, x in kwargs.items():
try:
hash(x)
except TypeError:
raise TypeError(
"Keyword argument %r is not hashable: %r" %
(k, x))
if not isinstance(args, tuple):
args = tuple(args)
self.__hook = hook
self.__args = args
self.__kwargs = kwargs
self.__hookable = hookable
self.__hash = None
def __cmp__(self, obj):
return (
self.__hook == obj.__hook and
self.__args == obj.__args and
self.__kwargs == obj.__kwargs)
def __hash__(self):
if not self.__hash:
self.__hash = self._compute_hash()
return self.__hash
def _compute_hash(self):
hashvalue = hash(self.__hook)
hashvalue = hash(hashvalue) ^ hash(self.__args)
hashvalue = hash(hashvalue) ^ hash(
tuple(sorted(self.__kwargs.items())))
return hashvalue
def run(self):
if self.__hookable:
self.__hook(self.__hookable, *self.__args, **self.__kwargs)
else:
self.__hook(*self.__args, **self.__kwargs)
class Hookable(with_metaclass(HookableType, object)):
"""An object which calls registered hooks on changes."""
@property
def __hooks__(self, *p, **k):
if not hasattr(self, "__real_hooks__"):
self.__real_hooks__ = set()
return self.__real_hooks__
def _get_hooks_enabled(self):
if not hasattr(self, "__hooks_enabled__"):
self.__hooks_enabled__ = True
return self.__hooks_enabled__
def _set_hooks_enabled(self, enabled):
self.__hooks_enabled__ = enabled
hooks_enabled = property(_get_hooks_enabled, _set_hooks_enabled)
def _get_hooks_frozen(self):
if not hasattr(self, "__hooks_frozen__"):
self.__hooks_frozen__ = False
return self.__hooks_frozen__
def _set_hooks_frozen(self, freeze):
if freeze == self.hooks_frozen:
return
self.__hooks_frozen__ = freeze
if freeze:
self.__hooks_frozen_entries__ = set()
else:
for hookentry in self.__hooks_frozen_entries__:
hookentry.run()
del self.__hooks_frozen_entries__
hooks_frozen = property(_get_hooks_frozen, _set_hooks_frozen)
def freeze_hooks(self):
self.hooks_frozen = True
def thaw_hooks(self):
self.hooks_frozen = False
def add_hook(self, hook, *args, **kwargs):
self.__add_hook(hook, None, *args, **kwargs)
def add_hook_hookable(self, hook, *args, **kwargs):
self.__add_hook(hook, self, *args, **kwargs)
def __add_hook(self, hook, _hookable, *args, **kwargs):
assert isinstance(hook, collections.Callable)
assert isinstance(_hookable, Hookable)
hookentry = _HookEntry(hook, args, kwargs, hookable=_hookable)
self.__hooks__.add(hookentry)
def remove_hook(self, hook, *args, **kwargs):
self.__hooks__.remove(_HookEntry(hook, args, kwargs))
def _run_hooks(self):
if self.hooks_enabled:
if not self.hooks_frozen:
for hookentry in self.__hooks__:
hookentry.run()
else:
self.__hooks_frozen_entries__.update(self.__hooks__)
class HookableSet(set, Hookable):
"""A set object which calls registered hooks on changes."""
_hookable_change_methods = (
"add", "clear", "difference_update", "discard", "intersection_update",
"pop", "remove", "symmetric_difference_update", "update")
def copy(self):
obj = set.copy(self)
obj.__real_hooks__ = set()
return obj
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