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# Authors:
# Jason Gerard DeRose <jderose@redhat.com>
#
# Copyright (C) 2008 Red Hat
# see file 'COPYING' for use and warranty information
#
# 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; version 2 only
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""
Base classes for plug-in architecture and generative API.
"""
import re
import inspect
import errors
class NameSpace(object):
"""
A read-only namespace of (key, value) pairs that can be accessed
both as instance attributes and as dictionary items. For example:
>>> ns = NameSpace(dict(my_message='Hello world!'))
>>> ns.my_message
'Hello world!'
>>> ns['my_message']
'Hello world!'
Keep in mind that Python doesn't offer true ready-only attributes. A
NameSpace is read-only in that it prevents programmers from
*accidentally* setting its attributes, but a motivated programmer can
still set them.
For example, setting an attribute the normal way will raise an exception:
>>> ns.my_message = 'some new value'
(raises errors.SetError)
But a programmer could still set the attribute like this:
>>> ns.__dict__['my_message'] = 'some new value'
You should especially not implement a security feature that relies upon
NameSpace being strictly read-only.
"""
__locked = False # Whether __setattr__ has been locked
def __init__(self, kw, order=None):
"""
The `kw` argument is a dict of the (key, value) pairs to be in this
NameSpace instance. The optional `order` keyword argument specifies
the order of the keys in this namespace; if omitted, the default is
to sort the keys in ascending order.
"""
assert isinstance(kw, dict)
self.__kw = dict(kw)
for (key, value) in self.__kw.items():
assert not key.startswith('_')
setattr(self, key, value)
if order is None:
self.__keys = sorted(self.__kw)
else:
self.__keys = list(order)
assert set(self.__keys) == set(self.__kw)
self.__locked = True
def __setattr__(self, name, value):
"""
Raises an exception if trying to set an attribute after the
NameSpace has been locked; otherwise calls object.__setattr__().
"""
if self.__locked:
raise errors.SetError(name)
super(NameSpace, self).__setattr__(name, value)
def __getitem__(self, key):
"""
Returns item from namespace named `key`.
"""
return self.__kw[key]
def __hasitem__(self, key):
"""
Returns True if namespace has an item named `key`.
"""
return bool(key in self.__kw)
def __iter__(self):
"""
Yields the names in this NameSpace in ascending order, or in the
the order specified in `order` kw arg.
For example:
>>> ns = NameSpace(dict(attr_b='world', attr_a='hello'))
>>> list(ns)
['attr_a', 'attr_b']
>>> [ns[k] for k in ns]
['hello', 'world']
"""
for key in self.__keys:
yield key
def __call__(self):
"""
Iterates through the values in this NameSpace in the same order as
the keys.
"""
for key in self.__keys:
yield self.__kw[key]
def __len__(self):
"""
Returns number of items in this NameSpace.
"""
return len(self.__keys)
class Named(object):
__name = None
def _get_name(self):
return self.__class__.__name__
def __get_loc(self):
cls = self.__class__
return '%s.%s' % (cls.__module__, cls.__name__)
loc = property(__get_loc)
def __get_name(self):
if self.__name is None:
self.__name = self._get_name()
return self.__name
name = property(__get_name)
def __get_cli_name(self):
return self.name.replace('_', '-')
cli_name = property(__get_cli_name)
class AbstractCommand(object):
def __call__(self):
print 'You called %s.%s()' % (
self.__class__.__module__,
self.__class__.__name__
)
def get_doc(self, _):
"""
This should return a gettext translated summarary of the command.
For example, if you were documenting the 'add-user' command, you're
method would look something like this.
>>> def get_doc(self, _):
>>> return _('add new user')
"""
raise NotImplementedError('%s.%s.%s()' % (
self.__class__.__module__,
self.__class__.__name__,
'get_doc',
)
)
class Attribute(Named):
__locked = False
__obj = None
def __init__(self):
m = re.match('^([a-z]+)__([a-z]+)$', self.__class__.__name__)
assert m
self.__obj_name = m.group(1)
self.__attr_name = m.group(2)
def __get_obj(self):
return self.__obj
def __set_obj(self, obj):
if self.__obj is not None:
raise errors.TwiceSetError(self.__class__.__name__, 'obj')
assert isinstance(obj, Object)
self.__obj = obj
assert self.obj is obj
obj = property(__get_obj, __set_obj)
def __get_obj_name(self):
return self.__obj_name
obj_name = property(__get_obj_name)
def __get_attr_name(self):
return self.__attr_name
attr_name = property(__get_attr_name)
class Method(AbstractCommand, Attribute):
def _get_name(self):
return '%s_%s' % (self.attr_name, self.obj_name)
class Property(Attribute):
def _get_name(self):
return self.attr_name
class Command(AbstractCommand, Named):
pass
class Object(Named):
__methods = None
__properties = None
def __get_methods(self):
return self.__methods
def __set_methods(self, methods):
if self.__methods is not None:
raise errors.TwiceSetError(
self.__class__.__name__, 'methods'
)
assert type(methods) is NameSpace
self.__methods = methods
assert self.methods is methods
methods = property(__get_methods, __set_methods)
def __get_properties(self):
return self.__properties
def __set_properties(self, properties):
if self.__properties is not None:
raise errors.TwiceSetError(
self.__class__.__name__, 'properties'
)
assert type(properties) is NameSpace
self.__properties = properties
assert self.properties is properties
properties = property(__get_properties, __set_properties)
class AttributeCollector(object):
def __init__(self):
self.__d = {}
def __getitem__(self, key):
assert isinstance(key, str)
if key not in self.__d:
self.__d[key] = {}
return self.__d[key]
def __iter__(self):
for key in self.__d:
yield key
def add(self, i):
assert isinstance(i, Attribute)
self[i.obj_name][i.attr_name] = i
def namespaces(self):
for key in self:
yield (key, NameSpace(self[key]))
class Collector(object):
def __init__(self):
self.__d = {}
def __get_d(self):
return dict(self.__d)
d = property(__get_d)
def __iter__(self):
for key in self.__d:
yield key
def add(self, i):
assert isinstance(i, Named)
self.__d[i.name] = i
def ns(self):
return NameSpace(self.__d)
class Proxy(object):
def __init__(self, d):
self.__d = d
def __getattr__(self, name):
if name not in self.__d:
raise AttributeError(name)
return self.__d[name]
class Registrar(object):
__allowed = (
Command,
Object,
Method,
Property,
)
def __init__(self, d=None):
if d is None:
self.__d = {}
else:
assert isinstance(d, dict)
assert d == {}
self.__d = d
for base in self.__allowed:
assert inspect.isclass(base)
assert base.__name__ not in self.__d
sub_d = {}
self.__d[base.__name__] = sub_d
setattr(self, base.__name__, Proxy(sub_d))
def __iter__(self):
for key in self.__d:
yield key
def __getitem__(self, key):
return dict(self.__d[key])
def items(self):
for key in self:
yield (key, self[key])
def __findbase(self, cls):
if not inspect.isclass(cls):
raise errors.RegistrationError('not a class', cls)
for base in self.__allowed:
if issubclass(cls, base):
return base
raise errors.RegistrationError(
'not subclass of an allowed base',
cls,
)
def __call__(self, cls):
base = self.__findbase(cls)
ns = self.__d[base.__name__]
assert cls.__name__ not in ns
ns[cls.__name__] = cls
def get_instances(self, base_name):
for cls in self[base_name].values():
yield cls()
def get_attrs(self, base_name):
d = {}
for i in self.get_instances(base_name):
if i.obj_name not in d:
d[i.obj_name] = []
d[i.obj_name].append(i)
return d
class RegistrarOld(object):
def __init__(self):
self.__tmp_commands = Collector()
self.__tmp_objects = Collector()
self.__tmp_methods = AttributeCollector()
self.__tmp_properties = AttributeCollector()
def __get_objects(self):
return self.__objects
objects = property(__get_objects)
def __get_commands(self):
return self.__commands
commands = property(__get_commands)
def __get_target(self, i):
if isinstance(i, Command):
return self.__tmp_commands
if isinstance(i, Object):
return self.__tmp_objects
if isinstance(i, Method):
return self.__tmp_methods
assert isinstance(i, Property)
return self.__tmp_properties
def register(self, cls):
assert inspect.isclass(cls)
assert issubclass(cls, Named)
i = cls()
self.__get_target(i).add(i)
def finalize(self):
self.__objects = self.__tmp_objects.ns()
for (key, ns) in self.__tmp_methods.namespaces():
self.__objects[key].methods = ns
for (key, ns) in self.__tmp_properties.namespaces():
self.__objects[key].properties = ns
commands = self.__tmp_commands.d
for obj in self.__objects():
assert isinstance(obj, Object)
if obj.methods is None:
obj.methods = NameSpace({})
if obj.properties is None:
obj.properties = NameSpace({})
for m in obj.methods():
m.obj = obj
assert m.name not in commands
commands[m.name] = m
for p in obj.properties():
p.obj = obj
self.__commands = NameSpace(commands)
class API(object):
__max_cmd_len = None
__objects = None
__commands = None
def __init__(self, registrar):
assert isinstance(registrar, Registrar)
self.__r = registrar
def __get_objects(self):
return self.__objects
objects = property(__get_objects)
def __get_commands(self):
return self.__commands
commands = property(__get_commands)
def __get_max_cmd_len(self):
if self.__max_cmd_len is None:
if self.commands is None:
return None
self.__max_cmd_len = max(len(n) for n in self.commands)
return self.__max_cmd_len
max_cmd_len = property(__get_max_cmd_len)
def __items(self, base, name):
for cls in self.__r[base].values():
i = cls()
yield (getattr(i, name), i)
def __namespace(self, base, name):
return NameSpace(dict(self.__items(base, name)))
def finalize(self):
self.__objects = self.__namespace('Object', 'name')
m = {}
for obj in self.__objects():
if obj.name not in m:
m[obj.name] = {}
for cls in self.__r['Method'].values():
meth = cls()
assert meth.obj_name in m
return
for (key, ns) in self.__tmp_methods.namespaces():
self.__objects[key].methods = ns
for (key, ns) in self.__tmp_properties.namespaces():
self.__objects[key].properties = ns
commands = self.__tmp_commands.d
for obj in self.__objects():
assert isinstance(obj, Object)
if obj.methods is None:
obj.methods = NameSpace({})
if obj.properties is None:
obj.properties = NameSpace({})
for m in obj.methods():
m.obj = obj
assert m.name not in commands
commands[m.name] = m
for p in obj.properties():
p.obj = obj
self.__commands = NameSpace(commands)
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