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# plugin.py - plugin base class for computerjanitor
# Copyright (C) 2008 Canonical, Ltd.
#
# 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 3 of the License.
#
# 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/>.
import imp
import inspect
import logging
import os
import computerjanitor
_ = computerjanitor.setup_gettext()
import logging
class Plugin(object):
"""Base class for plugins.
These plugins only do one thing: identify cruft. See the 'get_cruft'
method for details.
"""
def get_condition(self):
if hasattr(self, "_condition"):
return self._condition
else:
return []
def set_condition(self, condition):
self._condition = condition
condition = property(get_condition, set_condition)
def set_application(self, app):
"""Set the Application instance this plugin belongs to.
This is used by the plugin manager when creating the plugin
instance. In a perfect world, this would be done via the
__init__ method, but since I took a wrong left turn, I ended
up in an imperfect world, and therefore giving the Application
instance to __init__ would mandate that all sub-classes would
have to deal with that explicitly. That is a lot of unnecessary
make-work, which we should avoid. Therefore, we do it via this
method.
The class may access the Application instance via the
'app' attribute.
"""
self.app = app
def do_cleanup_cruft(self): # pragma: no cover
"""Find cruft and clean it up.
This is a helper method.
"""
for cruft in self.get_cruft():
cruft.cleanup()
self.post_cleanup()
def get_cruft(self):
"""Find some cruft in the system.
This method MUST return an iterator (see 'yield' statement).
This interface design allows cruft to be collected piecemeal,
which makes it easier to show progress in the user interface.
The base class default implementation of this raises an
exception. Subclasses MUST override this method.
"""
raise computerjanitor.UnimplementedMethod(self.get_cruft)
def post_cleanup(self):
"""Does plugin wide cleanup after the individual cleanup
was performed.
This is useful for stuff that needs to be proccessed
in batches (e.g. for performance reasons) like package
removal.
"""
pass
class PluginManager(object):
"""Class to find and load plugins.
Plugins are stored in files named '*_plugin.py' in the list of
directories given to the initializer.
"""
def __init__(self, app, plugin_dirs):
self._app = app
self._plugin_dirs = plugin_dirs
self._plugins = None
def get_plugin_files(self):
"""Return all filenames in which plugins may be stored."""
names = []
for dirname in self._plugin_dirs:
if not os.path.exists(dirname):
continue
basenames = [x for x in os.listdir(dirname)
if x.endswith("_plugin.py")]
logging.debug("Plugin modules in %s: %s" %
(dirname, " ".join(basenames)))
names += [os.path.join(dirname, x) for x in basenames]
return names
def _find_plugins(self, module):
"""Find and instantiate all plugins in a module."""
plugins = []
for dummy, member in inspect.getmembers(module):
if inspect.isclass(member) and issubclass(member, Plugin):
plugins.append(member)
logging.debug("Plugins in %s: %s" %
(module, " ".join(str(x) for x in plugins)))
return [plugin() for plugin in plugins]
def _load_module(self, filename):
"""Load a module from a filename."""
logging.debug("Loading module %s" % filename)
module_name, dummy = os.path.splitext(os.path.basename(filename))
f = file(filename, "r")
try:
module = imp.load_module(module_name, f, filename,
(".py", "r", imp.PY_SOURCE))
except Exception, e: # pragma: no cover
logging.warning("Failed to load plugin '%s' (%s)" %
(module_name, e))
return None
f.close()
return module
def get_plugins(self, condition=[], callback=None):
"""Return all plugins that have been found.
If callback is specified, it is called after each plugin has
been found, with the following arguments: filename, index of
filename in list of files to be examined (starting with 0), and
total number of files to be examined. The purpose of this is to
allow the callback to inform the user in case things take a long
time.
"""
if self._plugins is None:
self._plugins = []
filenames = self.get_plugin_files()
for i in range(len(filenames)):
if callback:
callback(filenames[i], i, len(filenames))
module = self._load_module(filenames[i])
for plugin in self._find_plugins(module):
plugin.set_application(self._app)
self._plugins.append(plugin)
# get the matching plugins
plugins = [p for p in self._plugins
if (p.condition == condition) or
(condition in p.condition) or
(condition == "*") ]
logging.debug("plugins for condition '%s' are '%s'" %
(condition, plugins))
return plugins
