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# Copyright (C) 2008, 2009, 2010 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/>.
"""Application interface for use by plugins.
This primarily makes certain apt functionality available to the plugin.
"""
from __future__ import absolute_import, unicode_literals
__metaclass__ = type
__all__ = [
'Application',
'SourcesListError',
]
import apt
import computerjanitor
import computerjanitorapp
from computerjanitord.errors import (
MissingLandmarkError, NonDownloadableError)
_ = computerjanitorapp.setup_gettext()
SYNTAPTIC_PREFERENCES_FILE = '/var/lib/synaptic/preferences'
# There really isn't anything special about these packages. These really just
# represent landmarks in the package namespace that we look for to try to
# judge the sanity of the apt cache. If these are missing, things are really
# messed up and we can't actually figure out how to continue.
LANDMARK_PACKAGES = [
'dash',
'gzip',
]
class Application:
"""Interface for plugins requesting apt actions."""
def __init__(self, apt_cache=None):
"""Create the application interface.
:param apt_cache: Alternative apt cache for testing purposes. When
`None` use the default apt cache.
"""
if apt_cache is None:
# Use the real apt cache.
self.apt_cache = apt.Cache()
else:
self.apt_cache = apt_cache
self.refresh_apt_cache()
def refresh_apt_cache(self):
"""Refresh the apt cache.
This API is used by plugins.
"""
self.apt_cache.open()
# For historical purposes, Synaptic has a different way of pinning
# packages than apt, so we have to load its preferences file in order
# to know what it's pinning.
self.apt_cache._depcache.ReadPinFile(SYNTAPTIC_PREFERENCES_FILE)
def verify_apt_cache(self):
"""Verify that essential packages are available in the apt cache.
This API is used by plugins.
:raises MissingLandmarkError: When an essential package is not
available.
:raises NonDownloadableError: When an essential package cannot be
downloaded.
"""
for name in LANDMARK_PACKAGES:
if name not in self.apt_cache:
raise MissingLandmarkError(name)
if not any(v.downloadable for v in self.apt_cache[name].versions):
raise NonDownloadableError(name)
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