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task.py
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task.py
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# task.py
# Abstract class for tasks.
#
# Copyright (C) 2015 Red Hat, Inc.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions of
# the GNU General Public License v.2, or (at your option) any later version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY expressed or implied, including the implied warranties 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., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA. Any Red Hat trademarks that are incorporated in the
# source code or documentation are not subject to the GNU General Public
# License and may only be used or replicated with the express permission of
# Red Hat, Inc.
#
# Red Hat Author(s): Anne Mulhern <amulhern@redhat.com>
import abc
from six import add_metaclass
@add_metaclass(abc.ABCMeta)
class Task(object):
""" An abstract class that represents some task. """
# Whether or not the functionality is implemented in the task class.
# It is True by default. Only NotImplementedClass and its descendants
# should have a False value.
implemented = True
description = abc.abstractproperty(doc="Brief description for this task.")
@property
def availabilityErrors(self):
""" Reasons if this task or the tasks it depends on are unavailable. """
return self._availabilityErrors + \
[e for t in self.dependsOn for e in t.availabilityErrors]
@property
def available(self):
""" True if the task is available, otherwise False.
:returns: True if the task is available
:rtype: bool
"""
return self.availabilityErrors == []
_availabilityErrors = abc.abstractproperty(
doc="Reasons if the necessary external tools are unavailable.")
dependsOn = abc.abstractproperty(doc="tasks that this task depends on")
@abc.abstractmethod
def doTask(self, *args, **kwargs):
""" Do the task for this class. """
raise NotImplementedError()
class UnimplementedTask(Task):
""" A null Task, which returns a negative or empty for all properties."""
description = "an unimplemented task"
implemented = False
@property
def _availabilityErrors(self):
return ["Not implemented task can not succeed."]
dependsOn = []
def doTask(self, *args, **kwargs):
raise NotImplementedError()
@add_metaclass(abc.ABCMeta)
class BasicApplication(Task):
""" A task representing an application. """
ext = abc.abstractproperty(doc="The object representing the external resource.")
# TASK methods
@property
def _availabilityErrors(self):
errors = self.ext.availabilityErrors
if errors:
return ["application %s is not available: %s" % (self.ext, " and ".join(errors))]
else:
return []
@property
def dependsOn(self):
return []