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# Copyright (C) 2015 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman 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
# GNU Mailman. If not, see <http://www.gnu.org/licenses/>.
"""Generic workflow."""
__all__ = [
'Workflow',
]
import json
import logging
from collections import deque
from mailman.interfaces.workflow import IWorkflowStateManager
from zope.component import getUtility
COMMASPACE = ', '
log = logging.getLogger('mailman.error')
class Workflow:
"""Generic workflow."""
SAVE_ATTRIBUTES = ()
INITIAL_STATE = None
def __init__(self):
self.token = None
self._next = deque()
self.push(self.INITIAL_STATE)
def __iter__(self):
return self
def push(self, step):
self._next.append(step)
def _pop(self):
name = self._next.popleft()
step = getattr(self, '_step_{}'.format(name))
return name, step
def __next__(self):
try:
name, step = self._pop()
return step()
except IndexError:
raise StopIteration
except:
log.exception('deque: {}'.format(COMMASPACE.join(self._next)))
raise
def run_thru(self, stop_after):
"""Run the state machine through and including the given step.
:param stop_after: Name of method, sans prefix to run the
state machine through. In other words, the state machine runs
until the named method completes.
"""
results = []
while True:
try:
name, step = self._pop()
except (StopIteration, IndexError):
# We're done.
break
results.append(step())
if name == stop_after:
break
return results
def run_until(self, stop_before):
"""Trun the state machine until (not including) the given step.
:param stop_before: Name of method, sans prefix that the
state machine is run until the method is reached. Unlike
`run_thru()` the named method is not run.
"""
results = []
while True:
try:
name, step = self._pop()
except (StopIteration, IndexError):
# We're done.
break
if name == stop_before:
# Stop executing, but not before we push the last state back
# onto the deque. Otherwise, resuming the state machine would
# skip this step.
self._next.appendleft(step)
break
results.append(step())
return results
def save(self):
assert self.token, 'Workflow token must be set'
state_manager = getUtility(IWorkflowStateManager)
data = {attr: getattr(self, attr) for attr in self.SAVE_ATTRIBUTES}
# Note: only the next step is saved, not the whole stack. This is not
# an issue in practice, since there's never more than a single step in
# the queue anyway. If we want to support more than a single step in
# the queue *and* want to support state saving/restoring, change this
# method and the restore() method.
if len(self._next) == 0:
step = None
elif len(self._next) == 1:
step = self._next[0]
else:
raise AssertionError(
"Can't save a workflow state with more than one step "
"in the queue")
state_manager.save(
self.__class__.__name__,
self.token,
step,
json.dumps(data))
def restore(self):
state_manager = getUtility(IWorkflowStateManager)
state = state_manager.restore(self.__class__.__name__, self.token)
if state is not None:
self._next.clear()
if state.step:
self._next.append(state.step)
if state.data is not None:
for attr, value in json.loads(state.data).items():
setattr(self, attr, value)
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