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# Copyright (C) 2015-2017 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."""
import sys
import json
import logging
from collections import deque
from mailman.interfaces.workflows import IWorkflowStateManager
from public import public
from zope.component import getUtility
COMMASPACE = ', '
log = logging.getLogger('mailman.error')
@public
class Workflow:
"""Generic workflow."""
initial_state = None
save_attributes = ()
def __init__(self):
self.token = None
self._next = deque()
self.push(self.initial_state)
self.debug = False
self._count = 0
def __iter__(self):
"""See `IWorkflow`."""
return self
def __next__(self):
"""See `IWorkflow`."""
try:
name, step = self._pop()
return step()
except IndexError:
raise StopIteration
except:
log.exception('deque: {}'.format(COMMASPACE.join(self._next)))
raise
def push(self, step):
"""See `IWorkflow`."""
self._next.append(step)
def _pop(self):
name = self._next.popleft()
step = getattr(self, '_step_{}'.format(name))
self._count += 1
if self.debug: # pragma: nocover
print('[{:02d}] -> {}'.format(self._count, name), file=sys.stderr)
return name, step
def run_thru(self, stop_after):
"""See `IWorkflow`."""
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):
"""See `IWorkflow`."""
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(name)
break
results.append(step())
return results
def save(self):
"""See `IWorkflow`."""
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.token, step, json.dumps(data))
def restore(self):
"""See `IWorkflow`."""
state_manager = getUtility(IWorkflowStateManager)
state = state_manager.restore(self.token)
if state is None:
# The token doesn't exist in the database.
raise LookupError(self.token)
self._next.clear()
if state.step:
self._next.append(state.step)
data = json.loads(state.data)
for attr in self.save_attributes:
try:
setattr(self, attr, data[attr])
except KeyError:
pass
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