1 files changed, 139 insertions, 0 deletions
diff --git a/src/mailman/workflows/base.py b/src/mailman/workflows/base.py
new file mode 100644
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+++ b/src/mailman/workflows/base.py
@@ -0,0 +1,139 @@
+# 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 IWorkflow, IWorkflowStateManager
+from mailman.utilities.modules import abstract_component
+from public import public
+from zope.component import getUtility
+from zope.interface import implementer
+
+
+COMMASPACE = ', '
+log = logging.getLogger('mailman.error')
+
+
+@public
+@abstract_component
+@implementer(IWorkflow)
+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.pop()
+        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}
+        # Save the workflow stack.
+        if len(self._next) == 0:
+            steps = '[]'
+        else:
+            steps = json.dumps(list(self._next))
+        state_manager.save(self.token, steps, 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.steps:
+            self._next.extend(json.loads(state.steps))
+        data = json.loads(state.data)
+        for attr in self.save_attributes:
+            try:
+                setattr(self, attr, data[attr])
+            except KeyError:
+                pass