1 files changed, 102 insertions, 0 deletions
diff --git a/src/mailman/app/workflow.py b/src/mailman/app/workflow.py
new file mode 100644
index 000000000..f9a951157
--- /dev/null
+++ b/src/mailman/app/workflow.py
@@ -0,0 +1,102 @@
+# 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 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)