1 files changed, 81 insertions, 0 deletions
diff --git a/taskflow/patterns/graph_workflow.py b/taskflow/patterns/graph_workflow.py
new file mode 100644
index 0000000..d9864b8
--- /dev/null
+++ b/taskflow/patterns/graph_workflow.py
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+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from collections import defaultdict
+
+import logging
+
+from networkx import exception as g_exc
+from networkx.algorithms import dag
+from networkx.classes import digraph
+
+from taskflow import exceptions as exc
+from taskflow import patterns
+
+LOG = logging.getLogger(__name__)
+
+
+class Workflow(patterns.OrderedWorkflow):
+    def __init__(self, name, tolerant=False, parents=None):
+        super(Workflow, self).__init__(name, tolerant, parents)
+        self._graph = digraph.DiGraph()
+        self._connected = False
+
+    def add(self, task):
+        # Do something with the task, either store it for later
+        # or add it to the graph right now...
+        #
+        # Only insert the node to start, connect all the edges
+        # together later after all nodes have been added.
+        self._graph.add_node(task)
+
+    def run(self, context, *args, **kwargs):
+        self.connect()
+        return super(Workflow, self).run(context, *args, **kwargs)
+
+    def order(self):
+        self.connect()
+        try:
+            return dag.topological_sort(self._graph)
+        except g_exc.NetworkXUnfeasible:
+            raise exc.InvalidStateException("Unable to correctly determine "
+                                            "the path through the provided "
+                                            "workflow which will satisfy the "
+                                            "tasks needed inputs and outputs.")
+
+    def connect(self):
+        """Connects the edges of the graph together."""
+        if self._connected:
+            return
+        provides_what = defaultdict(list)
+        requires_what = defaultdict(list)
+        for t in self._graph.nodes_iter():
+            for r in t.requires:
+                requires_what[r].append(t)
+            for p in t.provides:
+                provides_what[p].append(t)
+        for (i_want, n) in requires_what.items():
+            if i_want not in provides_what:
+                raise exc.InvalidStateException("Task %s requires input %s "
+                                                "but no other task produces "
+                                                "said output" % (n, i_want))
+            for p in provides_what[i_want]:
+                # P produces for N so thats why we link P->N and not N->P
+                self._graph.add_edge(p, n)
+
+        self._connected = True