1 files changed, 74 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/taskgraph.py b/taskcluster/taskgraph/taskgraph.py
new file mode 100644
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+++ b/taskcluster/taskgraph/taskgraph.py
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+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+from .graph import Graph
+from .task import Task
+
+import attr
+import six
+
+
+@attr.s(frozen=True)
+class TaskGraph(object):
+    """
+    Representation of a task graph.
+
+    A task graph is a combination of a Graph and a dictionary of tasks indexed
+    by label. TaskGraph instances should be treated as immutable.
+
+    In the graph, tasks are said to "link to" their dependencies. Whereas
+    tasks are "linked from" their dependents.
+    """
+
+    tasks = attr.ib()
+    graph = attr.ib()
+
+    def __attrs_post_init__(self):
+        assert set(self.tasks) == self.graph.nodes
+
+    def for_each_task(self, f, *args, **kwargs):
+        for task_label in self.graph.visit_postorder():
+            task = self.tasks[task_label]
+            f(task, self, *args, **kwargs)
+
+    def __getitem__(self, label):
+        "Get a task by label"
+        return self.tasks[label]
+
+    def __contains__(self, label):
+        return label in self.tasks
+
+    def __iter__(self):
+        "Iterate over tasks in undefined order"
+        return six.itervalues(self.tasks)
+
+    def to_json(self):
+        "Return a JSON-able object representing the task graph, as documented"
+        named_links_dict = self.graph.named_links_dict()
+        # this dictionary may be keyed by label or by taskid, so let's just call it 'key'
+        tasks = {}
+        for key in self.graph.visit_postorder():
+            tasks[key] = self.tasks[key].to_json()
+            # overwrite dependencies with the information in the taskgraph's edges.
+            tasks[key]["dependencies"] = named_links_dict.get(key, {})
+        return tasks
+
+    @classmethod
+    def from_json(cls, tasks_dict):
+        """
+        This code is used to generate the a TaskGraph using a dictionary
+        which is representative of the TaskGraph.
+        """
+        tasks = {}
+        edges = set()
+        for key, value in six.iteritems(tasks_dict):
+            tasks[key] = Task.from_json(value)
+            if "task_id" in value:
+                tasks[key].task_id = value["task_id"]
+            for depname, dep in six.iteritems(value["dependencies"]):
+                edges.add((key, dep, depname))
+        task_graph = cls(tasks, Graph(set(tasks), edges))
+        return tasks, task_graph