1 files changed, 40 insertions, 0 deletions
diff --git a/pym/_emerge/TaskSequence.py b/pym/_emerge/TaskSequence.py
new file mode 100644
index 000000000..d0609f43e
--- /dev/null
+++ b/pym/_emerge/TaskSequence.py
@@ -0,0 +1,40 @@
+from _emerge.CompositeTask import CompositeTask
+from _emerge.AsynchronousTask import AsynchronousTask
+import os
+from collections import deque
+class TaskSequence(CompositeTask):
+	"""
+	A collection of tasks that executes sequentially. Each task
+	must have a addExitListener() method that can be used as
+	a means to trigger movement from one task to the next.
+	"""
+
+	__slots__ = ("_task_queue",)
+
+	def __init__(self, **kwargs):
+		AsynchronousTask.__init__(self, **kwargs)
+		self._task_queue = deque()
+
+	def add(self, task):
+		self._task_queue.append(task)
+
+	def _start(self):
+		self._start_next_task()
+
+	def cancel(self):
+		self._task_queue.clear()
+		CompositeTask.cancel(self)
+
+	def _start_next_task(self):
+		self._start_task(self._task_queue.popleft(),
+			self._task_exit_handler)
+
+	def _task_exit_handler(self, task):
+		if self._default_exit(task) != os.EX_OK:
+			self.wait()
+		elif self._task_queue:
+			self._start_next_task()
+		else:
+			self._final_exit(task)
+			self.wait()
+