Add SWF endpoint PollForActivityTask

moto/swf/models/__init__.py

@@ -256,6 +256,37 @@ class SWFBackend(BaseBackend):
                                        decisions=decisions,
                                        execution_context=execution_context)
 
+    def poll_for_activity_task(self, domain_name, task_list, identity=None):
+        self._check_string(domain_name)
+        self._check_string(task_list)
+        domain = self._get_domain(domain_name)
+        # Real SWF cases:
+        # - case 1: there's an activity task to return, return it
+        # - case 2: there's no activity task to return, so wait for timeout
+        #           and if a new activity is scheduled, return it
+        # - case 3: timeout reached, no activity task, return an empty response
+        #           (e.g. a response with an empty "taskToken")
+        #
+        # For the sake of simplicity, we forget case 2 for now, so either
+        # there's an ActivityTask to return, either we return a blank one.
+        #
+        # SWF client libraries should cope with that easily as long as tests
+        # aren't distributed.
+        #
+        # TODO: handle long polling (case 2) for activity tasks
+        candidates = []
+        for _task_list, tasks in domain.activity_task_lists.iteritems():
+            if _task_list == task_list:
+                candidates += filter(lambda t: t.state == "SCHEDULED", tasks)
+        if any(candidates):
+            # TODO: handle task priorities (but not supported by boto for now)
+            task = min(candidates, key=lambda d: d.scheduled_at)
+            wfe = task.workflow_execution
+            wfe.start_activity_task(task.task_token, identity=identity)
+            return task
+        else:
+            return None
+
 
 swf_backends = {}
 for region in boto.swf.regions():

moto/swf/models/activity_task.py

@@ -1,16 +1,34 @@
 from __future__ import unicode_literals
+from datetime import datetime
 import uuid
 
 
 class ActivityTask(object):
-    def __init__(self, activity_id, activity_type, workflow_execution, input=None):
+    def __init__(self, activity_id, activity_type, scheduled_event_id,
+                 workflow_execution, input=None):
         self.activity_id = activity_id
         self.activity_type = activity_type
         self.input = input
+        self.scheduled_event_id = scheduled_event_id
         self.started_event_id = None
         self.state = "SCHEDULED"
         self.task_token = str(uuid.uuid4())
         self.workflow_execution = workflow_execution
+        # this is *not* necessarily coherent with workflow execution history,
+        # but that shouldn't be a problem for tests
+        self.scheduled_at = datetime.now()
+
+    def to_full_dict(self):
+        hsh = {
+            "activityId": self.activity_id,
+            "activityType": self.activity_type.to_short_dict(),
+            "taskToken": self.task_token,
+            "startedEventId": self.started_event_id,
+            "workflowExecution": self.workflow_execution.to_short_dict(),
+        }
+        if self.input:
+            hsh["input"] = self.input
+        return hsh
 
     def start(self, started_event_id):
         self.state = "STARTED"

moto/swf/models/history_event.py

@@ -105,6 +105,14 @@ class HistoryEvent(object):
                 "cause": self.cause,
                 "decisionTaskCompletedEventId": self.decision_task_completed_event_id,
             }
+        elif self.event_type == "ActivityTaskStarted":
+            # TODO: merge it with DecisionTaskStarted
+            hsh = {
+                "scheduledEventId": self.scheduled_event_id
+            }
+            if hasattr(self, "identity") and self.identity:
+                hsh["identity"] = self.identity
+            return hsh
         else:
             raise NotImplementedError(
                 "HistoryEvent does not implement attributes for type '{}'".format(self.event_type)

moto/swf/models/workflow_execution.py

@@ -396,19 +396,37 @@ class WorkflowExecution(object):
                                             "{}_UNDEFINED".format(error_key.upper()))
                 return
 
-        task = ActivityTask(
-            activity_id=attributes["activityId"],
-            activity_type=activity_type,
-            input=attributes.get("input"),
-            workflow_execution=self,
-        )
-        # Only add event and increment counters if nothing went wrong
-        self.domain.add_to_activity_task_list(task_list, task)
-        self._add_event(
+        # Only add event and increment counters now that nothing went wrong
+        evt = self._add_event(
             "ActivityTaskScheduled",
             decision_task_completed_event_id=event_id,
             activity_type=activity_type,
             attributes=attributes,
             task_list=task_list,
         )
+        task = ActivityTask(
+            activity_id=attributes["activityId"],
+            activity_type=activity_type,
+            input=attributes.get("input"),
+            scheduled_event_id=evt.event_id,
+            workflow_execution=self,
+        )
+        self.domain.add_to_activity_task_list(task_list, task)
         self.open_counts["openActivityTasks"] += 1
+
+    def _find_activity_task(self, task_token):
+        for task in self.activity_tasks:
+            if task.task_token == task_token:
+                return task
+        raise ValueError(
+            "No activity task with token: {}".format(task_token)
+        )
+
+    def start_activity_task(self, task_token, identity=None):
+        task = self._find_activity_task(task_token)
+        evt = self._add_event(
+            "ActivityTaskStarted",
+            scheduled_event_id=task.scheduled_event_id,
+            identity=identity
+        )
+        task.start(evt.event_id)