Create StatefulComponent which yields values from a generator instead of returning a static value

src/components/stateful_component.py

@@ -0,0 +1,39 @@
+import json
+from functools import partial
+
+import zmq
+
+from component_base import ComponentBase
+
+
+class StatefulComponent(ComponentBase):
+    def __init__(self, anchor, event_handler, zmq_context=None):
+        super().__init__(anchor, event_handler, zmq_context)
+        self.generator = None
+        self.subscribe('reset')
+
+        def wrapper(msg_parts, handler):
+            anchor, message = msg_parts
+            if anchor == b'reset':
+                self.generator = None
+                self.unsubscribe_all()
+                self.subscribe(self.anchor)
+                self.subscribe('reset')
+                return
+            data_json = json.loads(message)
+            if self.generator is None:
+                self.generator = handler(data_json, self)
+            response_anchor, response_data = next(self.generator)
+            if response_anchor is None:
+                return
+            if response_anchor not in self.subscriptions:
+                self.subscriptions.add(response_anchor)
+                self.zmq_sub_socket.setsockopt_string(zmq.SUBSCRIBE, response_anchor)
+            response_data = json.dumps({
+                'anchor': response_anchor,
+                'data': response_data,
+            })
+            response = [r.encode('utf-8') for r in (response_anchor, response_data)]
+            self.zmq_push_socket.send_multipart(response)
+
+        self.zmq_sub_stream.on_recv(partial(wrapper, handler=event_handler))