Adding EventDispatcher (mediator pattern) to decouple your system fro…

…m StepperMotors

src/stepper_motors_juanmf1/EventDispatcher.py

@@ -0,0 +1,56 @@
+import uuid
+
+from stepper_motors_juanmf1.BlockingQueueWorker import BlockingQueueWorker
+from stepper_motors_juanmf1.ThreadOrderedPrint import tprint
+
+
+class EventDispatcher(BlockingQueueWorker):
+    MAX_EVENTS = 100
+
+    def __new__(cls, *args, **kwargs):
+        """
+        Singleton
+        """
+        if not hasattr(cls, 'instance'):
+            cls.instance = super().__new__(cls)
+        return cls.instance
+
+    def __init__(self):
+        super().__init__(self.dispatchMainLoop, jobQueueMaxSize=self.MAX_EVENTS, workerName="EventDispatcher_")
+        self.events = {}
+        self.markForUnregister = []
+
+    def dispatchMainLoop(self, eventName, eventInfo):
+        # Todo: should I add eventId to callee parameters?
+        tprint("dispatchMainLoop")
+        tprint("eventName, eventInfo")
+        tprint(eventName, eventInfo)
+        tprint("")
+        for calleeId, callee in self.events.get(eventName, {}).items():
+            callee(calleeId=calleeId, eventInfo=eventInfo)
+        else:
+            tprint(f"Missed event {eventName}")
+        while self.markForUnregister:
+            self.unregister(self.markForUnregister.pop(0))
+
+    def register(self, eventName, callee, oneTimeHandler=False):
+        self.events.setdefault(eventName, {})
+        cId = uuid.uuid4()
+        tprint(f"Register eventName {eventName}; calleeId {cId}")
+        self.events[eventName][cId] = lambda calleeId, eventInfo: self.callThenUnregister(calleeId, eventInfo, callee) \
+                                           if oneTimeHandler else callee
+        return cId
+
+    def unregister(self, calleeId):
+        tprint(f"Unregister calleeId {calleeId}")
+        for event_dict in self.events.values():
+            if calleeId in event_dict:
+                del event_dict[calleeId]
+                break
+
+    def callThenUnregister(self, calleeId, eventInfo, callee):
+        callee(calleeId=calleeId, eventInfo=eventInfo)
+        self.markForUnregister.append(calleeId)
+
+    def publishMainLoop(self, eventName, eventInfo=None):
+        self.work([eventName, eventInfo], block=False)