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config/custom_components/pyscript/mqtt.py

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+"""Handles mqtt messages and notification."""
+
+import json
+import logging
+
+from homeassistant.components import mqtt
+
+from .const import LOGGER_PATH
+
+_LOGGER = logging.getLogger(LOGGER_PATH + ".mqtt")
+
+
+class Mqtt:
+    """Define mqtt functions."""
+
+    #
+    # Global hass instance
+    #
+    hass = None
+
+    #
+    # notify message queues by mqtt message topic
+    #
+    notify = {}
+    notify_remove = {}
+
+    def __init__(self):
+        """Warn on Mqtt instantiation."""
+        _LOGGER.error("Mqtt class is not meant to be instantiated")
+
+    @classmethod
+    def init(cls, hass):
+        """Initialize Mqtt."""
+
+        cls.hass = hass
+
+    @classmethod
+    def mqtt_message_handler_maker(cls, subscribed_topic):
+        """Closure for mqtt_message_handler."""
+
+        async def mqtt_message_handler(mqttmsg):
+            """Listen for MQTT messages."""
+            func_args = {
+                "trigger_type": "mqtt",
+                "topic": mqttmsg.topic,
+                "payload": mqttmsg.payload,
+                "qos": mqttmsg.qos,
+            }
+
+            try:
+                func_args["payload_obj"] = json.loads(mqttmsg.payload)
+            except ValueError:
+                pass
+
+            await cls.update(subscribed_topic, func_args)
+
+        return mqtt_message_handler
+
+    @classmethod
+    async def notify_add(cls, topic, queue):
+        """Register to notify for mqtt messages of given topic to be sent to queue."""
+
+        if topic not in cls.notify:
+            cls.notify[topic] = set()
+            _LOGGER.debug("mqtt.notify_add(%s) -> adding mqtt subscription", topic)
+            cls.notify_remove[topic] = await mqtt.async_subscribe(
+                cls.hass, topic, cls.mqtt_message_handler_maker(topic), encoding="utf-8", qos=0
+            )
+        cls.notify[topic].add(queue)
+
+    @classmethod
+    def notify_del(cls, topic, queue):
+        """Unregister to notify for mqtt messages of given topic for given queue."""
+
+        if topic not in cls.notify or queue not in cls.notify[topic]:
+            return
+        cls.notify[topic].discard(queue)
+        if len(cls.notify[topic]) == 0:
+            cls.notify_remove[topic]()
+            _LOGGER.debug("mqtt.notify_del(%s) -> removing mqtt subscription", topic)
+            del cls.notify[topic]
+            del cls.notify_remove[topic]
+
+    @classmethod
+    async def update(cls, topic, func_args):
+        """Deliver all notifications for an mqtt message on the given topic."""
+
+        _LOGGER.debug("mqtt.update(%s, %s, %s)", topic, vars, func_args)
+        if topic in cls.notify:
+            for queue in cls.notify[topic]:
+                await queue.put(["mqtt", func_args.copy()])