api: implement abstraction for connecting to CCUJACK MQTT broker

api/src/dooris_api/mqtt_client.py

@@ -0,0 +1,92 @@
+#
+# This whole implementation is adapted from the upstream GitHub example
+# https://github.com/eclipse-paho/paho.mqtt.python/blob/master/examples/loop_asyncio.py
+# 
+
+from typing import Any
+import logging
+import asyncio
+import socket
+
+import paho.mqtt.client as mqtt
+
+
+logger = logging.getLogger(__name__)
+
+
+class AsyncLooper:
+    """
+    Helper class to implement loopgin with asyncio for the underlying mqtt IO  
+    """
+
+    def __init__(self, loop: asyncio.AbstractEventLoop, client: mqtt.Client):
+        self.loop = loop
+
+        self.client = client
+        self.client.on_socket_open = self.on_socket_open
+        self.client.on_socket_close = self.on_socket_close
+        self.client.on_socket_register_write = self.on_socket_register_write
+        self.client.on_socket_unregister_write = self.on_socket_unregister_write
+
+    def on_socket_open(self, client, userdata, sock):
+        def cb():
+            client.loop_read()
+
+        self.loop.add_reader(sock, cb)
+        self.task_misc = self.loop.create_task(self.misc_loop())
+
+    def on_socket_close(self, client, userdata, sock):
+        self.loop.remove_reader(sock)
+        self.task_misc.cancel()
+
+    def on_socket_register_write(self, client, userdata, sock):
+        def cb():
+            client.loop_write()
+
+        self.loop.add_writer(sock, cb)
+
+    def on_socket_unregister_write(self, client, userdata, sock):
+        self.loop.remove_writer(sock)
+
+    async def misc_loop(self):
+        while self.client.loop_misc() == mqtt.MQTT_ERR_SUCCESS:
+            try:
+                await asyncio.sleep(1)
+            except asyncio.CancelledError:
+                break
+
+
+class AsyncMqttClient:
+    loop: asyncio.AbstractEventLoop
+    
+    def __init__(self, connection_string: str, username: str, password: str):
+        self.connection_string = connection_string
+        self.client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, client_id="dooris")
+        self.client.username = username
+        self.client.password = password
+        self.client.on_connect = self.on_connect
+        self.client.on_message = self.on_message
+        self.client.on_disconnect = self.on_disconnect
+
+    def on_connect(self, client: mqtt.Client, userdata: Any, flags: mqtt.ConnectFlags, reason_code, properties: mqtt.Properties):
+        logger.debug(f"mqtt client connected with message '{reason_code}'")
+
+    def on_disconnect(self, client: mqtt.Client, userdata: Any, flags: mqtt.DisconnectFlags, reason_code, properties: mqtt.Properties):
+        logger.debug("mqtt client disconnected")
+        print("flags", type(flags), flags)
+        print("reason_code", type(reason_code), reason_code)
+        print("properties", type(properties), properties)
+
+    def on_message(self, client: mqtt.Client, userdata: Any, msg):
+        logger.debug("mqtt client got message")
+        print("msg", type(msg), msg)
+
+    async def connect(self):
+        server_host, server_port = self.connection_string.rsplit(":", maxsplit=1)
+        
+        looper = AsyncLooper(asyncio.get_running_loop(), self.client)
+
+        logger.info("Connecting to mqtt server at %s:%s", server_host, server_port)
+        self.client.connect(server_host, int(server_port))
+        self.client.socket().setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 2048)    
+