Improve snapshot payload debugging and handling

- Added a check for payload length and print debugging information.
- Print part of the payload to help diagnose issues with image data.

dayglo_detector/dayglo_detector.py

@@ -29,13 +29,11 @@ initial_snapshot_processed = False
 def on_connect(client, userdata, flags, rc):
     if rc == 0:
         print("Connected successfully to MQTT broker")
-        client.subscribe(MQTT_SNAPSHOT_TOPIC)
+        client.subscribe(MQTT_SNAPSHOT_TOPIC, qos=1)
         print(f"Subscribed to topic: {MQTT_SNAPSHOT_TOPIC}")
         publish_discovery_configurations()
         # Publish initial rating of 0
         publish_rating(0)
-        # Request the retained snapshot to process the initial image
-        client.publish(MQTT_SNAPSHOT_TOPIC, "", qos=1)
     else:
         print(f"Failed to connect, return code {rc}")
 
@@ -59,6 +57,11 @@ def on_message(client, userdata, msg):
     global initial_snapshot_processed
     if msg.topic == MQTT_SNAPSHOT_TOPIC:
         print("Snapshot received")
+        if len(msg.payload) == 0:
+            print("Received an empty payload, skipping processing.")
+        else:
+            print(f"Payload length: {len(msg.payload)} bytes")
+            print(f"Payload (first 100 bytes): {msg.payload[:100]}...")
             process_snapshot(msg.payload)
             initial_snapshot_processed = True