Update decoder to match correct Meshtastic MQTT topic structure

CLAUDE.md

@@ -1 +1,52 @@
-- Never run the program, you may build it and run tests, but I will run the program manually.
+# Meshtastic MQTT Protocol Structure
+
+## Topic Structure
+
+The Meshtastic MQTT topic structure follows this pattern:
+```
+msh/REGION/2/e/CHANNELNAME/USERID
+```
+
+- `msh`: Fixed prefix for all Meshtastic topics
+- `REGION`: Geographic region code (e.g., `US`, `EU`, `AU`)
+- `2`: Protocol version
+- `e`: Encrypted channel indicator (versions before 2.3.0 used `/c/` instead)
+- `CHANNELNAME`: The channel name used in the Meshtastic network
+- `USERID`: Unique identifier for the device, formats include:
+  - `!` followed by hex characters for MAC address based IDs
+  - `+` followed by phone number for Signal-based IDs
+
+## Message Types
+
+### Protobuf Messages (Binary)
+Topic pattern: `msh/REGION/2/e/CHANNELNAME/USERID`
+- Raw MeshPacket transmissions in protobuf format
+- Can be encrypted or unencrypted based on channel settings
+
+### JSON Messages
+Topic pattern: `msh/REGION/2/json/CHANNELNAME/USERID`
+- Structured JSON payloads with fields like:
+  - `id`: Message ID
+  - `from`: Node ID of sender
+  - `to`: Node ID of recipient (or blank for broadcast)
+  - `payload`: The actual message content
+  - `timestamp`: Time the message was received
+
+Note: JSON format is not supported on nRF52 platform devices.
+
+### Special Topics
+- MQTT Downlink: `msh/REGION/2/json/mqtt/`
+  - Used for sending instructions to gateway nodes
+
+## Important Notes
+
+- The public MQTT server implements a zero-hop policy (only direct messages)
+- JSON messages may include specific data types like:
+  - NodeInfo
+  - Telemetry
+  - Text Messages
+  - Position Updates
+- Position data on public servers has reduced precision for privacy
+- Binary messages use the protocol buffers format defined in the Meshtastic codebase
+
+This corrects the previous assumption that the topic structure was `msh/REGION/STATE/NAME`, which was incorrect.

decoder/decoder.go

@@ -19,7 +19,9 @@ const (
 // DecodedPacket contains information about a decoded packet
 type DecodedPacket struct {
 	Topic     string
+	Region    string
 	Channel   string
+	UserID    string
 	Type      PacketType
 	JSONData  map[string]interface{}
 	FromNode  string
@@ -38,20 +40,40 @@ func DecodePacket(topic string, payload []byte) (*DecodedPacket, error) {
 	}
 
 	// Extract channel and other info from topic
+	// Format: msh/REGION/2/e/CHANNELNAME/USERID
+	// or:     msh/REGION/2/json/CHANNELNAME/USERID
 	parts := strings.Split(topic, "/")
 	if len(parts) < 4 {
 		return packet, fmt.Errorf("invalid topic format: %s", topic)
 	}
 
-	// Set channel info (typically msh/REGION/STATE/NAME)
-	packet.Channel = strings.Join(parts[1:4], "/")
+	// Set the region
+	if len(parts) >= 2 {
+		packet.Region = parts[1]
+	}
 
-	// Try to determine type from topic structure
+	// Extract channel name - should be part 4 for binary or part 5 for JSON
 	if len(parts) >= 5 {
-		typeIndicator := parts[4]
-		
-		switch typeIndicator {
-		case "json":
+		if parts[3] == "e" || parts[3] == "c" {
+			// Binary format: msh/REGION/2/e/CHANNELNAME/USERID
+			if len(parts) >= 5 {
+				packet.Channel = parts[4]
+			}
+			if len(parts) >= 6 {
+				packet.UserID = parts[5]
+			}
+			// This is a binary protobuf packet
+			packet.Type = TypeBinary
+		} else if parts[3] == "json" {
+			// JSON format: msh/REGION/2/json/CHANNELNAME/USERID
+			if len(parts) >= 5 {
+				packet.Channel = parts[4]
+			}
+			if len(parts) >= 6 {
+				packet.UserID = parts[5]
+			}
+			
+			// This is a JSON packet
 			packet.Type = TypeJSON
 			if err := json.Unmarshal(payload, &packet.JSONData); err != nil {
 				return packet, fmt.Errorf("failed to parse JSON: %v", err)
@@ -70,19 +92,8 @@ func DecodePacket(topic string, payload []byte) (*DecodedPacket, error) {
 			if ts, ok := packet.JSONData["timestamp"].(string); ok {
 				packet.Timestamp = ts
 			}
-			
-		case "binary":
-			// Binary protobuf payload
-			packet.Type = TypeBinary
-			// Note: Actual protobuf decoding would be done here
-			
-		case "text":
-			// Plain text payload
-			packet.Type = TypeText
-			packet.Text = string(payload)
-			
-		default:
-			// Try to infer type from payload
+		} else {
+			// Unknown format, try to infer from content
 			if len(payload) > 0 && payload[0] == '{' {
 				// Looks like JSON
 				packet.Type = TypeJSON
@@ -113,7 +124,7 @@ func DecodePacket(topic string, payload []byte) (*DecodedPacket, error) {
 			}
 		}
 	}
-
+	
 	return packet, nil
 }
 
@@ -139,7 +150,13 @@ func FormatPacket(packet *DecodedPacket) string {
 	var builder strings.Builder
 	
 	builder.WriteString(fmt.Sprintf("Topic: %s\n", packet.Topic))
+	
+	// Show basic topic structure
+	builder.WriteString(fmt.Sprintf("Region: %s\n", packet.Region))
 	builder.WriteString(fmt.Sprintf("Channel: %s\n", packet.Channel))
+	if packet.UserID != "" {
+		builder.WriteString(fmt.Sprintf("User ID: %s\n", packet.UserID))
+	}
 	
 	switch packet.Type {
 	case TypeJSON:

main.go

@@ -67,7 +67,10 @@ func main() {
 		log.Fatalf("Error connecting to MQTT broker: %v", token.Error())
 	}
 
-	// Subscribe to topic
+	// Subscribe to all topics for this region
+	// This will capture:
+	// - msh/US/CA/Motherlode/2/e/# (binary protobuf data)
+	// - msh/US/CA/Motherlode/2/json/# (JSON formatted data)
 	topic := mqttTopicPrefix + "/#"
 	token := client.Subscribe(topic, 0, nil)
 	token.Wait()