separate code

src/udi/mqtt/mqtt.go

@@ -1,9 +1,126 @@
 package mqtt
 
 import "log"
+import "fmt"
+import "os"
+import "strings"
+// import "time"
+import MQTT "github.com/eclipse/paho.mqtt.golang"
+import "github.com/google/uuid"
+import "crypto/tls"
 
-
-func TestMqtt() {
-  log.Println("test mqtt")
+type Message struct {
+  Topic string
+  Payload []byte
+}
+
+var InputChannel chan Message = make(chan Message, 100)
+var OutputChannel chan Message = make(chan Message, 100)
+
+var mqttClient MQTT.Client
+
+func onMessageReceived(client MQTT.Client, message MQTT.Message) {
+  // log.Printf("Message received, topic: %s, payload: %s\n", message.Topic(), message.Payload())
+  m := Message { 
+    Topic: message.Topic(), 
+    Payload: message.Payload(),
+  }
+  select {
+  case InputChannel <- m:
+    {}
+    //log.Println("Message sent to channel")
+  default:
+    log.Println("Channel full, message lost")
+  }
+}
+
+func onConnectionLost(client MQTT.Client, error error) {
+  log.Printf("Connection lost, error %s", error)
+}
+
+func onReconnecting(client MQTT.Client, clientOpts *MQTT.ClientOptions) {
+  log.Println("Oops, connection lost, already reconnecting ...")
+}
+
+
+func onConnect(client MQTT.Client) {
+  topicsStr := os.Getenv("MQTT_SUBSCRIBE_TOPICS")
+  if topicsStr == "" {
+    log.Fatal("No topics given, set env var MQTT_SUBSCRIBE_TOPICS")
+  }
+  topics := strings.Split(topicsStr, ",")
+  for _, topic := range topics {
+    if token := client.Subscribe(topic, 0, onMessageReceived); token.Wait() && token.Error() != nil {
+      log.Fatalf("Unable to subscribe to topic %s, error %s", topic, token.Error())
+    }
+    log.Printf("Successfully subscribed to topic %s", topic)
+  }
+}
+
+func outputDispatcher(client MQTT.Client) {
+  for {
+    select {
+    case message := <- OutputChannel:
+      log.Printf("Message arrived in outputDispatcher, topic: %s, payload: %s\n", message.Topic, message.Payload)
+      if token := client.Publish(message.Topic, 0, false, message.Payload); token.Wait() && token.Error() != nil {
+        log.Printf("Unable to publish, error %s", token.Error())
+      }
+      log.Println("Successfully published")
+    }
+  }
+}
+
+func StartMqttClient() {
+  broker := os.Getenv("MQTT_BROKER")
+  if broker == "" {
+    log.Fatal("No broker given, set env var MQTT_BROKER")
+  }
+
+  prefix := "UDI"
+  uuid := uuid.New()
+  clientId := fmt.Sprintf("%s-%s", prefix, uuid)
+
+  opts := MQTT.NewClientOptions().
+    AddBroker(broker).
+    SetClientID(clientId).
+    SetConnectionLostHandler(onConnectionLost).
+    SetOnConnectHandler(onConnect).
+    SetReconnectingHandler(onReconnecting).
+    SetConnectRetry(true)
+
+  username := os.Getenv("MQTT_USERNAME")
+  if username != "" {
+    opts.SetUsername(username)
+  }
+
+  password := os.Getenv("MQTT_PASSWORD")
+  if password != "" {
+    opts.SetPassword(password)
+  }
+
+  enableTls := os.Getenv("MQTT_ENABLE_TLS")
+  if enableTls == "true" {
+    log.Println("Enableing TLS connection")
+    tlsConfig := &tls.Config { 
+      InsecureSkipVerify: true, 
+    }
+    opts.SetTLSConfig(tlsConfig)
+	}
+
+  log.Println("Trying to connect to broker")
+  mqttClient = MQTT.NewClient(opts)
+  if token := mqttClient.Connect(); token.Wait() && token.Error() != nil {
+    log.Fatalf("Unable to connect to broker %s, error %s", broker, token.Error())
+  }
+  log.Printf("Successfully connected to broker %s", broker)
+
+  go outputDispatcher(mqttClient)
+
+  return
+}
+
+func StopMqttClient() {
+  log.Println("Disconnecting from broker")
+  mqttClient.Disconnect(250)
 }