package mqtt

import (
  "log"
  "os"
  "fmt"
  MQTT "github.com/eclipse/paho.mqtt.golang"
  "github.com/google/uuid"
)



type MqttHandle struct {
  initialized bool
  pubTopic string
  client MQTT.Client
}

func New() *MqttHandle {
  var mqttHandle MqttHandle
  mqttHandle.initialized = true

  mqttOpts := MQTT.NewClientOptions().
    AddBroker(os.Getenv("MQTT_BROKER")).
    SetClientID(fmt.Sprintf("locsrv-%s", uuid.New())).
    SetConnectRetry(true)
  mqttHandle.client= MQTT.NewClient(mqttOpts)
  if token := mqttHandle.client.Connect(); token.Wait() && token.Error() != nil {
    log.Printf("Unable to connect to broker, error %v", token.Error())
    mqttHandle.initialized = false
  }

  mqttHandle.pubTopic = os.Getenv("MQTT_TOPIC")
  if mqttHandle.pubTopic == "" {
    log.Printf("No topic set")
    mqttHandle.initialized = false
  }
  log.Printf("MQTT connection established")
  return &mqttHandle
}

func (self *MqttHandle) Publish(topicPost string, message string) error {
  if ! self.initialized {
    return fmt.Errorf("MQTT connection not initialized")
  }

  topic := fmt.Sprintf("%s/%s", self.pubTopic, topicPost)
  token := self.client.Publish(topic, 0, true, message) 
  token.Wait()
  if token.Error() != nil {
    return fmt.Errorf("MQTT publish failed: %v", token.Error())
  }

  return nil
}