package main

import (
	"log"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
)

const (
	BROKER                     = `tcp://127.0.0.1:1883`
	CLIENT_ID                  = `siaserver`
	TOPIC_PREFIX               = `sia`
	QOS                        = byte(1)
	RETAINED                   = true
	MQTT_CONNECT_TIMEOUT       = 1 * time.Second
	MQTT_DISCONNECT_TIMEOUT_US = 500
	MQTT_KEEPALIVE_PERIOD      = 2 * time.Second
)

type MQTTMessage struct {
	Topic   string
	Payload []byte
}

func MQTTRun(tx chan MQTTMessage) {
	opts := mqtt.NewClientOptions()
	opts.AddBroker(BROKER)
	opts.SetClientID(CLIENT_ID)
	opts.SetCleanSession(true)
	opts.SetOnConnectHandler(MQTTOnConnectHandler)
	opts.SetConnectionLostHandler(MQTTConnectionLostHandler)
	opts.SetAutoReconnect(true)
	opts.SetConnectRetry(true)
	opts.SetConnectTimeout(MQTT_CONNECT_TIMEOUT)
	opts.SetKeepAlive(MQTT_KEEPALIVE_PERIOD)

	client := mqtt.NewClient(opts)

	token := client.Connect()

	success := token.WaitTimeout(MQTT_CONNECT_TIMEOUT)
	if !success {
		log.Fatal("Initial connection to MQTT broker failed.")
	}
	defer client.Disconnect(MQTT_DISCONNECT_TIMEOUT_US)

	for message := range tx {
		client.Publish(message.Topic, QOS, RETAINED, message.Payload)
	}
}

func MQTTOnConnectHandler(c mqtt.Client) {
	log.Printf("Connected to MQTT broker (%s)", BROKER)
}

func MQTTConnectionLostHandler(c mqtt.Client, err error) {
	log.Printf("Connection to MQTT broker lost: %v", err)
}