res_levis_backend/cmd/bridge/main.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"log/slog"
	"os"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/AFASystems/presence/internal/pkg/common/appcontext"
	"github.com/AFASystems/presence/internal/pkg/config"
	"github.com/AFASystems/presence/internal/pkg/kafkaclient"
	"github.com/AFASystems/presence/internal/pkg/model"
	mqtt "github.com/eclipse/paho.mqtt.golang"
	"github.com/segmentio/kafka-go"
)

var wg sync.WaitGroup

func mqtthandler(writer *kafka.Writer, topic string, message []byte, appState *appcontext.AppState) {
	hostname := strings.Split(topic, "/")[1]
	msgStr := string(message)

	if strings.HasPrefix(msgStr, "[") {
		var readings []model.RawReading
		err := json.Unmarshal(message, &readings)
		if err != nil {
			log.Printf("Error parsing JSON: %v", err)
			return
		}

		for _, reading := range readings {
			if reading.Type == "Gateway" {
				continue
			}
			// fmt.Printf("reading: %+v\n", reading)
			if !appState.BeaconExists(reading.MAC) {
				continue
			}

			fmt.Printf("Tracking beacon: %s\n", reading.MAC)

			adv := model.BeaconAdvertisement{
				Hostname: hostname,
				MAC:      reading.MAC,
				RSSI:     int64(reading.RSSI),
				Data:     reading.RawData,
			}

			encodedMsg, err := json.Marshal(adv)
			if err != nil {
				fmt.Println("Error in marshaling: ", err)
				break
			}

			msg := kafka.Message{
				Value: encodedMsg,
			}
			err = writer.WriteMessages(context.Background(), msg)
			if err != nil {
				fmt.Println("Error in writing to Kafka: ", err)
				time.Sleep(1 * time.Second)
				break
			}
		}
	}
	// } else {
	// 	s := strings.Split(string(message), ",")
	// 	if len(s) < 6 {
	// 		log.Printf("Messaggio CSV non valido: %s", msgStr)
	// 		return
	// 	}

	// 	rawdata := s[4]
	// 	buttonCounter := parseButtonState(rawdata)
	// 	if buttonCounter > 0 {
	// 		adv := model.BeaconAdvertisement{}
	// 		i, _ := strconv.ParseInt(s[3], 10, 64)
	// 		adv.Hostname = hostname
	// 		adv.BeaconType = "hb_button"
	// 		adv.MAC = s[1]
	// 		adv.RSSI = i
	// 		adv.Data = rawdata
	// 		adv.HSButtonCounter = buttonCounter

	// 		read_line := strings.TrimRight(string(s[5]), "\r\n")
	// 		it, err33 := strconv.Atoi(read_line)
	// 		if err33 != nil {
	// 			fmt.Println(it)
	// 			fmt.Println(err33)
	// 			os.Exit(2)
	// 		}
	// 	}
	// }
}

var messagePubHandler = func(msg mqtt.Message, writer *kafka.Writer, appState *appcontext.AppState) {
	mqtthandler(writer, msg.Topic(), msg.Payload(), appState)
}

var connectHandler mqtt.OnConnectHandler = func(client mqtt.Client) {
	fmt.Println("Connected")
}

var connectLostHandler mqtt.ConnectionLostHandler = func(client mqtt.Client, err error) {
	fmt.Printf("Connect lost: %v", err)
}

func main() {
	// Load global context to init beacons and latest list
	appState := appcontext.NewAppState()
	cfg := config.Load()

	// Create log file -> this section and below can be moved in a package, as it is always the same
	logFile, err := os.OpenFile("server.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		log.Fatalf("Failed to open log file: %v\n", err)
	}
	// shell and log file multiwriter
	w := io.MultiWriter(os.Stderr, logFile)
	logger := slog.New(slog.NewJSONHandler(w, nil))
	slog.SetDefault(logger)

	// define context
	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGTERM, syscall.SIGINT)
	defer stop()

	// define kafka reader
	apiReader := appState.AddKafkaReader(cfg.KafkaURL, "apibeacons", "bridge-api")
	// define kafka writer
	writer := appState.AddKafkaWriter(cfg.KafkaURL, "rawbeacons")

	slog.Info("Bridge initialized, subscribed to kafka topics")

	chApi := make(chan model.ApiUpdate, 200)

	wg.Add(1)
	go kafkaclient.Consume(apiReader, chApi, ctx, &wg)

	opts := mqtt.NewClientOptions()
	opts.AddBroker(fmt.Sprintf("tcp://%s:%d", cfg.MQTTHost, 1883))
	opts.SetClientID("go_mqtt_client")
	opts.SetUsername("emqx")
	opts.SetPassword("public")
	opts.SetDefaultPublishHandler(func(c mqtt.Client, m mqtt.Message) { messagePubHandler(m, writer, appState) })
	opts.OnConnect = connectHandler
	opts.OnConnectionLost = connectLostHandler
	client := mqtt.NewClient(opts)
	if token := client.Connect(); token.Wait() && token.Error() != nil {
		panic(token.Error())
	}

	sub(client)

eventloop:
	for {
		select {
		case <-ctx.Done():
			break eventloop
		case msg := <-chApi:
			switch msg.Method {
			case "POST":
				id := msg.Beacon.ID
				appState.AddBeaconToLookup(id)
				lMsg := fmt.Sprintf("Beacon added to lookup: %s", id)
				slog.Info(lMsg)
			case "DELETE":
				id := msg.Beacon.ID
				appState.RemoveBeaconFromLookup(id)
				lMsg := fmt.Sprintf("Beacon removed from lookup: %s", id)
				slog.Info(lMsg)
			}
		}
	}

	slog.Info("broken out of the main event loop")
	wg.Wait()

	slog.Info("All go routines have stopped, Beggining to close Kafka connections")
	appState.CleanKafkaReaders()
	appState.CleanKafkaWriters()

	client.Disconnect(250)
	slog.Info("Closing connection to MQTT broker")
}

func publish(client mqtt.Client) {
	num := 10
	for i := 0; i < num; i++ {
		text := fmt.Sprintf("Message %d", i)
		token := client.Publish("topic/test", 0, false, text)
		token.Wait()
		time.Sleep(time.Second)
	}
}

func sub(client mqtt.Client) {
	topic := "publish_out/#"
	token := client.Subscribe(topic, 1, nil)
	token.Wait()
	fmt.Printf("Subscribed to topic: %s\n", topic)
}