res_levis_backend/internal/pkg/service/beacon_service.go

package service

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"slices"
	"strings"
	"time"

	"github.com/AFASystems/presence/internal/pkg/model"
	"github.com/segmentio/kafka-go"
	"gorm.io/gorm"
)

// KafkaWriter defines the interface for writing Kafka messages (allows mocking in tests)
type KafkaWriter interface {
	WriteMessages(ctx context.Context, msgs ...kafka.Message) error
}

func LocationToBeaconService(msg model.HTTPLocation, db *gorm.DB, writer KafkaWriter, ctx context.Context) {
	if msg.ID == "" {
		msg := "empty ID"
		slog.Error(msg)
		return
	}

	var zones []model.TrackerZones
	if err := db.Select("zoneList").Where("tracker = ?", msg.ID).Find(&zones).Error; err != nil {
		msg := fmt.Sprintf("Error in selecting zones: %v", err)
		slog.Error(msg)
		return
	}

	var tracker model.Tracker
	if err := db.Where("id = ?", msg.ID).Find(&tracker).Error; err != nil {
		msg := fmt.Sprintf("Error in selecting tracker: %v", err)
		slog.Error(msg)
		return
	}

	var allowedZones []string
	for _, z := range zones {
		allowedZones = append(allowedZones, z.ZoneList...)
	}

	var gw model.Gateway
	mac := formatMac(msg.Location)
	if err := db.Select("id").Where("mac = ?", mac).First(&gw).Error; err != nil {
		msg := fmt.Sprintf("Gateway not found for MAC: %s", mac)
		slog.Error(msg)
		return
	}	

	if len(allowedZones) != 0 && !slices.Contains(allowedZones, gw.ID) {
		alert := model.Alert{
			ID:    msg.ID,
			Type:  "Restricted zone",
			Value: gw.ID,
		}

		eMsg, err := json.Marshal(alert)
		if err != nil {
			msg := "Error in marshaling"
			slog.Error(msg)
			return
		} else {
			msg := kafka.Message{
				Value: eMsg,
			}
			writer.WriteMessages(ctx, msg)
			return
		}
	}

	// status, subject, subject name?
	if err := db.Create(&model.Tracks{UUID: msg.ID, Timestamp: time.Now(), Gateway: gw.ID, GatewayMac: gw.MAC, Tracker: msg.ID, Floor: gw.Floor, Building: gw.Building, TrackerMac: tracker.MAC, Signal: msg.RSSI}).Error; err != nil {
		msg := fmt.Sprintf("Error in saving distance for beacon: %v", err)
		slog.Error(msg)
		return
	}

	if err := db.Updates(&model.Tracker{ID: msg.ID, Location: gw.ID, Distance: msg.Distance, X: gw.X, Y: gw.Y}).Error; err != nil {
		msg := fmt.Sprintf("Error in saving distance for beacon: %v", err)
		slog.Error(msg)
		return
	}
}

func formatMac(MAC string) string {
	var res strings.Builder
	for i := 0; i < len(MAC); i += 2 {
		if i > 0 {
			res.WriteByte(':')
		}

		end := min(i+2, len(MAC))

		res.WriteString(MAC[i:end])
	}

	return res.String()
}