res_levis_backend/cmd/location/main.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"math"
	"strconv"
	"time"

	"github.com/AFASystems/presence/internal/pkg/config"
	"github.com/AFASystems/presence/internal/pkg/kafkaclient"
	"github.com/AFASystems/presence/internal/pkg/model"
	"github.com/segmentio/kafka-go"
)

func main() {
	// Load global context to init beacons and latest list
	appCtx := model.AppContext{
		Settings: model.Settings{
			Settings: model.SettingsVal{
				LocationConfidence:   4,
				LastSeenThreshold:    15,
				BeaconMetricSize:     30,
				HASendInterval:       5,
				HASendChangesOnly:    false,
				RSSIEnforceThreshold: true,
				RSSIMinThreshold:     100,
			},
		},
		BeaconsLookup: make(map[string]struct{}),
		LatestList: model.LatestBeaconsList{
			LatestList: make(map[string]model.Beacon),
		},
	}

	cfg := config.Load()

	// Kafka reader for Raw MQTT beacons
	rawReader := kafkaclient.KafkaReader(cfg.KafkaURL, "rawbeacons", "gid-raw-loc")
	defer rawReader.Close()

	// Kafka reader for API server updates
	apiReader := kafkaclient.KafkaReader(cfg.KafkaURL, "apibeacons", "gid-api-loc")
	defer apiReader.Close()

	writer := kafkaclient.KafkaWriter(cfg.KafkaURL, "locevents")
	defer writer.Close()

	fmt.Println("Locations algorithm initialized, subscribed to Kafka topics")

	locTicker := time.NewTicker(1 * time.Second)
	defer locTicker.Stop()

	chRaw := make(chan model.BeaconAdvertisement, 2000)
	chApi := make(chan model.ApiUpdate, 2000)

	go kafkaclient.Consume(rawReader, chRaw)
	go kafkaclient.Consume(apiReader, chApi)

	for {
		select {
		case <-locTicker.C:
			getLikelyLocations(&appCtx, writer)
		case msg := <-chRaw:
			assignBeaconToList(msg, &appCtx)
		case msg := <-chApi:
			switch msg.Method {
			case "POST":
				id := msg.Beacon.ID
				appCtx.BeaconsLookup[id] = struct{}{}
			case "DELETE":
				fmt.Println("Incoming delete message")
			}
		}
	}
}

func getLikelyLocations(ctx *model.AppContext, writer *kafka.Writer) {
	ctx.Beacons.Lock.Lock()
	beacons := ctx.Beacons.Beacons

	for _, beacon := range beacons {

		// Shrinking the model because other properties have nothing to do with the location
		r := model.HTTPLocation{
			Method:   "Standard",
			Distance: 999,
			Name:     beacon.Name,
			ID:       beacon.ID,
			Location: "",
			LastSeen: 999,
		}

		mSize := len(beacon.BeaconMetrics)

		if (int64(time.Now().Unix()) - (beacon.BeaconMetrics[mSize-1].Timestamp)) > ctx.Settings.Settings.LastSeenThreshold {
			continue
		}

		locList := make(map[string]float64)
		seenW := 1.5
		rssiW := 0.75
		for _, metric := range beacon.BeaconMetrics {
			res := seenW + (rssiW * (1.0 - (float64(metric.RSSI) / -100.0)))
			locList[metric.Location] += res
		}

		bestLocName := ""
		maxScore := 0.0
		for locName, score := range locList {
			if score > maxScore {
				maxScore = score
				bestLocName = locName
			}
		}

		bestLocation := model.BestLocation{
			Name:     bestLocName,
			Distance: beacon.BeaconMetrics[mSize-1].Distance,
			LastSeen: beacon.BeaconMetrics[mSize-1].Timestamp,
		}

		if bestLocName == beacon.PreviousLocation {
			beacon.LocationConfidence++
		} else {
			beacon.LocationConfidence = 0
		}

		r.Distance = bestLocation.Distance
		r.Location = bestLocName
		r.LastSeen = bestLocation.LastSeen

		if beacon.LocationConfidence == ctx.Settings.Settings.LocationConfidence && beacon.PreviousConfidentLocation != bestLocName {
			beacon.LocationConfidence = 0

			// Who do I need this if I am sending entire structure anyways? who knows
			js, err := json.Marshal(model.LocationChange{
				Method:           "LocationChange",
				BeaconRef:        beacon,
				Name:             beacon.Name,
				PreviousLocation: beacon.PreviousConfidentLocation,
				NewLocation:      bestLocName,
				Timestamp:        time.Now().Unix(),
			})

			if err != nil {
				beacon.PreviousConfidentLocation = bestLocName
				beacon.PreviousLocation = bestLocName
				ctx.Beacons.Beacons[beacon.ID] = beacon
				continue
			}

			msg := kafka.Message{
				Value: js,
			}

			err = writer.WriteMessages(context.Background(), msg)
			if err != nil {
				fmt.Println("Error in sending Kafka message")
			}
		}

		beacon.PreviousLocation = bestLocName
		ctx.Beacons.Beacons[beacon.ID] = beacon

		js, err := json.Marshal(r)
		if err != nil {
			continue
		}

		msg := kafka.Message{
			Value: js,
		}

		err = writer.WriteMessages(context.Background(), msg)
		if err != nil {
			fmt.Println("Error in sending Kafka message")
		}
	}
}

func assignBeaconToList(adv model.BeaconAdvertisement, ctx *model.AppContext) {
	id := adv.MAC
	_, ok := ctx.BeaconsLookup[id]

	now := time.Now().Unix()

	if !ok {
		// handle removing from the list somewhere else, probably at the point where this is being used which is nowhere in the original code
		ctx.LatestList.Lock.Lock()
		ctx.LatestList.LatestList[id] = model.Beacon{ID: id, BeaconType: adv.BeaconType, LastSeen: now, IncomingJSON: adv, BeaconLocation: adv.Hostname, Distance: getBeaconDistance(adv)}
		ctx.LatestList.Lock.Unlock()
		return
	}

	if ctx.Settings.Settings.RSSIEnforceThreshold && (int64(adv.RSSI) < ctx.Settings.Settings.RSSIMinThreshold) {
		return
	}

	ctx.Beacons.Lock.Lock()
	beacon := ctx.Beacons.Beacons[id]

	beacon.IncomingJSON = adv
	beacon.LastSeen = now
	beacon.BeaconType = adv.BeaconType
	beacon.HSButtonCounter = adv.HSButtonCounter
	beacon.HSBattery = adv.HSBatteryLevel
	beacon.HSRandomNonce = adv.HSRandomNonce
	beacon.HSButtonMode = adv.HSButtonMode

	if beacon.BeaconMetrics == nil {
		beacon.BeaconMetrics = make([]model.BeaconMetric, 0, ctx.Settings.Settings.BeaconMetricSize)
	}

	metric := model.BeaconMetric{
		Distance:  getBeaconDistance(adv),
		Timestamp: now,
		RSSI:      int64(adv.RSSI),
		Location:  adv.Hostname,
	}

	if len(beacon.BeaconMetrics) >= ctx.Settings.Settings.BeaconMetricSize {
		copy(beacon.BeaconMetrics, beacon.BeaconMetrics[1:])
		beacon.BeaconMetrics[ctx.Settings.Settings.BeaconMetricSize-1] = metric
	} else {
		beacon.BeaconMetrics = append(beacon.BeaconMetrics, metric)
	}

	ctx.Beacons.Beacons[id] = beacon
	ctx.Beacons.Lock.Unlock()
}

func getBeaconDistance(adv model.BeaconAdvertisement) float64 {
	ratio := float64(adv.RSSI) * (1.0 / float64(twosComp(adv.TXPower)))
	distance := 100.0
	if ratio < 1.0 {
		distance = math.Pow(ratio, 10)
	} else {
		distance = (0.89976)*math.Pow(ratio, 7.7095) + 0.111
	}
	return distance
}

func twosComp(inp string) int64 {
	i, _ := strconv.ParseInt("0x"+inp, 0, 64)
	return i - 256
}