res_levis_backend/cmd/decoder/main.go

package main

import (
	"bytes"
	"context"
	"encoding/binary"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"math"
	"strconv"
	"strings"
	"time"

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

func main() {
	// Load global context to init beacons and latest list
	appCtx := model.AppContext{
		Beacons: model.BeaconsList{
			Beacons: make(map[string]model.Beacon),
		},
		Settings: model.Settings{
			Settings: model.SettingsVal{
				Location_confidence:  4,
				Last_seen_threshold:  15,
				Beacon_metrics_size:  30,
				HA_send_interval:     5,
				HA_send_changes_only: false,
			},
		},
		BeaconEvents: model.BeaconEventList{
			Beacons: make(map[string]model.BeaconEvent),
		},
		BeaconsLookup: make(map[string]struct{}),
	}

	cfg := config.Load()

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

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

	alertWriter := kafkaclient.KafkaWriter(cfg.KafkaURL, "alertbeacons")
	defer alertWriter.Close()

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

	// // Kafka reader for latest list updates
	// latestReader := kafkaclient.KafkaReader(cfg.KafkaURL, "latestbeacons", "gid-latest")
	// defer latestReader.Close()

	// // Kafka reader for settings updates
	// settingsReader := kafkaclient.KafkaReader(cfg.KafkaURL, "settings", "gid-settings")
	// defer settingsReader.Close()

	// declare channel for collecting Kafka messages
	chRaw := make(chan model.Incoming_json, 2000)
	chApi := make(chan model.ApiUpdate, 2000)
	// chLatest := make(chan model.Incoming_json, 2000)
	// chSettings := make(chan model.SettingsVal, 10)

	go kafkaclient.Consume(rawReader, chRaw)
	go kafkaclient.Consume(apiReader, chApi)
	// go kafkaclient.Consume(latestReader, chLatest)
	// go kafkaclient.Consume(settingsReader, chSettings)

	for {
		select {
		case msg := <-chRaw:
			processIncoming(msg, &appCtx, alertWriter)
		case msg := <-chApi:
			switch msg.Method {
			case "POST":
				id := msg.Beacon.Beacon_id
				appCtx.BeaconsLookup[id] = struct{}{}
			case "DELETE":
				fmt.Println("Incoming delete message")
			}
			// case msg := <-chLatest:
			// 	fmt.Println("latest msg: ", msg)
			// case msg := <-chSettings:
			// 	appCtx.Settings.Lock.Lock()
			// 	appCtx.Settings.Settings = msg
			// 	fmt.Println("settings channel: ", msg)
			// 	appCtx.Settings.Lock.Unlock()
		}
	}
}

func processIncoming(incoming model.Incoming_json, ctx *model.AppContext, writer *kafka.Writer) {
	id := mqttclient.GetBeaconID(incoming)
	_, ok := ctx.BeaconsLookup[id]
	if !ok {
		return
	}

	err := decodeBeacon(incoming, ctx, writer)
	if err != nil {
		fmt.Println("error in decoding")
		return
	}
}

func decodeBeacon(incoming model.Incoming_json, ctx *model.AppContext, writer *kafka.Writer) error {
	beacon := strings.TrimSpace(incoming.Data)
	id := mqttclient.GetBeaconID(incoming)
	if beacon == "" {
		return nil // How to return error?, do I even need to return error
	}

	b, err := hex.DecodeString(beacon)
	if err != nil {
		return err
	}

	// check for flag byte, if first AD structure is flag bytes, remove it
	if len(b) > 1 && b[1] == 0x01 {
		l := int(b[0]) // length of AD structure
		if 1+l <= len(b) {
			b = b[1+l:]
		}
	}

	adStructureIndeces := ParseADFast(b)
	event := model.BeaconEvent{}
	for _, r := range adStructureIndeces {
		ad := b[r[0]:r[1]]
		if checkIngics(ad) {
			event = parseIngicsState(ad)
			event.Id = id
			event.Name = id
			break
		} else if checkEddystoneTLM(ad) {
			event = parseEddystoneState(ad)
			event.Id = id
			event.Name = id
			break
		} else if checkMinewB7(ad) {
			fmt.Println("Minew B7 vendor format")
			break
		}
	}

	if event.Id != "" {
		prevEvent, ok := ctx.BeaconEvents.Beacons[id]
		ctx.BeaconEvents.Beacons[id] = event
		if ok && bytes.Equal(prevEvent.Hash(), event.Hash()) {
			return nil
		}

		eMsg, err := json.Marshal(event)
		if err != nil {
			return err
		}

		err = writer.WriteMessages(context.Background(), kafka.Message{
			Value: eMsg,
		})

		if err != nil {
			return err
		}

		fmt.Println("Message sent")
	}

	return nil
}

func checkIngics(ad []byte) bool {
	if len(ad) >= 6 &&
		ad[1] == 0xFF &&
		ad[2] == 0x59 &&
		ad[3] == 0x00 &&
		ad[4] == 0x80 &&
		ad[5] == 0xBC {
		return true
	}

	return false
}

func parseIngicsState(ad []byte) model.BeaconEvent {
	return model.BeaconEvent{
		Battery: uint32(binary.LittleEndian.Uint16(ad[6:8])),
		Event:   int(ad[8]),
		Type:    "Ingics",
	}
}

func checkEddystoneTLM(ad []byte) bool {
	if len(ad) >= 4 &&
		ad[1] == 0x16 &&
		ad[2] == 0xAA &&
		ad[3] == 0xFE &&
		ad[4] == 0x20 {
		return true
	}

	return false
}

func parseEddystoneState(ad []byte) model.BeaconEvent {
	return model.BeaconEvent{
		Battery: uint32(binary.BigEndian.Uint16(ad[6:8])),
		Type:    "Eddystone",
	}
}

// I dont think this is always true, but for testing is ok
func checkMinewB7(ad []byte) bool {
	if len(ad) >= 4 &&
		ad[1] == 0x16 &&
		ad[2] == 0xE1 &&
		ad[3] == 0xFF {
		return true
	}

	return false
}

func ParseADFast(b []byte) [][2]int {
	var res [][2]int
	i := 0

	for i < len(b) {
		l := int(b[i])
		if l == 0 || i+1+l > len(b) {
			break
		}

		res = append(res, [2]int{i, i + 1 + l})

		i += 1 + l
	}

	return res
}

func getBeaconDistance(incoming model.Incoming_json) float64 {
	rssi := incoming.RSSI
	power := incoming.TX_power
	distance := 100.0

	ratio := float64(rssi) * (1.0 / float64(twos_comp(power)))
	if ratio < 1.0 {
		distance = math.Pow(ratio, 10)
	} else {
		distance = (0.89976)*math.Pow(ratio, 7.7095) + 0.111
	}
	return distance
}

func updateBeacon(beacon *model.Beacon, incoming model.Incoming_json) {
	now := time.Now().Unix()

	beacon.Incoming_JSON = incoming
	beacon.Last_seen = now
	beacon.Beacon_type = incoming.Beacon_type
	beacon.HB_ButtonCounter = incoming.HB_ButtonCounter
	beacon.HB_Battery = incoming.HB_Battery
	beacon.HB_RandomNonce = incoming.HB_RandomNonce
	beacon.HB_ButtonMode = incoming.HB_ButtonMode

	if beacon.Beacon_metrics == nil {
		beacon.Beacon_metrics = make([]model.BeaconMetric, 10)
	}

	metric := model.BeaconMetric{}
	metric.Distance = getBeaconDistance(incoming)
	metric.Timestamp = now
	metric.Rssi = int64(incoming.RSSI)
	metric.Location = incoming.Hostname
	beacon.Beacon_metrics = append(beacon.Beacon_metrics, metric)
}

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