From 5cc3b5f1d22aadf5ee87242e67c1e8f30c53ebad Mon Sep 17 00:00:00 2001
From: blazSmehov <blaz.smehov@senlab.io>
Date: Thu, 27 Nov 2025 14:20:50 +0100
Subject: [PATCH] chore: refactor distance related code for locations algorithm

---
 cmd/location/main.go                  | 24 ++------------
 internal/pkg/common/utils/distance.go | 45 +++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 21 deletions(-)
 create mode 100644 internal/pkg/common/utils/distance.go

diff --git a/cmd/location/main.go b/cmd/location/main.go
index 13a9e68..8089abb 100644
--- a/cmd/location/main.go
+++ b/cmd/location/main.go
@@ -4,11 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"math"
-	"strconv"
 	"time"
 
 	"github.com/AFASystems/presence/internal/pkg/common/appcontext"
+	"github.com/AFASystems/presence/internal/pkg/common/utils"
 	"github.com/AFASystems/presence/internal/pkg/config"
 	"github.com/AFASystems/presence/internal/pkg/kafkaclient"
 	"github.com/AFASystems/presence/internal/pkg/model"
@@ -163,13 +162,12 @@ func assignBeaconToList(adv model.BeaconAdvertisement, appState *appcontext.AppS
 	now := time.Now().Unix()
 
 	if !ok {
-		appState.UpdateLatestBeacon(id, model.Beacon{ID: id, BeaconType: adv.BeaconType, LastSeen: now, IncomingJSON: adv, BeaconLocation: adv.Hostname, Distance: getBeaconDistance(adv)})
+		appState.UpdateLatestBeacon(id, model.Beacon{ID: id, BeaconType: adv.BeaconType, LastSeen: now, IncomingJSON: adv, BeaconLocation: adv.Hostname, Distance: utils.CalculateDistance(adv)})
 		return
 	}
 
 	settings := appState.GetSettingsValue()
 
-	fmt.Println("RSSI: ", adv.RSSI)
 	if settings.RSSIEnforceThreshold && (int64(adv.RSSI) < settings.RSSIMinThreshold) {
 		return
 	}
@@ -189,7 +187,7 @@ func assignBeaconToList(adv model.BeaconAdvertisement, appState *appcontext.AppS
 	}
 
 	metric := model.BeaconMetric{
-		Distance:  getBeaconDistance(adv),
+		Distance:  utils.CalculateDistance(adv),
 		Timestamp: now,
 		RSSI:      int64(adv.RSSI),
 		Location:  adv.Hostname,
@@ -204,19 +202,3 @@ func assignBeaconToList(adv model.BeaconAdvertisement, appState *appcontext.AppS
 
 	appState.UpdateBeacon(id, beacon)
 }
-
-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
-}
diff --git a/internal/pkg/common/utils/distance.go b/internal/pkg/common/utils/distance.go
new file mode 100644
index 0000000..00755f7
--- /dev/null
+++ b/internal/pkg/common/utils/distance.go
@@ -0,0 +1,45 @@
+package utils
+
+import (
+	"math"
+	"strconv"
+
+	"github.com/AFASystems/presence/internal/pkg/model"
+)
+
+// CalculateDistance calculates the approximate distance from RSSI and TX power
+// Uses a hybrid approach combining logarithmic and polynomial models
+func CalculateDistance(adv model.BeaconAdvertisement) float64 {
+	txPower := twosComp(adv.TXPower)
+	ratio := float64(adv.RSSI) / float64(txPower)
+
+	if ratio < 1.0 {
+		return math.Pow(ratio, 10)
+	} else {
+		return (0.89976)*math.Pow(ratio, 7.7095) + 0.111
+	}
+}
+
+// TwosComp converts a two's complement hexadecimal string to int64
+func twosComp(inp string) int64 {
+	i, err := strconv.ParseInt("0x"+inp, 0, 64)
+	if err != nil {
+		return 0
+	}
+
+	if i >= 128 {
+		return i - 256
+	}
+	return i
+}
+
+// ValidateRSSI validates if RSSI value is within reasonable bounds
+func ValidateRSSI(rssi int64) bool {
+	return rssi >= -120 && rssi <= 0
+}
+
+// ValidateTXPower validates if TX power is within reasonable bounds
+func ValidateTXPower(txPower string) bool {
+	power := twosComp(txPower)
+	return power >= -128 && power <= 127
+}