From 5502c0affe70fc70e1ca2949fbd8b554300bb660 Mon Sep 17 00:00:00 2001
From: Julian Kornberger <jk+github@digineo.de>
Date: Sat, 8 Apr 2017 13:57:33 +0200
Subject: [PATCH] Fix airtime calculation

---
 data/airtime.go      | 36 +++++++++-------------
 data/airtime_test.go | 73 +++++++++++++++++++++-----------------------
 2 files changed, 50 insertions(+), 59 deletions(-)

diff --git a/data/airtime.go b/data/airtime.go
index 6533963..884e791 100644
--- a/data/airtime.go
+++ b/data/airtime.go
@@ -1,8 +1,6 @@
 package data
 
-import (
-	"math"
-)
+import "math"
 
 // Wireless struct
 type Wireless struct {
@@ -29,7 +27,7 @@ type WirelessAirtime struct {
 	Frequency  uint32 `json:"frequency"`
 }
 
-// FrequencyName to 11g or 11a
+// FrequencyName returns 11g or 11a
 func (airtime WirelessAirtime) FrequencyName() string {
 	if airtime.Frequency < 5000 {
 		return "11g"
@@ -37,32 +35,28 @@ func (airtime WirelessAirtime) FrequencyName() string {
 	return "11a"
 }
 
-// SetUtilization Calculates the utilization values in regard to the previous values
+// SetUtilization calculates the utilization values in regard to the previous values
 func (current WirelessStatistics) SetUtilization(previous WirelessStatistics) {
 	for _, c := range current {
 		for _, p := range previous {
-			if c.Frequency == p.Frequency {
-				c.SetUtilization(p)
+			// Same frequency and time passed?
+			if c.Frequency == p.Frequency && p.ActiveTime < c.ActiveTime {
+				c.setUtilization(p)
 			}
 		}
 	}
 }
 
-// SetUtilization Calculates the utilization values in regard to the previous values
-func (airtime *WirelessAirtime) SetUtilization(prev *WirelessAirtime) {
-	if airtime.ActiveTime <= prev.ActiveTime {
-		return
-	}
-
+// setUtilization updates the utilization values in regard to the previous values
+func (airtime *WirelessAirtime) setUtilization(prev *WirelessAirtime) {
+	// Calculate deltas
 	active := float64(airtime.ActiveTime) - float64(prev.ActiveTime)
 	busy := float64(airtime.BusyTime) - float64(prev.BusyTime)
-	rx := float64(airtime.TxTime) - float64(prev.TxTime)
-	tx := float64(airtime.RxTime) - float64(prev.RxTime)
+	rx := float64(airtime.RxTime) - float64(prev.RxTime)
+	tx := float64(airtime.TxTime) - float64(prev.TxTime)
 
-	// Calculate utilizations
-	if active > 0 {
-		airtime.ChanUtil = float32(math.Min(100, 100*(busy+rx+tx)/active))
-		airtime.RxUtil = float32(math.Min(100, 100*rx/active))
-		airtime.TxUtil = float32(math.Min(100, 100*tx/active))
-	}
+	// Update utilizations
+	airtime.ChanUtil = float32(math.Min(100, 100*busy/active))
+	airtime.RxUtil = float32(math.Min(100, 100*rx/active))
+	airtime.TxUtil = float32(math.Min(100, 100*tx/active))
 }
diff --git a/data/airtime_test.go b/data/airtime_test.go
index e5ecfb7..63e51f6 100644
--- a/data/airtime_test.go
+++ b/data/airtime_test.go
@@ -19,62 +19,59 @@ func TestUtilization(t *testing.T) {
 
 	t1 := &WirelessAirtime{
 		ActiveTime: 20,
-		BusyTime:   0,
+		BusyTime:   5,
 		TxTime:     5,
 		RxTime:     0,
 	}
 	t2 := &WirelessAirtime{
 		ActiveTime: 120,
-		BusyTime:   10,
+		BusyTime:   50,
 		TxTime:     25,
 		RxTime:     15,
 	}
-	t3 := &WirelessAirtime{
-		ActiveTime: 200,
-		BusyTime:   40,
-		TxTime:     35,
-		RxTime:     15,
-	}
 
-	t1.SetUtilization(t2)
-	assert.Zero(t1.ChanUtil)
-	assert.Zero(t1.TxUtil)
-	assert.Zero(t1.RxUtil)
+	t1.setUtilization(t1)
+	assert.NotZero(t1.ChanUtil)
+	assert.EqualValues(0, t2.ChanUtil)
+	assert.EqualValues(0, t2.RxUtil)
+	assert.EqualValues(0, t2.TxUtil)
 
-	t2.SetUtilization(t1)
+	t2.setUtilization(t1)
 	assert.NotZero(t2.ChanUtil)
 	assert.EqualValues(45, t2.ChanUtil)
-	assert.EqualValues(20, t2.RxUtil)
-	assert.EqualValues(15, t2.TxUtil)
-
-	t3.SetUtilization(t2)
-	assert.EqualValues(50, t3.ChanUtil)
-	assert.EqualValues(12.5, t3.RxUtil)
-	assert.EqualValues(0, t3.TxUtil)
+	assert.EqualValues(15, t2.RxUtil)
+	assert.EqualValues(20, t2.TxUtil)
 }
 
 func TestWirelessStatistics(t *testing.T) {
 	assert := assert.New(t)
 
+	// This is the current value
 	stats := WirelessStatistics([]*WirelessAirtime{{
-		Frequency:   2400,
-		ActiveTime: 20,
-		TxTime:     10,
-	}})
-
-	// Different Frequency, should not change anything
-	stats.SetUtilization([]*WirelessAirtime{{
-		Frequency:   5000,
-		ActiveTime: 15,
-		TxTime:     1,
-	}})
-	assert.EqualValues(0, stats[0].ChanUtil)
-
-	// Same Frequency, should set the utilization
-	stats.SetUtilization([]*WirelessAirtime{{
-		Frequency:   2400,
+		Frequency:  2400,
 		ActiveTime: 10,
-		TxTime:     5,
+		BusyTime:   4,
+		RxTime:     3,
 	}})
-	assert.EqualValues(50, stats[0].ChanUtil)
+
+	// previous value: Different Frequency, should not change anything
+	stats.SetUtilization([]*WirelessAirtime{{
+		Frequency:  5000,
+		ActiveTime: 5,
+		RxTime:     1,
+	}})
+	assert.Zero(0, stats[0].ChanUtil)
+	assert.Zero(0, stats[0].RxUtil)
+	assert.Zero(0, stats[0].TxUtil)
+
+	// previous value: Same Frequency, should set the utilization
+	stats.SetUtilization([]*WirelessAirtime{{
+		Frequency:  2400,
+		ActiveTime: 5,
+		RxTime:     2,
+		BusyTime:   1,
+	}})
+	assert.EqualValues(60, stats[0].ChanUtil)
+	assert.EqualValues(20, stats[0].RxUtil)
+	assert.EqualValues(0, stats[0].TxUtil)
 }