fix gauge percentage calculation for the case when min value is not zero

component/gauge/gauge.go

@@ -82,10 +82,7 @@ func (g *Gauge) Draw(buffer *ui.Buffer) {
 
 	g.Block.Draw(buffer)
 
-	percent := 0.0
+	percent := calculatePercent(g)
-	if g.curValue != 0 && g.maxValue != g.minValue {
-		percent = (100 * g.curValue) / (g.maxValue - g.minValue)
-	}
 
 	var label string
 	if g.percentOnly {
@@ -121,3 +118,10 @@ func (g *Gauge) Draw(buffer *ui.Buffer) {
 
 	component.RenderAlert(g.Alert, g.Rectangle, buffer)
 }
+
+func calculatePercent(g *Gauge) float64 {
+	if g.curValue != g.minValue && g.maxValue != g.minValue {
+		return (100 * (g.curValue - g.minValue)) / (g.maxValue - g.minValue)
+	}
+	return 0
+}

component/gauge/gauge_test.go

@@ -0,0 +1,27 @@
+package gauge
+
+import "testing"
+
+func Test_calculatePercent(t *testing.T) {
+	type args struct {
+		g *Gauge
+	}
+	tests := []struct {
+		name string
+		args args
+		want float64
+	}{
+		{"should calculate percent between 0 and 60", args{&Gauge{minValue: 0, maxValue: 60, curValue: 45}}, 75},
+		{"should calculate percent between 10 and 60", args{&Gauge{minValue: 10, maxValue: 60, curValue: 59}}, 98},
+		{"should calculate percent between -20 and 60", args{&Gauge{minValue: -20, maxValue: 60, curValue: 0}}, 25},
+		{"should calculate percent when cur value = min value", args{&Gauge{minValue: -10, maxValue: 60, curValue: -10}}, 0},
+		{"should calculate percent when min value = max value", args{&Gauge{minValue: -124, maxValue: -124, curValue: -124}}, 0},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := calculatePercent(tt.args.g); got != tt.want {
+				t.Errorf("calculatePercent() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}