Add volume changing logic

internal/mixer/mixer.go

@@ -247,6 +247,16 @@ func SetAllSinkVolumes(level float64) error {
 	return nil
 }
 
+// ConvertVolume converts a desired volume percentage (0%, 25%, 33%, 90%, etc) to
+// the float64 value needed to pass to SetAllSinkVolumes 0..1.0
+// Percentages should be passed as integers. 25% -> 25
+func ConvertVolume(volPerc int) float64 {
+	if volPerc == 0 {
+		return 0.0
+	}
+	return float64(volPerc) / 100.0
+}
+
 // parseSinks parses the output of `wpctl status` and extracts audio sinks.
 func parseSinks(data []byte) ([]Sink, error) {
 	var sinks []Sink

internal/mixer/mixer_test.go

@@ -0,0 +1,34 @@
+package mixer_test
+
+import (
+	"math"
+	"testing"
+
+	"rhemawavetech.com/rhemawave/internal/mixer"
+)
+
+func TestConvertVolume(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    int
+		expected float64
+	}{
+		{"0 percent", 0, 0.0},
+		{"25 percent", 25, 0.25},
+		{"33 percent", 33, 0.33},
+		{"50 percent", 50, 0.50},
+		{"90 percent", 90, 0.90},
+		{"100 percent", 100, 1.0},
+	}
+
+	const epsilon = 1e-9
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := mixer.ConvertVolume(tt.input)
+			if math.Abs(got-tt.expected) > epsilon {
+				t.Errorf("ConvertVolume(%d) = %v, want %v", tt.input, got, tt.expected)
+			}
+		})
+	}
+}