1 files changed, 54 insertions, 0 deletions
diff --git a/volume/volume.go b/volume/volume.go
new file mode 100644
index 0000000..020d1a6
--- /dev/null
+++ b/volume/volume.go
@@ -0,0 +1,54 @@
+package volume
+
+import (
+	"errors"
+	"fmt"
+)
+
+type unit float32
+
+const (
+	CubicCentimetre unit = 1
+	Litre           unit = 1_000
+	CubicMetre      unit = 1_000_000
+	CubicInch       unit = 16.38706
+)
+
+// UnitStrings returns a slice of strings, each representing a
+// unit.
+// This is necessary because giu.Combo only works with strings.
+func UnitStrings() []string {
+	return []string{"cc", "L", "m³", "in³"}
+}
+
+const (
+	DefaultUnit unit = CubicCentimetre
+	// DefaulUnitIndex is used to index UnitStrings().
+	DefaultUnitIndex int32 = 0 // cc
+)
+
+func UnitFromString(s string) (unit, error) {
+	// Each case corresponds to a value in UnitStrings().
+	switch s {
+	case "cc":
+		return CubicCentimetre, nil
+	case "L":
+		return Litre, nil
+	case "m³":
+		return CubicMetre, nil
+	case "in³":
+		return CubicInch, nil
+	default:
+		return *new(unit), errors.New(fmt.Sprintf("invalid volume unit: '%s'", s))
+	}
+}
+
+type Volume struct {
+	Val  float32
+	Unit unit
+}
+
+func (v Volume) AsUnit(u unit) float32 {
+	cc := v.Val * float32(v.Unit) // Convert to cubic centimetres.
+	return cc / float32(u)        // Convert to desired unit.
+}