Initial Commit

units/units.go

@@ -0,0 +1,118 @@
+package units
+
+import (
+	"strings"
+)
+
+// Speed represents a unit of speed
+type Speed string
+
+// Speed units
+const (
+	MetersPerSecond   Speed = "MPS"
+	KilometersPerHour Speed = "KMH"
+	Knots             Speed = "KT"
+)
+
+var speedNames = map[Speed]string{
+	MetersPerSecond:   "m/s",
+	KilometersPerHour: "kph",
+	Knots:             "kts",
+}
+
+func (su Speed) String() string {
+	name, ok := speedNames[su]
+	if !ok {
+		return "<unknown>"
+	}
+	return name
+}
+
+// Convert converts a value from one unit to another
+func (sf Speed) Convert(st Speed, val int) int {
+	switch {
+	case sf == MetersPerSecond && st == KilometersPerHour:
+		return int(float64(val) * 3.6)
+	case sf == KilometersPerHour && st == MetersPerSecond:
+		return int(float64(val) / 3.6)
+	case sf == Knots && st == KilometersPerHour:
+		return int(float64(val) * 1.852)
+	case sf == KilometersPerHour && st == Knots:
+		return int(float64(val) / 1.852)
+	case sf == MetersPerSecond && st == Knots:
+		return int(float64(val) * 1.94384)
+	case sf == Knots && st == MetersPerSecond:
+		return int(float64(val) / 1.94384)
+	default:
+		return val
+	}
+}
+
+// ParseSpeed parses a speed value. Valid inputs include:
+// mps, m/s, kmh, kph, kt, and kts.
+// This function is case-insensitive.
+func ParseSpeed(s string) (Speed, bool) {
+	if _, ok := speedNames[Speed(s)]; ok {
+		return Speed(s), true
+	}
+
+	for su, name := range speedNames {
+		if strings.EqualFold(s, name) ||
+			strings.EqualFold(s, string(su)) {
+			return su, true
+		}
+	}
+
+	return "", false
+}
+
+// Distance represents a unit of distance
+type Distance string
+
+// Distance units
+const (
+	StatuteMiles Distance = "SM"
+	Meters       Distance = "M"
+)
+
+var distanceNames = map[Distance]string{
+	StatuteMiles: "mi",
+	Meters:       "m",
+}
+
+func (du Distance) String() string {
+	name, ok := distanceNames[du]
+	if !ok {
+		return "<unknown>"
+	}
+	return name
+}
+
+// Convert converts a value from one unit to another
+func (df Distance) Convert(dt Distance, val float64) float64 {
+	switch {
+	case df == StatuteMiles && dt == Meters:
+		return val * 1609
+	case df == Meters && dt == StatuteMiles:
+		return val / 1609
+	default:
+		return val
+	}
+}
+
+// ParseDistance parses a speed value. Valid inputs include:
+// sm, mi, and m. This function is case-insensitive.
+func ParseDistance(s string) (Distance, bool) {
+	if _, ok := distanceNames[Distance(s)]; ok {
+		return Distance(s), true
+	}
+
+	for d, name := range distanceNames {
+		if strings.EqualFold(s, name) ||
+			strings.EqualFold(s, string(d)) {
+			return d, true
+		}
+	}
+
+	return "", false
+}