Initial MVP commit

internal/application/units/converter.go

@@ -0,0 +1,35 @@
+package units
+
+import (
+	"math"
+
+	"gitea.maximumdirect.net/ejr/weatherapi/internal/platform/constants"
+)
+
+type Converter interface {
+	TemperatureCToOutput(celsius *float64) *float64
+	SpeedKmhToOutput(kmh *float64) *float64
+}
+
+type USConverter struct{}
+
+func (USConverter) TemperatureCToOutput(celsius *float64) *float64 {
+	if celsius == nil {
+		return nil
+	}
+	f := round(constants.CelsiusToFahrenheit(*celsius), constants.TempFahrenheitPrecision)
+	return &f
+}
+
+func (USConverter) SpeedKmhToOutput(kmh *float64) *float64 {
+	if kmh == nil {
+		return nil
+	}
+	mph := round(constants.KmhToMph(*kmh), constants.WindMphPrecision)
+	return &mph
+}
+
+func round(v float64, precision int) float64 {
+	pow := math.Pow(10, float64(precision))
+	return math.Round(v*pow) / pow
+}

internal/application/units/converter_test.go

@@ -0,0 +1,43 @@
+package units
+
+import "testing"
+
+func TestUSConverterTemperatureCToOutput(t *testing.T) {
+	c := USConverter{}
+
+	if got := c.TemperatureCToOutput(nil); got != nil {
+		t.Fatalf("expected nil for nil input")
+	}
+
+	zeroC := 0.0
+	got := c.TemperatureCToOutput(&zeroC)
+	if got == nil || *got != 32.0 {
+		t.Fatalf("expected 32.0F, got %v", got)
+	}
+
+	v := 20.56 // 69.008F -> 69.0 at precision 1
+	got = c.TemperatureCToOutput(&v)
+	if got == nil || *got != 69.0 {
+		t.Fatalf("expected 69.0F, got %v", got)
+	}
+}
+
+func TestUSConverterSpeedKmhToOutput(t *testing.T) {
+	c := USConverter{}
+
+	if got := c.SpeedKmhToOutput(nil); got != nil {
+		t.Fatalf("expected nil for nil input")
+	}
+
+	v := 10.0 // 6.21371 mph -> 6.2 at precision 1
+	got := c.SpeedKmhToOutput(&v)
+	if got == nil || *got != 6.2 {
+		t.Fatalf("expected 6.2 mph, got %v", got)
+	}
+
+	exact := 16.09344 // exact 10 mph
+	got = c.SpeedKmhToOutput(&exact)
+	if got == nil || *got != 10.0 {
+		t.Fatalf("expected 10.0 mph, got %v", got)
+	}
+}