more functionality

pkg/libyear/libyear.go

@@ -1,6 +1,9 @@
 package libyear
 
-import "time"
+import (
+	"fmt"
+	"time"
+)
 
 type Info struct {
 	Version string    // version string
@@ -13,6 +16,8 @@ type Pair struct {
 	Current Info
 }
 
+// TODO: sum can only represent ~290 years before overflowing, but we don't actually need nanosecond precision!
+// Probably worth switching to hour-based summing here.
 func Calc(p ...Pair) time.Duration {
 	sum := time.Duration(0)
 	for i := range p {
@@ -20,3 +25,7 @@ func Calc(p ...Pair) time.Duration {
 	}
 	return sum
 }
+
+func DecimalYear(d time.Duration) string {
+	return fmt.Sprintf("%.2f", float64(d.Truncate(time.Hour)/time.Hour)/float64(8760))
+}

pkg/libyear/libyear_test.go

@@ -0,0 +1,23 @@
+package libyear
+
+import (
+	"testing"
+	"time"
+)
+
+func TestDecimalYear(t *testing.T) {
+	values := map[time.Duration]string{
+		time.Hour:           "0.00",
+		time.Hour * 8760:    "1.00",
+		time.Hour * 4380:    "0.50",
+		time.Hour * 12264:   "1.40",
+		time.Hour * 27520:   "3.14",
+		time.Hour * 1000000: "114.16",
+	}
+	for d, s := range values {
+		if r := DecimalYear(d); r != s {
+			t.Logf("Expected %s, got %s for %d", s, r, d)
+			t.Fail()
+		}
+	}
+}