Bug fixed with more than a 365 days.

Refactoring in tests according to: https://gist.github.com/posener/92a55c4cd441fc5e5e85f27bca008721
Added constants for precisions.
Added documentation.

README.md

@@ -12,7 +12,7 @@ The allowed precisions are year, day, hour, minute and second
 ```go
 import "github.com/davidbanham/human_duration"
 
-example := time.Hour * 25 + time.Minute * 4 + time.Second * 8
+example := time.Hour * 24 + time.Minute * 4 + time.Second * 8
 
 fmt.Println(human_duration.String(example, "second") // 1 day 4 minutes 8 seconds
 fmt.Println(human_duration.String(example, "minute") // 1 day 4 minutes

main.go

@@ -1,3 +1,5 @@
+// Package human_duration provides human readable output of
+// time.Duration
 package human_duration
 
 import (
@@ -7,9 +9,21 @@ import (
 	"time"
 )
 
+// Available precisions
+const (
+	Second = "second"
+	Minute = "minute"
+	Hour   = "hour"
+	Day    = "day"
+	Year   = "year"
+)
+
+// String converts duration to human readable format, according to precision.
+// Example:
+//	fmt.Println(human_duration.String(time.Hour*24), human_duration.Hour)
 func String(duration time.Duration, precision string) string {
 	years := int64(duration.Hours() / 24 / 365)
-	days := int64(duration.Hours() / 24)
+	days := int64(math.Mod(float64(int64(duration.Hours()/24)), 365))
 	hours := int64(math.Mod(duration.Hours(), 24))
 	minutes := int64(math.Mod(duration.Minutes(), 60))
 	seconds := int64(math.Mod(duration.Seconds(), 60))
@@ -26,7 +40,6 @@ func String(duration time.Duration, precision string) string {
 	}
 
 	parts := []string{}
-
 	preciseEnough := false
 
 	for _, chunk := range chunks {
@@ -45,5 +58,6 @@ func String(duration time.Duration, precision string) string {
 			parts = append(parts, fmt.Sprintf("%d %ss", chunk.amount, chunk.singularName))
 		}
 	}
+
 	return strings.Join(parts, " ")
 }

main_test.go

@@ -1,6 +1,7 @@
 package human_duration
 
 import (
+	"fmt"
 	"testing"
 	"time"
 )
@@ -11,25 +12,36 @@ type fixture struct {
 	result    string
 }
 
-func TestString(t *testing.T) {
-	t.Parallel()
+func ExampleString() {
+	duration := time.Hour*24*365 + time.Hour*8 + time.Minute*33 + time.Second*24
+	fmt.Println(String(duration, Second))
+
+	start, _ := time.Parse(time.RFC3339, "2012-11-01T22:08:41+00:00")
+	stop, _ := time.Parse(time.RFC3339, "2013-12-04T23:09:42+00:00")
+
+	fmt.Println(String(stop.Sub(start), Second))
+
+	// Output: 1 year 8 hours 33 minutes 24 seconds
+	// 1 year 33 days 1 hour 1 minute 1 second
+}
 
+func TestString(t *testing.T) {
 	day := time.Hour * 24
 	year := day * 365
 
 	data := []fixture{
 		{
-			duration:  time.Hour*25 + time.Minute*4 + time.Second*8,
+			duration:  day + time.Minute*4 + time.Second*8,
 			precision: "second",
 			result:    "1 day 4 minutes 8 seconds",
 		},
 		{
-			duration:  time.Hour*25 + time.Minute*4 + time.Second*8,
+			duration:  day + time.Minute*4 + time.Second*8,
 			precision: "minute",
 			result:    "1 day 4 minutes",
 		},
 		{
-			duration:  time.Hour*25 + time.Minute*4 + time.Second*8,
+			duration:  day + time.Minute*4 + time.Second*8,
 			precision: "day",
 			result:    "1 day",
 		},
@@ -64,7 +76,7 @@ func TestString(t *testing.T) {
 			result:    "1 hour 1 minute 10 seconds",
 		},
 		{
-			duration:  time.Hour * 23,
+			duration:  time.Hour * 24,
 			precision: "day",
 			result:    "1 day",
 		},
@@ -93,15 +105,20 @@ func TestString(t *testing.T) {
 			precision: "hours",
 			result:    "1 hour",
 		},
+		{
+			duration:  year + day + time.Hour*2,
+			precision: "hours",
+			result:    "1 year 1 day 2 hours",
+		},
 	}
 
 	for _, fixture := range data {
-		t.Run(fixture.result+fixture.duration.String(), func(t *testing.T) {
+		f := fixture
+		t.Run(f.result+" "+f.duration.String(), func(t *testing.T) {
 			t.Parallel()
-
-			result := String(fixture.duration, fixture.precision)
-			if result != fixture.result {
-				t.Errorf("got %s, want %s", result, fixture.result)
+			result := String(f.duration, f.precision)
+			if result != f.result {
+				t.Errorf("got %s, want %s", result, f.result)
 			}
 		})
 	}