Properly format itunes duration.

feed.go

@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/xml"
 	"io"
+	"strconv"
+	"strings"
 	"time"
 )
 
@@ -34,6 +36,50 @@ func (p PubDate) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
 	return e.EncodeToken(xml.EndElement{Name: start.Name})
 }
 
+// NewDuration returns a new Duration.
+func NewDuration(d time.Duration) *Duration {
+	return &Duration{d}
+}
+
+// Duration represents itunes:duration attribute of given podcast item.
+type Duration struct {
+	time.Duration
+}
+
+// MarshalXML marshalls duration using HH:MM:SS, H:MM:SS, MM:SS, M:SS formats.
+func (d Duration) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+	if err := e.EncodeToken(xml.CharData(formatDuration(d.Duration))); err != nil {
+		return err
+	}
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// formatDuration formats duration in these formats: HH:MM:SS, H:MM:SS, MM:SS, M:SS.
+func formatDuration(d time.Duration) string {
+	total := int(d.Seconds())
+	hours := total / 3600
+	total %= 3600
+	minutes := total / 60
+	total %= 60
+
+	var b strings.Builder
+	if hours > 0 {
+		b.WriteString(strconv.Itoa(hours) + ":")
+	}
+	if hours > 0 && minutes < 10 {
+		b.WriteString("0")
+	}
+	b.WriteString(strconv.Itoa(minutes) + ":")
+	if total < 10 {
+		b.WriteString("0")
+	}
+	b.WriteString(strconv.Itoa(total))
+	return b.String()
+}
+
 // ItunesOwner represents the itunes:owner of given channel.
 type ItunesOwner struct {
 	XMLName xml.Name `xml:"itunes:owner"`
@@ -76,7 +122,7 @@ type Item struct {
 	PubDate         *PubDate       `xml:"pubDate"`
 	Author          string         `xml:"itunes:author,omitempty"`
 	Block           string         `xml:"itunes:block,omitempty"`
-	Duration        time.Duration  `xml:"itunes:duration,omitempty"`
+	Duration        *Duration      `xml:"itunes:duration,omitempty"`
 	Explicit        string         `xml:"itunes:explicit,omitempty"`
 	ClosedCaptioned string         `xml:"itunes:isClosedCaptioned,omitempty"`
 	Order           int            `xml:"itunes:order,omitempty"`

feed_test.go

@@ -18,3 +18,48 @@ func TestPubDateMarshalling(t *testing.T) {
 		t.Errorf("expected %v got %v", want, got)
 	}
 }
+
+func TestDurationMarshalling(t *testing.T) {
+	cases := []struct {
+		dur  time.Duration
+		want string
+	}{
+		{
+			dur:  0,
+			want: "<Duration>0:00</Duration>",
+		},
+		{
+			dur:  time.Second * 6,
+			want: "<Duration>0:06</Duration>",
+		},
+		{
+			dur:  time.Second * 64,
+			want: "<Duration>1:04</Duration>",
+		},
+		{
+			dur:  time.Second * 125,
+			want: "<Duration>2:05</Duration>",
+		},
+		{
+			dur:  time.Second * 3600,
+			want: "<Duration>1:00:00</Duration>",
+		},
+		{
+			dur:  time.Second * 37000,
+			want: "<Duration>10:16:40</Duration>",
+		},
+	}
+
+	for _, cs := range cases {
+		t.Run(cs.want, func(t *testing.T) {
+			dur := NewDuration(cs.dur)
+			out, err := xml.Marshal(dur)
+			if err != nil {
+				t.Errorf("unexpected error %v", err)
+			}
+			if got := string(out); cs.want != got {
+				t.Errorf("expected %v got %v", cs.want, got)
+			}
+		})
+	}
+}

podcast_test.go

@@ -17,6 +17,8 @@ var (
 		enclosureURL    string
 		enclosureLength string
 		enclosureType   string
+		duration        time.Duration
+		durationStr     string
 	}{
 		{
 			title:           "Item 1",
@@ -35,6 +37,8 @@ var (
 			enclosureURL:    "http://www.example-podcast.com/my-podcast/2/episode-two",
 			enclosureLength: "56445",
 			enclosureType:   "WAV",
+			duration:        time.Second * 94,
+			durationStr:     "1:34",
 		},
 	}
 )
@@ -294,6 +298,11 @@ func TestContainsItemElements(t *testing.T) {
 			if want := fmt.Sprintf(`<enclosure url="%v" length="%v" type="%v"></enclosure>`, item.enclosureURL, item.enclosureLength, item.enclosureType); !strings.Contains(data, want) {
 				t.Errorf("expected %v to contain %v", data, want)
 			}
+			if item.durationStr != "" {
+				if want := fmt.Sprintf("<itunes:duration>%v</itunes:duration>", item.durationStr); !strings.Contains(data, want) {
+					t.Errorf("expected %v to contain %v", data, want)
+				}
+			}
 			if want := "</item>"; !strings.Contains(data, want) {
 				t.Errorf("expected %v to contain %v", data, want)
 			}
@@ -326,9 +335,10 @@ func setupPodcast() *Podcast {
 	podcast := &Podcast{}
 	for _, item := range validItems {
 		podcast.AddItem(&Item{
-			Title:   item.title,
-			GUID:    item.guid,
-			PubDate: NewPubDate(item.pubDate),
+			Title:    item.title,
+			GUID:     item.guid,
+			PubDate:  NewPubDate(item.pubDate),
+			Duration: NewDuration(item.duration),
 			Enclosure: &Enclosure{
 				URL:    item.enclosureURL,
 				Length: item.enclosureLength,