Implemented a functionality for storing and showing most listened song.

internal/radio/mostlistened.go

@@ -0,0 +1,76 @@
+package radio
+
+import (
+	"bytes"
+	"errors"
+	"strconv"
+	"time"
+)
+
+type MostListenedSong struct {
+	Listeners int
+	Date      time.Time
+	Song      string
+}
+
+func (mls *MostListenedSong) DateString() string {
+	return mls.Date.Format("02 January 2006")
+}
+
+var mostListened MostListenedSong
+
+// CheckAndUpdateMostListenedSong compares current most played song with
+// provided `cur`rent song's listeners, and if it is larger, then it takes
+// `prev`ious song's name.
+//
+// Why we take a previous song's name? Experimentally I noticed that Icecast
+// writes amount of listeners that was by the very start of a next song. So
+// it means that it was actually amount of listeners by the end of
+// the previous song.
+//
+// So it would be fairer to give these listeners back to a song they was
+// listening to.
+func CheckAndUpdateMostListenedSong(cur, prev Song) {
+	l, _ := strconv.Atoi(cur.Listeners)
+	if l > mostListened.Listeners {
+		mostListened = MostListenedSong{
+			Listeners: l,
+			Date:      time.Now().UTC(),
+			Song:      prev.Song}
+	}
+}
+
+// MostListened returns song that currently is the song with most simultaneous
+// listeners.
+func MostListened() *MostListenedSong {
+	return &mostListened
+}
+
+func LoadMostListenedSong(data []byte) (err error) {
+	lines := bytes.Split(data, []byte{'\n'})
+	if len(lines) != 3 {
+		return errors.New("lines count mismatch, should be 3")
+	}
+	mostListened = MostListenedSong{}
+	if mostListened.Date, err = time.Parse(time.RFC3339, string(lines[0])); err != nil {
+		return err
+	}
+	if mostListened.Listeners, err = strconv.Atoi(string(lines[1])); err != nil {
+		return err
+	}
+	mostListened.Song = string(lines[2])
+	return nil
+}
+
+func StoreMostListenedSong() []byte {
+	buf := make([]byte, 0, 30+len(mostListened.Song))
+	b := bytes.NewBuffer(buf)
+
+	b.WriteString(mostListened.Date.Format(time.RFC3339))
+	b.WriteByte('\n')
+	b.WriteString(strconv.Itoa(mostListened.Listeners))
+	b.WriteByte('\n')
+	b.WriteString(mostListened.Song)
+
+	return b.Bytes()
+}