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dwelling-radio/internal/radio/mostlistened.go

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package radio
import (
"bytes"
"encoding/json"
"errors"
"strconv"
"time"
)
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const MostListenedDateFormat = "02 January 2006"
var mlsChanged = false
type MostListenedSong struct {
Listeners int
Date time.Time
Song string
}
func (mls *MostListenedSong) DateString() string {
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return mls.Date.Format(MostListenedDateFormat)
}
func (mls *MostListenedSong) MarshalJSON() ([]byte, error) {
return json.Marshal(&struct {
Song string `json:"song"`
Listeners int `json:"listeners"`
Date string `json:"date"`
}{
Song: mls.Song,
Listeners: mls.Listeners,
Date: mls.Date.UTC().Format(time.RFC3339)})
}
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) {
if prev.Artist == "" {
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return
}
if cur.MaxListeners > mostListened.Listeners {
mostListened = MostListenedSong{
Listeners: cur.MaxListeners,
Date: time.Now().UTC(),
Song: prev.ArtistTitle()}
}
mlsChanged = true
}
// MostListened returns song that currently is the song with most simultaneous
// listeners.
func MostListened() *MostListenedSong {
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if mostListened.Date.Year() == 1 {
return nil
}
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 {
if !mlsChanged {
return nil
}
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()
}