MostListenedSong was rewritten.

cmd/dwelling-radio/main.go

@@ -37,8 +37,9 @@ func main() {
 		return
 	}
 
+	var mostListenedSong radio.MostListenedSong
 	if data, err := os.ReadFile(*mostListenedSongPath); err == nil {
-		if err := radio.LoadMostListenedSong(data); err != nil {
+		if err := mostListenedSong.Load(data); err != nil {
 			log.Fatalln(err)
 		}
 	}
@@ -50,7 +51,7 @@ func main() {
 		log.Fatalln(err)
 	}
 
-	hand := ihttp.NewHandlers(*filelistPath, songList, lstnrs)
+	hand := ihttp.NewHandlers(*filelistPath, songList, lstnrs, &mostListenedSong)
 	r := httpr.New()
 
 	r.Handler(http.MethodGet, "/", hand.Index)
@@ -64,7 +65,7 @@ func main() {
 
 	r.ServeStatic("/assets/*filepath", web.Assets())
 
-	djh := ihttp.NewDJHandlers(lstnrs, plylst, songList, *songListLen)
+	djh := ihttp.NewDJHandlers(lstnrs, plylst, songList, &mostListenedSong)
 
 	s := r.Sub("/api/listener")
 	s.Handler(http.MethodGet, "/", djh.ListenersGet)
@@ -86,7 +87,7 @@ func main() {
 	}
 
 	defer func() {
-		fileData := radio.StoreMostListenedSong()
+		fileData := mostListenedSong.Store()
 		if fileData != nil {
 			err := os.WriteFile(*mostListenedSongPath, fileData, fs.ModePerm)
 			if err != nil {

internal/http/dj_handlers.go

@@ -14,10 +14,11 @@ type DJHandlers struct {
 	listeners *radio.ListenerCounter
 	playlist  *radio.Playlist
 	songList  *radio.SongList
+	mostLSong *radio.MostListenedSong
 }
 
-func NewDJHandlers(l *radio.ListenerCounter, p *radio.Playlist, sl *radio.SongList, slLen int) *DJHandlers {
+func NewDJHandlers(l *radio.ListenerCounter, p *radio.Playlist, sl *radio.SongList, mls *radio.MostListenedSong) *DJHandlers {
-	return &DJHandlers{listeners: l, playlist: p, songList: sl}
+	return &DJHandlers{listeners: l, playlist: p, songList: sl, mostLSong: mls}
 }
 
 func (dj *DJHandlers) ListenersGet(w http.ResponseWriter, _ *http.Request) {
@@ -65,8 +66,12 @@ func (dj *DJHandlers) PlaylistNext(w http.ResponseWriter, _ *http.Request) {
 				Duration:     oggf.GetDuration(),
 				MaxListeners: dj.listeners.Current(),
 				StartAt:      time.Now()}
+
+			if dj.songList.Current() != nil {
+				dj.mostLSong.Update(*dj.songList.Current())
+			}
+
 			dj.songList.Add(song)
-			radio.CheckAndUpdateMostListenedSong(*dj.songList.Current())
 		}()
 	}
 	fmt.Fprintln(w, nxt)
@@ -106,7 +111,7 @@ func (dj *DJHandlers) Status(w http.ResponseWriter, r *http.Request) {
 		Current:   curSong,
 		Listeners: dj.listeners,
 		List:      dj.songList.List(),
-		Mls:       radio.MostListened()})
+		Mls:       dj.mostLSong.Get()})
 	if err != nil {
 		log.Println("DJHandlers.Status:", err)
 		http.Error(w, "status parsing failed", http.StatusInternalServerError)
@@ -115,7 +120,7 @@ func (dj *DJHandlers) Status(w http.ResponseWriter, r *http.Request) {
 
 func (dj *DJHandlers) MostListenedSong(w http.ResponseWriter, r *http.Request) {
 	w.Header().Add("Content-Type", "application/json")
-	mls := radio.MostListened()
+	mls := dj.mostLSong.Get()
 	if mls == nil {
 		w.WriteHeader(http.StatusNotFound)
 		return

internal/http/handlers.go

@@ -11,18 +11,20 @@ import (
 type Handlers struct {
 	songList     *radio.SongList
 	listeners    *radio.ListenerCounter
+	mostLSong    *radio.MostListenedSong
 	filelistPath string
 }
 
-func NewHandlers(filelistPath string, songList *radio.SongList, listeners *radio.ListenerCounter) *Handlers {
+func NewHandlers(filelistPath string, songList *radio.SongList, listeners *radio.ListenerCounter, mls *radio.MostListenedSong) *Handlers {
 	return &Handlers{
 		songList:     songList,
 		filelistPath: filelistPath,
-		listeners:    listeners}
+		listeners:    listeners,
+		mostLSong:    mls}
 }
 
 func (h *Handlers) Index(w http.ResponseWriter, r *http.Request) {
-	web.Index(utils.MainSite(r.Host), h.songList, h.listeners, r, w)
+	web.Index(utils.MainSite(r.Host), h.songList, h.listeners, h.mostLSong.Get(), r, w)
 }
 
 func (h *Handlers) Playlist(w http.ResponseWriter, _ *http.Request) {

internal/radio/mostlistened.go

@@ -2,101 +2,96 @@ package radio
 
 import (
 	"bytes"
-	"encoding/json"
-	"errors"
 	"strconv"
+	"sync"
 	"time"
+
+	"github.com/pkg/errors"
 )
 
-const MostListenedDateFormat = "02 January 2006"
+const MostListenedDateFormat string = "02 January 2006"
-
-var mlsChanged = false
 
+// MostListenedSong holds a metadata for a most listened song.
 type MostListenedSong struct {
-	Listeners int
+	sync.RWMutex
-	Date      time.Time
+	Date      time.Time `json:"date"`
-	Song      string
+	Listeners int       `json:"listeners"`
+	Song      string    `json:"song"`
+	changed   bool
 }
 
-func (mls *MostListenedSong) DateString() string {
+func (mls *MostListenedSong) Update(song Song) {
-	return mls.Date.Format(MostListenedDateFormat)
+	mls.Lock()
-}
+	defer mls.Unlock()
-
+	if song.Artist == "" {
-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 Song) {
-	if cur.Artist == "" {
 		return
 	}
-	if cur.MaxListeners > mostListened.Listeners {
+	if song.MaxListeners > mls.Listeners {
-		mostListened = MostListenedSong{
+		mls.Listeners = song.MaxListeners
-			Listeners: cur.MaxListeners,
+		mls.Date = song.StartAt
-			Date:      cur.StartAt,
+		mls.Song = song.Artist + " - " + song.Title
-			Song:      cur.Artist + " - " + cur.Title}
+		mls.changed = true
 	}
-	mlsChanged = true
 }
 
-// MostListened returns song that currently is the song with most simultaneous
+func (mls *MostListenedSong) Get() *MostListenedSong {
-// listeners.
+	mls.RLock()
-func MostListened() *MostListenedSong {
+	defer mls.RUnlock()
-	if mostListened.Date.Year() == 1 {
+
+	if mls.Date.Year() == 1 {
 		return nil
 	}
-	return &mostListened
+
+	return &MostListenedSong{
+		Date:      mls.Date,
+		Listeners: mls.Listeners,
+		Song:      mls.Song}
 }
 
-func LoadMostListenedSong(data []byte) (err error) {
+// Load parses given data and fill a MostListenedSong.
+func (mls *MostListenedSong) Load(data []byte) (err error) {
+	mls.Lock()
+	defer mls.Unlock()
+
 	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 {
+	var date time.Time
-		return err
+	if date, err = time.Parse(time.RFC3339, string(lines[0])); err != nil {
+		return errors.Wrap(err, "wrong date/time format")
 	}
-	if mostListened.Listeners, err = strconv.Atoi(string(lines[1])); err != nil {
+
-		return err
+	var listeners int
+	if listeners, err = strconv.Atoi(string(lines[1])); err != nil {
+		return errors.Wrap(err, "a listeners number failed to parse")
 	}
-	mostListened.Song = string(lines[2])
+
+	if len(lines[2]) == 0 {
+		return errors.New("a song is empty")
+	}
+
+	mls.Date = date
+	mls.Listeners = listeners
+	mls.Song = string(lines[2])
 	return nil
 }
 
-func StoreMostListenedSong() []byte {
+// Store returns a byte slice of a marshalled to text MostListenedSong.
-	if !mlsChanged {
+func (mls *MostListenedSong) Store() []byte {
+	if !mls.changed {
 		return nil
 	}
 
-	buf := make([]byte, 0, 30+len(mostListened.Song))
+	buf := make([]byte, 0, 30+len(mls.Song))
 	b := bytes.NewBuffer(buf)
 
-	b.WriteString(mostListened.Date.Format(time.RFC3339))
+	b.WriteString(mls.Date.Format(time.RFC3339))
 	b.WriteByte('\n')
-	b.WriteString(strconv.Itoa(mostListened.Listeners))
+	b.WriteString(strconv.Itoa(mls.Listeners))
 	b.WriteByte('\n')
-	b.WriteString(mostListened.Song)
+	b.WriteString(mls.Song)
 
 	return b.Bytes()
 }

web/templates/index.pug

@@ -1,4 +1,4 @@
-:go:func Index(mainSite string, songList *radio.SongList, listeners *radio.ListenerCounter, r *http.Request)
+:go:func Index(mainSite string, songList *radio.SongList, listeners *radio.ListenerCounter, mls *radio.MostListenedSong, r *http.Request)
 
 :go:import "dwelling-radio/internal/radio"
 :go:import "dwelling-radio/pkg/utils"
@@ -65,8 +65,7 @@ html(lang='en')
                             else
                                 td
                             td #{song.Artist} - #{song.Title}
-        - ml := radio.MostListened()
+        if mls != nil
-        if ml.Song != ""
+            p.right Most listened song was "#{mls.Song}" on #{utils.ToClientTimezone(mls.Date, r).Format(radio.MostListenedDateFormat)} with #[b #{mls.Listeners}] listeners.
-            p.right Most listened song was "#{ml.Song}" on #{utils.ToClientTimezone(ml.Date, r).Format(radio.MostListenedDateFormat)} with #[b #{ml.Listeners}] listeners.
         footer
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