SongList struct was removed. A Song struct got UpdateMaxListeners() and IncListeners() methods. A mutex was Introduced for it. A Listeners field to store overall number of listeners during a song playing was introduced as well. A comment for the Song struct was removed.

internal/radio/song.go

@@ -6,18 +6,35 @@ import (
 	"time"
 )
 
-// Song stores artist and title of a song, a timestamp of when it started, its
-// duration, and a maximum number of listeners.
 type Song struct {
+	mutex        sync.Mutex
 	Artist       string
 	Title        string
 	Duration     time.Duration
-	MaxListeners int
+	Listeners    int64
+	MaxListeners int64
 	StartAt      time.Time
 }
 
+func (s *Song) UpdateMaxListeners(listeners int64) {
+	s.mutex.Lock()
+	if listeners > s.MaxListeners {
+		s.MaxListeners = listeners
+	}
+	s.mutex.Unlock()
+}
+
+// IncListeners increments by one an overall amount of listeners of this song.
+func (s *Song) IncListeners() {
+	s.mutex.Lock()
+	s.Listeners++
+	s.mutex.Unlock()
+}
+
 // DurationString returns song's duration as a string formatted as [H:]M:SS.
 func (s *Song) DurationString() string {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
 	if s.Duration.Hours() >= 1 {
 		return time.UnixMilli(s.Duration.Milliseconds()).Format("3:4:05")
 	}
@@ -25,85 +42,20 @@ func (s *Song) DurationString() string {
 }
 
 func (s *Song) MarshalJSON() ([]byte, error) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
 	return json.Marshal(&struct {
 		Artist       string `json:"artist"`
 		Title        string `json:"title"`
-		DurationMill int64  `json:"duration_msec"`
+		DurationMill int64  `json:"duration_msec,omitempty"`
-		MaxListeners int    `json:"listeners"`
+		Listeners    int64  `json:"listeners"`
+		MaxListeners int64  `json:"max_listeners"`
 		StartAt      string `json:"start_at"`
 	}{
 		Artist:       s.Artist,
 		Title:        s.Title,
 		DurationMill: s.Duration.Milliseconds(),
+		Listeners:    s.Listeners,
 		MaxListeners: s.MaxListeners,
 		StartAt:      s.StartAt.UTC().Format(time.RFC3339)})
 }
-
-// SongList holds a currently playing song and a list of previously played ones
-// with a maximal length of maxLen.
-type SongList struct {
-	mutex     sync.RWMutex
-	current   Song
-	lastSongs []Song
-	maxLen    int
-}
-
-// NewSongList returns a new SongList with a maximal length set with maxLen.
-func NewSongList(maxLen int) *SongList {
-	return &SongList{maxLen: maxLen, lastSongs: make([]Song, 0, maxLen)}
-}
-
-// Add a new song that is currently playing and update a list.
-func (sl *SongList) Add(newSong Song) {
-	sl.mutex.Lock()
-	defer sl.mutex.Unlock()
-
-	if sl.current.StartAt.Year() == 1 {
-		sl.current = newSong
-		return
-	}
-
-	if len(sl.lastSongs) == sl.maxLen {
-		sl.lastSongs = append(sl.lastSongs[1:], sl.current)
-	} else {
-		sl.lastSongs = append(sl.lastSongs, sl.current)
-	}
-	sl.current = newSong
-}
-
-// Current returns a currently playing song or nil if it isn't set yet.
-func (sl *SongList) Current() *Song {
-	sl.mutex.RLock()
-	defer sl.mutex.RUnlock()
-	if sl.current.StartAt.Year() == 1 {
-		return nil
-	}
-	return &Song{
-		Artist:       sl.current.Artist,
-		Title:        sl.current.Title,
-		Duration:     sl.current.Duration,
-		MaxListeners: sl.current.MaxListeners,
-		StartAt:      sl.current.StartAt}
-}
-
-// UpdateCurrentMaxListeners checks and updates a maximal number of listeners
-// for a current song.
-func (sl *SongList) UpdateCurrentMaxListeners(listeners int) {
-	sl.mutex.Lock()
-	defer sl.mutex.Unlock()
-	if listeners > sl.current.MaxListeners {
-		sl.current.MaxListeners = listeners
-	}
-}
-
-// List returns a list of lastly played songs.
-func (sl *SongList) List() []Song {
-	sl.mutex.RLock()
-	defer sl.mutex.RUnlock()
-	return sl.lastSongs
-}
-
-// MaxLen returns a maximal length of a song list.
-func (sl *SongList) MaxLen() int {
-	return sl.maxLen
-}