Removed list_generator completely

core/nowplaying.go

@@ -0,0 +1,106 @@
+package core
+
+import (
+	"container/list"
+	"sync"
+	"time"
+)
+
+const NowPlayingExpire = 60 * time.Minute
+
+type NowPlayingInfo struct {
+	TrackID    string
+	Start      time.Time
+	Username   string
+	PlayerId   int
+	PlayerName string
+}
+
+// This repo must have the semantics of a FIFO queue, for each playerId
+type NowPlaying interface {
+	// Insert at the head of the queue
+	Enqueue(*NowPlayingInfo) error
+
+	// Returns all heads from all playerIds
+	GetAll() ([]*NowPlayingInfo, error)
+}
+
+var playerMap = sync.Map{}
+
+type nowPlayingRepository struct{}
+
+func NewNowPlayingRepository() NowPlaying {
+	r := &nowPlayingRepository{}
+	return r
+}
+
+func (r *nowPlayingRepository) Enqueue(info *NowPlayingInfo) error {
+	l := r.getList(info.PlayerId)
+	l.PushFront(info)
+	return nil
+}
+
+func (r *nowPlayingRepository) GetAll() ([]*NowPlayingInfo, error) {
+	var all []*NowPlayingInfo
+	playerMap.Range(func(playerId, l interface{}) bool {
+		ll := l.(*list.List)
+		e := checkExpired(ll, ll.Front)
+		if e != nil {
+			all = append(all, e.Value.(*NowPlayingInfo))
+		}
+		return true
+	})
+	return all, nil
+}
+
+func (r *nowPlayingRepository) getList(id int) *list.List {
+	l, _ := playerMap.LoadOrStore(id, list.New())
+	return l.(*list.List)
+}
+
+func (r *nowPlayingRepository) dequeue(playerId int) (*NowPlayingInfo, error) {
+	l := r.getList(playerId)
+	e := checkExpired(l, l.Back)
+	if e == nil {
+		return nil, nil
+	}
+	l.Remove(e)
+	return e.Value.(*NowPlayingInfo), nil
+}
+
+func (r *nowPlayingRepository) head(playerId int) (*NowPlayingInfo, error) {
+	l := r.getList(playerId)
+	e := checkExpired(l, l.Front)
+	if e == nil {
+		return nil, nil
+	}
+	return e.Value.(*NowPlayingInfo), nil
+}
+
+func (r *nowPlayingRepository) tail(playerId int) (*NowPlayingInfo, error) {
+	l := r.getList(playerId)
+	e := checkExpired(l, l.Back)
+	if e == nil {
+		return nil, nil
+	}
+	return e.Value.(*NowPlayingInfo), nil
+}
+
+func (r *nowPlayingRepository) count(playerId int) (int64, error) {
+	l := r.getList(playerId)
+	return int64(l.Len()), nil
+}
+
+func checkExpired(l *list.List, f func() *list.Element) *list.Element {
+	for {
+		e := f()
+		if e == nil {
+			return nil
+		}
+		start := e.Value.(*NowPlayingInfo).Start
+		if time.Since(start) < NowPlayingExpire {
+			return e
+		}
+		l.Remove(e)
+	}
+}