New NowPlaying and Skip detection implementation

engine/nowplaying.go

@@ -12,8 +12,17 @@ type NowPlayingInfo struct {
 	PlayerName string
 }
 
+// This repo has the semantics of a FIFO queue, for each playerId
 type NowPlayingRepository interface {
-	Set(trackId, username string, playerId int, playerName string) error
-	Clear(playerId int) (*NowPlayingInfo, error)
-	GetAll() (*[]NowPlayingInfo, error)
+	// Insert at the head of the queue
+	Enqueue(playerId int, playerName string, trackId, username string) error
+
+	// Returns the element at the head of the queue (last inserted one)
+	Head(playerId int) (*NowPlayingInfo, error)
+
+	// Removes and returns the element at the end of the queue
+	Dequeue(playerId int) (*NowPlayingInfo, error)
+
+	// Returns all heads from all playerIds
+	GetAll() ([]*NowPlayingInfo, error)
 }