Do not overwrite mostlistenedsong file if a song wasn't changed.

cmd/dwelling-radio/main.go

@@ -74,9 +74,12 @@ func main() {
 	}
 
 	defer func() {
-		err := os.WriteFile(*mostListenedSongPath, radio.StoreMostListenedSong(), fs.ModePerm)
-		if err != nil {
-			log.Println("failed to store a most listened song:", err)
+		fileData := radio.StoreMostListenedSong()
+		if fileData != nil {
+			err := os.WriteFile(*mostListenedSongPath, fileData, fs.ModePerm)
+			if err != nil {
+				log.Println("failed to store a most listened song:", err)
+			}
 		}
 
 		if err := srv.Stop(); err != nil {

internal/radio/mostlistened.go

@@ -9,6 +9,8 @@ import (
 
 const MostListenedDateFormat = "02 January 2006"
 
+var mlsChanged = false
+
 type MostListenedSong struct {
 	Listeners int
 	Date      time.Time
@@ -43,6 +45,7 @@ func CheckAndUpdateMostListenedSong(cur, prev Song) {
 			Date:      time.Now().UTC(),
 			Song:      prev.Song}
 	}
+	mlsChanged = true
 }
 
 // MostListened returns song that currently is the song with most simultaneous
@@ -68,6 +71,10 @@ func LoadMostListenedSong(data []byte) (err error) {
 }
 
 func StoreMostListenedSong() []byte {
+	if !mlsChanged {
+		return nil
+	}
+
 	buf := make([]byte, 0, 30+len(mostListened.Song))
 	b := bytes.NewBuffer(buf)