add similar songs fallback when server returns none

backend/mediaprovider/helpers/similar.go

@@ -0,0 +1,22 @@
+package helpers
+
+import (
+	"github.com/dweymouth/supersonic/backend/mediaprovider"
+	"github.com/dweymouth/supersonic/sharedutil"
+)
+
+func GetSimilarSongsFallback(mp mediaprovider.MediaProvider, track *mediaprovider.Track, count int) []*mediaprovider.Track {
+	var tracks []*mediaprovider.Track
+	if len(track.ArtistIDs) > 0 {
+		tracks, _ = mp.GetSimilarTracks(track.ArtistIDs[0], count)
+		if len(tracks) > 0 {
+			return tracks
+		}
+	}
+	tracks, _ = mp.GetRandomTracks(track.Genre, count)
+
+	// make sure to exclude the song itself from the similar list
+	return sharedutil.FilterSlice(tracks, func(t *mediaprovider.Track) bool {
+		return t.ID != track.ID
+	})
+}

backend/mediaprovider/jellyfin/jellyfinmediaprovider.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/dweymouth/go-jellyfin"
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
+	"github.com/dweymouth/supersonic/backend/mediaprovider/helpers"
 	"github.com/dweymouth/supersonic/sharedutil"
 )
 
@@ -480,5 +481,12 @@ func (j *jellyfinMediaProvider) GetSongRadio(trackID string, count int) ([]*medi
 	if err != nil {
 		return nil, err
 	}
+	if len(tr) == 0 {
+		track, err := j.GetTrack(trackID)
+		if err != nil {
+			return nil, err
+		}
+		return helpers.GetSimilarSongsFallback(j, track, count), nil
+	}
 	return sharedutil.MapSlice(tr, toTrack), nil
 }

backend/mediaprovider/subsonic/subsonicmediaprovider.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/dweymouth/go-subsonic/subsonic"
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
+	"github.com/dweymouth/supersonic/backend/mediaprovider/helpers"
 	"github.com/dweymouth/supersonic/sharedutil"
 )
 
@@ -622,5 +623,12 @@ func (s *subsonicMediaProvider) GetSongRadio(trackID string, count int) ([]*medi
 	if err != nil {
 		return nil, err
 	}
+	if len(tr) == 0 {
+		track, err := s.GetTrack(trackID)
+		if err != nil {
+			return nil, err
+		}
+		return helpers.GetSimilarSongsFallback(s, track, count), nil
+	}
 	return sharedutil.MapSlice(tr, toTrack), nil
 }