RealmSongRepository.kt

class RealmSongRepository : SongRepository {
  override fun addSongToLibrary(filePath: String): Single<SongId> {
    return Single.fromCallable {
      scanSongIntoLibrary(filePath)
    }
        .subscribeOn(io())
        .observeOn(mainThread())
  }

  override fun scanSongIntoLibrary(filePath: String): SongId {
   var newSongId: SongId = InvalidSongId
    realmTransaction {
      if (getSongForFilepath(it, filePath) == null) {
        val song = Song {
          id = Database.getNextId(it, Song::class.java)
          newSongId = // get next ValidSongId
          // Initialize title, artist, and album for the song
        }
        it.copyToRealm(song)
      }
    }
    return newSongId
  }
}