public void MoveToPrevSong()
{
if (!SongArchive.Any())
{
return;
}
// shrink list of upcoming songs
UpcomingSongs.Insert(0, CurrentSong);
UpcomingSongs.Remove(UpcomingSongs.Last());
// reassign current song (take last song from archive)
CurrentSong = SongArchive.Last();
// update archive
SongArchive.Remove(SongArchive.Last());
}
/// <summary>
/// Switching to previous song is done synchronously
/// since his operation is very cheap (just recombinate songs in collections)
/// </summary>
public Task MoveToPrevSongAsync()
{
if (SongArchive.Any())
{
// shrink list of upcoming songs
UpcomingSongs.Insert(0, CurrentSong);
UpcomingSongs.Remove(UpcomingSongs.Last());
// reassign current song (take last song from archive)
CurrentSong = SongArchive.Last();
// update archive
SongArchive.Remove(SongArchive.Last());
}
return(Task.CompletedTask);
}
/// <summary>
/// Same as synchronous version but with async calls to EF
/// </summary>
private async Task <Song> SelectRandomSongAsync(int maxAttempts = 15)
{
var attempts = 0;
Song song;
// keep selecting song randomly until the song file is actually present in the file system...
// ...and while it isn't present in archive of recently played songs and upcoming songs
do
{
if (attempts++ == maxAttempts)
{
return(_songSelector.DefaultSong());
}
song = await _songSelector.SelectSongAsync().ConfigureAwait(false);
}while (SongArchive.Any(s => s.Id == song.Id) || // true, if the archive already contains this song
UpcomingSongs.Any(s => s.Id == song.Id) || // true, if it is already in songlist
song.Id == CurrentSong.Id || // true, if it's currently playing
FileLocator.FindSongPath(song) == ""); // true, if the file with this song doesn't exist
return(song);
}