private void __GoBack()
{
// Note: CanGoBack で呼び分けが行われている前提の元で例外送出を行っている
var prevItem = default(PlaylistItem);
int prevIndex = CurrentIndex - 1;
if (PlaylistSettings.IsShuffleEnable)
{
prevItem = PlayedItems.Dequeue();
}
else
{
if (prevIndex < 0)
{
if (RepeatMode != MediaPlaybackAutoRepeatMode.List)
{
throw new Exception();
}
else
{
prevIndex = SourceItems.Count - 1;
}
}
prevItem = SourceItems.ElementAt(prevIndex);
}
if (prevItem != null)
{
Current = prevItem;
CurrentIndex = prevIndex;
PlayRequested?.Invoke(this, prevItem);
}
else
{
throw new Exception();
}
}