namespace System.Threading.Tasks;

public static class TaskExtensions
{
	private const TaskContinuationOptions opt = TaskContinuationOptions.ExecuteSynchronously;

	public static Task<TResult> Unwrap<TResult>(this Task<Task<TResult>> task)
	{
		if (task == null)
		{
			throw new ArgumentNullException("task");
		}
		TaskCompletionSource<TResult> src = new TaskCompletionSource<TResult>();
		task.ContinueWith(delegate(Task<Task<TResult>> t1)
		{
			CopyCat(t1, src, delegate
			{
				t1.Result.ContinueWith(delegate(Task<TResult> t2)
				{
					CopyCat(t2, src, delegate
					{
						src.SetResult(t2.Result);
					});
				}, TaskContinuationOptions.ExecuteSynchronously);
			});
		}, TaskContinuationOptions.ExecuteSynchronously);
		return src.Task;
	}

	public static Task Unwrap(this Task<Task> task)
	{
		if (task == null)
		{
			throw new ArgumentNullException("task");
		}
		TaskCompletionSource<object> src = new TaskCompletionSource<object>();
		task.ContinueWith(delegate(Task<Task> t1)
		{
			CopyCat(t1, src, delegate
			{
				t1.Result.ContinueWith(delegate(Task t2)
				{
					CopyCat(t2, src, delegate
					{
						src.SetResult(null);
					});
				}, TaskContinuationOptions.ExecuteSynchronously);
			});
		}, TaskContinuationOptions.ExecuteSynchronously);
		return src.Task;
	}

	private static void CopyCat<TResult>(Task source, TaskCompletionSource<TResult> dest, Action normalAction)
	{
		if (source.IsCanceled)
		{
			dest.SetCanceled();
		}
		else if (source.IsFaulted)
		{
			dest.SetException(source.Exception.InnerExceptions);
		}
		else
		{
			normalAction();
		}
	}
}