using System.Threading;
using System.Threading.Tasks;

namespace PerfectNumbers.Core;

public sealed class UnboundedTaskScheduler : TaskScheduler
{
	public static UnboundedTaskScheduler Instance { get; } = new();

	private UnboundedTaskScheduler()
	{
		ThreadPool.SetMaxThreads(100_000, 100_000);
		ThreadPool.SetMinThreads(10_300, 100);
	}

	public override int MaximumConcurrencyLevel => int.MaxValue;

	protected override void QueueTask(Task task)
	{
		ThreadPool.UnsafeQueueUserWorkItem(static state =>
		{
			(UnboundedTaskScheduler Scheduler, Task Task) tuple = ((UnboundedTaskScheduler, Task))state!;
			tuple.Scheduler.TryExecuteTask(tuple.Task);
		}, (this, task));
	}

	protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
	{
		return TryExecuteTask(task);
	}

	protected override IEnumerable<Task>? GetScheduledTasks()
	{
		return null;
	}
}