namespace Zcbot.WindowsNode;

internal sealed class JobExecutionGate : IDisposable
{
    private readonly SemaphoreSlim gate = new(1, 1);
    private int activeCount;

    internal bool IsActive => Volatile.Read(ref activeCount) > 0;

    internal async Task<IDisposable> EnterAsync(CancellationToken cancellationToken)
    {
        await gate.WaitAsync(cancellationToken);
        Interlocked.Increment(ref activeCount);
        return new Lease(this);
    }

    public void Dispose() => gate.Dispose();

    private void Release()
    {
        Interlocked.Decrement(ref activeCount);
        gate.Release();
    }

    private sealed class Lease(JobExecutionGate owner) : IDisposable
    {
        private JobExecutionGate? current = owner;

        public void Dispose() => Interlocked.Exchange(ref current, null)?.Release();
    }
}