IdentityCacheObject.cs

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using System;
using System.Threading;
using System.Threading.Tasks;
using Tgstation.Server.Host.Core;

namespace Tgstation.Server.Host.Security
{
    sealed class IdentityCacheObject : IDisposable
    {
        public ISystemIdentity SystemIdentity { get; }

        readonly CancellationTokenSource cancellationTokenSource;

        readonly Task task;

        public IdentityCacheObject(ISystemIdentity systemIdentity, IAsyncDelayer asyncDelayer, Action onExpiry, DateTimeOffset expiry)
        {
            SystemIdentity = systemIdentity ?? throw new ArgumentNullException(nameof(systemIdentity));

            if (asyncDelayer == null)
                throw new ArgumentNullException(nameof(asyncDelayer));

            if (onExpiry == null)
                throw new ArgumentNullException(nameof(onExpiry));
            var now = DateTimeOffset.Now;
            if (expiry < now)
                throw new ArgumentOutOfRangeException(nameof(expiry), expiry, "expiry must be greater than DateTimeOffset.Now!");

            cancellationTokenSource = new CancellationTokenSource();

            async Task DisposeOnExipiry(CancellationToken cancellationToken)
            {
                using (SystemIdentity)
                    try
                    {
                        await asyncDelayer.Delay(expiry - now, cancellationToken).ConfigureAwait(false);
                    }
                    finally
                    {
                        onExpiry();
                    }
            }

            task = DisposeOnExipiry(cancellationTokenSource.Token);
        }

        public void Dispose()
        {
            cancellationTokenSource.Cancel();
            try
            {
                task.GetAwaiter().GetResult();
            }
            catch (OperationCanceledException) { }
            cancellationTokenSource.Dispose();
        }
    }
}