SwappableDmbProvider.cs

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using System;
using System.Threading;
using System.Threading.Tasks;
 
using Tgstation.Server.Api.Models;
using Tgstation.Server.Host.IO;
 
namespace Tgstation.Server.Host.Components.Deployment
{
    abstract class SwappableDmbProvider : IDmbProvider
    {
        public const string LiveGameDirectory = "Live";
 
        public string DmbName => BaseProvider.DmbName;
 
        public string Directory => IOManager.ResolvePath(LiveGameDirectory);
 
        public Models.CompileJob CompileJob => BaseProvider.CompileJob;
 
        public EngineVersion EngineVersion => BaseProvider.EngineVersion;
 
        public bool Swapped => swapped != 0;
 
        protected IDmbProvider BaseProvider { get; }
 
        protected IIOManager IOManager { get; }
 
        protected IFilesystemLinkFactory LinkFactory { get; }
 
        volatile int swapped;
 
        public SwappableDmbProvider(IDmbProvider baseProvider, IIOManager ioManager, IFilesystemLinkFactory symlinkFactory)
        {
            BaseProvider = baseProvider ?? throw new ArgumentNullException(nameof(baseProvider));
            IOManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
            LinkFactory = symlinkFactory ?? throw new ArgumentNullException(nameof(symlinkFactory));
        }
 
        public virtual ValueTask DisposeAsync() => BaseProvider.DisposeAsync();
 
        public void KeepAlive() => BaseProvider.KeepAlive();
 
        public ValueTask MakeActive(CancellationToken cancellationToken)
        {
            if (Interlocked.Exchange(ref swapped, 1) != 0)
                throw new InvalidOperationException("Already swapped!");
 
            return DoSwap(cancellationToken);
        }
 
        public abstract Task FinishActivationPreparation(CancellationToken cancellationToken);
 
        protected abstract ValueTask DoSwap(CancellationToken cancellationToken);
    }
}