// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Composition;
using System.Threading;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.ServiceHub.Framework;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Remote.Host;
 
internal interface IGlobalServiceBroker
{
    IServiceBroker Instance { get; }
}
 
/// <summary>
/// Hacky way to expose a <see cref="IServiceBroker"/> to workspace services that expect there to be a global
/// singleton (like in visual studio).  Effectively the first service that gets called into will record its
/// broker here for these services to use.
/// </summary>
// Note: this Export is only so MEF picks up the exported member internally.
[Export(typeof(IGlobalServiceBroker)), Shared]
internal class GlobalServiceBroker : IGlobalServiceBroker
{
    private static IServiceBroker? s_instance;
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public GlobalServiceBroker()
    {
    }
 
    public static void RegisterServiceBroker(IServiceBroker serviceBroker)
    {
        Interlocked.CompareExchange(ref s_instance, serviceBroker, null);
    }
 
    public IServiceBroker Instance
    {
        get
        {
            Contract.ThrowIfNull(s_instance, "Global service broker not registered");
            return s_instance;
        }
    }
}