// 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.
 
#nullable disable
 
using System;
using Microsoft.VisualStudio.OLE.Interop;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation;
 
internal sealed class ComEventSink
{
    public static ComEventSink Advise<T>(object obj, T sink) where T : class
    {
        if (!typeof(T).IsInterface)
        {
            throw new InvalidOperationException();
        }
 
        if (obj is not IConnectionPointContainer connectionPointContainer)
        {
            throw new ArgumentException("Not an IConnectionPointContainer", nameof(obj));
        }
 
        connectionPointContainer.FindConnectionPoint(typeof(T).GUID, out var connectionPoint);
        if (connectionPoint == null)
        {
            throw new InvalidOperationException("Could not find connection point for " + typeof(T).FullName);
        }
 
        connectionPoint.Advise(sink, out var cookie);
 
        return new ComEventSink(connectionPoint, cookie);
    }
 
    private readonly IConnectionPoint _connectionPoint;
    private readonly uint _cookie;
    private bool _unadvised;
 
    public ComEventSink(IConnectionPoint connectionPoint, uint cookie)
    {
        _connectionPoint = connectionPoint;
        _cookie = cookie;
    }
 
    public void Unadvise()
    {
        if (_unadvised)
        {
            throw new InvalidOperationException("Already unadvised.");
        }
 
        _connectionPoint.Unadvise(_cookie);
        _unadvised = true;
    }
}