// 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;
 
namespace Microsoft.CodeAnalysis;
 
public sealed class WorkspaceRegistration
{
    private readonly object _gate = new();
 
    internal WorkspaceRegistration()
    {
    }
 
    public Workspace? Workspace { get; private set; }
 
    public event EventHandler? WorkspaceChanged;
 
    internal void SetWorkspaceAndRaiseEvents(Workspace? workspace)
    {
        SetWorkspace(workspace);
        RaiseEvents();
    }
 
    internal void SetWorkspace(Workspace? workspace)
        => Workspace = workspace;
 
    internal void RaiseEvents()
    {
        lock (_gate)
        {
            // this is a workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/744145
            // for preview 2.
            //
            // it is a workaround since we are calling event handler under a lock to make sure
            // we don't raise event concurrently
            //
            // we have this issue to track proper fix for preview 3 or later
            // https://github.com/dotnet/roslyn/issues/32551
            //
            // issue we are working around is the fact this event can happen concurrently
            // if RegisteryText happens and then UnregisterText happens in perfect timing, 
            // RegisterText got slightly delayed since it is async event, and UnregisterText happens 
            // at the same time since it is a synchronous event, and they my happens in 2 different threads, 
            // cause this event to be raised concurrently.
            // that can cause some listener to mess up its internal state like the issue linked above
            WorkspaceChanged?.Invoke(this, EventArgs.Empty);
        }
    }
}