// 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 Roslyn.Utilities
{
    internal static class WeakEventHandler<TArgs>
    {
        /// <summary>
        /// Creates an event handler that holds onto the target weakly.
        /// </summary>
        /// <param name="target">The target that is held weakly, and passed as an argument to the invoker.</param>
        /// <param name="invoker">An action that will receive the event arguments as well as the target instance. 
        /// The invoker itself must not capture any state.</param>
        public static EventHandler<TArgs> Create<TTarget>(TTarget target, Action<TTarget, object?, TArgs> invoker)
            where TTarget : class
        {
            var weakTarget = new WeakReference<TTarget>(target);
 
            return (sender, args) =>
            {
                if (weakTarget.TryGetTarget(out var targ))
                {
                    invoker(targ, sender, args);
                }
            };
        }
    }
}