RobustToolbox/Robust.Shared/GameObjects/EntityEvents.cs

using System;
using Robust.Shared.Players;

namespace Robust.Shared.GameObjects
{
    public interface IEntityEventSubscriber { }

    public delegate void EntityEventHandler<in T>(T ev);

    public delegate void EntitySessionEventHandler<in T>(T msg, EntitySessionEventArgs args);

    public class EntityEventArgs : EventArgs { }

    public readonly struct EntitySessionEventArgs
    {
        public EntitySessionEventArgs(ICommonSession senderSession)
        {
            SenderSession = senderSession;
        }

        public ICommonSession SenderSession { get; }
    }

    internal readonly struct EntitySessionMessage<T>
    {
        public EntitySessionMessage(EntitySessionEventArgs eventArgs, T message)
        {
            EventArgs = eventArgs;
            Message = message;
        }

        public EntitySessionEventArgs EventArgs { get; }
        public T Message { get; }

        public void Deconstruct(out EntitySessionEventArgs eventArgs, out T message)
        {
            eventArgs = EventArgs;
            message = Message;
        }
    }
}