using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Reflection;

namespace Revolucent.Dasso.Core
{
    [Serializable]
    public class WeakEventManager<E>
        where E : EventArgs
    {
        class WeakEventSubscriber : IEquatable<WeakEventSubscriber>
        {
            private readonly WeakReference target = null;
            private MethodInfo method = null;

            public WeakEventSubscriber(Delegate del)
            {
                target = new WeakReference(del.Target);
                method = del.Method;
            }

            public bool IsAlive { get { return target.IsAlive; } }

            public void Invoke(object sender, E e)
            {
                if (!IsAlive)
                    return;
                method.Invoke(target.Target, new object[] { sender, e });
            }

            public bool Equals(WeakEventSubscriber other)
            {
                return Object.ReferenceEquals(target.Target, other.target.Target) && (method == other.method);
            }
        }

        private readonly List<WeakEventSubscriber> subscribers = new List<WeakEventSubscriber>();

        public void Add(Delegate del)
        {
            subscribers.Add(new WeakEventSubscriber(del));
        }

        public void Remove(Delegate del)
        {
            subscribers.Remove(new WeakEventSubscriber(del));
        }

        public void Invoke(object sender, E e)
        {
            subscribers.RemoveAll(subscriber => !subscriber.IsAlive);
            subscribers.ForEach(subscriber => subscriber.Invoke(sender, e));
        }
    }
}