maki/Maki/BaseManager.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Maki
{
    internal abstract class BaseManager<T> : IDisposable
    {
        protected readonly HashSet<T> Collection = new HashSet<T>();
        public IEnumerable<T> Items => Collection;
        public int Count => Collection.Count;

        public event Action<T> OnAdd;
        public event Action<T> OnRemove;

        protected virtual bool DisposeOnRemove => true;

        protected bool IsDisposed = false;

        ~BaseManager()
            => Dispose(false);

        public void Dispose()
            => Dispose(true);

        protected void Dispose(bool disposing)
        {
            if (IsDisposed)
                return;

            IsDisposed = true;
            Collection.ToList().ForEach(x => Remove(x));
            Collection.Clear();

            if (disposing)
                GC.SuppressFinalize(this);
        }

        public virtual void Add(T item)
        {
            if (item == null)
                return;
            
            lock (Collection)
                Collection.Add(item);

            OnAdd?.Invoke(item);
        }

        public virtual void Remove(T item)
        {
            if (item == null)
                return;

            lock (Collection)
                Collection.Remove(item);

            OnRemove?.Invoke(item);

            if (DisposeOnRemove && item is IDisposable)
                (item as IDisposable).Dispose();
        }
    }
}