using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BrewMonster
{
    public abstract class Singleton<T> where T : class, new()
    {
        private static readonly Lazy<T> _instance = new Lazy<T>(() => new T());
        public static T Instance => _instance.Value;

        // Protected constructor prevents external instantiation
        protected Singleton()
        {
            if (_instance.IsValueCreated)
                throw new InvalidOperationException($"Singleton<{typeof(T).Name}> already created!");
        }
    }
}