using System;
using System.Reflection;

namespace AibisDream.Kit
{
    public class SingletonProp<T> where T : class, ISingleton
    {
        /// <summary>
        /// 静态实例
        /// </summary>
        private static T _instance;

        /// <summary>
        /// 标签锁
        /// </summary>
        private static readonly object _lock = new();

        public static T Instance
        {
            get
            {
                lock (_lock)
                {
                    if (_instance == null)
                    {
                        // 先获取所有非public的构造方法
                        var ctors = typeof(T).GetConstructors(BindingFlags.Instance | BindingFlags.NonPublic);
                        // 从ctors中获取无参的构造方法
                        var ctor = Array.Find(ctors, c => c.GetParameters().Length == 0);
                        if (ctor == null)
                            throw new Exception("Non-public ctor() not found!");
                        // 调用构造方法
                        _instance = ctor.Invoke(null) as T;
                        _instance?.OnSingletonInit();

                        return _instance;
                    }
                }

                return _instance;
            }
        }
        
        /// <summary>
        /// 资源释放
        /// </summary>
        public static void Dispose()
        {
            _instance = null;
        }
    }
}