using System;
using System.Reflection;

namespace MAX.Core.Infrastructure;

/// <summary>
/// 单例，需要在当前类中定义
/// </summary>
/// <typeparam name="T"></typeparam>
public class SingleInstance<T> where T : class
{
	private static readonly object lockObj = new();
	private static T mySelf;//= default(T);
	public static T Instance
	{
		get
		{
			lock (lockObj)
			{
				mySelf ??= InstanceCreator.CreateInstance<T>();
			}

			return mySelf;
		}
	}
}

public static class InstanceCreator
{
	public static T CreateInstance<T>()
	{
		Type type = typeof(T);
		try
		{
			return (T)type.Assembly.CreateInstance(type.FullName, true, BindingFlags.NonPublic | BindingFlags.Instance, null, null, null, null);
		}
		catch (MissingMethodException ex)
		{
			throw new Exception($"{ex.Message}\n(单例模式下，构造函数必须为 private)");
		}
	}
}