/* author: YKMoon
 * 单例模式基类，可以直接继承
 * 继承ISingletonEventHandler接口可以接收事件
 */
using UnityEngine;
using System.Collections;

namespace YKMoon
{
	/// <summary>
	/// 单例初始化接口，想在单例创建时调用自定义初始化函数时继承
	/// </summary>
	public interface IUSingletonEventHandler
	{
		/// <summary>
		/// 创建单例时调用，主要用于像mono这种不能在构造函数写东西的
		/// </summary>
		void OnCreateSingleton();
	}
	/// <summary>
	/// 单例类
	/// <example>使用例子：
	/// <code>public class A: USingleton&lt;A&gt;</code>
	/// </example>
	/// </summary>
	public class USingleton<T> where T : new()
	{
		private static T _instance;
		public static T Instance {
			get {
				if(_instance == null) {
					_instance = new T();
					if(_instance is IUSingletonEventHandler) {
						(_instance as IUSingletonEventHandler).OnCreateSingleton();
					}
				}
				return _instance;
			}
		}
	}
	/// <summary>
	/// 单例类，继承自YKMono，有MonoBehaviour特性会产生GameObject
	/// <example>使用例子：
	/// <code>public class A: USingletonMono&lt;A&gt;</code>
	/// </example>
	/// </summary>
	public class USingletonMono<T> : YKMono where T : YKMono
	{
		private static T _instance;
		public static T Instance {
			get {
				if(_instance == null) {
					GameObject obj = new GameObject(typeof(T).Name);
					GameObject.DontDestroyOnLoad(obj);
					_instance = obj.AddComponent<T>();
					if(_instance is IUSingletonEventHandler) {
						(_instance as IUSingletonEventHandler).OnCreateSingleton();
					}
				}
				return _instance;
			}
		}
	}
	public class USingletonHidingMono<T> : YKMono where T: YKMono
    {
		private static T _instance;
		public static T Instance {
			get {
				if(_instance == null) {
					GameObject obj = new GameObject(typeof(T).Name);
					GameObject.DontDestroyOnLoad(obj);
					obj.hideFlags |= HideFlags.HideInHierarchy;
					_instance = obj.AddComponent<T>();
					if(_instance is IUSingletonEventHandler) {
						(_instance as IUSingletonEventHandler).OnCreateSingleton();
					}
				}
				return _instance;
			}
		}
	}
	/// <summary>
	/// 单例类，继承自YKMono，自定义注册型，会在Awake时注册到Instance.
	/// 使用时要注意为null的情况.
	/// </summary>
	public class USingletonMonoCustom<T> : YKMono where T : YKMono
	{
		private static T _instance;
		public static T Instance {
			get {
				if(_instance == null) {
					throw new System.NullReferenceException("Singleton is not regist.Call Instance after mono Awake.");
				}
				return _instance;
			}
		}
		protected override void Awake()
        {
			_instance = gameObject.GetComponent<T>();
			GameObject.DontDestroyOnLoad(gameObject);
			if(_instance is IUSingletonEventHandler) {
				(_instance as IUSingletonEventHandler).OnCreateSingleton();
			}
			base.Awake();
        }
    }
	/// <summary>
	/// 单例类，线程安全型
	/// </summary>
	public class UTFSingleton<T> where T : new()
	{
		private static T _instance = default(T);
		private static readonly object padlock = new object();
		public static T Instance {
			get {
				lock(padlock) {
					if(_instance == null) {
						_instance = new T();
						if(_instance is IUSingletonEventHandler) {
							(_instance as IUSingletonEventHandler).OnCreateSingleton();
						}
					}
					return _instance;
				}
			}
		}
	}
}