using UnityEngine;

namespace A2W
{
    public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
    {
        private static T _instance;
        private static object _lock = new object();
        public static T instance
        {
            get
            {
                //if (applicationIsQuitting)
                //{
                //    return null;
                //}

                if (_instance == null)
                {
                    lock (_lock)
                    {
                        if (_instance == null)
                        {
                            var objs = FindObjectsByType<T>(FindObjectsSortMode.None);
                            if (objs.Length > 0)
                            {
                                _instance = objs[0];
                                if (objs.Length > 1)
                                {
                                    for (var i = 1; i < objs.Length; i++)
                                    {
                                        Destroy(objs[i].gameObject);
                                    }
                                }
                            }

                            if (_instance == null)
                            {
                                var singleton = new GameObject();
                                _instance = singleton.AddComponent<T>();
                                singleton.name = "(singleton)" + typeof(T).ToString();

                                DontDestroyOnLoad(singleton);
                            }
                        }

                    }
                }

                return _instance;
            }
        }

        //private static bool applicationIsQuitting = false;

        //public void OnDestroy()
        //{
        //    applicationIsQuitting = true;
        //}
    }
}