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;
                }
                lock (_lock)
                {
                    if (_instance == null)
                    {
                        _instance = (T)FindObjectOfType(typeof(T));

                        if (FindObjectsOfType(typeof(T)).Length > 1)
                        {
                            return _instance;
                        }

                        if (_instance == null)
                        {
                            GameObject 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;
        }
    }
}