using UnityEngine;

namespace TemporalRealms.Utility {

    /// <summary>
    /// Generic singleton base class for global, single-instance MonoBehaviors.
    /// </summary>
    /// <typeparam name="T">The class type to define</typeparam>
    public class SingletonMonoBehaviour<T> : MonoBehaviour where T : Component {
        /// <summary>
        /// Storage for the singleton instance.
        /// </summary>
        private static T instance;

        /// <summary>
        /// Property that either creates or returns the existing singleton instance.
        /// </summary>
        public static T Instance {
            get {
                if (instance != null) return instance;
                instance = FindObjectOfType<T>();
                if (instance != null) return instance;

                var obj = new GameObject { name = typeof(T).Name };
                instance = obj.AddComponent<T>();
                return instance;
            }
        }

        /// <summary>
        /// Makes sure that the instance doesn't get destroyed when switching screens.
        /// </summary>
        public virtual void Awake() {
            if (instance == null) {
                instance = this as T;
                DontDestroyOnLoad(gameObject);
            } else {
                Destroy(gameObject);
            }
        }
    }

}