using System;
using System.IO;
using System.Reflection;
using UnityEngine;

namespace ModTool.Shared
{
	/// <summary>
	/// A singleton class for ScriptableObjecs, which stores itself as an asset in a Resources folder.
	/// </summary>
	/// <typeparam name="T"></typeparam>
	public abstract class Singleton<T> : ScriptableObject where T : Singleton<T>
	{
		public static T instance
		{
			get
			{			   
				GetInstance();				
				return _instance;
			}
		}

		private static T _instance;

		protected Singleton()
		{
			if (_instance == null)
				_instance = this as T;
		}
		
		protected static void GetInstance()
		{
			if (_instance != null)
				return;
			
			_instance = Resources.Load<T>(typeof(T).Name);

			if (_instance == null)
			{
				_instance = CreateInstance<T>();

				if (Application.isEditor)
					CreateAsset();
			}		   
		}
		
		private static void CreateAsset()
		{
			string modToolDirectory = Path.GetDirectoryName(typeof(ModInfo).Assembly.Location);
			string resourcesDirectory = Path.Combine(modToolDirectory, "Resources");

			resourcesDirectory = resourcesDirectory.Substring(Application.dataPath.Length - 6);

			if (Directory.Exists(resourcesDirectory))
				Directory.CreateDirectory(resourcesDirectory);

			string assetPath = Path.Combine(resourcesDirectory, typeof(T).Name + ".asset");

			Type type = Type.GetType("UnityEditor.AssetDatabase, UnityEditor");

			if (type == null)
				return;

			MethodInfo method = type.GetMethod("CreateAsset", BindingFlags.Public | BindingFlags.Static);

			method.Invoke(null, new object[] { _instance, assetPath });
		}
	}
}