using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace MoonSharp.Interpreter.Loaders
{
	/// <summary>
	/// A script loader which can load scripts from assets in Unity3D.
	/// Scripts should be saved as .txt files in a subdirectory of Assets/Resources.
	/// 
	/// When MoonSharp is activated on Unity3D and the default script loader is used,
	/// scripts should be saved as .txt files in Assets/Resources/MoonSharp/Scripts.
	/// </summary>
	public class UnityAssetsScriptLoader : ScriptLoaderBase
	{
		Dictionary<string, string> m_Resources = new Dictionary<string, string>();

		/// <summary>
		/// The default path where scripts are meant to be stored (if not changed)
		/// </summary>
		public const string DEFAULT_PATH = "MoonSharp/Scripts";

		/// <summary>
		/// Initializes a new instance of the <see cref="UnityAssetsScriptLoader"/> class.
		/// </summary>
		/// <param name="assetsPath">The path, relative to Assets/Resources. For example
		/// if your scripts are stored under Assets/Resources/Scripts, you should
		/// pass the value "Scripts". If null, "MoonSharp/Scripts" is used. </param>
		public UnityAssetsScriptLoader(string assetsPath = null)
		{
			assetsPath = assetsPath ?? DEFAULT_PATH;
#if UNITY_5
                LoadResourcesUnityNative(assetsPath);
#else
			LoadResourcesWithReflection(assetsPath);
#endif
		}


		/// <summary>
		/// Initializes a new instance of the <see cref="UnityAssetsScriptLoader"/> class.
		/// </summary>
		/// <param name="scriptToCodeMap">A dictionary mapping filenames to the proper Lua script code.</param>
		public UnityAssetsScriptLoader(Dictionary<string, string> scriptToCodeMap)
		{
			m_Resources = scriptToCodeMap;
		}

#if UNITY_5
        void LoadResourcesUnityNative(string assetsPath)
        {
            try
            {
                UnityEngine.Object[] array = UnityEngine.Resources.LoadAll(assetsPath, typeof(UnityEngine.TextAsset));

                for (int i = 0; i < array.Length; i++)
                {
                    UnityEngine.TextAsset o = (UnityEngine.TextAsset)array[i];

                    string name = o.name;
                    string text = o.text;

                    m_Resources.Add(name, text);
                }
            }
            catch (Exception ex)
            {
                UnityEngine.Debug.LogErrorFormat("Error initializing UnityScriptLoader : {0}", ex);
            }
        }
#endif

		void LoadResourcesWithReflection(string assetsPath)
		{
			try
			{
				Type resourcesType = Type.GetType("UnityEngine.Resources, UnityEngine");
				Type textAssetType = Type.GetType("UnityEngine.TextAsset, UnityEngine");

				MethodInfo textAssetNameGet = textAssetType.GetProperty("name").GetGetMethod();
				MethodInfo textAssetTextGet = textAssetType.GetProperty("text").GetGetMethod();

				MethodInfo loadAll = resourcesType.GetMethod("LoadAll",
					new Type[] { typeof(string), typeof(Type) });

				Array array = (Array)loadAll.Invoke(null, new object[] { assetsPath, textAssetType });

				for (int i = 0; i < array.Length; i++)
				{
					object o = array.GetValue(i);

					string name = textAssetNameGet.Invoke(o, null) as string;
					string text = textAssetTextGet.Invoke(o, null) as string;

					m_Resources.Add(name, text);
				}
			}
			catch (Exception ex)
			{
#if !(PCL || ENABLE_DOTNET)
				Console.WriteLine("Error initializing UnityScriptLoader : {0}", ex);
#endif
			}
		}

		private string GetFileName(string filename)
		{
			int b = Math.Max(filename.LastIndexOf('\\'), filename.LastIndexOf('/'));

			if (b > 0)
				filename = filename.Substring(b + 1);

			return filename;
		}

		/// <summary>
		/// Opens a file for reading the script code.
		/// It can return either a string, a byte[] or a Stream.
		/// If a byte[] is returned, the content is assumed to be a serialized (dumped) bytecode. If it's a string, it's
		/// assumed to be either a script or the output of a string.dump call. If a Stream, autodetection takes place.
		/// </summary>
		/// <param name="file">The file.</param>
		/// <param name="globalContext">The global context.</param>
		/// <returns>
		/// A string, a byte[] or a Stream.
		/// </returns>
		/// <exception cref="System.Exception">UnityAssetsScriptLoader.LoadFile : Cannot load  + file</exception>
		public override object LoadFile(string file, Table globalContext)
		{
			file = GetFileName(file);

			if (m_Resources.ContainsKey(file))
				return m_Resources[file];
			else
			{
				var error = string.Format(
@"Cannot load script '{0}'. By default, scripts should be .txt files placed under a Assets/Resources/{1} directory.
If you want scripts to be put in another directory or another way, use a custom instance of UnityAssetsScriptLoader or implement
your own IScriptLoader (possibly extending ScriptLoaderBase).", file, DEFAULT_PATH);

				throw new Exception(error);
			}
		}

		/// <summary>
		/// Checks if a given file exists
		/// </summary>
		/// <param name="file">The file.</param>
		/// <returns></returns>
		public override bool ScriptFileExists(string file)
		{
			file = GetFileName(file);
			return m_Resources.ContainsKey(file);
		}


		/// <summary>
		/// Gets the list of loaded scripts filenames (useful for debugging purposes).
		/// </summary>
		/// <returns></returns>
		public string[] GetLoadedScripts()
		{
			return m_Resources.Keys.ToArray();
		}



	}
}