using IllusionPlugin;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;

namespace IllusionInjector
{
    public static class PluginManager
    {
        private static List<IPlugin> _Plugins = null;

        internal static readonly Logger debugLogger = new Logger("IllusionInjector");
        
        /// <summary>
        /// Gets the list of loaded plugins and loads them if necessary.
        /// </summary>
        public static IEnumerable<IPlugin> Plugins
        {
            get
            {
                if(_Plugins == null)
                {
                    LoadPlugins();
                }
                return _Plugins;
            }
        }


        private static void LoadPlugins()
        {
            string pluginDirectory = Path.Combine(Environment.CurrentDirectory, "Plugins");

            // Process.GetCurrentProcess().MainModule crashes the game and Assembly.GetEntryAssembly() is NULL,
            // so we need to resort to P/Invoke
            string exeName = Path.GetFileNameWithoutExtension(AppInfo.StartupPath);
            debugLogger.Log(exeName);
            _Plugins = new List<IPlugin>();

            if (!Directory.Exists(pluginDirectory)) return;

            if (!Directory.Exists(Path.Combine(pluginDirectory, ".cache")))
            {
                Directory.CreateDirectory(Path.Combine(pluginDirectory, ".cache"));
            }
            else
            {
                foreach (string plugin in Directory.GetFiles(Path.Combine(pluginDirectory, ".cache"), "*"))
                {
                    File.Delete(plugin);
                }
            }

            //Copy plugins to .cache
            string[] originalPlugins = Directory.GetFiles(pluginDirectory, "*.dll");
            foreach (string s in originalPlugins)
            {
                string pluginCopy = pluginDirectory + "\\.cache" + s.Substring(s.LastIndexOf('\\'));
                File.Copy(Path.Combine(pluginDirectory, s), pluginCopy);
            }

            //Load copied plugins
            string copiedPluginsDirectory = pluginDirectory + "\\.cache";
            string[] copiedPlugins = Directory.GetFiles(copiedPluginsDirectory, "*.dll");
            foreach (string s in copiedPlugins)
            {
                _Plugins.AddRange(LoadPluginsFromFile(s, exeName));
            }


            // DEBUG
            debugLogger.Log($"Running on Unity {UnityEngine.Application.unityVersion}");
            debugLogger.Log("-----------------------------");
            debugLogger.Log($"Loading plugins from {pluginDirectory} and found {_Plugins.Count}");
            debugLogger.Log("-----------------------------");
            foreach (var plugin in _Plugins)
            {
                debugLogger.Log($"{plugin.Name}: {plugin.Version}");
            }
            debugLogger.Log("-----------------------------");
        }

        private static IEnumerable<IPlugin> LoadPluginsFromFile(string file, string exeName)
        {
            List<IPlugin> plugins = new List<IPlugin>();

            if (!File.Exists(file) || !file.EndsWith(".dll", true, null))
                return plugins;

            try
            {
                Assembly assembly = Assembly.LoadFrom(file);

                foreach (Type t in assembly.GetTypes())
                {
                    if (t.GetInterface("IPlugin") != null)
                    {
                        try
                        {

                            IPlugin pluginInstance = Activator.CreateInstance(t) as IPlugin;
                            string[] filter = null;

                            if (pluginInstance is IEnhancedPlugin)
                            {
                                filter = ((IEnhancedPlugin)pluginInstance).Filter;
                            }
                            
                            if(filter == null || filter.Contains(exeName, StringComparer.OrdinalIgnoreCase))
                                plugins.Add(pluginInstance);
                        }
                        catch (Exception e)
                        {
                            debugLogger.Exception($"Could not load plugin {t.FullName} in {Path.GetFileName(file)}! {e}");
                        }
                    }
                }

            }
            catch (Exception e)
            {
                debugLogger.Error($"Could not load {Path.GetFileName(file)}! {e}");
            }

            return plugins;
        }

        public class AppInfo
        {
            [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = false)]
            private static extern int GetModuleFileName(HandleRef hModule, StringBuilder buffer, int length);
            private static HandleRef NullHandleRef = new HandleRef(null, IntPtr.Zero);
            public static string StartupPath
            {
                get
                {
                    StringBuilder stringBuilder = new StringBuilder(260);
                    GetModuleFileName(NullHandleRef, stringBuilder, stringBuilder.Capacity);
                    return stringBuilder.ToString();
                }
            }
        }

    }
}