using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Metadata.Ecma335;
using System.Text;
using System.Threading.Tasks;

namespace Pilz.Plugins
{
    public class PluginManager<TPluginInterface, TPluginRuntimeInfo> where TPluginInterface : class where TPluginRuntimeInfo : PluginRuntimeInfo<TPluginInterface>
    {
        private readonly List<TPluginRuntimeInfo> loadedPlugins = [];

        /// <summary>
        /// Returns a list of all currently loaded plugins.
        /// </summary>
        public IEnumerable<TPluginRuntimeInfo> LoadedPlugins => loadedPlugins.AsReadOnly();

        private void CurrentDomain_AssemblyLoad(object? sender, AssemblyLoadEventArgs args)
        {
            LoadPlugin(args.LoadedAssembly);
        }

        /// <summary>
        /// Loads assembly from the given file paths and then loads the plugins from the assemblies.
        /// </summary>
        /// <param name="paths"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public IEnumerable<TPluginRuntimeInfo> LoadPlugins(string[] paths, params object?[]? parameters)
        {
            foreach (var path in paths)
                yield return LoadPlugin(path, parameters);
        }

        /// <summary>
        /// Loads plugins from the given assemblies.
        /// </summary>
        /// <param name="paths"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public IEnumerable<TPluginRuntimeInfo> LoadPlugins(Assembly[] assemblies, params object?[]? parameters)
        {
            foreach (var assembly in assemblies)
                yield return LoadPlugin(assembly, parameters);
        }

        /// <summary>
        /// Loads plugins from already loaded assemblies for the current <see cref="AppDomain.CurrentDomain"/>.
        /// </summary>
        /// <param name="listenAssemblyLoadContext">Do also load plugins from all yet not loaded assemblies by listening the event <see cref="AppDomain.AssemblyLoad"/>.
        /// <returns></returns>
        public IEnumerable<TPluginRuntimeInfo> LoadOwnPlugins(bool listenAssemblyLoadContext, params object?[]? parameters)
        {
            if (listenAssemblyLoadContext)
                AppDomain.CurrentDomain.AssemblyLoad += CurrentDomain_AssemblyLoad;

            foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
                yield return LoadPlugin(assembly, parameters);
        }

        /// <summary>
        /// Loads an assembly from the given file path and then loads the plugin from the assembly.
        /// </summary>
        /// <param name="path"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public TPluginRuntimeInfo LoadPlugin(string path, params object?[]? parameters)
        {
            var info = Activator.CreateInstance<TPluginRuntimeInfo>();
            var loadContext = new PluginLoadContext(path);

            if (File.Exists(path))
            {
                try
                {
                    info.Assembly = loadContext.LoadFromAssemblyName(new AssemblyName(Path.GetFileNameWithoutExtension(path)));
                }
                catch
                {
                    info.Status = PluginStatus.ErrorAtLoading;
                }
            }
            else
                info.Status = PluginStatus.FileNotFound;
            
            if (info.Assembly != null)
                info = LoadPlugin(info.Assembly, parameters);

            return info;
        }

        /// <summary>
        /// Loads the plugin from a given assembly.
        /// </summary>
        /// <param name="assembly"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public TPluginRuntimeInfo LoadPlugin(Assembly assembly, params object?[]? parameters)
        {
            var info = Activator.CreateInstance<TPluginRuntimeInfo>();
            info.Assembly = assembly;
            LoadPlugin(info);
            return info;
        }

        private void LoadPlugin(TPluginRuntimeInfo info, params object?[]? parameters)
        {
            var irmplugin = typeof(TPluginInterface);

            if (info.Assembly == null)
                info.Status = PluginStatus.NoValidPlugin;
            else if (loadedPlugins.Any(n => n.Assembly == info.Assembly))
                info.Status = PluginStatus.AlreadyLoaded;
            else
            {
                foreach (var type in info.Assembly.GetTypes())
                {
                    if (info.Plugin == null && irmplugin.IsAssignableFrom(type))
                    {
                        try
                        {
                            if (Activator.CreateInstance(type, parameters) is TPluginInterface plugin)
                            {
                                info.Plugin = plugin;
                                info.Status = PluginStatus.Success;
                                loadedPlugins.Add(info);
                            }
                        }
                        catch
                        {
                            info.Status = PluginStatus.ErrorAtInitializing;
                        }
                    }
                }
            }

            if (info.Plugin == null)
                info.Status = PluginStatus.NoValidPlugin;
        }
    }
}