MARKUS

/*

   Copyright 2013 Christoph Gattnar

   Licensed under the Apache License, Version 2.0 (the "License");

   you may not use this file except in compliance with the License.

   You may obtain a copy of the License at

	   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software

   distributed under the License is distributed on an "AS IS" BASIS,

   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

   See the License for the specific language governing permissions and

   limitations under the License.

*/

using System;

using System.Collections.Generic;

using System.IO;

using System.Reflection;

using System.Linq;

namespace Markus.Service.Extensions

{

	public static class GenericPluginLoader<T>

	{

		public static ICollection<T> LoadPlugins(string path)

		{

			string[] dllFileNames = null;

			if(Directory.Exists(path))

            {

                ICollection<Assembly> assemblies = new List<Assembly>();

                ICollection<T> plugins = new List<T>();

				Type pluginType = typeof(T);

				dllFileNames = Directory.GetFiles(path, "*.dll",SearchOption.AllDirectories);

                if(dllFileNames.Count() == 0)

                {

                    throw new Exception($"Plugin Not Found. {path}");

                }

				foreach(string dllFile in dllFileNames)

				{

                    try

                    {

                        AssemblyName an = AssemblyName.GetAssemblyName(dllFile);

                        Assembly assembly = Assembly.Load(an);

                        if (assembly.GetTypes()?.Count() > 0)

                        {

                            if (assembly.GetTypes()[0].GetInterfaces().Count(x => x == pluginType) > 0)

                            {

                                assemblies.Add(assembly);

                            }

                        }

                        else

                        {

                        }

                    }

                    catch (Exception ex)

                    {

                        throw new Exception($"{dllFile} Get InterFaces Error",ex);

                    }

                }

                ICollection<Type> pluginTypes = new List<Type>();

                foreach (Assembly assembly in assemblies)

                {

                    if (assembly != null)

                    {

                        Type[] types = assembly.GetTypes();

                        foreach (Type type in types)

                        {

                            if (type.IsInterface || type.IsAbstract)

                            {

                                continue;

                            }

                            else

                            {

                                if (type.GetInterface(pluginType.FullName) != null)

                                {

                                    pluginTypes.Add(type);

                                }

                            }

                        }

                    }

                }

                foreach (Type type in pluginTypes)

                {

                    try

                    {

                        T plugin = (T)Activator.CreateInstance(type);

                        plugins.Add(plugin);

                    }

                    catch (Exception ex)

                    {

                        throw new Exception($"{type.Name} Get InterFaces Error", ex);

                    }

                }

                return plugins;

			}

			return null;

		}

	}

}