/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.common;
  
  import java.io.File;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.util.Optional;
  
  public class MCRClassTools {
      private static volatile ClassLoader extendedClassLoader;
  
      static {
          updateClassLoader(); //first init
      }
  
      public static Object loadClassFromURL(String classPath, String className)
          throws MalformedURLException, ReflectiveOperationException {
          return loadClassFromURL(new File(classPath), className);
      }
  
      public static Object loadClassFromURL(File file, String className)
          throws MalformedURLException, ReflectiveOperationException {
          if (file.exists()) {
              URL url = file.toURI().toURL();
              URLClassLoader urlClassLoader = new URLClassLoader(new URL[] { url },
                  Thread.currentThread().getContextClassLoader());
              Class<?> clazz = urlClassLoader.loadClass(className);
              return clazz.getDeclaredConstructor().newInstance();
          }
  
          return null;
      }
  
      /**
       * Loads a class via default ClassLoader or <code>Thread.currentThread().getContextClassLoader()</code>.
       * @param classname Name of class
       * @param <T> Type of Class
       * @return the initialized class
       * @throws ClassNotFoundException if both ClassLoader cannot load the Class
       */
      public static <T> Class<? extends T> forName(String classname) throws ClassNotFoundException {
          @SuppressWarnings("unchecked")
          Class<? extends T> forName;
          try {
              forName = (Class<? extends T>) Class.forName(classname);
          } catch (ClassNotFoundException cnfe) {
              forName = (Class<? extends T>) Class.forName(classname, true, extendedClassLoader);
          }
          return forName;
      }
  
      /**
       * @return a ClassLoader that should be used to load resources
       */
      public static ClassLoader getClassLoader() {
          return extendedClassLoader;
      }
  
      public static void updateClassLoader() {
          extendedClassLoader = Optional.ofNullable(Thread.currentThread().getContextClassLoader())
              .orElseGet(MCRClassTools.class::getClassLoader);
      }
  
  }