/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.
   */
  
  package org.apache.hadoop.chukwa.util;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  import java.net.JarURLConnection;
  import java.net.URL;
  import java.net.URLDecoder;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.List;
  import java.util.jar.JarEntry;
  import java.util.jar.JarFile;
  
  import org.apache.log4j.Logger;
  
  public class ClassUtils {
    static Logger log = Logger.getLogger(ClassUtils.class);
    
    /**
     * Attempts to list all the classes in the specified package as determined
     * by the context class loader
     * 
     * @param pckgname
     *            the package name to search
     * @return a list of classes that exist within that package
     * @throws ClassNotFoundException
     *             if something went wrong
     */
    public static List<Class> getClassesForPackage(String pckgname)
        throws ClassNotFoundException {
      // This will hold a list of directories matching the pckgname.
      // There may be more than one if a package is split over multiple jars/paths
      List<Class> classes = new ArrayList<Class>();
      ArrayList<File> directories = new ArrayList<File>();
      try {
        ClassLoader cld = Thread.currentThread().getContextClassLoader();
        if (cld == null) {
          throw new ClassNotFoundException("Can't get class loader.");
        }
        // Ask for all resources for the path
        Enumeration<URL> resources = cld.getResources(pckgname.replace('.', '/'));
        while (resources.hasMoreElements()) {
          URL res = resources.nextElement();
          if (res.getProtocol().equalsIgnoreCase("jar")) {
            JarURLConnection conn = (JarURLConnection) res.openConnection();
            JarFile jar = conn.getJarFile();
            for (JarEntry e : Collections.list(jar.entries())) {
  
              if (e.getName().startsWith(pckgname.replace('.', '/'))
                  && e.getName().endsWith(".class") && !e.getName().contains("$")) {
                String className = e.getName().replace("/", ".").substring(0,
                    e.getName().length() - 6);
                classes.add(Class.forName(className));
              }
            }
          } else
            directories.add(new File(URLDecoder.decode(res.getPath(), "UTF-8")));
        }
      } catch (NullPointerException x) {
        throw new ClassNotFoundException(pckgname + " does not appear to be "
            + "a valid package (Null pointer exception)");
      } catch (UnsupportedEncodingException encex) {
        throw new ClassNotFoundException(pckgname + " does not appear to be "
            + "a valid package (Unsupported encoding)");
      } catch (IOException ioex) {
        throw new ClassNotFoundException("IOException was thrown when trying "
            + "to get all resources for " + pckgname);
      }
  
      // For every directory identified capture all the .class files
      for (File directory : directories) {
        if (directory.exists()) {
          // Get the list of the files contained in the package
          String[] files = directory.list();
          for (String file : files) {
            // we are only interested in .class files
            if (file.endsWith(".class")) {
              // removes the .class extension
             classes.add(Class.forName(pckgname + '.'
                 + file.substring(0, file.length() - 6)));
           }
         }
       } else {
         throw new ClassNotFoundException(pckgname + " (" + directory.getPath()
             + ") does not appear to be a valid package");
       }
     }
     return classes;
   }
 
   public static List<Class> getClassessOfInterface(String thePackage,
       Class theInterface) {
     List<Class> classList = new ArrayList<Class>();
     try {
       for (Class discovered : getClassesForPackage(thePackage)) {
         if (Arrays.asList(discovered.getInterfaces()).contains(theInterface)) {
           classList.add(discovered);
         }
       }
     } catch (ClassNotFoundException ex) {
       log.error(ExceptionUtil.getStackTrace(ex));
     }
 
     return classList;
   }
   
 
 }