/**

  * Copyright 2009 Martin Vysny.

  *

  * This file is part of WebVM.

  *

  * WebVM 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.

  *

  * WebVM 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 WebVM.  If not, see <http://www.gnu.org/licenses/>.

  */

 package sk.baka.webvm.analyzer.classloader;

 import java.net.URI;

 import java.net.URISyntaxException;

 import java.net.URL;

 import java.net.URLClassLoader;

 import java.util.ArrayList;

 import java.util.HashMap;

 import java.util.Iterator;

 import java.util.List;

 import java.util.Map;

 /**

  * Contains utilities for classloader analysis.

  * @author Martin Vysny

  */

 public final class ClassLoaderUtils {

     private ClassLoaderUtils() {

         throw new AssertionError();

     }

     private static final URL[] EMPTY_URL_ARRAY = new URL[0];

     /**

      * Returns URLs which given class loader claims to see. Uses {@link URLClassLoader#getURLs()}.

      * @param cl the class loader to analyze

      * @return never null, may be empty array in case the classloader is not an URLClassLoader.

      */

     public static URL[] getURLs(final ClassLoader cl) {

         if (!(cl instanceof URLClassLoader)) {

             return EMPTY_URL_ARRAY;

         }

         final URL[] result = ((URLClassLoader) cl).getURLs();

         if (result == null) {

             return EMPTY_URL_ARRAY;

         }

         return result;

     }

     /**

      * Return the class loader parent chain as a list.

      * @param cl the class loader to analyze

      * @return the chain with given class loader first and the root class loader last.

      */

     public static List<ClassLoader> getClassLoaderChain(final ClassLoader cl) {

         final List<ClassLoader> result = new ArrayList<ClassLoader>();

         for (ClassLoader c = cl; c != null; c = c.getParent()) {

             result.add(c);

         }

         return result;

     }

     /**

      * Returns a map of URIs visible to class loaders.

      * @param cl the class loader to analyze

      * @return maps URIs loadable by a class loader to a list of class loaders which are able to load the URI.

      * @throws java.net.URISyntaxException

      */

     public static Map<URI, List<ClassLoader>> getClassLoaderURIs(final ClassLoader cl) throws URISyntaxException {

         final Map<URI, List<ClassLoader>> result = new HashMap<URI, List<ClassLoader>>();

         final List<ClassLoader> cls = getClassLoaderChain(cl);

         for (final ClassLoader c : cls) {

             final URL[] urls = getURLs(c);

             for (final URL url : urls) {

                 final URI uri = url.toURI();

                 List<ClassLoader> list = result.get(uri);

                 if (list == null) {

                     list = new ArrayList<ClassLoader>();

                     result.put(uri, list);

                 }

                 list.add(c);

             }

         }

         return result;

     }

     /**

      * Filters out regular class loader items, leaving only URIs loadable by multiple class loaders.

      * @param map URI - ClassLoaders map, must not be null.

      */

     public static void filterClashes(final Map<URI, List<ClassLoader>> map) {

         for (final Iterator<Map.Entry<URI, List<ClassLoader>>> i = map.entrySet().iterator(); i.hasNext();) {

             final Map.Entry<URI, List<ClassLoader>> e = i.next();

             if (e.getValue().size() <= 1) {

                 i.remove();

             }

         }

     }

 }