package org.codehaus.mojo.jaxb2.shared.environment.classloading;
   
   /*
    * 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.
   */
  
  import org.apache.maven.plugin.logging.Log;
  import org.codehaus.mojo.jaxb2.shared.Validate;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.net.URLDecoder;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * <p>Utility class which assists in synthesizing a URLClassLoader for use as a ThreadLocal ClassLoader.
   * Typical use:</p>
   * <pre>
   *     <code>
   *         // Create and set the ThreadContext ClassLoader
   *         ThreadContextClassLoaderHolder holder = null;
   *
   *         try {
   *
   *          holder = ThreadContextClassLoaderBuilder.createFor(getClass())
   *              .addPath("some/path")
   *              .addURL(someURL)
   *              .addPaths(aPathList)
   *              .buildAndSet();
   *
   *          // ... perform operations using the newly set ThreadContext ClassLoader...
   *
   *         } finally {
   *          // Restore the original ClassLoader
   *          holder.restoreClassLoaderAndReleaseThread();
   *         }
   *     </code>
   * </pre>
   *
   * @author <a href="mailto:lj@jguru.se">Lennart J&ouml;relid</a>, jGuru Europe AB
   * @since 2.0
   */
  public class ThreadContextClassLoaderBuilder {
  
      // Internal state
      private ClassLoader originalClassLoader;
      private List<URL> urlList;
      private Log log;
      private String encoding;
  
      private ThreadContextClassLoaderBuilder(final ClassLoader classLoader, final Log aLog, final String encoding) {
          log = aLog;
          originalClassLoader = classLoader;
          urlList = new ArrayList<URL>();
          this.encoding = encoding;
      }
  
      /**
       * Adds the supplied anURL to the list of internal URLs which should be used to build an URLClassLoader.
       * Will only add an URL once, and warns about trying to re-add an URL.
       *
       * @param anURL The URL to add.
       * @return This ThreadContextClassLoaderBuilder, for builder pattern chaining.
       */
      public ThreadContextClassLoaderBuilder addURL(final URL anURL) {
  
          // Check sanity
          Validate.notNull(anURL, "anURL");
  
          // Add the segment unless already added.
          for (URL current : urlList) {
              if (current.toString().equalsIgnoreCase(anURL.toString())) {
  
                  if (log.isWarnEnabled()) {
                      log.warn("Not adding URL [" + anURL.toString() + "] twice. Check your plugin configuration.");
                  }
  
                  // Don't re-add the supplied URL.
                 return this;
             }
         }
 
         // Add the supplied URL to the urlList
         if (log.isDebugEnabled()) {
             log.debug("Adding URL [" + anURL.toString() + "]");
         }
 
         //
         // According to the URLClassLoader's documentation:
         // "Any URL that ends with a '/' is assumed to refer to a directory.
         // Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed."
         //
         // ... uhm ... instead of using the 'protocol' property of the URL itself?
         //
         // So ... we need to ensure that any file-protocol URLs which point to directories are actually
         // terminated with a '/'. Otherwise the URLClassLoader treats those URLs as JARs - and hence ignores them.
         //
         urlList.add(addSlashToDirectoryUrlIfRequired(anURL));
 
         return this;
     }
 
     /**
      * Converts the supplied path to an URL and adds it to this ThreadContextClassLoaderBuilder.
      *
      * @param path A path to convert to an URL and add.
      * @return This ThreadContextClassLoaderBuilder, for builder pattern chaining.
      * @see #addURL(java.net.URL)
      */
     public ThreadContextClassLoaderBuilder addPath(final String path) {
 
         // Check sanity
         Validate.notEmpty(path, "path");
 
         // Convert to an URL, and delegate.
         final URL anUrl;
         try {
             anUrl = new File(path).toURI().toURL();
         } catch (MalformedURLException e) {
             throw new IllegalArgumentException("Could not convert path [" + path + "] to an URL.", e);
         }
 
         // Delegate
         return addURL(anUrl);
     }
 
     /**
      * Converts the supplied path to an URL and adds it to this ThreadContextClassLoaderBuilder.
      *
      * @param paths A List of path to convert to URLs and add.
      * @return This ThreadContextClassLoaderBuilder, for builder pattern chaining.
      * @see #addPath(String)
      */
     public ThreadContextClassLoaderBuilder addPaths(final List<String> paths) {
 
         // Check sanity
         Validate.notNull(paths, "paths");
 
         // Delegate
         for (String path : paths) {
             addPath(path);
         }
 
         return this;
     }
 
     /**
      * <p>This method performs 2 things in order:</p>
      * <ol>
      * <li>Builds a ThreadContext ClassLoader from the URLs supplied to this Builder, and assigns the
      * newly built ClassLoader to the current Thread.</li>
      * <li>Stores the ThreadContextClassLoaderHolder for later restoration.</li>
      * </ol>
      * References to the original ThreadContextClassLoader and the currentThread are stored within the returned
      * ThreadContextClassLoaderHolder, and can be restored by a call to
      * {@code ThreadContextClassLoaderHolder.restoreClassLoaderAndReleaseThread()}.
      *
      * @return A fully set up ThreadContextClassLoaderHolder which is used to set the
      */
     public ThreadContextClassLoaderHolder buildAndSet() {
 
         // Create the URLClassLoader from the supplied URLs
         final URL[] allURLs = new URL[urlList.size()];
         urlList.toArray(allURLs);
         final URLClassLoader classLoader = new URLClassLoader(allURLs, originalClassLoader);
 
         // Assign the ThreadContext ClassLoader
         final Thread currentThread = Thread.currentThread();
         currentThread.setContextClassLoader(classLoader);
 
         // Build the classpath argument
         StringBuilder builder = new StringBuilder();
         try {
             for (URL current : Collections.list(classLoader.getResources(""))) {
 
                 final String toAppend = getClassPathElement(current, encoding);
                 if (toAppend != null) {
                     builder.append(toAppend).append(File.pathSeparator);
                 }
             }
         } catch (IOException e) {
 
             // Restore the original ClassLoader to the active thread before failing.
             currentThread.setContextClassLoader(originalClassLoader);
             throw new IllegalStateException("Could not synthesize classPath from original ClassLoader.", e);
         }
 
         final String classPathString = builder.length() > 0
                 ? builder.toString().substring(0, builder.length() - File.pathSeparator.length())
                 : "";
 
         // All done.
         return new DefaultHolder(currentThread, this.originalClassLoader, classPathString);
     }
 
     /**
      * Creates a new ThreadContextClassLoaderBuilder using the supplied original classLoader, as well
      * as the supplied Maven Log.
      *
      * @param classLoader The original ClassLoader which should be used as the parent for the ThreadContext
      *                    ClassLoader produced by the ThreadContextClassLoaderBuilder generated by this builder method.
      *                    Cannot be null.
      * @param log         The active Maven Log. Cannot be null.
      * @param encoding    The encoding used by Maven. Cannot be null.
      * @return A ThreadContextClassLoaderBuilder wrapping the supplied members.
      */
     public static ThreadContextClassLoaderBuilder createFor(final ClassLoader classLoader,
             final Log log,
             final String encoding) {
 
         // Check sanity
         Validate.notNull(classLoader, "classLoader");
         Validate.notNull(log, "log");
 
         // All done.
         return new ThreadContextClassLoaderBuilder(classLoader, log, encoding);
     }
 
     /**
      * Creates a new ThreadContextClassLoaderBuilder using the original ClassLoader from the supplied Class, as well
      * as the given Maven Log.
      *
      * @param aClass   A non-null class from which to extract the original ClassLoader.
      * @param log      The active Maven Log. Cannot be null.
      * @param encoding The encoding used by Maven. Cannot be null.
      * @return A ThreadContextClassLoaderBuilder wrapping the supplied members.
      */
     public static ThreadContextClassLoaderBuilder createFor(final Class<?> aClass,
             final Log log,
             final String encoding) {
 
         // Check sanity
         Validate.notNull(aClass, "aClass");
 
         // Delegate
         return createFor(aClass.getClassLoader(), log, encoding);
     }
 
     /**
      * Converts the supplied URL to a class path element.
      *
      * @param anURL    The non-null URL for which to acquire a classPath element.
      * @param encoding The encoding used by Maven.
      * @return The full (i.e. non-chopped) classpath element corresponding to the supplied URL.
      * @throws java.lang.IllegalArgumentException if the supplied URL had an unknown protocol.
      */
     public static String getClassPathElement(final URL anURL, final String encoding) throws IllegalArgumentException {
 
         // Check sanity
         Validate.notNull(anURL, "anURL");
 
         final String protocol = anURL.getProtocol();
         String toReturn = null;
 
         if ("file".equalsIgnoreCase(protocol)) {
 
             final String originalPath = anURL.getPath();
             try {
                 return URLDecoder.decode(anURL.getPath(), encoding);
             } catch (UnsupportedEncodingException e) {
                 throw new IllegalArgumentException("Could not URLDecode path [" + originalPath
                         + "] using encoding [" + encoding + "]", e);
             }
         } else if ("jar".equalsIgnoreCase(protocol)) {
             toReturn = anURL.getPath();
         } else if ("http".equalsIgnoreCase(protocol) || "https".equalsIgnoreCase(protocol)) {
             toReturn = anURL.toString();
         } else {
             throw new IllegalArgumentException("Unknown protocol [" + protocol + "]; could not handle URL ["
                     + anURL + "]");
         }
 
         return toReturn;
     }
 
     //
     // Private helpers
     //
 
     private URL addSlashToDirectoryUrlIfRequired(final URL anURL) {
 
         // Check sanity
         Validate.notNull(anURL, "anURL");
 
         URL toReturn = anURL;
         if ("file".equalsIgnoreCase(anURL.getProtocol())) {
 
             final File theFile = new File(anURL.getPath());
             if (theFile.isDirectory()) {
                 try {
 
                     // This ensures that an URL pointing to a File directory
                     // actually is terminated by a '/', which is required by
                     // the URLClassLoader to operate properly.
                     toReturn = theFile.toURI().toURL();
                 } catch (MalformedURLException e) {
                     // This should never happen
                     throw new IllegalArgumentException("Could not convert a File to an URL", e);
                 }
             }
         }
 
         // All done.
         return toReturn;
     }
 
     /**
      * Default implementation of the ThreadContextClassLoaderCleaner specification,
      * with added finalizer to ensure we release the Thread reference no matter
      * what happens with any DefaultCleaner objects.
      */
     class DefaultHolder implements ThreadContextClassLoaderHolder {
 
         // Internal state
         private Thread affectedThread;
         private ClassLoader originalClassLoader;
         private String classPathArgument;
 
         public DefaultHolder(final Thread affectedThread,
                 final ClassLoader originalClassLoader,
                 final String classPathArgument) {
 
             // Check sanity
             Validate.notNull(affectedThread, "affectedThread");
             Validate.notNull(originalClassLoader, "originalClassLoader");
             Validate.notNull(classPathArgument, "classPathArgument");
 
             // Assign internal state
             this.affectedThread = affectedThread;
             this.originalClassLoader = originalClassLoader;
             this.classPathArgument = classPathArgument;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void restoreClassLoaderAndReleaseThread() {
             if (affectedThread != null) {
 
                 // Restore original state
                 affectedThread.setContextClassLoader(originalClassLoader);
 
                 // Null out the internal state
                 affectedThread = null;
                 originalClassLoader = null;
                 classPathArgument = null;
             }
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public String getClassPathAsArgument() {
             return classPathArgument;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         protected void finalize() throws Throwable {
             try {
                 // First, release all resources held by this object.
                 restoreClassLoaderAndReleaseThread();
             } finally {
                 // Now, perform standard finalization.
                 super.finalize();
             }
         }
     }
 }