/**

  * This file is part of the equanda project.

  *

  * The contents of this file are subject to the Mozilla Public License Version 1.1 (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.mozilla.org/MPL/

  *

  * Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF

  * ANY KIND, either express or implied. See the License for the specific language governing rights and

  * limitations under the License.

  *

  * Alternatively, the contents of this file may be used under the terms of

  * either the GNU General Public License Version 2 or later (the "GPL"), or

  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

  * in which case the provisions of the GPL or the LGPL are applicable instead

  * of those above. If you wish to allow use of your version of this file only

  * under the terms of either the GPL or the LGPL, and not to allow others to

  * use your version of this file under the terms of the MPL, indicate your

  * decision by deleting the provisions above and replace them with the notice

  * and other provisions required by the GPL or the LGPL. If you do not delete

  * the provisions above, a recipient may use your version of this file under

  * the terms of any one of the MPL, the GPL or the LGPL.

  */

 package org.equanda.tapestry5.bindings;

 import org.apache.tapestry5.Binding;

 import java.io.IOException;

 import java.io.InputStream;

 import java.lang.annotation.Annotation;

 import java.net.URL;

 import java.util.Enumeration;

 import java.util.Map;

 import java.util.concurrent.ConcurrentHashMap;

 import java.util.jar.Manifest;

 /**

  * Binding prefix which allows you to get a value from a manifest file. As multiple files may contain a value for the

  * same key, the first encountered is used.

  *

  * @author <a href="mailto:joachim@progs.be">Joachim Van der Auwera</a>

  */

 public class ManifestBindingPrefix

     implements Binding

 {

     private static final Map<String, String> cache = new ConcurrentHashMap<String, String>();

     private String expression;

     public ManifestBindingPrefix( String expression )

     {

         this.expression = expression;

     }

     public Object get()

     {

         try

         {

             // first try to get the value from the cache (these things don't really change at runtime after all)

             String res = cache.get( expression );

             if ( res != null ) return res;

             ClassLoader cl = Thread.currentThread().getContextClassLoader();

             if ( null == cl ) cl = this.getClass().getClassLoader();

             Enumeration<URL> urls = cl.getResources( "META-INF/MANIFEST.MF" );

             while ( null == res && urls.hasMoreElements() )

             {

                 URL url = urls.nextElement();

                 res = get( url );

             }

             if ( res != null ) cache.put( expression, res );

             return res;

         }

         catch ( Exception ex )

         {

             return null;

         }

     }

     private String get( URL url )

         throws IOException

     {

         InputStream in = null;

         try

         {

             in = url.openStream();

             Manifest mf = new Manifest( in );

             return mf.getMainAttributes().getValue( expression );

         }

         finally

         {

             if ( null != in ) in.close();

         }

     }

     @SuppressWarnings( "unchecked" )

     public Class getBindingType()

     {

         return String.class;

     }

     public boolean isInvariant()

     {

         return false;

     }

     public void set( Object value )

     {

         // do nothing

     }

     public <T extends Annotation> T getAnnotation( Class<T> annotationClass )

     {

         return null;

     }

 }