/**
    * This file Copyright (c) 2008-2011 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.beanmerger;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  import net.sf.cglib.proxy.Enhancer;
  
  import org.apache.commons.beanutils.MethodUtils;
  import org.apache.commons.proxy.Invoker;
  import org.apache.commons.proxy.factory.cglib.CglibProxyFactory;
  
  
  /**
   * Proxy-based bean merger.
   *
   * @version $Id$
   */
  public class ProxyBasedBeanMerger extends BeanMergerBase {
  
      @Override
      protected Object mergeBean(List sources) {
          Set<Class> types = new HashSet<Class>();
          Class< ? > mostSpecificAssignableClass = sources.get(0).getClass();
          while (Enhancer.isEnhanced(mostSpecificAssignableClass)) {
              mostSpecificAssignableClass = mostSpecificAssignableClass.getSuperclass();
          }
  
          for (Object source : sources) {
  
              // Skip up the class hierarchy to avoid proxying cglib proxy classes
              Class clazz = source.getClass();
              while (Enhancer.isEnhanced(clazz)) {
                  clazz = clazz.getSuperclass();
              }
  
              Collections.addAll(types, clazz.getInterfaces());
  
              if (mostSpecificAssignableClass.isAssignableFrom(clazz)) {
                  mostSpecificAssignableClass = clazz;
              }
          }
          types.add(mostSpecificAssignableClass);
          try {
              return new CglibProxyFactory().createInvokerProxy(newInvoker(sources), types.toArray(new Class< ? >[types.size()]));
          } catch (RuntimeException e) {
              log.error("Failed to create proxy for sources {} with types {}", sources, types);
              throw e;
          }
      }
  
      protected MergeInvoker newInvoker(List sources) {
          return new MergeInvoker(this, sources);
      }
  
      /**
       * Merge Invoker.
       *
       * @version $Id$
       */
      protected static final class MergeInvoker implements Invoker {
  
         private final List sources;
 
         private final BeanMerger merger;
 
         private MergeInvoker(BeanMerger merger, List sources) {
             this.merger = merger;
             this.sources = sources;
         }
 
         @Override
         public Object invoke(Object proxy, Method method, Object[] arguments) throws Throwable {
             // only merge calls to property getters
             if (arguments.length > 0) {
                 // invoke the method on the first possibility
                 for (Object source : sources) {
                     if(method.getDeclaringClass().isInstance(source)){
                         return method.invoke(source, arguments);
                     }
                 }
                 throw new IllegalStateException("Can't call method " + method.getName() + " on any of the sources.");
             }
 
             List values = new ArrayList();
             for (Object obj : sources) {
                 values.add(evaluate(obj, method, arguments));
             }
 
             return merger.merge(values);
         }
 
         private Object evaluate(Object obj, Method method, Object[] arguments) throws IllegalAccessException, InvocationTargetException {
 
             // direct method call
             if (method.getDeclaringClass().isAssignableFrom(obj.getClass())) {
                 return method.invoke(obj, arguments);
             }
 
             // ducking
             try {
                 return MethodUtils.invokeMethod(obj, method.getName(), arguments);
             } catch (NoSuchMethodException e) {
                 return null;
             }
         }
     }
 
 }