/**
    * This file Copyright (c) 2008-2016 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.Modifier;
  import java.net.URL;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.commons.collections4.CollectionUtils;
  import org.apache.commons.collections4.functors.NotNullPredicate;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Base implementation of interface BeanMerge.
   */
  public abstract class BeanMergerBase implements BeanMerger {
  
      protected Logger log = LoggerFactory.getLogger(this.getClass());
  
      @Override
      public Object merge(List sources) {
          CollectionUtils.filter(sources, NotNullPredicate.INSTANCE);
          if (sources.isEmpty()) {
              return null;
          }
  
          if (sources.size() == 1 || isSimpleType(sources.get(0).getClass()) || !isMergeable(sources.get(0).getClass())) {
              return sources.get(0);
          }
  
          if (sources.get(0) instanceof Collection) {
              return mergeCollections(sources);
          }
  
          if (sources.get(0) instanceof Map) {
              return mergeMaps(sources);
          }
  
          return mergeBean(sources);
      }
  
      protected abstract Object mergeBean(List sources);
  
      protected Map mergeMaps(List<Map> sources) {
          try {
              Map mergedMap = this.instantiateOneOf(sources);
              for (Map map : sources) {
                  for (Object key : map.keySet()) {
                      List values = new ArrayList();
                      for (Map map2 : sources) {
                          if (map2.containsKey(key)) {
                              values.add(map2.get(key));
                          }
                      }
                      mergedMap.put(key, merge(values));
                  }
              }
              return mergedMap;
          } catch (Exception e) {
              log.error(e.getMessage(), e);
              return sources.get(0);
          }
      }
 
     protected Collection mergeCollections(List<Collection> sources) {
         try {
             Collection mergedCol = this.instantiateOneOf(sources);
             for (Collection col : sources) {
                 mergedCol.addAll(col);
             }
             return mergedCol;
         } catch (Exception e) {
             log.error(e.getMessage(), e);
             return sources.get(0);
         }
     }
 
     /**
      * Checks whether type represents
      * <ul>
      * <li>a primitive
      * <li>a boxed primitive, e.g {@link Double} or {@link Integer}
      * <li>a {@link String}, {@link Class} or {@link URL}.
      * </ul>
      */
     protected boolean isSimpleType(Class type) {
         return type.isPrimitive() ||
                 type == Object.class ||
                 type == Boolean.class ||
                 type == Byte.class ||
                 type == Character.class ||
                 type == Short.class ||
                 type == Integer.class ||
                 type == Long.class ||
                 type == Float.class ||
                 type == Double.class ||
                 type == Void.class ||
                 // well, at least property wise
                 type == String.class ||
                 type == Class.class ||
                 type == URL.class;
     }
 
     /**
      * @return <code>true</code> if type is
      * <ul>
      * <li>not a final class
      * <li>not an interface, with the exclusion of {@link Map} and {@link Collection}.
      * </ul>
      */
     protected boolean isMergeable(Class type) {
         if (Modifier.isFinal(type.getModifiers())) {
             return false;
         }
         if (Modifier.isInterface(type.getModifiers())) {
             return Map.class.isAssignableFrom(type) || Collection.class.isAssignableFrom(type);
         }
         return true;
     }
 
     private <T>T instantiateOneOf(List<T> sources) throws IllegalAccessException, InstantiationException {
         for (T object : sources) {
             try {
                 return (T) object.getClass().newInstance();
             } catch (ReflectiveOperationException e) {
                 if (object == sources.get(sources.size() - 1)) {
                     throw e;
                 }
             }
         }
         return null;
     }
 
 }