/**
    * This file Copyright (c) 2010-2011 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.module.blossom.support;
  
  import java.util.Enumeration;
  import java.util.NoSuchElementException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletRequestWrapper;
  
  import org.apache.commons.lang.ObjectUtils;
  import org.springframework.web.util.WebUtils;
  
  /**
   * Request wrapper for overriding special attributes.
   *
   * @since 1.2
   */
  public class SpecialAttributeRequestWrapper extends HttpServletRequestWrapper {
  
      private static final String[] specialNames = new String[]{
              WebUtils.INCLUDE_REQUEST_URI_ATTRIBUTE,
              WebUtils.INCLUDE_CONTEXT_PATH_ATTRIBUTE,
              WebUtils.INCLUDE_SERVLET_PATH_ATTRIBUTE,
              WebUtils.INCLUDE_PATH_INFO_ATTRIBUTE,
              WebUtils.INCLUDE_QUERY_STRING_ATTRIBUTE,
              WebUtils.FORWARD_REQUEST_URI_ATTRIBUTE,
              WebUtils.FORWARD_CONTEXT_PATH_ATTRIBUTE,
              WebUtils.FORWARD_SERVLET_PATH_ATTRIBUTE,
              WebUtils.FORWARD_PATH_INFO_ATTRIBUTE,
              WebUtils.FORWARD_QUERY_STRING_ATTRIBUTE,
              WebUtils.ERROR_STATUS_CODE_ATTRIBUTE,
              WebUtils.ERROR_EXCEPTION_TYPE_ATTRIBUTE,
              WebUtils.ERROR_MESSAGE_ATTRIBUTE,
              WebUtils.ERROR_EXCEPTION_ATTRIBUTE,
              WebUtils.ERROR_REQUEST_URI_ATTRIBUTE,
              WebUtils.ERROR_SERVLET_NAME_ATTRIBUTE
      };
  
      private final Object[] localValues = new Object[specialNames.length];
      private final Object[] originalValues = new Object[specialNames.length];
  
      public SpecialAttributeRequestWrapper(HttpServletRequest request) {
          super(request);
      }
  
      public boolean setSpecialAttribute(String name, Object value) {
          for (int i = 0; i < specialNames.length; i++) {
              if (name.equals(specialNames[i])) {
                  localValues[i] = value;
                  originalValues[i] = super.getAttribute(name);
                  return true;
              }
          }
          return false;
      }
  
      @Override
      public Object getAttribute(String name) {
          for (int i = 0; i < specialNames.length; i++) {
              if (specialNames[i].equals(name) && localValues[i] != null) {
                  if (shouldMasquerade(name)) {
                      return localValues[i];
                  } else {
                      break;
                  }
              }
          }
          return super.getAttribute(name);
     }
 
     protected boolean shouldMasquerade(String name) {
         for (int i = 0; i < specialNames.length; i++) {
             if (localValues[i] != null && !ObjectUtils.equals(super.getAttribute(specialNames[i]), originalValues[i])) {
                 return false;
             }
         }
         return true;
     }
 
     @Override
     public Enumeration getAttributeNames() {
 
         return new Enumeration() {
 
             private int pos = 0;
             private String next = null;
             private Enumeration parentEnumeration = getRequest().getAttributeNames();
 
             @Override
             public boolean hasMoreElements() {
                 while (pos < localValues.length) {
                     if (localValues[pos] != null) {
                         return true;
                     }
                     pos++;
                 }
                 if (next != null) {
                     return true;
                 }
                 next = findNext();
                 return next != null;
             }
 
             @Override
             public Object nextElement() {
                 while (pos < localValues.length) {
                     if (localValues[pos] != null) {
                         String name = specialNames[pos];
                         pos++;
                         return name;
                     }
                     pos++;
                 }
                 if (next == null) {
                     next = findNext();
                     if (next == null) {
                         throw new NoSuchElementException();
                     }
                 }
                 Object result = next;
                 next = null;
                 return result;
             }
 
             private String findNext() {
                 while (parentEnumeration.hasMoreElements()) {
                     String name = (String) parentEnumeration.nextElement();
                     if (!hasLocalValue(name)) {
                         return name;
                     }
                 }
                 return null;
             }
         };
     }
 
     @Override
     public void setAttribute(String name, Object o) {
         if (!hasLocalValue(name)) {
             super.setAttribute(name, o);
         }
     }
 
     @Override
     public void removeAttribute(String name) {
         if (!hasLocalValue(name)) {
             super.removeAttribute(name);
         }
     }
 
     private boolean hasLocalValue(String name) {
         for (int i = 0; i < specialNames.length; i++) {
             if (name.equals(specialNames[i]) && localValues[i] != null) {
                 return true;
             }
         }
         return false;
     }
 }