/*
 * Copyright (C) 2010 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.web.security.proxy;

import org.exoplatform.container.PortalContainer;
import org.exoplatform.container.xml.InitParams;
import org.exoplatform.container.xml.ValuesParam;
import org.gatein.common.logging.Logger;
import org.gatein.common.logging.LoggerFactory;

import javax.servlet.http.HttpServletRequest;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.regex.Pattern;

/**
 * The proxy filter service is used for filtering http access when it is performed by GateIn.
 * The following rules applies to the filtering:
 *
 * <ul>
 * <li>Same host URI grants access</li>
 * <li>A black list match of the host denies access</li>
 * <li>A white list match of the host grants access</li>
 * <li>Access is denied</li>
 * </ul>
 *
 * The service is configured by
 * <ul>
 * <li>a <code>white-list</code> parameter that specifies a list of white list rules</li>
 * <li>a <code>black-list</code> parameter that specifies a list of black list rules</li>
 * </ul>
 *
 * Rules are trimmed and the wildcard character can be used to match any number of character.
 *
 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a>
 * @version $Revision$
 */
public class ProxyFilterService
{

   /** . */
   private static final Logger log = LoggerFactory.getLogger(ProxyFilterService.class);

   /** . */
   private final List<Pattern> whiteList;

   /** . */
   private final List<Pattern> blackList;

   public ProxyFilterService(InitParams params)
   {
      this.whiteList = createList(params.getValuesParam("white-list"));
      this.blackList = createList(params.getValuesParam("black-list"));

      // A bit of logging
      log.debug("Proxy filter service white list " + whiteList);
      log.debug("Proxy filter service black list " + blackList);
   }

   private List<Pattern> createList(ValuesParam values)
   {
      if (values != null)
      {
         ArrayList<Pattern> patterns = new ArrayList<Pattern>();
         for (Object value : values.getValues())
         {
            String s = ((String)value).trim();
            StringBuilder sb = new StringBuilder("^");
            for (int i = 0;i < s.length();i++)
            {
               char c = s.charAt(i);
               switch (c)
               {
                  case '*':
                     sb.append(".*");
                     break;
                  case '[':
                  case '\\':
                  case '^':
                  case '$':
                  case '.':
                  case '|':
                  case '?':
                  case '+':
                  case '(':
                  case ')':
                     sb.append("\\");
                     sb.append(c);
                     break;
                  default:
                     sb.append(c);
                     break;
               }
            }
            sb.append("$");
            Pattern pattern = Pattern.compile(sb.toString());
            patterns.add(pattern);
         }
         return Collections.unmodifiableList(patterns);
      }
      else
      {
         return Collections.emptyList();
      }
   }

   /**
    * Returns true if access to a remote URI should be granted.
    *
    * @param request the servlet request doing the request
    * @param container the portal container associated with the request
    * @param remoteURI the remote URI to check
    * @return the access to the remote URI
    */
   public boolean accept(
      HttpServletRequest request,
      PortalContainer container,
      URI remoteURI)
   {
      boolean trace = log.isTraceEnabled();

      //
      String remoteHost = remoteURI.getHost();

      // Filter based on same server name
      String remoteServerName = request.getServerName();
      if (remoteHost.equals(remoteServerName))
      {
         if (trace)
         {
            log.trace("Same host matching for URI " + remoteURI);
         }
         return true;
      }

      // Otherwise go through black list first
      for (int i = 0;i < blackList.size();i++)
      {
         Pattern pattern = blackList.get(i);
         boolean rejected = pattern.matcher(remoteHost).matches();
         if (trace)
         {
            log.trace("Black list " +  pattern + (rejected ? " matched URI " : " did not match URI") + remoteURI);
         }
         if (rejected)
         {
            return false;
         }
      }

      // Finally go through white list first
      for (int i = 0;i < whiteList.size();i++)
      {
         Pattern pattern = whiteList.get(i);
         boolean accepted = pattern.matcher(remoteHost).matches();
         if (trace)
         {
            log.trace("White list " +  pattern + (accepted ? " matched URI " : " did not match URI") + remoteURI);
         }
         if (accepted)
         {
            return true;
         }
      }

      //
      if (trace)
      {
         log.trace("Rejected implicitely uri " + remoteURI);
      }

      //
      return false;
   }
}
