/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.hadoop.chukwa.util;
  
  import java.util.Enumeration;
  import java.util.regex.Pattern;
  import java.util.regex.Matcher;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpSession;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import com.josephoconnell.html.HTMLInputFilter;
  
  public class XssFilter {
      private HttpServletRequest request = null;
      private static Log log = LogFactory.getLog(XssFilter.class);
      private HttpSession session = null;
  
      public XssFilter() {
      }
  
      public XssFilter(HttpServletRequest request) {
        this.request = request;
        try {
          this.session = request.getSession();
          for (Enumeration e = request.getParameterNames() ; e.hasMoreElements() ;) {
            Pattern p = Pattern.compile("_session\\.(.*)");
            String name = (String) e.nextElement();
            Matcher matcher = p.matcher(name);
            if(matcher.find()) {
              String realName = matcher.group(1);
              if(session!=null) {
                session.setAttribute(realName,filter(request.getParameter(name)));
              }
            }
          }
        } catch(NullPointerException ex) {
          // Do nothing if session does not exist.
          log.debug(ExceptionUtil.getStackTrace(ex));
        }
      }
      
      public String getParameter(String key) {
  	String value=null;
  	try {
  	    value=this.request.getParameter(key);  
  	} catch (Exception e) {
  	    log.info("XssFilter.getParameter: Cannot get parameter for: "+key);
  	}
  	return filter(value);
      }
      
      public String[] getParameterValues(String key) {
        String[] values=null;
        try {
  	  values  = this.request.getParameterValues(key);
  	  if(values!=null) {
  	      for(int i=0;i<values.length;i++) {
  		  values[i] = filter(values[i]);
  	      }
  	  }
        } catch (Exception e) {
  	  log.info("XssFilter.getParameterValues: cannot get parameter for: "+key);
        }
        return values;
      }
      
      public static String filter( String input ) {
          if(input==null) {
              return null;
          }
          String clean = new HTMLInputFilter().filter( input.replaceAll("\"", "%22").replaceAll("\'","%27"));
          return clean.replaceAll("<", "%3C").replaceAll(">", "%3E");
      }
  }