/**
 * <copyright> Copyright 2006 by Know-Center, Graz, Austria </copyright>
 * PDF-AS has been contracted by the E-Government Innovation Center EGIZ, a
 * joint initiative of the Federal Chancellery Austria and Graz University of
 * Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */
package at.gv.egiz.pdfas.web.i18n;

import java.io.IOException;
import java.util.Locale;
import java.util.StringTokenizer;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.apache.commons.lang.LocaleUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;

public class LocaleParamFilter implements Filter {

   private static final Logger LOG = Logger.getLogger(LocaleParamFilter.class);
   public static final String LOCALE_SESSION_KEY = "at.gv.egiz.pdfas.web.i18n:currentLocale";
   public static final String LOCALE_PARAM_KEY = "locale";
   
   public void destroy() {
   }

   public static String normalizeLocaleString(String localeString) {
      if (localeString == null) {
         return null;
      }
      int jsessionIdIndex = localeString.toLowerCase().indexOf(";jsessionid");
      if (jsessionIdIndex != -1) {
         localeString = localeString.substring(0, jsessionIdIndex);
      }
      StringTokenizer tokenizer = new StringTokenizer(localeString, "_", false);
      StringBuffer buffer = new StringBuffer();
      int index = 0;
      while (tokenizer.hasMoreTokens()) {
         String token = tokenizer.nextToken();
         switch (++index) {
         case 1:
            buffer.append(token.toLowerCase());
            break;
         case 2:
            buffer.append(token.toUpperCase());
            break;
         default:
            buffer.append(token);
            break;
         }
         if (tokenizer.hasMoreTokens()) {
            buffer.append("_");
         }
      }
      return buffer.toString();
   }
   
   public static Locale getLocale(HttpServletRequest request) {
      Locale locale = null;
      HttpSession session = request.getSession();
      
      LOG.trace("Looking for locale parameter \"" + LOCALE_PARAM_KEY + "\".");
      String language = request.getParameter(LOCALE_PARAM_KEY);
      if (!StringUtils.isEmpty(language)) {
         LOG.debug("Locale parameter \"" + language + "\" found.");
         String code = normalizeLocaleString(language.trim());
         LOG.debug("Normalizing locale -> " + code);
         try {
            locale = LocaleUtils.toLocale(code);
            LOG.info("Setting locale flag in session (ID=" + session.getId() + ") to \"" + locale.toString() + "\".");
            session.setAttribute(LOCALE_SESSION_KEY, locale);
         } catch (IllegalArgumentException e) {
            LOG.error("Locale \"" + code + "\" is not valid. Flag will not be set.");
         }
      } else {
         LOG.trace("No locale parameter found.");
      }
      
      return locale;
   }

   public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
      HttpServletRequest request = (HttpServletRequest) servletRequest;
      
      LOG.trace("LocaleParamFilter invoked.");
      getLocale(request);
      
      filterChain.doFilter(servletRequest, servletResponse);
   }

   public void init(FilterConfig filterConfig) throws ServletException {
   }

}