/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
    *
    * Licensed 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.acegisecurity.ui.savedrequest;
  
  import java.text.DateFormat;
  import java.text.ParseException;
  import java.text.SimpleDateFormat;
  
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Locale;
  import java.util.TimeZone;
  
  
  /**
   * <p>Utility class to generate HTTP dates.</p>
   * <p>This class is based on code in Apache Tomcat.</p>
   *
   * @author Remy Maucherat
   * @author Andrey Grebnev
   * @version $Id: FastHttpDateFormat.java 1784 2007-02-24 21:00:24Z luke_t $
   */
  public class FastHttpDateFormat {
      //~ Static fields/initializers =====================================================================================
  
      /** HTTP date format. */
      protected static final SimpleDateFormat format = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US);
  
      /** The set of SimpleDateFormat formats to use in <code>getDateHeader()</code>. */
      protected static final SimpleDateFormat[] formats = {
              new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US),
              new SimpleDateFormat("EEEEEE, dd-MMM-yy HH:mm:ss zzz", Locale.US),
              new SimpleDateFormat("EEE MMMM d HH:mm:ss yyyy", Locale.US)
          };
  
      /** GMT timezone - all HTTP dates are on GMT */
      protected static final TimeZone gmtZone = TimeZone.getTimeZone("GMT");
  
      static {
          format.setTimeZone(gmtZone);
  
          formats[0].setTimeZone(gmtZone);
          formats[1].setTimeZone(gmtZone);
          formats[2].setTimeZone(gmtZone);
      }
  
      /** Instant on which the currentDate object was generated. */
      protected static long currentDateGenerated = 0L;
  
      /** Current formatted date. */
      protected static String currentDate = null;
  
      /** Formatter cache. */
      protected static final HashMap formatCache = new HashMap();
  
      /** Parser cache. */
      protected static final HashMap parseCache = new HashMap();
  
      //~ Methods ========================================================================================================
  
      /**
       * Formats a specified date to HTTP format. If local format is not <code>null</code>, it's used instead.
       *
       * @param value Date value to format
       * @param threadLocalformat The format to use (or <code>null</code> -- then HTTP format will be used)
       *
       * @return Formatted date
       */
      public static final String formatDate(long value, DateFormat threadLocalformat) {
          String cachedDate = null;
          Long longValue = new Long(value);
  
          try {
              cachedDate = (String) formatCache.get(longValue);
          } catch (Exception e) {}
  
          if (cachedDate != null) {
              return cachedDate;
          }
  
          String newDate = null;
          Date dateValue = new Date(value);
  
          if (threadLocalformat != null) {
              newDate = threadLocalformat.format(dateValue);
  
             synchronized (formatCache) {
                 updateCache(formatCache, longValue, newDate);
             }
         } else {
             synchronized (formatCache) {
                 newDate = format.format(dateValue);
                 updateCache(formatCache, longValue, newDate);
             }
         }
 
         return newDate;
     }
 
     /**
      * Gets the current date in HTTP format.
      *
      * @return Current date in HTTP format
      */
     public static final String getCurrentDate() {
         long now = System.currentTimeMillis();
 
         if ((now - currentDateGenerated) > 1000) {
             synchronized (format) {
                 if ((now - currentDateGenerated) > 1000) {
                     currentDateGenerated = now;
                     currentDate = format.format(new Date(now));
                 }
             }
         }
 
         return currentDate;
     }
 
     /**
      * Parses date with given formatters.
      *
      * @param value The string to parse
      * @param formats Array of formats to use
      *
      * @return Parsed date (or <code>null</code> if no formatter mached)
      */
     private static Long internalParseDate(String value, DateFormat[] formats) {
         Date date = null;
 
         for (int i = 0; (date == null) && (i < formats.length); i++) {
             try {
                 date = formats[i].parse(value);
             } catch (ParseException e) {
                 ;
             }
         }
 
         if (date == null) {
             return null;
         }
 
         return new Long(date.getTime());
     }
 
     /**
      * Tries to parse the given date as an HTTP date. If local format list is not <code>null</code>, it's used
      * instead.
      *
      * @param value The string to parse
      * @param threadLocalformats Array of formats to use for parsing. If <code>null</code>, HTTP formats are used.
      *
      * @return Parsed date (or -1 if error occured)
      */
     public static final long parseDate(String value, DateFormat[] threadLocalformats) {
         Long cachedDate = null;
 
         try {
             cachedDate = (Long) parseCache.get(value);
         } catch (Exception e) {}
 
         if (cachedDate != null) {
             return cachedDate.longValue();
         }
 
         Long date = null;
 
         if (threadLocalformats != null) {
             date = internalParseDate(value, threadLocalformats);
 
             synchronized (parseCache) {
                 updateCache(parseCache, value, date);
             }
         } else {
             synchronized (parseCache) {
                 date = internalParseDate(value, formats);
                 updateCache(parseCache, value, date);
             }
         }
 
         if (date == null) {
             return (-1L);
         } else {
             return date.longValue();
         }
     }
 
     /**
      * Updates cache.
      *
      * @param cache Cache to be updated
      * @param key Key to be updated
      * @param value New value
      */
     private static void updateCache(HashMap cache, Object key, Object value) {
         if (value == null) {
             return;
         }
 
         if (cache.size() > 1000) {
             cache.clear();
         }
 
         cache.put(key, value);
     }
 }