/*
 * Copyright (C) 2009 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.commons.utils;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.TimeZone;

/**
 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a>
 * @version $Revision$
 */
public class Tools
{
   /**
    * All the time zones already registered
    */
   private static volatile Map<String, TimeZone> TIME_ZONES = new HashMap<String, TimeZone>();
   
   /**
    * Instantiates a {@link HashSet} object and fills it with the provided element array.
    *
    * @param elements the list of elements to add
    * @param <E> the element type
    * @return the set of elements
    * @throws NullPointerException if the element array is null
    */
   public static <E> Set<E> set(E... elements) throws NullPointerException
   {
      if (elements == null)
      {
         throw new NullPointerException("No null element array accepted");
      }
      HashSet<E> set = new HashSet<E>();
      if (elements.length > 0)
      {
         for (E element : elements)
         {
            set.add(element);
         }
      }
      return set;
   }

   /**
    * Parse the provided list according to the comma separator. The string is sliced
    * first using the {@link String#split(String)} method with the <code>","</code>
    * argument. Each chunk is then trimmed and if its length is not zero then it is
    * added to the returned set.
    *
    * @param s the list to parse
    * @return the set of string found in the list
    * @throws NullPointerException if the string argument is null
    */
   public static Set<String> parseCommaList(String s) throws NullPointerException
   {
      if (s == null)
      {
         throw new NullPointerException("No null string list accepted");
      }
      Set<String> set = new HashSet<String>();
      for (String v : s.split(","))
      {
         v = v.trim();
         if (v.length() > 0)
         {
            set.add(v);
         }
      }
      return set;
   }

   /**
    * Copy the provided map and returns it as a modifiable properties object.
    *
    * @param map the map to copy
    * @return the properties copy
    * @throws NullPointerException if the map argument is null
    */
   public static Properties asProperties(Map<String, String> map) throws NullPointerException
   {
      if (map == null)
      {
         throw new NullPointerException("No null map accepted");
      }
      Properties props = new Properties();
      for (Map.Entry<String, String> entry : map.entrySet())
      {
         props.setProperty(entry.getKey(), entry.getValue());
      }
      return props;
   }

   /**
    * Copy the properties state and returns it as a modifiable map. Only the
    * key and value of type string are copied.
    *
    * @param props the properties object to copy
    * @return the properties copy as a map
    * @throws NullPointerException if the props argument is null
    */
   public static Map<String, String> asMap(Properties props) throws NullPointerException
   {
      if (props == null)
      {
         throw new NullPointerException("No null properties accepted");
      }
      Map<String, String> map = new HashMap<String, String>();
      for (Object key : props.keySet())
      {
         Object value = props.get(key);
         if (key instanceof String && value instanceof String)
         {
            map.put((String)key, (String)value);
         }
      }
      return map;
   }

   /**
    * Returns true if the string s ends with the end string ignoring the case.
    * @param s the string to test
    * @param end the string suffix
    * @return true if the string s ends with the end string ignoring the case
    * @throws NullPointerException if any string is null
    */
   public static boolean endsWithIgnoreCase(String s, String end) throws NullPointerException
   {
      if (s == null)
      {
         throw new NullPointerException();
      }
      if (end == null)
      {
         throw new NullPointerException();
      }
      if (s.length() < end.length())
      {
         return false;
      }
      String suffix = s.substring(s.length() - end.length());
      return suffix.equalsIgnoreCase(end); 
   }
   
   /**
    * This method is similar to {@link TimeZone#getTimeZone(String)} with less contention
    */
   public static TimeZone getTimeZone(String ID)
   {
      if (ID == null)
      {
         throw new NullPointerException("ID of the timezone cannot be null");
      }
      if (ID.length() == 0)
      {
         throw new IllegalArgumentException("ID of the timezone cannot be empty");
      }
      TimeZone tz = TIME_ZONES.get(ID);
      if (tz == null)
      {
         synchronized (TimeZone.class)
         {
            tz = TIME_ZONES.get(ID);
            if (tz == null)
            {
               tz = TimeZone.getTimeZone(ID);
               Map<String, TimeZone> tzs = new HashMap<String, TimeZone>(TIME_ZONES);
               tzs.put(ID, tz);
               TIME_ZONES = tzs;
            }
         }
      }
      return tz;
   }
}
