/*
 * 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.
 */
/*
 * $Id$
 */
package org.apache.xalan.lib;

import java.util.StringTokenizer;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.xpath.NodeSet;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

/**
 * This class contains EXSLT strings extension functions.
 *
 * It is accessed by specifying a namespace URI as follows:
 * <pre>
 *    xmlns:str="http://exslt.org/strings"
 * </pre>
 * The documentation for each function has been copied from the relevant
 * EXSLT Implementer page.
 * 
 * @see <a href="http://www.exslt.org/">EXSLT</a>

 * @xsl.usage general
 */
public class ExsltStrings extends ExsltBase
{
  /**
   * The str:align function aligns a string within another string. 
   * <p>
   * The first argument gives the target string to be aligned. The second argument gives 
   * the padding string within which it is to be aligned. 
   * <p>
   * If the target string is shorter than the padding string then a range of characters 
   * in the padding string are repaced with those in the target string. Which characters 
   * are replaced depends on the value of the third argument, which gives the type of 
   * alignment. It can be one of 'left', 'right' or 'center'. If no third argument is 
   * given or if it is not one of these values, then it defaults to left alignment. 
   * <p>
   * With left alignment, the range of characters replaced by the target string begins 
   * with the first character in the padding string. With right alignment, the range of 
   * characters replaced by the target string ends with the last character in the padding 
   * string. With center alignment, the range of characters replaced by the target string 
   * is in the middle of the padding string, such that either the number of unreplaced 
   * characters on either side of the range is the same or there is one less on the left 
   * than there is on the right. 
   * <p>
   * If the target string is longer than the padding string, then it is truncated to be 
   * the same length as the padding string and returned.
   *
   * @param targetStr The target string
   * @param paddingStr The padding string
   * @param type The type of alignment
   * 
   * @return The string after alignment
   */
  public static String align(String targetStr, String paddingStr, String type)
  {
    if (targetStr.length() >= paddingStr.length())
      return targetStr.substring(0, paddingStr.length());
    
    if (type.equals("right"))
    {
      return paddingStr.substring(0, paddingStr.length() - targetStr.length()) + targetStr;
    }
    else if (type.equals("center"))
    {
      int startIndex = (paddingStr.length() - targetStr.length()) / 2;
      return paddingStr.substring(0, startIndex) + targetStr + paddingStr.substring(startIndex + targetStr.length());
    }
    // Default is left
    else
    {
      return targetStr + paddingStr.substring(targetStr.length());
    }    
  }

  /**
   * See above
   */
  public static String align(String targetStr, String paddingStr)
  {
    return align(targetStr, paddingStr, "left");
  }
  
  /**
   * The str:concat function takes a node set and returns the concatenation of the 
   * string values of the nodes in that node set. If the node set is empty, it returns 
   * an empty string.
   *
   * @param nl A node set
   * @return The concatenation of the string values of the nodes in that node set
   */
  public static String concat(NodeList nl)
  {
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < nl.getLength(); i++)
    {
      Node node = nl.item(i);
      String value = toString(node);
      
      if (value != null && value.length() > 0)
        sb.append(value);
    }
    
    return sb.toString();
  }
    
  /**
   * The str:padding function creates a padding string of a certain length. 
   * The first argument gives the length of the padding string to be created. 
   * The second argument gives a string to be used to create the padding. This 
   * string is repeated as many times as is necessary to create a string of the 
   * length specified by the first argument; if the string is more than a character 
   * long, it may have to be truncated to produce the required length. If no second 
   * argument is specified, it defaults to a space (' '). If the second argument is 
   * an empty string, str:padding returns an empty string.
   *
   * @param length The length of the padding string to be created
   * @param pattern The string to be used as pattern
   *
   * @return A padding string of the given length
   */
  public static String padding(double length, String pattern)
  {
    if (pattern == null || pattern.length() == 0)
      return "";
    
    StringBuffer sb = new StringBuffer();
    int len = (int)length;
    int numAdded = 0;
    int index = 0;
    while (numAdded < len)
    {
      if (index == pattern.length())
        index = 0;
        
      sb.append(pattern.charAt(index));
      index++;
      numAdded++;
    }
  
    return sb.toString();
  }

  /**
   * See above
   */
  public static String padding(double length)
  {
    return padding(length, " ");
  }
    
  /**
   * The str:split function splits up a string and returns a node set of token 
   * elements, each containing one token from the string. 
   * <p>
   * The first argument is the string to be split. The second argument is a pattern 
   * string. The string given by the first argument is split at any occurrence of 
   * this pattern. For example: 
   * <pre>
   * str:split('a, simple, list', ', ') gives the node set consisting of: 
   *
   * <token>a</token>
   * <token>simple</token>
   * <token>list</token>
   * </pre>
   * If the second argument is omitted, the default is the string '&#x20;' (i.e. a space).
   *
   * @param str The string to be split
   * @param pattern The pattern
   *
   * @return A node set of split tokens
   */
  public static NodeList split(String str, String pattern)
  {

    
    NodeSet resultSet = new NodeSet();
    resultSet.setShouldCacheNodes(true);
    
    boolean done = false;
    int fromIndex = 0;
    int matchIndex = 0;
    String token = null;
    
    while (!done && fromIndex < str.length())
    {
      matchIndex = str.indexOf(pattern, fromIndex);
      if (matchIndex >= 0)
      {
	token = str.substring(fromIndex, matchIndex);
	fromIndex = matchIndex + pattern.length();
      }
      else
      {
        done = true;
        token = str.substring(fromIndex);
      }

      Document doc = DocumentHolder.m_doc;
      synchronized (doc)
      {
        Element element = doc.createElement("token");
        Text text = doc.createTextNode(token);
        element.appendChild(text);
        resultSet.addNode(element);      
      }
    }
    
    return resultSet;
  }
  
  /**
   * See above
   */
  public static NodeList split(String str)
  {
    return split(str, " ");
  }

  /**
   * The str:tokenize function splits up a string and returns a node set of token 
   * elements, each containing one token from the string. 
   * <p>
   * The first argument is the string to be tokenized. The second argument is a 
   * string consisting of a number of characters. Each character in this string is 
   * taken as a delimiting character. The string given by the first argument is split 
   * at any occurrence of any of these characters. For example: 
   * <pre>
   * str:tokenize('2001-06-03T11:40:23', '-T:') gives the node set consisting of: 
   *
   * <token>2001</token>
   * <token>06</token>
   * <token>03</token>
   * <token>11</token>
   * <token>40</token>
   * <token>23</token>
   * </pre>
   * If the second argument is omitted, the default is the string '&#x9;&#xA;&#xD;&#x20;' 
   * (i.e. whitespace characters). 
   * <p>
   * If the second argument is an empty string, the function returns a set of token 
   * elements, each of which holds a single character.
   * <p>
   * Note: This one is different from the tokenize extension function in the Xalan
   * namespace. The one in Xalan returns a set of Text nodes, while this one wraps
   * the Text nodes inside the token Element nodes.
   *
   * @param toTokenize The string to be tokenized
   * @param delims The delimiter string
   *
   * @return A node set of split token elements
   */
  public static NodeList tokenize(String toTokenize, String delims)
  {


    NodeSet resultSet = new NodeSet();
    
    if (delims != null && delims.length() > 0)
    {
      StringTokenizer lTokenizer = new StringTokenizer(toTokenize, delims);

      Document doc = DocumentHolder.m_doc;
      synchronized (doc)
      {
        while (lTokenizer.hasMoreTokens())
        {
          Element element = doc.createElement("token");
          element.appendChild(doc.createTextNode(lTokenizer.nextToken()));
          resultSet.addNode(element);      
        }
      }
    }
    // If the delimiter is an empty string, create one token Element for 
    // every single character.
    else
    {

      Document doc = DocumentHolder.m_doc;
      synchronized (doc)
      {
        for (int i = 0; i < toTokenize.length(); i++)
        {
          Element element = doc.createElement("token");
          element.appendChild(doc.createTextNode(toTokenize.substring(i, i+1)));
          resultSet.addNode(element);              
        }
      }
    }

    return resultSet;
  }

  /**
   * See above
   */
  public static NodeList tokenize(String toTokenize)
  {
    return tokenize(toTokenize, " \t\n\r");
  }
    /**
     * This class is not loaded until first referenced (see Java Language
     * Specification by Gosling/Joy/Steele, section 12.4.1)
     *
     * The static members are created when this class is first referenced, as a
     * lazy initialization not needing checking against null or any
     * synchronization.
     *
     */
    private static class DocumentHolder 
    {
        // Reuse the Document object to reduce memory usage.
        private static final Document m_doc;
        static {
            try
            {
                m_doc =DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
            }
           
            catch(ParserConfigurationException pce)
            {
                  throw new org.apache.xml.utils.WrappedRuntimeException(pce);
            }

        }
    }
  
}
