/*

  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/TranslateFunction.java,v 1.10 2006/02/05 21:47:41 elharo Exp $

  * $Revision: 1.10 $

  * $Date: 2006/02/05 21:47:41 $

  *

  * ====================================================================

  *

  * Copyright 2000-2002 bob mcwhirter & James Strachan.

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions are

  * met:

  * 

  *   * Redistributions of source code must retain the above copyright

  *     notice, this list of conditions and the following disclaimer.

  * 

  *   * Redistributions in binary form must reproduce the above copyright

  *     notice, this list of conditions and the following disclaimer in the

  *     documentation and/or other materials provided with the distribution.

  * 

  *   * Neither the name of the Jaxen Project nor the names of its

  *     contributors may be used to endorse or promote products derived 

  *     from this software without specific prior written permission.

  * 

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER

  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  *

  * ====================================================================

  * This software consists of voluntary contributions made by many 

  * individuals on behalf of the Jaxen Project and was originally 

  * created by bob mcwhirter <bob@werken.com> and 

  * James Strachan <jstrachan@apache.org>.  For more information on the 

  * Jaxen Project, please see <http://www.jaxen.org/>.

  * 

  * $Id: TranslateFunction.java,v 1.10 2006/02/05 21:47:41 elharo Exp $

  */

 package org.jaxen.function;

 import java.util.HashMap;

 import java.util.List;

 import java.util.Map;

 import org.jaxen.Context;

 import org.jaxen.Function;

 import org.jaxen.FunctionCallException;

 import org.jaxen.Navigator;

 /**

  * <p>

  * <b>4.2</b>

  * <code><i>string</i> translate(<i>string</i>,<i>string</i>,<i>string</i>)</code>

  * </p>

  * 

  * <blockquote src="http://www.w3.org/TR/xpath#function-translate">

  * <p>

  * The <b><a href="http://www.w3.org/TR/xpath#function-translate">translate</a></b> function

  * returns the first argument string with occurrences of characters in

  * the second argument string replaced by the character at the

  * corresponding position in the third argument string. For example,

  * <code>translate("bar","abc","ABC")</code> returns the string

  * <code>BAr</code>. If there is a character in the second argument

  * string with no character at a corresponding position in the third

  * argument string (because the second argument string is longer than

  * the third argument string), then occurrences of that character in the

  * first argument string are removed. For example,

  * <code>translate("--aaa--","abc-","ABC")</code> returns

  * <code>"AAA"</code>. If a character occurs more than once in the

  * second argument string, then the first occurrence determines the

  * replacement character. If the third argument string is longer than

  * the second argument string, then excess characters are ignored.

  * </p>

  * 

  * <blockquote> <b>NOTE: </b>The <b>translate</b> function is not a

  * sufficient solution for case conversion in all languages. A future

  * version of XPath may provide additional functions for case

  * conversion.</blockquote>

  * 

  * </blockquote>

  * 

  * @author Jan Dvorak ( jan.dvorak @ mathan.cz )

  * 

  * @see <a href="http://www.w3.org/TR/xpath#function-translate"

  *      target="_top">Section 4.2 of the XPath Specification</a>

  */

 public class TranslateFunction implements Function

 {

      /* The translation is done thru a HashMap. Performance tip (for anyone

       * who needs to improve the performance of this particular function):

       * Cache the HashMaps, once they are constructed. */

     /**

      * Create a new <code>TranslateFunction</code> object.

      */

     public TranslateFunction() {}

     /** Returns a copy of the first argument in which

      * characters found in the second argument are replaced by

      * corresponding characters from the third argument.

      *

      * @param context the context at the point in the

      *         expression when the function is called

      * @param args a list that contains exactly three items

      * 

      * @return a <code>String</code> built from <code>args.get(0)</code> 

      *     in which occurrences of characters in <code>args.get(1)</code> 

      *     are replaced by the corresponding characters in <code>args.get(2)</code> 

      * 

      * @throws FunctionCallException if <code>args</code> does not have exactly three items

      */

     public Object call(Context context,

                        List args) throws FunctionCallException

     {

         if (args.size() == 3) {

             return evaluate( args.get(0),

                              args.get(1),

                              args.get(2),

                              context.getNavigator() );

         }

         throw new FunctionCallException( "translate() requires three arguments." );

     }

     /** 

      * Returns a copy of <code>strArg</code> in which

      * characters found in <code>fromArg</code> are replaced by

      * corresponding characters from <code>toArg</code>.

      * If necessary each argument is first converted to it string-value

      * as if by the XPath <code>string()</code> function.

      * 

      * @param strArg the base string

      * @param fromArg the characters to be replaced

      * @param toArg the characters they will be replaced by

      * @param nav the <code>Navigator</code> used to calculate the string-values of the arguments.

      * 

      * @return a copy of <code>strArg</code> in which

      *  characters found in <code>fromArg</code> are replaced by

      *  corresponding characters from <code>toArg</code>

      *  

      * @throws FunctionCallException if one of the arguments is a malformed Unicode string;

      *     that is, if surrogate characters don't line up properly

      * 

      */

     public static String evaluate(Object strArg,

                                   Object fromArg,

                                   Object toArg,

                                   Navigator nav) throws FunctionCallException

     {

         String inStr = StringFunction.evaluate( strArg, nav );

         String fromStr = StringFunction.evaluate( fromArg, nav );

         String toStr = StringFunction.evaluate( toArg, nav );

         // Initialize the mapping in a HashMap

         Map characterMap = new HashMap();

         String[] fromCharacters = toUnicodeCharacters(fromStr);

         String[] toCharacters = toUnicodeCharacters(toStr);

         int fromLen = fromCharacters.length;

         int toLen = toCharacters.length;

         for ( int i = 0; i < fromLen; i++ ) {

             String cFrom = fromCharacters[i];

             if ( characterMap.containsKey( cFrom ) ) {

                 // We've seen the character before, ignore

                 continue;

             }

             if ( i < toLen ) {

                 // Will change

                 characterMap.put( cFrom, toCharacters[i] );

             } 

             else {

                 // Will delete

                 characterMap.put( cFrom, null );

             }

         }

         // Process the input string thru the map

         StringBuffer outStr = new StringBuffer( inStr.length() );

         String[] inCharacters = toUnicodeCharacters(inStr);

         int inLen = inCharacters.length;

         for ( int i = 0; i < inLen; i++ ) {

             String cIn = inCharacters[i];

             if ( characterMap.containsKey( cIn ) ) {

                 String cTo = (String) characterMap.get( cIn );

                 if ( cTo != null ) {

                     outStr.append( cTo );

                 }

             } 

             else {

                 outStr.append( cIn );

             }

         }

         return outStr.toString();

     }

     private static String[] toUnicodeCharacters(String s) throws FunctionCallException {

         String[] result = new String[s.length()];

         int stringLength = 0;

         for (int i = 0; i < s.length(); i++) {

             char c1 = s.charAt(i);

             if (isHighSurrogate(c1)) {

                 try {

                     char c2 = s.charAt(i+1);

                     if (isLowSurrogate(c2)) {

                         result[stringLength] = (c1 + "" + c2).intern();

                         i++;

                     }

                     else {

                         throw new FunctionCallException("Mismatched surrogate pair in translate function");

                     }

                 }

                 catch (StringIndexOutOfBoundsException ex) {

                     throw new FunctionCallException("High surrogate without low surrogate at end of string passed to translate function");

                 }

             }

             else {

                 result[stringLength]=String.valueOf(c1).intern();

             }

             stringLength++;

         }

         if (stringLength == result.length) return result;

         // trim array

         String[] trimmed = new String[stringLength];

         System.arraycopy(result, 0, trimmed, 0, stringLength);

         return trimmed;

     }

     private static boolean isHighSurrogate(char c) {

         return c >= 0xD800 && c <= 0xDBFF;

     }

     private static boolean isLowSurrogate(char c) {

         return c >= 0xDC00 && c <= 0xDFFF;

     }

 }