/*

  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StringFunction.java,v 1.33 2006/02/05 21:47:41 elharo Exp $

  * $Revision: 1.33 $

  * $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: StringFunction.java,v 1.33 2006/02/05 21:47:41 elharo Exp $

  */

 package org.jaxen.function;

 import org.jaxen.Context;

 import org.jaxen.Function;

 import org.jaxen.FunctionCallException;

 import org.jaxen.Navigator;

 import org.jaxen.UnsupportedAxisException;

 import org.jaxen.JaxenRuntimeException;

 import java.text.DecimalFormat;

 import java.text.NumberFormat;

 import java.text.DecimalFormatSymbols;

 import java.util.List;

 import java.util.Iterator;

 import java.util.Locale;

 /**

  * <p>

  * <b>4.2</b> <code><i>string</i> string(<i>object</i>)</code>

  * </p>

  * 

  * 

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

  * <p>

  * The <b>string</b> function converts

  * an object to a string as follows:

  * </p>

  * 

  * <ul>

  * 

  * <li>

  * <p>

  * A node-set is converted to a string by returning the <a

  * href="http://www.w3.org/TR/xpath#dt-string-value" target="_top">string-value</a> of the node in the node-set

  * that is first in <a href="http://www.w3.org/TR/xpath#dt-document-order" target="_top">document order</a>. If

  * the node-set is empty, an empty string is returned.

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * A number is converted to a string as follows

  * </p>

  * 

  * <ul>

  * 

  * <li>

  * <p>

  * NaN is converted to the string <code>NaN</code>

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * positive zero is converted to the string <code>0</code>

  * </p>

  * </li>

  * 

  * <li>

  * 

  * <p>

  * negative zero is converted to the string <code>0</code>

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * positive infinity is converted to the string <code>Infinity</code>

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * negative infinity is converted to the string <code>-Infinity</code>

  * 

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * if the number is an integer, the number is represented in decimal

  * form as a <a href="http://www.w3.org/TR/xpath#NT-Number" target="_top">Number</a> with no decimal point and

  * no leading zeros, preceded by a minus sign (<code>-</code>) if

  * the number is negative

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * otherwise, the number is represented in decimal form as a Number including a decimal point with at least

  * one digit before the decimal point and at least one digit after the

  * decimal point, preceded by a minus sign (<code>-</code>) if the

  * number is negative; there must be no leading zeros before the decimal

  * point apart possibly from the one required digit immediately before

  * the decimal point; beyond the one required digit after the decimal

  * point there must be as many, but only as many, more digits as are

  * needed to uniquely distinguish the number from all other IEEE 754

  * numeric values.

  * </p>

  * 

  * </li>

  * 

  * </ul>

  * 

  * </li>

  * 

  * <li>

  * <p>

  * The boolean false value is converted to the string <code>false</code>.

  * The boolean true value is converted to the string <code>true</code>.

  * </p>

  * </li>

  * 

  * <li>

  * <p>

  * An object of a type other than the four basic types is converted to a

  * string in a way that is dependent on that type.

  * </p>

  * 

  * </li>

  * 

  * </ul>

  * 

  * <p>

  * If the argument is omitted, it defaults to a node-set with the

  * context node as its only member.

  * </p>

  * 

  * </blockquote>

  * 

  * @author bob mcwhirter (bob @ werken.com)

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

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

  */

 public class StringFunction implements Function

 {

     private static DecimalFormat format = (DecimalFormat) NumberFormat.getInstance(Locale.ENGLISH);

     static {

         DecimalFormatSymbols symbols = new DecimalFormatSymbols(Locale.ENGLISH);

         symbols.setNaN("NaN");

         symbols.setInfinity("Infinity");

         format.setGroupingUsed(false);

         format.setMaximumFractionDigits(32);

         format.setDecimalFormatSymbols(symbols);

     }

     /**

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

      */

     public StringFunction() {}

     /**

      * Returns the string-value of <code>args.get(0)</code> 

      * or of the context node if <code>args</code> is empty.

      * 

      * @param context the context at the point in the

      *         expression where the function is called

      * @param args list with zero or one element

      * 

      * @return a <code>String</code> 

      * 

      * @throws FunctionCallException if <code>args</code> has more than one item

      */    

     public Object call(Context context,

                        List args) throws FunctionCallException

     {

         int size = args.size();

         if ( size == 0 )

         {

             return evaluate( context.getNodeSet(),

                              context.getNavigator() );

         }

         else if ( size == 1 )

         {

             return evaluate( args.get(0),

                              context.getNavigator() );

         }

         throw new FunctionCallException( "string() takes at most argument." );

     }

     /**

      * Returns the XPath string-value of <code>obj</code>.

      * This operation is only defined if obj is a node, node-set,

      * <code>String</code>, <code>Number</code>, or 

      * <code>Boolean</code>. For other types this function

      * returns the empty string. 

      * 

      * @param obj the node, node-set, string, number, or boolean

      *      whose string-value is calculated

      * @param nav the navigator used to calculate the string-value

      * 

      * @return a <code>String</code>. May be empty but is never null.

      */    

     public static String evaluate(Object obj,

                                   Navigator nav)

     {

         try

         {

             // Workaround because XOM uses lists for Text nodes

             // so we need to check for that first

             if (nav != null && nav.isText(obj))

             {

                 return nav.getTextStringValue(obj);

             }

             if (obj instanceof List)

             {

                 List list = (List) obj;

                 if (list.isEmpty())

                 {

                     return "";

                 }

                 // do not recurse: only first list should unwrap

                 obj = list.get(0);

             }

             if (nav != null) {

                 // This stack of instanceof really suggests there's 

                 // a failure to take advantage of polymorphism here

                 if (nav.isElement(obj))

                 {

                     return nav.getElementStringValue(obj);

                 }

                 else if (nav.isAttribute(obj))

                 {

                     return nav.getAttributeStringValue(obj);

                 }

                 else if (nav.isDocument(obj))

                 {

                     Iterator childAxisIterator = nav.getChildAxisIterator(obj);

                     while (childAxisIterator.hasNext())

                     {

                         Object descendant = childAxisIterator.next();

                         if (nav.isElement(descendant))

                         {

                             return nav.getElementStringValue(descendant);

                         }

                     }

                 }

                 else if (nav.isProcessingInstruction(obj))

                 {

                     return nav.getProcessingInstructionData(obj);

                 }

                 else if (nav.isComment(obj))

                 {

                     return nav.getCommentStringValue(obj);

                 }

                 else if (nav.isText(obj))

                 {

                     return nav.getTextStringValue(obj);

                 }

                 else if (nav.isNamespace(obj))

                 {

                     return nav.getNamespaceStringValue(obj);

                 }

             }

             if (obj instanceof String)

             {

                 return (String) obj;

             }

             else if (obj instanceof Boolean)

             {

                 return stringValue(((Boolean) obj).booleanValue());

             }

             else if (obj instanceof Number)

             {

                 return stringValue(((Number) obj).doubleValue());

             }

         }

         catch (UnsupportedAxisException e)

         {

             throw new JaxenRuntimeException(e);

         }

         return "";

     }

     private static String stringValue(double value)

     {

         // DecimalFormat formats negative zero as "-0".

         // Therefore we need to test for zero explicitly here.

         if (value == 0) return "0";

         // need to synchronize object for thread-safety

         String result = null;

         synchronized (format) {

             result = format.format(value);

         }

         return result;

     }

     private static String stringValue(boolean value)

     {

         return value ? "true" : "false";

     }

 }