/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 1999-2004 The Apache Software Foundation.

 *

 * 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.

 */

/*

 * $Id: ExsltMath.java,v 1.1.2.1 2005/08/01 02:08:50 jeffsuttor Exp $

 */

package com.sun.org.apache.xalan.internal.lib;

import com.sun.org.apache.xpath.internal.NodeSet;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

/**

 * This class contains EXSLT math extension functions.

 * It is accessed by specifying a namespace URI as follows:

 * <pre>

 *    xmlns:math="http://exslt.org/math"

 * </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 ExsltMath extends ExsltBase

{

  // Constants

  private static String PI = "3.1415926535897932384626433832795028841971693993751";

  private static String E  = "2.71828182845904523536028747135266249775724709369996";

  private static String SQRRT2 = "1.41421356237309504880168872420969807856967187537694";

  private static String LN2 = "0.69314718055994530941723212145817656807550013436025";

  private static String LN10 = "2.302585092994046";

  private static String LOG2E = "1.4426950408889633";

  private static String SQRT1_2 = "0.7071067811865476";

  /**

   * The math:max function returns the maximum value of the nodes passed as the argument.

   * The maximum value is defined as follows. The node set passed as an argument is sorted

   * in descending order as it would be by xsl:sort with a data type of number. The maximum

   * is the result of converting the string value of the first node in this sorted list to

   * a number using the number function.

   * <p>

   * If the node set is empty, or if the result of converting the string values of any of the

   * nodes to a number is NaN, then NaN is returned.

   *

   * @param nl The NodeList for the node-set to be evaluated.

   *

   * @return the maximum value found, NaN if any node cannot be converted to a number.

   *

   * @see <a href="http://www.exslt.org/">EXSLT</a>

   */

  public static double max (NodeList nl)

  {

    if (nl == null || nl.getLength() == 0)

      return Double.NaN;

    double m = - Double.MAX_VALUE;

    for (int i = 0; i < nl.getLength(); i++)

    {

      Node n = nl.item(i);

      double d = toNumber(n);

      if (Double.isNaN(d))

        return Double.NaN;

      else if (d > m)

        m = d;

    }

    return m;

  }

  /**

   * The math:min function returns the minimum value of the nodes passed as the argument.

   * The minimum value is defined as follows. The node set passed as an argument is sorted

   * in ascending order as it would be by xsl:sort with a data type of number. The minimum

   * is the result of converting the string value of the first node in this sorted list to

   * a number using the number function.

   * <p>

   * If the node set is empty, or if the result of converting the string values of any of

   * the nodes to a number is NaN, then NaN is returned.

   *

   * @param nl The NodeList for the node-set to be evaluated.

   *

   * @return the minimum value found, NaN if any node cannot be converted to a number.

   *

   * @see <a href="http://www.exslt.org/">EXSLT</a>

   */

  public static double min (NodeList nl)

  {

    if (nl == null || nl.getLength() == 0)

      return Double.NaN;

    double m = Double.MAX_VALUE;

    for (int i = 0; i < nl.getLength(); i++)

    {

      Node n = nl.item(i);

      double d = toNumber(n);

      if (Double.isNaN(d))

        return Double.NaN;

      else if (d < m)

        m = d;

    }

    return m;

  }

  /**

   * The math:highest function returns the nodes in the node set whose value is the maximum

   * value for the node set. The maximum value for the node set is the same as the value as

   * calculated by math:max. A node has this maximum value if the result of converting its

   * string value to a number as if by the number function is equal to the maximum value,

   * where the equality comparison is defined as a numerical comparison using the = operator.

   * <p>

   * If any of the nodes in the node set has a non-numeric value, the math:max function will

   * return NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any

   * of the nodes in the node set has a non-numeric value, math:highest will return an empty

   * node set.

   *

   * @param nl The NodeList for the node-set to be evaluated.

   *

   * @return node-set with nodes containing the maximum value found, an empty node-set

   * if any node cannot be converted to a number.

   */

  public static NodeList highest (NodeList nl)

  {

    double maxValue = max(nl);

    NodeSet highNodes = new NodeSet();

    highNodes.setShouldCacheNodes(true);

    if (Double.isNaN(maxValue))

      return highNodes;  // empty Nodeset

    for (int i = 0; i < nl.getLength(); i++)

    {

      Node n = nl.item(i);

      double d = toNumber(n);

      if (d == maxValue)

        highNodes.addElement(n);

    }

    return highNodes;

  }

  /**

   * The math:lowest function returns the nodes in the node set whose value is the minimum value

   * for the node set. The minimum value for the node set is the same as the value as calculated

   * by math:min. A node has this minimum value if the result of converting its string value to

   * a number as if by the number function is equal to the minimum value, where the equality

   * comparison is defined as a numerical comparison using the = operator.

   * <p>

   * If any of the nodes in the node set has a non-numeric value, the math:min function will return

   * NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any of the nodes

   * in the node set has a non-numeric value, math:lowest will return an empty node set.

   *

   * @param nl The NodeList for the node-set to be evaluated.

   *

   * @return node-set with nodes containing the minimum value found, an empty node-set

   * if any node cannot be converted to a number.

   *

   */

  public static NodeList lowest (NodeList nl)

  {

    double minValue = min(nl);

    NodeSet lowNodes = new NodeSet();

    lowNodes.setShouldCacheNodes(true);

    if (Double.isNaN(minValue))

      return lowNodes;  // empty Nodeset

    for (int i = 0; i < nl.getLength(); i++)

    {

      Node n = nl.item(i);

      double d = toNumber(n);

      if (d == minValue)

        lowNodes.addElement(n);

    }

    return lowNodes;

  }

  /**

   * The math:abs function returns the absolute value of a number.

   *

   * @param num A number

   * @return The absolute value of the number

   */

   public static double abs(double num)

   {

     return Math.abs(num);

   }

  /**

   * The math:acos function returns the arccosine value of a number.

   *

   * @param num A number

   * @return The arccosine value of the number

   */

   public static double acos(double num)

   {

     return Math.acos(num);

   }

  /**

   * The math:asin function returns the arcsine value of a number.

   *

   * @param num A number

   * @return The arcsine value of the number

   */

   public static double asin(double num)

   {

     return Math.asin(num);

   }

  /**

   * The math:atan function returns the arctangent value of a number.

   *

   * @param num A number

   * @return The arctangent value of the number

   */

   public static double atan(double num)

   {

     return Math.atan(num);

   }

  /**

   * The math:atan2 function returns the angle ( in radians ) from the X axis to a point (y,x).

   *

   * @param num1 The X axis value

   * @param num2 The Y axis value

   * @return The angle (in radians) from the X axis to a point (y,x)

   */

   public static double atan2(double num1, double num2)

   {

     return Math.atan2(num1, num2);

   }

  /**

   * The math:cos function returns cosine of the passed argument.

   *

   * @param num A number

   * @return The cosine value of the number

   */

   public static double cos(double num)

   {

     return Math.cos(num);

   }

  /**

   * The math:exp function returns e (the base of natural logarithms) raised to a power.

   *

   * @param num A number

   * @return The value of e raised to the given power

   */

   public static double exp(double num)

   {

     return Math.exp(num);

   }

  /**

   * The math:log function returns the natural logarithm of a number.

   *

   * @param num A number

   * @return The natural logarithm of the number

   */

   public static double log(double num)

   {

     return Math.log(num);

   }

  /**

   * The math:power function returns the value of a base expression taken to a specified power.

   *

   * @param num1 The base

   * @param num2 The power

   * @return The value of the base expression taken to the specified power

   */

   public static double power(double num1, double num2)

   {

     return Math.pow(num1, num2);

   }

  /**

   * The math:random function returns a random number from 0 to 1.

   *

   * @return A random double from 0 to 1

   */

   public static double random()

   {

     return Math.random();

   }

  /**

   * The math:sin function returns the sine of the number.

   *

   * @param num A number

   * @return The sine value of the number

   */

   public static double sin(double num)

   {

     return Math.sin(num);

   }

  /**

   * The math:sqrt function returns the square root of a number.

   *

   * @param num A number

   * @return The square root of the number

   */

   public static double sqrt(double num)

   {

     return Math.sqrt(num);

   }

  /**

   * The math:tan function returns the tangent of the number passed as an argument.

   *

   * @param num A number

   * @return The tangent value of the number

   */

   public static double tan(double num)

   {

     return Math.tan(num);

   }

  /**

   * The math:constant function returns the specified constant to a set precision.

   * The possible constants are:

   * <pre>

   *  PI

   *  E

   *  SQRRT2

   *  LN2

   *  LN10

   *  LOG2E

   *  SQRT1_2

   * </pre>

   * @param name The name of the constant

   * @param precision The precision

   * @return The value of the specified constant to the given precision

   */

   public static double constant(String name, double precision)

   {

     String value = null;

     if (name.equals("PI"))

       value = PI;

     else if (name.equals("E"))

       value = E;

     else if (name.equals("SQRRT2"))

       value = SQRRT2;

     else if (name.equals("LN2"))

       value = LN2;

     else if (name.equals("LN10"))

       value = LN10;

     else if (name.equals("LOG2E"))

       value = LOG2E;

     else if (name.equals("SQRT1_2"))

       value = SQRT1_2;

     if (value != null)

     {

       int bits = new Double(precision).intValue();

       if (bits <= value.length())

         value = value.substring(0, bits);

       return Double.parseDouble(value);

     }

     else

       return Double.NaN;

   }

}