/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * 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.

 */

package com.sun.org.apache.xpath.internal.functions;

import com.sun.org.apache.xalan.internal.res.XSLMessages;

import com.sun.org.apache.xml.internal.utils.XMLString;

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

import com.sun.org.apache.xpath.internal.objects.XObject;

import com.sun.org.apache.xpath.internal.objects.XString;

import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

/**

 * Execute the Substring() function.

 * @xsl.usage advanced

 */

public class FuncSubstring extends Function3Args

{

    static final long serialVersionUID = -5996676095024715502L;

  /**

   * Execute the function.  The function must return

   * a valid object.

   * @param xctxt The current execution context.

   * @return A valid XObject.

   *

   * @throws javax.xml.transform.TransformerException

   */

  public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException

  {

    XMLString s1 = m_arg0.execute(xctxt).xstr();

    double start = m_arg1.execute(xctxt).num();

    int lenOfS1 = s1.length();

    XMLString substr;

    if (lenOfS1 <= 0)

      return XString.EMPTYSTRING;

    else

    {

      int startIndex;

      if (Double.isNaN(start))

      {

        // Double.MIN_VALUE doesn't work with math below

        // so just use a big number and hope I never get caught.

        start = -1000000;

        startIndex = 0;

      }

      else

      {

        start = Math.round(start);

        startIndex = (start > 0) ? (int) start - 1 : 0;

      }

      if (null != m_arg2)

      {

        double len = m_arg2.num(xctxt);

        int end = (int) (Math.round(len) + start) - 1;

        // Normalize end index.

        if (end < 0)

          end = 0;

        else if (end > lenOfS1)

          end = lenOfS1;

        if (startIndex > lenOfS1)

          startIndex = lenOfS1;

        substr = s1.substring(startIndex, end);

      }

      else

      {

        if (startIndex > lenOfS1)

          startIndex = lenOfS1;

        substr = s1.substring(startIndex);

      }

    }

    return (XString)substr; // cast semi-safe

  }

  /**

   * Check that the number of arguments passed to this function is correct.

   *

   *

   * @param argNum The number of arguments that is being passed to the function.

   *

   * @throws WrongNumberArgsException

   */

  public void checkNumberArgs(int argNum) throws WrongNumberArgsException

  {

    if (argNum < 2)

      reportWrongNumberArgs();

  }

  /**

   * Constructs and throws a WrongNumberArgException with the appropriate

   * message for this function object.

   *

   * @throws WrongNumberArgsException

   */

  protected void reportWrongNumberArgs() throws WrongNumberArgsException {

      throw new WrongNumberArgsException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_TWO_OR_THREE, null)); //"2 or 3");

  }

}