/*
 * GenerateIdFunction.java
 * Copyright (C) 2004 The Free Software Foundation
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU JAXP is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version. 
 */

package gnu.xml.transform;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;
import org.w3c.dom.Node;
import gnu.xml.xpath.Expr;
import gnu.xml.xpath.Function;

/**
 * The XSLT <code>generate-id()</code>function.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
final class GenerateIdFunction
  extends Expr
  implements XPathFunction, Function
{

  List args;

  public Object evaluate(List args)
    throws XPathFunctionException
  {
    // Useless...
    return Collections.EMPTY_SET;
  }

  public void setArguments(List args)
  {
    this.args = args;
  }

  public Object evaluate(Node context, int pos, int len)
  {
    int arity = args.size();
    List values = new ArrayList(arity);
    for (int i = 0; i < arity; i++)
      {
        Expr arg = (Expr) args.get(i);
        values.add(arg.evaluate(context, pos, len));
      }
    Node node;
    Collection ns = (arity == 0) ? Collections.EMPTY_SET :
      (Collection) values.get(0);
    if (ns.isEmpty())
      {
        node = context;
      }
    else
      {
        List list = new ArrayList(ns);
        Collections.sort(list, documentOrderComparator);
        node = (Node) list.get(0);
      }

    String name = node.getNodeName();
    int index = 0, depth = 0;
    for (Node ctx = node.getPreviousSibling(); ctx != null;
         ctx = ctx.getPreviousSibling())
      {
        index++;
      }
    for (Node ctx = node.getParentNode(); ctx != null;
         ctx = ctx.getParentNode())
      {
        depth++;
      }
    return name + "-" + index + "-" + depth;
  }

  public Expr clone(Object context)
  {
    GenerateIdFunction f = new GenerateIdFunction();
    int len = args.size();
    List args2 = new ArrayList(len);
    for (int i = 0; i < len; i++)
      {
        args2.add(((Expr) args.get(i)).clone(context));
      }
    f.setArguments(args2);
    return f;
  }

}

