/*
 * ElementAvailableFunction.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 java.util.TreeSet;
import javax.xml.namespace.NamespaceContext;
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>element-available</code> function.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
class ElementAvailableFunction
  extends Expr
  implements Function, XPathFunction
{

  static final Collection elements;
  static
  {
    TreeSet acc = new TreeSet();
    acc.add("stylesheet");
    acc.add("template");
    acc.add("param");
    acc.add("variable");
    acc.add("include");
    acc.add("import");
    acc.add("output");
    acc.add("preserve-space");
    acc.add("strip-space");
    acc.add("key");
    acc.add("decimal-format");
    acc.add("namespace-alias");
    acc.add("attribute-set");
    acc.add("apply-templates");
    acc.add("call-template");
    acc.add("value-of");
    acc.add("for-each");
    acc.add("if");
    acc.add("choose");
    acc.add("when");
    acc.add("otherwise");
    acc.add("element");
    acc.add("attribute");
    acc.add("text");
    acc.add("copy");
    acc.add("processing-instruction");
    acc.add("comment");
    acc.add("number");
    acc.add("copy-of");
    acc.add("message");
    acc.add("sort");
    acc.add("with-param");
    acc.add("fallback");
    acc.add("apply-imports");
    elements = Collections.unmodifiableSet(acc);
  }

  final NamespaceContext nsctx;
  List args;

  ElementAvailableFunction(NamespaceContext nsctx)
  {
    this.nsctx = nsctx;
  }

  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)
  {
    Expr arg = (Expr) args.get(0);
    Object val = arg.evaluate(context, pos, len);
    String name = _string(context, val);
    String prefix, localName, uri;
    int ci = name.indexOf(':');
    if (ci == -1)
      {
        prefix = null;
        localName = name;
      }
    else
      {
        prefix = name.substring(0, ci);
        localName = name.substring(ci + 1);
      }
    uri = nsctx.getNamespaceURI(prefix);
    if (Stylesheet.XSL_NS.equals(uri))
      {
        return elements.contains(localName) ?
          Boolean.TRUE : Boolean.FALSE;
        // TODO extension elements
      }
    return Boolean.FALSE;
  }
  
  public Expr clone(Object context)
  {
    NamespaceContext n = nsctx;
    if (context instanceof NamespaceContext)
      {
        n = (NamespaceContext) context;
      }
    ElementAvailableFunction f = new ElementAvailableFunction(n);
    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;
  }

}

