/*
 * FunctionAvailableFunction.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>function-available</code> function.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
class FunctionAvailableFunction
  extends Expr
  implements Function, XPathFunction
{

  static final Collection xsltFunctions;
  static final Collection xpathFunctions;
  static
  {
    TreeSet acc = new TreeSet();
    acc.add("document");
    acc.add("key");
    acc.add("format-number");
    acc.add("current");
    acc.add("unparsed-entity-uri");
    acc.add("generate-id");
    acc.add("system-property");
    acc.add("element-available");
    acc.add("function-available");
    xsltFunctions = Collections.unmodifiableSet(acc);
    acc = new TreeSet();
    acc.add("boolean");
    acc.add("ceiling");
    acc.add("concat");
    acc.add("contains");
    acc.add("count");
    acc.add("false");
    acc.add("floor");
    acc.add("id");
    acc.add("lang");
    acc.add("last");
    acc.add("local-name");
    acc.add("name");
    acc.add("namespace-uri");
    acc.add("normalize-space");
    acc.add("not");
    acc.add("number");
    acc.add("position");
    acc.add("round");
    acc.add("starts-with");
    acc.add("string");
    acc.add("string-length");
    acc.add("substring-after");
    acc.add("substring-before");
    acc.add("substring");
    acc.add("sum");
    acc.add("translate");
    acc.add("true");
    xpathFunctions = Collections.unmodifiableSet(acc);
  }

  final NamespaceContext nsctx;
  List args;

  FunctionAvailableFunction(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 (uri == null)
      {
        return xsltFunctions.contains(localName) ||
          xpathFunctions.contains(localName) ?
          Boolean.TRUE : Boolean.FALSE;
        // TODO extension functions
      }
    return Boolean.FALSE;
  }
  
  public Expr clone(Object context)
  {
    NamespaceContext n = nsctx;
    if (context instanceof NamespaceContext)
      {
        n = (NamespaceContext) context;
      }
    FunctionAvailableFunction f = new FunctionAvailableFunction(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;
  }

}

