/*
 * KeyFunction.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.Iterator;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import gnu.xml.xpath.Expr;
import gnu.xml.xpath.Function;
import gnu.xml.xpath.Pattern;

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

  final Stylesheet stylesheet;
  List args;

  KeyFunction(Stylesheet stylesheet)
  {
    this.stylesheet = stylesheet;
  }

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

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

  public boolean matches(Node context)
  {
    Object ret = evaluate(context, 1, 1);
    return !((Collection) ret).isEmpty();
  }

  public Object evaluate(Node context, int pos, int len)
  {
    // Evaluate arguments
    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));
      }
    // Get key name
    QName keyName = QName.valueOf(_string(context, values.get(0)));
    // Expand qualified name
    String uri = keyName.getNamespaceURI();
    String prefix = keyName.getPrefix();
    if ((uri == null || uri.length() == 0) && 
        (prefix != null && prefix.length() > 0))
      {
        uri = stylesheet.getNamespaceURI(prefix);
        if (uri != null && uri.length() > 0)
          {
            String localName = keyName.getLocalPart();
            keyName = new QName(uri, localName, prefix);
          }
      }
    // Compute matching key set
    Collection keySet = new LinkedList();
    for (Iterator i = stylesheet.keys.iterator(); i.hasNext(); )
      {
        Key key = (Key) i.next();
        if (key.name.equals(keyName))
          {
            keySet.add(key);
          }
      }
    // Get target
    Object target = values.get(1);
    Collection acc = new LinkedHashSet();
    Document doc = (context instanceof Document) ? (Document) context :
      context.getOwnerDocument();
    if (target instanceof Collection)
      {
        for (Iterator i = ((Collection) target).iterator(); i.hasNext(); )
          {
            String val = Expr.stringValue((Node) i.next());
            addKeyNodes(doc, keySet, val, acc);
          }
      }
    else
      {
        String val = Expr._string(context, target);
        addKeyNodes(doc, keySet, val, acc);
      }
    List ret = new ArrayList(acc);
    Collections.sort(ret, documentOrderComparator);
    return ret;
  }

  final void addKeyNodes(Node node, Collection keySet,
                         String value, Collection acc)
  {
    addKeyNodeIfMatch(node, keySet, value, acc);
    // Apply children
    for (Node ctx = node.getFirstChild(); ctx != null;
         ctx = ctx.getNextSibling())
      {
        addKeyNodes(ctx, keySet, value, acc);
      }
  }
  
  final void addKeyNodeIfMatch(Node node, Collection keySet,
                               String value, Collection acc)
  {
    for (Iterator i = keySet.iterator(); i.hasNext(); )
      {
        Key key = (Key) i.next();
        if (key.match.matches(node))
          {
            Object eval = key.use.evaluate(node, 1, 1);
            if (eval instanceof Collection)
              {
                for (Iterator j = ((Collection) eval).iterator();
                     j.hasNext(); )
                  {
                    String keyValue = Expr.stringValue((Node) j.next());
                    if (value.equals(keyValue))
                      {
                        acc.add(node);
                        return;
                      }
                  }
              }
            else
              {
                String keyValue = Expr._string(node, eval);
                if (value.equals(keyValue))
                  {
                    acc.add(node);
                    return;
                  }
              }
          }
      }
  }

  public Expr clone(Object context)
  {
    Stylesheet s = stylesheet;
    if (context instanceof Stylesheet)
      {
        s = (Stylesheet) context;
      }
    KeyFunction f = new KeyFunction(s);
    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;
  }

}

