/*
 * AttributeNode.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 javax.xml.XMLConstants;
import javax.xml.namespace.QName;
import javax.xml.transform.TransformerException;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentFragment;
import org.w3c.dom.Attr;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import gnu.xml.xpath.Expr;

/**
 * A template node representing an XSL <code>attribute</code> instruction.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
final class AttributeNode
  extends TemplateNode
{

  final TemplateNode name;
  final TemplateNode namespace;
  final Node source;
  
  AttributeNode(TemplateNode children, TemplateNode next, TemplateNode name,
                TemplateNode namespace, Node source)
  {
    super(children, next);
    this.name = name;
    this.namespace = namespace;
    this.source = source;
  }

  TemplateNode clone(Stylesheet stylesheet)
  {
    return new AttributeNode((children == null) ? null :
                             children.clone(stylesheet),
                             (next == null) ? null : next.clone(stylesheet),
                             name.clone(stylesheet),
                             (namespace == null) ? null : 
                             namespace.clone(stylesheet),
                             source);
  }

  void doApply(Stylesheet stylesheet, QName mode,
               Node context, int pos, int len,
               Node parent, Node nextSibling)
    throws TransformerException
  {
    Document doc = (parent instanceof Document) ? (Document) parent :
      parent.getOwnerDocument();
    // Create a document fragment to hold the name
    DocumentFragment fragment = doc.createDocumentFragment();
    // Apply name to the fragment
    name.apply(stylesheet, mode,
               context, pos, len,
               fragment, null);
    // Use XPath string-value of fragment
    String nameValue = Expr.stringValue(fragment);
  
    String namespaceValue = null;
    if (namespace != null)
      {  
        // Create a document fragment to hold the namespace
        fragment = doc.createDocumentFragment();
        // Apply namespace to the fragment
        namespace.apply(stylesheet, mode,
                        context, pos, len,
                        fragment, null);
        // Use XPath string-value of fragment
        namespaceValue = Expr.stringValue(fragment);
        if (namespaceValue.length() == 0)
          {
            namespaceValue = null;
          }
      }
    
    String prefix = getPrefix(nameValue);
    if (namespaceValue == null)
      {
        if (prefix != null)
          {
            if (XMLConstants.XML_NS_PREFIX.equals(prefix))
              {
                namespaceValue = XMLConstants.XML_NS_URI;
              }
            else
              {
                // Resolve namespace for this prefix
                namespaceValue = source.lookupNamespaceURI(prefix);
              }
          }
      }
    else
      {
        if (prefix != null)
          {
            String ns2 = source.lookupNamespaceURI(prefix);
            if (ns2 != null && !ns2.equals(namespaceValue))
              {
                // prefix clashes, reset it
                prefix = null;
                int ci = nameValue.indexOf(':');
                nameValue = nameValue.substring(ci + 1);
              }
          }
      }
    if (prefix == null)
      {
        // Resolve prefix for this namespace
        prefix = source.lookupPrefix(namespaceValue);
        if (prefix != null)
          {
            nameValue = prefix + ":" + nameValue;
          }
        else
          {
            if (namespaceValue != null)
              {
                // Must invent a prefix
                prefix = inventPrefix(parent);
                nameValue = prefix + ":" + nameValue;
              }
          }
      }
    NamedNodeMap attrs = parent.getAttributes();
    boolean insert = true;
    if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(namespaceValue) ||
        XMLConstants.XMLNS_ATTRIBUTE.equals(nameValue) ||
        nameValue.startsWith("xmlns:"))
      {
        // Namespace declaration, do not output
        insert = false;
      }
    if (prefix != null && namespaceValue == null)
      {
        // Not a QName
        insert = false;
      }
    if (parent.getNodeType() == Node.ELEMENT_NODE &&
        parent.getFirstChild() != null)
      {
        // XSLT 7.1.3 Adding an attribute to an element after children have
        // been added to it is an error
        insert = false;
      }
    if (insert)
      {
        // Insert attribute
        Attr attr = (namespaceValue != null) ?
          doc.createAttributeNS(namespaceValue, nameValue) :
              doc.createAttribute(nameValue);
        if (attrs != null)
          {
            if (namespace != null)
              {
                attrs.setNamedItemNS(attr);
              }
            else
              {
                attrs.setNamedItem(attr);
              }
          }
        if (children != null)
          {
            children.apply(stylesheet, mode,
                           context, pos, len,
                           attr, null);
          }
      }
    if (next != null)
      {
        next.apply(stylesheet, mode,
                   context, pos, len,
                   parent, nextSibling);
      }
  }

  final String getPrefix(String name)
  {
    int ci = name.indexOf(':');
    return (ci == -1) ? null : name.substring(0, ci);
  }

  final String inventPrefix(Node parent)
  {
    String base = "ns";
    int count = 0;
    String ret = base + Integer.toString(count);
    while (parent.lookupNamespaceURI(ret) != null)
      {
        count++;
        ret = base + Integer.toString(count);
      }
    return ret;
  }
  
  public String toString()
  {
    StringBuffer buf = new StringBuffer(getClass().getName());
    buf.append('[');
    buf.append("name=");
    buf.append(name);
    buf.append(']');
    return buf.toString();
  }
  
}
