/*
 * Namespaces.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 library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */
package gnu.xml.libxmlj.sax;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;

/**
 * Helper class for managing namespaces.
 * 
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
class Namespaces
{

  ArrayList stack = new ArrayList ();
  
  /**
   * Increments the tree depth.
   * This allocates a new potential namespace entry.
   */
  void push ()
  {
    stack.add (null);
  }

  /**
   * Decrements the tree depth.
   * This removes namespaces defined at the extremity.
   */
  void pop ()
  {
    stack.remove (stack.size() - 1);
  }

  /**
   * Searches for the namespace URI corresponding to the specified prefix.
   */
  String getURI (String prefix)
  {
    for (int i = stack.size () - 1; i >= 0; i--)
    {
      HashMap ns = (HashMap) stack.get (i);
      if (ns != null && ns.containsKey (prefix))
      {
        String ret = (String) ns.get (prefix);
        return (ret == null) ? "" : ret;
      }
    }
    return "";
  }

  /**
   * Defines the specified prefix-URI mapping at the current depth in the
   * tree.
   */
  void define (String prefix, String uri)
  {
    int index = stack.size () - 1;
    HashMap ns = (HashMap) stack.get (index);
    if (ns == null)
    {
      ns = new HashMap ();
      stack.set (index, ns);
    }
    ns.put (prefix, uri);
  }

  /**
   * Returns an iterator over the prefixes defined at the current depth.
   */
  Iterator currentPrefixes ()
  {
    HashMap ns = (HashMap) stack.get (stack.size () - 1);
    if (ns == null)
      {
        return Collections.EMPTY_LIST.iterator ();
      }
    else
      {
        return ns.keySet ().iterator ();
      }
  }

}