/**
 * Redistribution and use of this software and associated documentation ("Software"), with or
 * without modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and notices. Redistributions
 * must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided with
 * the distribution.
 *
 * 3. The name "Exolab" must not be used to endorse or promote products derived from this Software
 * without prior written permission of Intalio, Inc. For written permission, please contact
 * info@exolab.org.
 *
 * 4. Products derived from this Software may not be called "Exolab" nor may "Exolab" appear in
 * their names without prior written permission of Intalio, Inc. Exolab is a registered trademark of
 * Intalio, Inc.
 *
 * 5. Due credit should be given to the Exolab Project (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTALIO, INC. OR ITS
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 1999 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 */

package org.exolab.castor.xml.schema;

import java.util.Hashtable;

/**
 * An implementation of Resolver that can be "scoped". Which means you can construct a
 * ScopableResovler and give it another Resolver (which can also be Scopable). If this Resolver
 * cannot "resolve" the id, then it will try to use the given Resolver to resolver it.
 * 
 * @author <a href="mailto:kvisco@intalio.com">Keith Visco</a>
 * @version $Revision$ $Date: 2006-04-13 06:47:36 -0600 (Thu, 13 Apr 2006) $
 **/
public class ScopableResolver implements Resolver {

  private final Hashtable<String, Referable> ids = new Hashtable<>();

  private final Resolver _resolver;

  public ScopableResolver() {
    this(null);
  } // -- ScopableResolver

  public ScopableResolver(Resolver resolver) {
    _resolver = resolver;
  } // -- ScopableResolver

  /**
   * Adds a resolvable object to this resolver identified by <tt>id</tt>. Subsequent calls to
   * {@link #resolve} with the same <tt>id</tt> will return <tt>referent</tt>.
   *
   * @param id The referent's identifier
   * @param referent The referent object
   */
  public void addResolvable(String id, Referable referent) {
    if (ids.get(id) != null) {
      // -- handle error
    }
    ids.put(id, referent);
  } // -- register

  /**
   * Removes a resolvable object from this resolver. Subsequent calls to {@link #resolve} with the
   * same <tt>id</tt> will return null.
   *
   * @param id The referent's identifier
   */
  public void removeResolvable(String id) {
    Object obj = ids.get(id);
    if (obj != null) {
      ids.remove(id);
    }
  } // -- removeResolvable

  public Referable resolve(String id) {
    Referable referable = (Referable) ids.get(id);
    if ((referable == null) && (_resolver != null)) {
      referable = _resolver.resolve(id);
    }
    return referable;
  } // -- resolve


} // -- ScopableResolver
