/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is the Kowari Metadata Store.
 *
 * The Initial Developer of the Original Code is Plugged In Software Pty
 * Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
 * created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
 * Plugged In Software Pty Ltd. All Rights Reserved.
 *
 * Contributor(s): N/A.
 *
 * [NOTE: The text of this Exhibit A may differ slightly from the text
 * of the notices in the Source Code files of the Original Code. You
 * should use the text of this Exhibit A rather than the text found in the
 * Original Code Source Code for Your Modifications.]
 *
 */

package org.mulgara.resolver;

// Java 2 standard packages
import java.lang.reflect.*;

// Third party packages
import org.apache.log4j.Logger;  // Apache Log4J

// Local packages
import org.mulgara.content.ContentHandler;

/**
 * Constructs {@link ContentHandler} instances, given a classname.
 *
 * @created 2004-10-07
 * @author <a href="http://www.pisoftware.com/raboczi">Simon Raboczi</a>
 * @version $Revision: 1.8 $
 * @modified $Date: 2005/01/05 04:58:23 $
 * @maintenanceAuthor $Author: newmana $
 * @company <a href="mailto:info@PIsoftware.com">Plugged In Software</a>
 * @copyright ©2004 <a href="http://www.tucanatech.com/">Tucana
 *   Technology, Inc</a>
 * @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
 */
abstract class ContentHandlerFactory
{
  /** Logger.  */
  private static final Logger logger =
    Logger.getLogger(ContentHandlerFactory.class.getName());

  /**
   * Construct a {@link ContentHandler}.
   *
   * @param className  the name of a class implementing {@link ContentHandler}
   * @return the constructed {@link ContentHandler}
   */
  static ContentHandler newContentHandler(String className)
  {
    if (logger.isDebugEnabled()) {
      logger.debug("Creating content handler " + className);
    }

    // Validate "className" parameter
    if (className == null) {
      throw new IllegalArgumentException("Null \"className\" parameter");
    }

    Class<?> contentHandlerClass;
    try {
      contentHandlerClass = Class.forName(className);
    } catch (ClassNotFoundException e) {
      logger.warn("Error generating content handler", e);
      IllegalArgumentException illegalArgumentException =
        new IllegalArgumentException(className + " is not installed");
      illegalArgumentException.initCause(e);
      throw illegalArgumentException;
    }
    assert contentHandlerClass != null;

    // Validate that the candidate supports the ContentHandler interface
    if (!ContentHandler.class.isAssignableFrom(contentHandlerClass)) {
      throw new IllegalArgumentException(
        className + " is not an " + ContentHandler.class.getName()
      );
    }

    try {
      // Instantiate the content handler
      return (ContentHandler) contentHandlerClass.getConstructor(new Class[] {})
                                                 .newInstance(new Object[] {});
    } catch (IllegalAccessException e) {
      logger.warn("Error generating content handler", e);
      IllegalArgumentException illegalArgumentException =
        new IllegalArgumentException("Unable to add content handler");
      illegalArgumentException.initCause(e);
      throw illegalArgumentException;
    } catch (InstantiationException e) {
      logger.warn("Error generating content handler", e);
      IllegalArgumentException illegalArgumentException =
        new IllegalArgumentException("Unable to add content handler");
      illegalArgumentException.initCause(e);
      throw illegalArgumentException;
    } catch (InvocationTargetException e) {
      logger.warn("Error generating content handler", e);
      IllegalArgumentException illegalArgumentException =
        new IllegalArgumentException("Unable to add content handler");
      illegalArgumentException.initCause(e);
      throw illegalArgumentException;
    } catch (NoSuchMethodException e) {
      logger.warn("Error generating content handler", e);
      IllegalArgumentException illegalArgumentException =
        new IllegalArgumentException("Unable to add content handler");
      illegalArgumentException.initCause(e);
      throw illegalArgumentException;
    }
  }
}