/*
 * Copyright 2007 Joachim Grueneis
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package org.exolab.castor.xml.util.resolvers;

import java.util.HashMap;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.exolab.castor.xml.ResolverException;
import org.exolab.castor.xml.XMLConstants;

/**
 * Resolve a class by looking for a descriptor class 'nearby'. The descriptor class has to follow
 * some specific naming conventions (and maybe be in a special package).
 * 
 * @author <a href="mailto:jgrueneis AT gmail DOT com">Joachim Grueneis</a>
 * @author <a href="mailto:stevendolg AT gxm DOT at">Steven Dolg</a>
 * @version $Revision$ $Date$
 * @since 1.2
 */
public class ByDescriptorClass extends AbstractResolverClassCommand {
  private static final Log LOG = LogFactory.getLog(ByDescriptorClass.class);

  /**
   * No specific stuff needed.
   */
  public ByDescriptorClass() {
    super();
  }

  /**
   * Tries to load an XMLClassDescriptor directly from an existing .class file. <br>
   * The file that is searched for must be located in the classpath, have the name
   * <code>className</code> + "Descriptor", and contain a valid XMLClassDescriptor. <br>
   * If a descriptor is found it is added to the internal descriptor cache. <br>
   * {@inheritDoc}
   */
  protected Map internalResolve(final String className, final ClassLoader classLoader,
      final Map properties) throws ResolverException {

    HashMap results = new HashMap();
    if (classLoader == null) {
      LOG.debug("No class loader available.");
      return results;
    }

    StringBuilder descriptorClassName = new StringBuilder(className);
    descriptorClassName.append(XMLConstants.DESCRIPTOR_SUFFIX);
    Class descriptorClass = ResolveHelpers.loadClass(classLoader, descriptorClassName.toString());

    // If we didn't find the descriptor, look in descriptor package
    if (descriptorClass == null) {
      int offset = descriptorClassName.lastIndexOf(".");
      if (offset != -1) {
        descriptorClassName.insert(offset, ".");
        descriptorClassName.insert(offset + 1, XMLConstants.DESCRIPTOR_PACKAGE);
        descriptorClass = ResolveHelpers.loadClass(classLoader, descriptorClassName.toString());
      }
    }

    if (descriptorClass != null) {
      try {
        LOG.debug("Found descriptor: " + descriptorClass);
        results.put(className, descriptorClass.newInstance());
      } catch (InstantiationException e) {
        LOG.debug("Ignored exception: " + e + "at loading descriptor class for: " + className);
      } catch (IllegalAccessException e) {
        LOG.debug("Ignored exception: " + e + "at loading descriptor class for: " + className);
      }
    }
    return results;
  }
}
