/*
    * 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;
    }
  }