/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.ejb.plugins.cmp.jdbc;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;

import javax.ejb.FinderException;

import org.jboss.ejb.EntityEnterpriseContext;
import org.jboss.ejb.GenericEntityObjectFactory;
import org.jboss.ejb.plugins.cmp.jdbc.metadata.JDBCReadAheadMetaData;
import org.jboss.logging.Logger;

/**
 * CMPStoreManager CustomFindByEntitiesCommand.
 * Implements bridge for custom implemented finders in container managed entity
 * beans. These methods are called ejbFindX in the EJB implementation class,
 * where X can be anything. Such methods are called findX in the Home and/or
 * the LocalHome interface.
 *
 * @see org.jboss.ejb.plugins.cmp.jdbc.JDBCFindEntitiesCommand
 * @author <a href="mailto:michel.anke@wolmail.nl">Michel de Groot</a>
 * @author <a href="mailto:john-jboss@freeborg.com">John Freeborg</a>
 * @version $Revision: 81030 $
 */
public final class JDBCCustomFinderQuery implements JDBCQueryCommand
{
   private final Logger log;
   private final Method finderMethod;
   private final JDBCReadAheadMetaData readAheadMetaData;
   private final ReadAheadCache readAheadCache;
   private final JDBCStoreManager manager;
   /**
    * Constructs a command which can handle multiple entity finders
    * that are BMP implemented.
    * @param finderMethod the EJB finder method implementation
    */
   public JDBCCustomFinderQuery(JDBCStoreManager manager, Method finderMethod)
   {
      this.finderMethod = finderMethod;
      this.manager = manager;

      JDBCReadAheadMetaData readAheadMetaData = manager.getMetaData().getReadAhead();
      if((readAheadMetaData != null) && readAheadMetaData.isOnLoad())
      {
         this.readAheadCache = manager.getReadAheadCache();
         this.readAheadMetaData = readAheadMetaData;
      }
      else
      {
         this.readAheadCache = null;
         this.readAheadMetaData = null;
      }

      this.log = Logger.getLogger(
         this.getClass().getName() +
         "." +
         manager.getMetaData().getName() +
         "." +
         finderMethod.getName());

      if(log.isDebugEnabled())
         log.debug("Finder: Custom finder " + finderMethod.getName());
   }

   public JDBCStoreManager getSelectManager()
   {
      return manager;
   }

   public Collection execute(Method unused,
                             Object[] args,
                             EntityEnterpriseContext ctx,
                             GenericEntityObjectFactory factory)
      throws FinderException
   {
      try
      {
         // invoke implementation method on ejb instance
         Object value = finderMethod.invoke(ctx.getInstance(), args);

         // if expected return type is Collection, return as is
         // if expected return type is not Collection, wrap value in Collection
         if(value instanceof Enumeration)
         {
            Enumeration enumeration = (Enumeration)value;
            List result = new ArrayList();
            while(enumeration.hasMoreElements())
            {
               result.add(enumeration.nextElement());
            }
            cacheResults(result);
            return GenericEntityObjectFactory.UTIL.getEntityCollection(factory, result);
         }
         else if(value instanceof Collection)
         {
            List result;
            if (value instanceof List)
               result = (List)value;
            else
               result = new ArrayList((Collection)value);
            cacheResults(result);
            return GenericEntityObjectFactory.UTIL.getEntityCollection(factory, result);
         }
         else
         {
            // Don't bother trying to cache this
            return Collections.singleton(factory.getEntityEJBObject(value));
         }
      }
      catch(IllegalAccessException e)
      {
         log.error("Error invoking custom finder " + finderMethod.getName(), e);
         throw new FinderException("Unable to access finder implementation: " +
            finderMethod.getName());
      }
      catch(IllegalArgumentException e)
      {
         log.error("Error invoking custom finder " + finderMethod.getName(), e);
         throw new FinderException("Illegal arguments for finder " +
            "implementation: " + finderMethod.getName());
      }
      catch(InvocationTargetException e)
      {
         // Throw the exception if its a FinderException
         Throwable ex = e.getTargetException();
         if( ex instanceof FinderException )
         {
            throw (FinderException) ex;
         }
         else
         {
            throw new FinderException("Errror invoking cutom finder " +
               finderMethod.getName() + ": " + ex);
         }
      }
   }

   private void cacheResults(List listOfPKs)
   {
      // the on-load read ahead cache strategy is the only one that makes
      // sense to support for custom finders since all we have is a list of
      // primary keys.
      if(readAheadCache != null)
      {
         readAheadCache.addFinderResults(listOfPKs, readAheadMetaData);
      }
   }
}