/*
    * Copyright (c) 2002-2014, Mairie de Paris
    * All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    *
    *  1. Redistributions of source code must retain the above copyright notice
   *     and the following disclaimer.
   *
   *  2. Redistributions in binary form must reproduce the above copyright notice
   *     and the following disclaimer in the documentation and/or other materials
   *     provided with the distribution.
   *
   *  3. Neither the name of 'Mairie de Paris' nor 'Lutece' nor the names of its
   *     contributors may be used to endorse or promote products derived from
   *     this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS 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 THE COPYRIGHT HOLDERS OR 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.
   *
   * License 1.0
   */
  package fr.paris.lutece.util.jpa;
  
  import org.apache.log4j.Logger;
  
  import org.springframework.dao.DataAccessResourceFailureException;
  
  import org.springframework.orm.jpa.EntityManagerFactoryUtils;
  
  import org.springframework.transaction.support.TransactionSynchronizationManager;
  
  import java.lang.reflect.ParameterizedType;
  
  import java.util.List;
  
  import javax.persistence.EntityManager;
  import javax.persistence.EntityManagerFactory;
  import javax.persistence.Query;
  
  
  /**
   * Class JPAGenericDAO
   * @param <K> Type of the entity's key
   * @param <E> Type of the entity
   */
  public abstract class JPAGenericDAO<K, E> implements IGenericDAO<K, E>
  {
      private static final Logger _log = Logger.getLogger( JPAConstants.JPA_LOGGER );
      private Class<E> _entityClass;
  
      /**
       * Constructor
       */
      @SuppressWarnings( "unchecked" )
      public JPAGenericDAO(  )
      {
          _entityClass = (Class<E>) ( (ParameterizedType) getClass(  ).getGenericSuperclass(  ) ).getActualTypeArguments(  )[1];
      }
  
      /**
       * Inherit classes should provide their Entity Manager Factory
       * @return The Entity Manager Factory that will create Entity Manager for this DAO
       */
      public abstract EntityManagerFactory getEntityManagerFactory(  );
  
      /**
       * Returns the entity class name
       * @return The entity class name
       */
      public String getEntityClassName(  )
      {
          return _entityClass.getName(  );
      }
  
      /**
       * Gets the entity class
       * @return the entity class
       */
      public Class<E> getEntityClass(  )
      {
          return _entityClass;
      }
  
      /**
       * Return the Entity Manager
       * @return The Entity Manager
       */
     public EntityManager getEM(  )
     {
         EntityManagerFactory emf = getEntityManagerFactory(  );
 
         if ( TransactionSynchronizationManager.isSynchronizationActive(  ) )
         {
             // first, get Spring entitymanager (if available)
             try
             {
                 EntityManager em = EntityManagerFactoryUtils.getTransactionalEntityManager( emf );
 
                 if ( em == null )
                 {
                     _log.error( 
                         "getEM(  ) : no EntityManager found. Will use native entity manager factory [Transaction will not be supported]" );
                 }
                 else
                 {
                     _log.debug( "EntityManager found for the current transaction : " + em.toString(  ) +
                         " - using Factory : " + emf.toString(  ) );
 
                     return em;
                 }
             }
             catch ( DataAccessResourceFailureException ex )
             {
                 _log.error( ex );
             }
         }
 
         _log.error( 
             "getEM(  ) : no EntityManager found. Will use native entity manager factory [Transaction will not be supported]" );
 
         return emf.createEntityManager(  );
     }
 
     /**
      * {@inheritDoc }
      */
     public void create( E entity )
     {
         _log.debug( "Creating entity : " + entity.toString(  ) );
 
         EntityManager em = getEM(  );
         em.persist( entity );
         _log.debug( "Entity created : " + entity.toString(  ) );
     }
 
     /**
      * {@inheritDoc }
      */
     public void remove( K key )
     {
         EntityManager em = getEM(  );
         E entity = em.find( _entityClass, key );
         _log.debug( "Removing entity : " + entity.toString(  ) );
         em.remove( entity );
         _log.debug( "Entity removed : " + entity.toString(  ) );
     }
 
     /**
      * {@inheritDoc }
      */
     public void update( E entity )
     {
         _log.debug( "Updating entity : " + entity.toString(  ) );
 
         EntityManager em = getEM(  );
         em.merge( entity );
         _log.debug( "Entity Updated : " + entity.toString(  ) );
     }
 
     /**
      * {@inheritDoc }
      */
     public E findById( K key )
     {
         _log.debug( "Selecting entity " + getEntityClassName(  ) + " by ID : " + key.toString(  ) );
 
         return (E) getEM(  ).find( _entityClass, key );
     }
 
     /**
      * {@inheritDoc }
      */
     public List<E> findAll(  )
     {
         _log.debug( "Selecting all entities of type : " + getEntityClassName(  ) );
 
         Query query = getEM(  ).createQuery( "SELECT e FROM " + getEntityClassName(  ) + " e " );
 
         return query.getResultList(  );
     }
 
     /**
      *
      *{@inheritDoc}
      */
     public void flush(  )
     {
         getEM(  ).flush(  );
     }
 
     /**
      *
      *{@inheritDoc}
      */
     public void detach( E entity )
     {
         getEM(  ).detach( entity );
     }
 }