/*
    * Copyright (c) 2002-2022, City of 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.logging.log4j.LogManager;
  import org.apache.logging.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 = LogManager.getLogger( JPAConstants.JPA_LOGGER );
      private Class<E> _entityClass;
      private EntityManager _defaultEM;
  
      /**
       * Constructor
       */
      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 : {}  - using Factory :  {}", em::toString, 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]" );
 
         if ( _defaultEM == null )
         {
             _defaultEM = emf.createEntityManager( );
         }
         return _defaultEM;
     }
 
     /**
      * {@inheritDoc }
      */
     @Override
     public void create( E entity )
     {
         LOG.debug( "Creating entity : {}", entity::toString );
 
         EntityManager em = getEM( );
 
         if ( em == _defaultEM )
         {
             em.getTransaction( ).begin( );
         }
         em.persist( entity );
         if ( em == _defaultEM )
         {
             em.getTransaction( ).commit( );
         }
 
         LOG.debug( "Entity created : {}", entity::toString );
     }
 
     /**
      * {@inheritDoc }
      */
     @Override
     public void remove( K key )
     {
         EntityManager em = getEM( );
         E entity = em.find( _entityClass, key );
         if ( entity == null )
         {
             LOG.debug( "Did not find entity to remove for key {} ", key::toString );
             return;
         }
         LOG.debug( "Removing entity : {}", entity::toString );
         if ( em == _defaultEM )
         {
             em.getTransaction( ).begin( );
         }
         em.remove( entity );
         if ( em == _defaultEM )
         {
             em.getTransaction( ).commit( );
         }
         LOG.debug( "Entity removed : {}", entity::toString );
     }
 
     /**
      * {@inheritDoc }
      */
     @Override
     public void update( E entity )
     {
         LOG.debug( "Updating entity : {}", entity::toString );
 
         EntityManager em = getEM( );
         if ( em == _defaultEM )
         {
             em.getTransaction( ).begin( );
         }
         em.merge( entity );
         if ( em == _defaultEM )
         {
             em.getTransaction( ).commit( );
         }
 
         LOG.debug( "Entity Updated : {}", entity::toString );
     }
 
     /**
      * {@inheritDoc }
      */
     @Override
     public E findById( K key )
     {
         LOG.debug( "Selecting entity {} by Id ", ( ) -> getEntityClassName( ), key::toString );
 
         return getEM( ).find( _entityClass, key );
     }
 
     /**
      * {@inheritDoc }
      */
     @Override
     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}
      */
     @Override
     public void flush( )
     {
         getEM( ).flush( );
     }
 
     /**
      *
      * {@inheritDoc}
      */
     @Override
     public void detach( E entity )
     {
         getEM( ).detach( entity );
     }
 }