/*******************************************************************************
 * Copyright 2014 Federal Chancellery Austria
 * MOA-ID has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
package at.gv.egovernment.moa.id.commons.db;

import java.util.Properties;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

import org.hibernate.HibernateException;

import at.gv.egovernment.moa.id.commons.db.ex.MOADatabaseException;
import at.gv.egovernment.moa.logging.Logger;

public final class ConfigurationDBUtils {

   private static EntityManagerFactory entitymanagerfactory;
   
   @SuppressWarnings("rawtypes")
   private static final ThreadLocal THREAD_LOCAL_CONFIG = new ThreadLocal();
   private static boolean automaticSessionHandling = false;
   
   protected ConfigurationDBUtils() { }
   	      
   public static void initHibernate(Properties props) throws MOADatabaseException { 
	   	    
	    try {

		    Logger.debug("Creating initial session factory...");
		    
			entitymanagerfactory = 
					Persistence.createEntityManagerFactory("at.gv.egovernment.moa.id.commons.db.dao.config", 
							props);
						
		    Logger.debug("Initial ConfigDB session factory successfully created.");
		    
		    
	    } catch (Throwable ex) {
	    	Logger.error("Initial session factory creation failed: " + ex.getMessage());
	        throw new MOADatabaseException("Initialization of Configuration Hibernate session factory failed.",ex);
	     }
   }
   
   
   /**
    * Checks if a session factory is currently available. If necessary a new
    * session factory is created.
    * 
    * @return current (or new) session factory
    * @throws HibernateException
    *            thrown if a hibernate error occurs
    */
   public static EntityManager getCurrentSession() {
      if (automaticSessionHandling) {
    	  
    	  return entitymanagerfactory.createEntityManager();
      }
      
      EntityManager session = (EntityManager) THREAD_LOCAL_CONFIG.get();
      
      if (session != null && session.isOpen()) {

    	  //maybe a hack, but sometimes we do not know if the session is closed (session already closed but isOpen()=true) 
    	  try {    		  
    	  	javax.persistence.Query query = session.createQuery("select userdatabase from UserDatabase userdatabase");  	
    	  	query.getResultList();
    		  
    	  } catch (Throwable e) {
    		  Logger.warn("JPA Session Handling Warning!!!! - This error should not occur.");
        	  session = getNewSession();
    	  }
    	  
      } else 
    	  session = getNewSession();
            
      return session;
   }

   @SuppressWarnings("unchecked")
  public static EntityManager getNewSession() {
      if (automaticSessionHandling) {
    	  Logger.warn("Session is being automatically handled by hibernate. Therefore this session maybe not being newly created. Use HibernateUtil.getCurrentSession() instead.");
    	  return entitymanagerfactory.createEntityManager();
      }
      EntityManager session = (EntityManager) THREAD_LOCAL_CONFIG.get();
      if (session != null ) {
    	  Logger.warn("Previous session has not been closed; closing ConfigDB session now.");
         closeSession();
      }
      Logger.debug("Opening new ConfigDB hibernate session...");
      try {
         session = entitymanagerfactory.createEntityManager();
         THREAD_LOCAL_CONFIG.set(session);
      } catch (HibernateException hex) {
    	  Logger.error(hex.getMessage());
      }
      return session;
   }

   /**
    * Closes the current session.
    * 
    * @throws HibernateException
    *            thrown if session is already closed or a hibernate error
    *            occurs.
    */
   @SuppressWarnings("unchecked")
  public static void closeSession() {
      if (automaticSessionHandling) {
    	  Logger.warn("Session is being automatically handled by hibernate. Therefore the current session cannot be closed on demand.");
         return;
      }
      Logger.debug("Closing current ConfigDB hibernate session...");
      EntityManager session = (EntityManager) THREAD_LOCAL_CONFIG.get();
      THREAD_LOCAL_CONFIG.set(null);
      if (session != null) {
         try {
            session.close();
            
         } catch (HibernateException hex) {
            Logger.error(hex.getMessage());
         }
      }
   }
   
   public static boolean save(Object dbo) throws MOADatabaseException {
	   EntityTransaction tx = null;
	   
	  	 try {
		  	 EntityManager session = ConfigurationDBUtils.getCurrentSession();
		  	 tx = session.getTransaction();
		
		  	synchronized (session) {
		  		tx.begin();
	  			session.persist(dbo);
		  		tx.commit();
		  		
		  		//session.clear();
		  	}
		     return true;
		     
	  	 } catch(HibernateException e) {
	  		Logger.warn("Error during Config database saveOrUpdate. Rollback.", e);
	  		tx.rollback();
	  		 throw new MOADatabaseException(e);
	  	 }
	   }
   
   
   public static boolean saveOrUpdate(Object dbo) throws MOADatabaseException {
	   EntityTransaction tx = null;
	   
	  	 try {
		  	 EntityManager session = ConfigurationDBUtils.getCurrentSession();
		  	 tx = session.getTransaction();
		
		  	synchronized (session) {
		  		tx.begin();
		  		
		  		session.merge(dbo);
		  		session.flush();
		  			
		  		tx.commit();
		  		
		  		//session.clear();
		  	}
		     return true;
		     
	  	 } catch(HibernateException e) {
	  		Logger.warn("Error during Config database saveOrUpdate. Rollback.", e);
	  		tx.rollback();
	  		 throw new MOADatabaseException(e);
	  	 }
	   }
	   
	   public static boolean delete(Object dbo) {
		   EntityTransaction tx = null;
	  	 try {
	  		EntityManager session = ConfigurationDBUtils.getCurrentSession();
	  		tx = session.getTransaction();
	  		
		  	 synchronized (session) {
		  		tx.begin();
			    session.remove(session.contains(dbo) ? dbo : session.merge(dbo));
			    tx.commit();
			}
		     
		     return true;
		     
	  	 } catch(HibernateException e) {
	  		Logger.warn("Error during Config database delete. Rollback.", e);
	  		 tx.rollback();
	  		 return false;
	  	 }
	   }
   
}