/**
 *   GRANITE DATA SERVICES
 *   Copyright (C) 2006-2013 GRANITE DATA SERVICES S.A.S.
 *
 *   This file is part of the Granite Data Services Platform.
 *
 *   Granite Data Services 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.
 *
 *   Granite Data Services 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 library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 *   USA, or see <http://www.gnu.org/licenses/>.
 */
package org.granite.tide.cdi.lazy;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import javax.el.ELResolver;
import javax.enterprise.context.ConversationScoped;
import javax.enterprise.inject.Any;
import javax.enterprise.inject.Instance;
import javax.enterprise.inject.spi.BeanManager;
import javax.inject.Inject;
import javax.naming.InitialContext;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

import org.granite.logging.Logger;
import org.granite.tide.TidePersistenceManager;
import org.granite.tide.cdi.PersistenceConfiguration;
import org.granite.tide.data.DataMergeContext;
import org.granite.tide.data.JPAPersistenceManager;


@ConversationScoped
public class CDIInitializer implements Serializable {

    private static final long serialVersionUID = 1L;
    
    private static final Logger log = Logger.getLogger(CDIInitializer.class);
    
    private transient TidePersistenceManager pm = null;
    
    private Set<Object> loadedEntities = new HashSet<Object>();
    
    @Inject
    private BeanManager manager;
    
    @Inject @Any
    private Instance<TidePersistenceManager> persistenceManagers;
    
    @Inject @Any
    private Instance<EntityManager> entityManagers;
    
    @Inject
    private PersistenceConfiguration persistenceConfiguration;
    
    
    /**
     * Initiliazes the property for the passed in entity. It is attached to an associated context
     * and then the property is accessed.
     * @return Returns result from initializing the property.   
     */
    public Object lazyInitialize(Object entity, String[] propertyNames) {
            if (entity instanceof String) {
            String expression = "${" + entity + "}";
            ELResolver elResolver = manager.getELResolver();
            entity = elResolver.getValue(null, expression, null);
            }
            
                if (pm == null) {
                    pm = getPersistenceManager();
                        if (pm == null)
                            throw new RuntimeException("TideInitializer is null, Entities with lazy relationships have to be retrieved in a conversation");
                }       
                
                return pm.attachEntity(entity, propertyNames);
        }
        
        
        /**
         * Try to determine what type of persistence the application is using. 
         * If the EntityManager is stored under entityManager or if the Hibernate session is 
         * stored under session. Then the context will be found and used. This is only called if a 
         * ITidePersistenceManager is not found, probably because the query was not run in a conversation.
         * @return The appropriate manager for the persistence context being used, if it can be determined
         * otherwise a null is returned. 
         */  
        public TidePersistenceManager getPersistenceManager() {
                try {
                        if (persistenceManagers != null && !persistenceManagers.isUnsatisfied()) {
                                if (persistenceManagers.isAmbiguous()) {
                                        log.error("The application defines more than one TidePersistenceManager, please define only one to be used for Tide lazy loading");
                                        return null;
                                }
                                return persistenceManagers.get();
                        }
                        InitialContext ic = new InitialContext();
                        if (persistenceConfiguration.getEntityManagerFactoryJndiName() != null) {
                                EntityManagerFactory emf = (EntityManagerFactory)ic.lookup(persistenceConfiguration.getEntityManagerFactoryJndiName());
                                return new JPAPersistenceManager(emf);
                        }
                        else if (persistenceConfiguration.getEntityManagerJndiName() != null) {
                                EntityManager em = (EntityManager)ic.lookup(persistenceConfiguration.getEntityManagerJndiName());
                                return new JPAPersistenceManager(em);
                        }
                        else if (entityManagers != null) {
                                // Try with injected EntityManager defined as Resource
                                Iterator<EntityManager> iem = entityManagers.iterator();
                                EntityManager em = iem.hasNext() ? iem.next() : null;
                                if (em == null || iem.hasNext()) {
                                        log.warn("The application defines zero or more than one Persistence Unit, please define which one should be used for lazy loading in entity-manager-jndi-name");
                                        return null;
                                }
                                return new JPAPersistenceManager(em);
                        }
                }
                catch (Exception e) {
                        log.error(e, "Could not get EntityManager");
                }
                return null;
        }
        
    
    public void restoreLoadedEntities() {
        DataMergeContext.restoreLoadedEntities(loadedEntities);
    }
    
    public void saveLoadedEntities() {
        for (Object entity : DataMergeContext.getLoadedEntities())
                loadedEntities.add(entity);
    }
}