/**
 * Licensed to Apereo under one or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information regarding copyright ownership. Apereo
 * licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use
 * this file except in compliance with the License. You may obtain a copy of the License at the
 * following location:
 *
 * <p>http://www.apache.org/licenses/LICENSE-2.0
 *
 * <p>Unless required by applicable law or agreed to in writing, software distributed under the
 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apereo.portal.jpa;

import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceException;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;

/**
 * Wraps the created {@link EntityManagerFactory} so that create/close of {@link EntityManager}
 * instances results in spring events being dispatched
 */
public class EventingLocalContainerEntityManagerFactoryBean
        extends LocalContainerEntityManagerFactoryBean
        implements ApplicationEventPublisherAware, ApplicationListener<ContextRefreshedEvent> {
    private static final AtomicLong EVENT_ID = new AtomicLong();
    private final AtomicBoolean contextReady = new AtomicBoolean(false);
    private ApplicationEventPublisher applicationEventPublisher;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        contextReady.set(true);
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;
    }

    @Override
    protected EntityManagerFactory createNativeEntityManagerFactory() throws PersistenceException {
        final String persistenceUnitName = this.getPersistenceUnitName();

        //Create actual EMF
        final EntityManagerFactory nativeEntityManagerFactory =
                super.createNativeEntityManagerFactory();

        //Add a proxy to the EMF which results in events
        final ProxyFactory proxyFactory = new ProxyFactory(nativeEntityManagerFactory);
        proxyFactory.addAdvice(
                new EventingEntityMangerFactoryInterceptor(
                        applicationEventPublisher, contextReady, persistenceUnitName));
        return (EntityManagerFactory) proxyFactory.getProxy();
    }

    /**
     * Interceptor that fires a {@link EntityManagerCreatedEvent} event when {@link
     * EntityManagerFactory#createEntityManager()} or {@link
     * EntityManagerFactory#createEntityManager(java.util.Map)} is called
     */
    private static final class EventingEntityMangerFactoryInterceptor implements MethodInterceptor {
        private final ApplicationEventPublisher applicationEventPublisher;
        private final AtomicBoolean contextReady;
        private final String persistenceUnitName;

        public EventingEntityMangerFactoryInterceptor(
                ApplicationEventPublisher applicationEventPublisher,
                AtomicBoolean contextReady,
                String persistenceUnitName) {
            this.applicationEventPublisher = applicationEventPublisher;
            this.contextReady = contextReady;
            this.persistenceUnitName = persistenceUnitName;
        }

        @Override
        public Object invoke(MethodInvocation invocation) throws Throwable {
            if ("createEntityManager".equals(invocation.getMethod().getName())
                    && contextReady.get()) {
                final EntityManager entityManager = (EntityManager) invocation.proceed();

                final long entityManagerId = EVENT_ID.getAndIncrement();

                final EntityManagerCreatedEvent entityManagerCreatedEvent =
                        new EntityManagerCreatedEvent(
                                this, entityManagerId, persistenceUnitName, entityManager);
                applicationEventPublisher.publishEvent(entityManagerCreatedEvent);

                //Add a proxy to the EMF which results in events
                final ProxyFactory proxyFactory = new ProxyFactory(entityManager);
                proxyFactory.addAdvice(
                        new EventingEntityMangerInterceptor(
                                applicationEventPublisher,
                                contextReady,
                                entityManagerId,
                                persistenceUnitName,
                                entityManager));
                return (EntityManager) proxyFactory.getProxy();
            }

            return invocation.proceed();
        }
    }

    /**
     * Interceptor that fires a {@link EntityManagerClosingEvent} event when {@link
     * EntityManager#close()} is called
     */
    private static final class EventingEntityMangerInterceptor implements MethodInterceptor {
        private final ApplicationEventPublisher applicationEventPublisher;
        private final AtomicBoolean contextReady;
        private final long entityManagerId;
        private final String persistenceUnitName;
        private final EntityManager entityManager;

        public EventingEntityMangerInterceptor(
                ApplicationEventPublisher applicationEventPublisher,
                AtomicBoolean contextReady,
                long entityManagerId,
                String persistenceUnitName,
                EntityManager entityManager) {
            this.applicationEventPublisher = applicationEventPublisher;
            this.contextReady = contextReady;
            this.entityManagerId = entityManagerId;
            this.persistenceUnitName = persistenceUnitName;
            this.entityManager = entityManager;
        }

        @Override
        public Object invoke(MethodInvocation invocation) throws Throwable {
            if ("close".equals(invocation.getMethod().getName()) && contextReady.get()) {
                final EntityManagerClosingEvent entityManagerClosingEvent =
                        new EntityManagerClosingEvent(
                                this,
                                this.entityManagerId,
                                this.persistenceUnitName,
                                this.entityManager);
                this.applicationEventPublisher.publishEvent(entityManagerClosingEvent);
            }

            return invocation.proceed();
        }
    }
}