/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed 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
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.springframework.orm.jpa;

import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.TransactionRequiredException;
import javax.persistence.spi.PersistenceUnitInfo;
import javax.persistence.spi.PersistenceUnitTransactionType;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.Ordered;
import org.springframework.dao.DataAccessException;
import org.springframework.dao.support.PersistenceExceptionTranslator;
import org.springframework.transaction.support.ResourceHolderSynchronization;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.CollectionUtils;

/**
 * Delegate for creating a variety of {@link javax.persistence.EntityManager}
 * proxies that follow the JPA spec's semantics for "extended" EntityManagers.
 *
 * <p>Supports several different variants of "extended" EntityManagers:
 * in particular, an "application-managed extended EntityManager", as defined
 * by {@link javax.persistence.EntityManagerFactory#createEntityManager()},
 * as well as a "container-managed extended EntityManager", as defined by
 * {@link javax.persistence.PersistenceContextType#EXTENDED}.
 *
 * <p>The original difference between "application-managed" and "container-managed"
 * was the need for explicit joining of an externally managed transaction through
 * the {@link EntityManager#joinTransaction()} method in the "application" case
 * versus the automatic joining on each user-level EntityManager operation in the
 * "container" case. As of JPA 2.1, both join modes are available with both kinds of
 * EntityManagers, so the difference between "application-" and "container-managed"
 * is now primarily in the join mode default and in the restricted lifecycle of a
 * container-managed EntityManager (i.e. tied to the object that it is injected into).
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @since 2.0
 * @see javax.persistence.EntityManagerFactory#createEntityManager()
 * @see javax.persistence.PersistenceContextType#EXTENDED
 * @see javax.persistence.EntityManager#joinTransaction()
 * @see SharedEntityManagerCreator
 */
public abstract class ExtendedEntityManagerCreator {

        /**
         * Create an application-managed extended EntityManager proxy.
         * @param rawEntityManager the raw EntityManager to decorate
         * @param emfInfo the EntityManagerFactoryInfo to obtain the JpaDialect
         * and PersistenceUnitInfo from
         * @return an application-managed EntityManager that can join transactions
         * but does not participate in them automatically
         */
        public static EntityManager createApplicationManagedEntityManager(
                        EntityManager rawEntityManager, EntityManagerFactoryInfo emfInfo) {

                return createProxy(rawEntityManager, emfInfo, false, false);
        }

        /**
         * Create an application-managed extended EntityManager proxy.
         * @param rawEntityManager the raw EntityManager to decorate
         * @param emfInfo the EntityManagerFactoryInfo to obtain the JpaDialect
         * and PersistenceUnitInfo from
         * @param synchronizedWithTransaction whether to automatically join ongoing
         * transactions (according to the JPA 2.1 SynchronizationType rules)
         * @return an application-managed EntityManager that can join transactions
         * but does not participate in them automatically
         * @since 4.0
         */
        public static EntityManager createApplicationManagedEntityManager(
                        EntityManager rawEntityManager, EntityManagerFactoryInfo emfInfo, boolean synchronizedWithTransaction) {

                return createProxy(rawEntityManager, emfInfo, false, synchronizedWithTransaction);
        }

        /**
         * Create a container-managed extended EntityManager proxy.
         * @param rawEntityManager the raw EntityManager to decorate
         * @param emfInfo the EntityManagerFactoryInfo to obtain the JpaDialect
         * and PersistenceUnitInfo from
         * @return a container-managed EntityManager that will automatically participate
         * in any managed transaction
         */
        public static EntityManager createContainerManagedEntityManager(
                        EntityManager rawEntityManager, EntityManagerFactoryInfo emfInfo) {

                return createProxy(rawEntityManager, emfInfo, true, true);
        }

        /**
         * Create a container-managed extended EntityManager proxy.
         * @param emf the EntityManagerFactory to create the EntityManager with.
         * If this implements the EntityManagerFactoryInfo interface, the corresponding
         * JpaDialect and PersistenceUnitInfo will be detected accordingly.
         * @return a container-managed EntityManager that will automatically participate
         * in any managed transaction
         * @see javax.persistence.EntityManagerFactory#createEntityManager()
         */
        public static EntityManager createContainerManagedEntityManager(EntityManagerFactory emf) {
                return createContainerManagedEntityManager(emf, null, true);
        }

        /**
         * Create a container-managed extended EntityManager proxy.
         * @param emf the EntityManagerFactory to create the EntityManager with.
         * If this implements the EntityManagerFactoryInfo interface, the corresponding
         * JpaDialect and PersistenceUnitInfo will be detected accordingly.
         * @param properties the properties to be passed into the {@code createEntityManager}
         * call (may be {@code null})
         * @return a container-managed EntityManager that will automatically participate
         * in any managed transaction
         * @see javax.persistence.EntityManagerFactory#createEntityManager(java.util.Map)
         */
        public static EntityManager createContainerManagedEntityManager(EntityManagerFactory emf, Map<?, ?> properties) {
                return createContainerManagedEntityManager(emf, properties, true);
        }

        /**
         * Create a container-managed extended EntityManager proxy.
         * @param emf the EntityManagerFactory to create the EntityManager with.
         * If this implements the EntityManagerFactoryInfo interface, the corresponding
         * JpaDialect and PersistenceUnitInfo will be detected accordingly.
         * @param properties the properties to be passed into the {@code createEntityManager}
         * call (may be {@code null})
         * @param synchronizedWithTransaction whether to automatically join ongoing
         * transactions (according to the JPA 2.1 SynchronizationType rules)
         * @return a container-managed EntityManager that expects container-driven lifecycle
         * management but may opt out of automatic transaction synchronization
         * @see javax.persistence.EntityManagerFactory#createEntityManager(java.util.Map)
         * @since 4.0
         */
        public static EntityManager createContainerManagedEntityManager(
                        EntityManagerFactory emf, Map<?, ?> properties, boolean synchronizedWithTransaction) {

                Assert.notNull(emf, "EntityManagerFactory must not be null");
                if (emf instanceof EntityManagerFactoryInfo) {
                        EntityManagerFactoryInfo emfInfo = (EntityManagerFactoryInfo) emf;
                        EntityManagerFactory nativeEmf = emfInfo.getNativeEntityManagerFactory();
                        EntityManager rawEntityManager = (!CollectionUtils.isEmpty(properties) ?
                                        nativeEmf.createEntityManager(properties) : nativeEmf.createEntityManager());
                        return createProxy(rawEntityManager, emfInfo, true, synchronizedWithTransaction);
                }
                else {
                        EntityManager rawEntityManager = (!CollectionUtils.isEmpty(properties) ?
                                        emf.createEntityManager(properties) : emf.createEntityManager());
                        return createProxy(rawEntityManager, null, null, null, null, true, synchronizedWithTransaction);
                }
        }


        /**
         * Actually create the EntityManager proxy.
         * @param rawEntityManager raw EntityManager
         * @param emfInfo the EntityManagerFactoryInfo to obtain the JpaDialect
         * and PersistenceUnitInfo from
         * @param containerManaged whether to follow container-managed EntityManager
         * or application-managed EntityManager semantics
         * @param synchronizedWithTransaction whether to automatically join ongoing
         * transactions (according to the JPA 2.1 SynchronizationType rules)
         * @return the EntityManager proxy
         */
        private static EntityManager createProxy(EntityManager rawEntityManager,
                        EntityManagerFactoryInfo emfInfo, boolean containerManaged, boolean synchronizedWithTransaction) {

                Assert.notNull(emfInfo, "EntityManagerFactoryInfo must not be null");
                JpaDialect jpaDialect = emfInfo.getJpaDialect();
                PersistenceUnitInfo pui = emfInfo.getPersistenceUnitInfo();
                Boolean jta = (pui != null ? pui.getTransactionType() == PersistenceUnitTransactionType.JTA : null);
                return createProxy(rawEntityManager, emfInfo.getEntityManagerInterface(),
                                emfInfo.getBeanClassLoader(), jpaDialect, jta, containerManaged, synchronizedWithTransaction);
        }

        /**
         * Actually create the EntityManager proxy.
         * @param rawEm raw EntityManager
         * @param emIfc the (potentially vendor-specific) EntityManager
         * interface to proxy, or {@code null} for default detection of all interfaces
         * @param cl the ClassLoader to use for proxy creation (maybe {@code null})
         * @param exceptionTranslator the PersistenceException translator to use
         * @param jta whether to create a JTA-aware EntityManager
         * (or {@code null} if not known in advance)
         * @param containerManaged whether to follow container-managed EntityManager
         * or application-managed EntityManager semantics
         * @param synchronizedWithTransaction whether to automatically join ongoing
         * transactions (according to the JPA 2.1 SynchronizationType rules)
         * @return the EntityManager proxy
         */
        private static EntityManager createProxy(
                        EntityManager rawEm, Class<? extends EntityManager> emIfc, ClassLoader cl,
                        PersistenceExceptionTranslator exceptionTranslator, Boolean jta,
                        boolean containerManaged, boolean synchronizedWithTransaction) {

                Assert.notNull(rawEm, "EntityManager must not be null");
                Set<Class<?>> ifcs = new LinkedHashSet<Class<?>>();
                if (emIfc != null) {
                        ifcs.add(emIfc);
                }
                else {
                        ifcs.addAll(ClassUtils.getAllInterfacesForClassAsSet(rawEm.getClass(), cl));
                }
                ifcs.add(EntityManagerProxy.class);
                return (EntityManager) Proxy.newProxyInstance(
                                (cl != null ? cl : ExtendedEntityManagerCreator.class.getClassLoader()),
                                ClassUtils.toClassArray(ifcs),
                                new ExtendedEntityManagerInvocationHandler(
                                                rawEm, exceptionTranslator, jta, containerManaged, synchronizedWithTransaction));
        }


        /**
         * InvocationHandler for extended EntityManagers as defined in the JPA spec.
         */
        @SuppressWarnings("serial")
        private static class ExtendedEntityManagerInvocationHandler implements InvocationHandler, Serializable {

                private static final Log logger = LogFactory.getLog(ExtendedEntityManagerInvocationHandler.class);

                private final EntityManager target;

                private final PersistenceExceptionTranslator exceptionTranslator;

                private final boolean jta;

                private final boolean containerManaged;

                private final boolean synchronizedWithTransaction;

                private ExtendedEntityManagerInvocationHandler(EntityManager target,
                                PersistenceExceptionTranslator exceptionTranslator, Boolean jta,
                                boolean containerManaged, boolean synchronizedWithTransaction) {

                        this.target = target;
                        this.exceptionTranslator = exceptionTranslator;
                        this.jta = (jta != null ? jta : isJtaEntityManager());
                        this.containerManaged = containerManaged;
                        this.synchronizedWithTransaction = synchronizedWithTransaction;
                }

                private boolean isJtaEntityManager() {
                        try {
                                this.target.getTransaction();
                                return false;
                        }
                        catch (IllegalStateException ex) {
                                logger.debug("Cannot access EntityTransaction handle - assuming we're in a JTA environment");
                                return true;
                        }
                }

                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        // Invocation on EntityManager interface coming in...

                        if (method.getName().equals("equals")) {
                                // Only consider equal when proxies are identical.
                                return (proxy == args[0]);
                        }
                        else if (method.getName().equals("hashCode")) {
                                // Use hashCode of EntityManager proxy.
                                return hashCode();
                        }
                        else if (method.getName().equals("getTargetEntityManager")) {
                                // Handle EntityManagerProxy interface.
                                return this.target;
                        }
                        else if (method.getName().equals("unwrap")) {
                                // Handle JPA 2.0 unwrap method - could be a proxy match.
                                Class<?> targetClass = (Class<?>) args[0];
                                if (targetClass == null) {
                                        return this.target;
                                }
                                else if (targetClass.isInstance(proxy)) {
                                        return proxy;
                                }
                        }
                        else if (method.getName().equals("isOpen")) {
                                if (this.containerManaged) {
                                        return true;
                                }
                        }
                        else if (method.getName().equals("close")) {
                                if (this.containerManaged) {
                                        throw new IllegalStateException("Invalid usage: Cannot close a container-managed EntityManager");
                                }
                                ExtendedEntityManagerSynchronization synch = (ExtendedEntityManagerSynchronization)
                                                TransactionSynchronizationManager.getResource(this.target);
                                if (synch != null) {
                                        // Local transaction joined - don't actually call close() before transaction completion
                                        synch.closeOnCompletion = true;
                                        return null;
                                }
                        }
                        else if (method.getName().equals("getTransaction")) {
                                if (this.synchronizedWithTransaction) {
                                        throw new IllegalStateException(
                                                        "Cannot obtain local EntityTransaction from a transaction-synchronized EntityManager");
                                }
                        }
                        else if (method.getName().equals("joinTransaction")) {
                                doJoinTransaction(true);
                                return null;
                        }
                        else if (method.getName().equals("isJoinedToTransaction")) {
                                // Handle JPA 2.1 isJoinedToTransaction method for the non-JTA case.
                                if (!this.jta) {
                                        return TransactionSynchronizationManager.hasResource(this.target);
                                }
                        }

                        // Do automatic joining if required. Excludes toString, equals, hashCode calls.
                        if (this.synchronizedWithTransaction && method.getDeclaringClass().isInterface()) {
                                doJoinTransaction(false);
                        }

                        // Invoke method on current EntityManager.
                        try {
                                return method.invoke(this.target, args);
                        }
                        catch (InvocationTargetException ex) {
                                throw ex.getTargetException();
                        }
                }

                /**
                 * Join an existing transaction, if not already joined.
                 * @param enforce whether to enforce the transaction
                 * (i.e. whether failure to join is considered fatal)
                 */
                private void doJoinTransaction(boolean enforce) {
                        if (this.jta) {
                                // Let's try whether we're in a JTA transaction.
                                try {
                                        this.target.joinTransaction();
                                        logger.debug("Joined JTA transaction");
                                }
                                catch (TransactionRequiredException ex) {
                                        if (!enforce) {
                                                logger.debug("No JTA transaction to join: " + ex);
                                        }
                                        else {
                                                throw ex;
                                        }
                                }
                        }
                        else {
                                if (TransactionSynchronizationManager.isSynchronizationActive()) {
                                        if (!TransactionSynchronizationManager.hasResource(this.target) &&
                                                        !this.target.getTransaction().isActive()) {
                                                enlistInCurrentTransaction();
                                        }
                                        logger.debug("Joined local transaction");
                                }
                                else {
                                        if (!enforce) {
                                                logger.debug("No local transaction to join");
                                        }
                                        else {
                                                throw new TransactionRequiredException("No local transaction to join");
                                        }
                                }
                        }
                }

                /**
                 * Enlist this application-managed EntityManager in the current transaction.
                 */
                private void enlistInCurrentTransaction() {
                        // Resource local transaction, need to acquire the EntityTransaction,
                        // start a transaction now and enlist a synchronization for commit or rollback later.
                        EntityTransaction et = this.target.getTransaction();
                        et.begin();
                        if (logger.isDebugEnabled()) {
                                logger.debug("Starting resource-local transaction on application-managed " +
                                                "EntityManager [" + this.target + "]");
                        }
                        ExtendedEntityManagerSynchronization extendedEntityManagerSynchronization =
                                        new ExtendedEntityManagerSynchronization(this.target, this.exceptionTranslator);
                        TransactionSynchronizationManager.bindResource(this.target, extendedEntityManagerSynchronization);
                        TransactionSynchronizationManager.registerSynchronization(extendedEntityManagerSynchronization);
                }
        }


        /**
         * TransactionSynchronization enlisting an extended EntityManager
         * with a current Spring transaction.
         */
        private static class ExtendedEntityManagerSynchronization
                        extends ResourceHolderSynchronization<EntityManagerHolder, EntityManager>
                        implements Ordered {

                private final EntityManager entityManager;

                private final PersistenceExceptionTranslator exceptionTranslator;

                public volatile boolean closeOnCompletion = false;

                public ExtendedEntityManagerSynchronization(
                                EntityManager em, PersistenceExceptionTranslator exceptionTranslator) {

                        super(new EntityManagerHolder(em), em);
                        this.entityManager = em;
                        this.exceptionTranslator = exceptionTranslator;
                }

                @Override
                public int getOrder() {
                        return EntityManagerFactoryUtils.ENTITY_MANAGER_SYNCHRONIZATION_ORDER - 1;
                }

                @Override
                protected void flushResource(EntityManagerHolder resourceHolder) {
                        try {
                                this.entityManager.flush();
                        }
                        catch (RuntimeException ex) {
                                throw convertException(ex);
                        }
                }

                @Override
                protected boolean shouldReleaseBeforeCompletion() {
                        return false;
                }

                @Override
                public void afterCommit() {
                        super.afterCommit();
                        // Trigger commit here to let exceptions propagate to the caller.
                        try {
                                this.entityManager.getTransaction().commit();
                        }
                        catch (RuntimeException ex) {
                                throw convertException(ex);
                        }
                }

                @Override
                public void afterCompletion(int status) {
                        try {
                                super.afterCompletion(status);
                                if (status != STATUS_COMMITTED) {
                                        // Haven't had an afterCommit call: trigger a rollback.
                                        try {
                                                this.entityManager.getTransaction().rollback();
                                        }
                                        catch (RuntimeException ex) {
                                                throw convertException(ex);
                                        }
                                }
                        }
                        finally {
                                if (this.closeOnCompletion) {
                                        EntityManagerFactoryUtils.closeEntityManager(this.entityManager);
                                }
                        }
                }

                private RuntimeException convertException(RuntimeException ex) {
                        DataAccessException daex = (this.exceptionTranslator != null) ?
                                        this.exceptionTranslator.translateExceptionIfPossible(ex) :
                                        EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(ex);
                        return (daex != null ? daex : ex);
                }
        }

}