/*
 * Copyright 2002-2013 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.jdo;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import javax.jdo.PersistenceManager;
import javax.jdo.PersistenceManagerFactory;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * Proxy for a target JDO {@link javax.jdo.PersistenceManagerFactory},
 * returning the current thread-bound PersistenceManager (the Spring-managed
 * transactional PersistenceManager or the single OpenPersistenceManagerInView
 * PersistenceManager) on {@code getPersistenceManager()}, if any.
 *
 * <p>Essentially, {@code getPersistenceManager()} calls get seamlessly
 * forwarded to {@link PersistenceManagerFactoryUtils#getPersistenceManager}.
 * Furthermore, {@code PersistenceManager.close} calls get forwarded to
 * {@link PersistenceManagerFactoryUtils#releasePersistenceManager}.
 *
 * <p>The main advantage of this proxy is that it allows DAOs to work with a
 * plain JDO PersistenceManagerFactory reference, while still participating in
 * Spring's (or a J2EE server's) resource and transaction management. DAOs will
 * only rely on the JDO API in such a scenario, without any Spring dependencies.
 *
 * <p>Note that the behavior of this proxy matches the behavior that the JDO spec
 * defines for a PersistenceManagerFactory as exposed by a JCA connector, when
 * deployed in a J2EE server. Hence, DAOs could seamlessly switch between a JNDI
 * PersistenceManagerFactory and this proxy for a local PersistenceManagerFactory,
 * receiving the reference through Dependency Injection. This will work without
 * any Spring API dependencies in the DAO code!
 *
 * <p>Of course, you can still access the target PersistenceManagerFactory
 * even when your DAOs go through this proxy, by defining a bean reference
 * that points directly at your target PersistenceManagerFactory bean.
 *
 * @author Juergen Hoeller
 * @since 1.2
 * @see javax.jdo.PersistenceManagerFactory#getPersistenceManager()
 * @see javax.jdo.PersistenceManager#close()
 * @see PersistenceManagerFactoryUtils#getPersistenceManager
 * @see PersistenceManagerFactoryUtils#releasePersistenceManager
 */
public class TransactionAwarePersistenceManagerFactoryProxy implements FactoryBean<PersistenceManagerFactory> {

        private PersistenceManagerFactory target;

        private boolean allowCreate = true;

        private PersistenceManagerFactory proxy;


        /**
         * Set the target JDO PersistenceManagerFactory that this proxy should
         * delegate to. This should be the raw PersistenceManagerFactory, as
         * accessed by JdoTransactionManager.
         * @see org.springframework.orm.jdo.JdoTransactionManager
         */
        public void setTargetPersistenceManagerFactory(PersistenceManagerFactory target) {
                Assert.notNull(target, "Target PersistenceManagerFactory must not be null");
                this.target = target;
                Class<?>[] ifcs = ClassUtils.getAllInterfacesForClass(target.getClass(), target.getClass().getClassLoader());
                this.proxy = (PersistenceManagerFactory) Proxy.newProxyInstance(
                                target.getClass().getClassLoader(), ifcs, new PersistenceManagerFactoryInvocationHandler());
        }

        /**
         * Return the target JDO PersistenceManagerFactory that this proxy delegates to.
         */
        public PersistenceManagerFactory getTargetPersistenceManagerFactory() {
                return this.target;
        }

        /**
         * Set whether the PersistenceManagerFactory proxy is allowed to create
         * a non-transactional PersistenceManager when no transactional
         * PersistenceManager can be found for the current thread.
         * <p>Default is "true". Can be turned off to enforce access to
         * transactional PersistenceManagers, which safely allows for DAOs
         * written to get a PersistenceManager without explicit closing
         * (i.e. a {@code PersistenceManagerFactory.getPersistenceManager()}
         * call without corresponding {@code PersistenceManager.close()} call).
         * @see PersistenceManagerFactoryUtils#getPersistenceManager(javax.jdo.PersistenceManagerFactory, boolean)
         */
        public void setAllowCreate(boolean allowCreate) {
                this.allowCreate = allowCreate;
        }

        /**
         * Return whether the PersistenceManagerFactory proxy is allowed to create
         * a non-transactional PersistenceManager when no transactional
         * PersistenceManager can be found for the current thread.
         */
        protected boolean isAllowCreate() {
                return this.allowCreate;
        }


        @Override
        public PersistenceManagerFactory getObject() {
                return this.proxy;
        }

        @Override
        public Class<? extends PersistenceManagerFactory> getObjectType() {
                return PersistenceManagerFactory.class;
        }

        @Override
        public boolean isSingleton() {
                return true;
        }


        /**
         * Invocation handler that delegates getPersistenceManager calls on the
         * PersistenceManagerFactory proxy to PersistenceManagerFactoryUtils
         * for being aware of thread-bound transactions.
         */
        private class PersistenceManagerFactoryInvocationHandler implements InvocationHandler {

                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        // Invocation on PersistenceManagerFactory 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 PersistenceManagerFactory proxy.
                                return System.identityHashCode(proxy);
                        }
                        else if (method.getName().equals("getPersistenceManager")) {
                                PersistenceManagerFactory target = getTargetPersistenceManagerFactory();
                                PersistenceManager pm =
                                                PersistenceManagerFactoryUtils.doGetPersistenceManager(target, isAllowCreate());
                                Class<?>[] ifcs = ClassUtils.getAllInterfacesForClass(pm.getClass(), pm.getClass().getClassLoader());
                                return Proxy.newProxyInstance(
                                                pm.getClass().getClassLoader(), ifcs, new PersistenceManagerInvocationHandler(pm, target));
                        }

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


        /**
         * Invocation handler that delegates close calls on PersistenceManagers to
         * PersistenceManagerFactoryUtils for being aware of thread-bound transactions.
         */
        private static class PersistenceManagerInvocationHandler implements InvocationHandler {

                private final PersistenceManager target;

                private final PersistenceManagerFactory persistenceManagerFactory;

                public PersistenceManagerInvocationHandler(PersistenceManager target, PersistenceManagerFactory pmf) {
                        this.target = target;
                        this.persistenceManagerFactory = pmf;
                }

                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        // Invocation on PersistenceManager 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 PersistenceManager proxy.
                                return System.identityHashCode(proxy);
                        }
                        else if (method.getName().equals("close")) {
                                // Handle close method: only close if not within a transaction.
                                PersistenceManagerFactoryUtils.doReleasePersistenceManager(
                                                this.target, this.persistenceManagerFactory);
                                return null;
                        }

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

}