/*
 * Copyright 2002-2012 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.jca.cci.connection;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import javax.resource.NotSupportedException;
import javax.resource.ResourceException;
import javax.resource.cci.Connection;
import javax.resource.cci.ConnectionFactory;
import javax.resource.cci.ConnectionSpec;

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

import org.springframework.beans.factory.DisposableBean;
import org.springframework.util.Assert;

/**
 * A CCI ConnectionFactory adapter that returns the same Connection on all
 * {@code getConnection} calls, and ignores calls to
 * {@code Connection.close()}.
 *
 * <p>Useful for testing and standalone environments, to keep using the same
 * Connection for multiple CciTemplate calls, without having a pooling
 * ConnectionFactory, also spanning any number of transactions.
 *
 * <p>You can either pass in a CCI Connection directly, or let this
 * factory lazily create a Connection via a given target ConnectionFactory.
 *
 * @author Juergen Hoeller
 * @since 1.2
 * @see #getConnection()
 * @see javax.resource.cci.Connection#close()
 * @see org.springframework.jca.cci.core.CciTemplate
 */
@SuppressWarnings("serial")
public class SingleConnectionFactory extends DelegatingConnectionFactory implements DisposableBean {

        protected final Log logger = LogFactory.getLog(getClass());

        /** Wrapped Connection */
        private Connection target;

        /** Proxy Connection */
        private Connection connection;

        /** Synchronization monitor for the shared Connection */
        private final Object connectionMonitor = new Object();


        /**
         * Create a new SingleConnectionFactory for bean-style usage.
         * @see #setTargetConnectionFactory
         */
        public SingleConnectionFactory() {
        }

        /**
         * Create a new SingleConnectionFactory that always returns the
         * given Connection.
         * @param target the single Connection
         */
        public SingleConnectionFactory(Connection target) {
                Assert.notNull(target, "Target Connection must not be null");
                this.target = target;
                this.connection = getCloseSuppressingConnectionProxy(target);
        }

        /**
         * Create a new SingleConnectionFactory that always returns a single
         * Connection which it will lazily create via the given target
         * ConnectionFactory.
         * @param targetConnectionFactory the target ConnectionFactory
         */
        public SingleConnectionFactory(ConnectionFactory targetConnectionFactory) {
                Assert.notNull(targetConnectionFactory, "Target ConnectionFactory must not be null");
                setTargetConnectionFactory(targetConnectionFactory);
        }


        /**
         * Make sure a Connection or ConnectionFactory has been set.
         */
        @Override
        public void afterPropertiesSet() {
                if (this.connection == null && getTargetConnectionFactory() == null) {
                        throw new IllegalArgumentException("Connection or 'targetConnectionFactory' is required");
                }
        }


        @Override
        public Connection getConnection() throws ResourceException {
                synchronized (this.connectionMonitor) {
                        if (this.connection == null) {
                                initConnection();
                        }
                        return this.connection;
                }
        }

        @Override
        public Connection getConnection(ConnectionSpec connectionSpec) throws ResourceException {
                throw new NotSupportedException(
                                "SingleConnectionFactory does not support custom ConnectionSpec");
        }

        /**
         * Close the underlying Connection.
         * The provider of this ConnectionFactory needs to care for proper shutdown.
         * <p>As this bean implements DisposableBean, a bean factory will
         * automatically invoke this on destruction of its cached singletons.
         */
        @Override
        public void destroy() {
                resetConnection();
        }


        /**
         * Initialize the single underlying Connection.
         * <p>Closes and reinitializes the Connection if an underlying
         * Connection is present already.
         * @throws javax.resource.ResourceException if thrown by CCI API methods
         */
        public void initConnection() throws ResourceException {
                if (getTargetConnectionFactory() == null) {
                        throw new IllegalStateException(
                                        "'targetConnectionFactory' is required for lazily initializing a Connection");
                }
                synchronized (this.connectionMonitor) {
                        if (this.target != null) {
                                closeConnection(this.target);
                        }
                        this.target = doCreateConnection();
                        prepareConnection(this.target);
                        if (logger.isInfoEnabled()) {
                                logger.info("Established shared CCI Connection: " + this.target);
                        }
                        this.connection = getCloseSuppressingConnectionProxy(this.target);
                }
        }

        /**
         * Reset the underlying shared Connection, to be reinitialized on next access.
         */
        public void resetConnection() {
                synchronized (this.connectionMonitor) {
                        if (this.target != null) {
                                closeConnection(this.target);
                        }
                        this.target = null;
                        this.connection = null;
                }
        }

        /**
         * Create a CCI Connection via this template's ConnectionFactory.
         * @return the new CCI Connection
         * @throws javax.resource.ResourceException if thrown by CCI API methods
         */
        protected Connection doCreateConnection() throws ResourceException {
                return getTargetConnectionFactory().getConnection();
        }

        /**
         * Prepare the given Connection before it is exposed.
         * <p>The default implementation is empty. Can be overridden in subclasses.
         * @param con the Connection to prepare
         */
        protected void prepareConnection(Connection con) throws ResourceException {
        }

        /**
         * Close the given Connection.
         * @param con the Connection to close
         */
        protected void closeConnection(Connection con) {
                try {
                        con.close();
                }
                catch (Throwable ex) {
                        logger.warn("Could not close shared CCI Connection", ex);
                }
        }

        /**
         * Wrap the given Connection with a proxy that delegates every method call to it
         * but suppresses close calls. This is useful for allowing application code to
         * handle a special framework Connection just like an ordinary Connection from a
         * CCI ConnectionFactory.
         * @param target the original Connection to wrap
         * @return the wrapped Connection
         */
        protected Connection getCloseSuppressingConnectionProxy(Connection target) {
                return (Connection) Proxy.newProxyInstance(
                                Connection.class.getClassLoader(),
                                new Class<?>[] {Connection.class},
                                new CloseSuppressingInvocationHandler(target));
        }


        /**
         * Invocation handler that suppresses close calls on CCI Connections.
         */
        private static class CloseSuppressingInvocationHandler implements InvocationHandler {

                private final Connection target;

                private CloseSuppressingInvocationHandler(Connection target) {
                        this.target = target;
                }

                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        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 Connection proxy.
                                return System.identityHashCode(proxy);
                        }
                        else if (method.getName().equals("close")) {
                                // Handle close method: don't pass the call on.
                                return null;
                        }
                        try {
                                return method.invoke(this.target, args);
                        }
                        catch (InvocationTargetException ex) {
                                throw ex.getTargetException();
                        }
                }
        }

}