/*

  * Copyright 2006-2011 The Kuali Foundation

  *

  * Licensed under the Educational Community 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

  *

  * http://www.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.ksb.messaging;

 import java.io.InterruptedIOException;

 import java.lang.reflect.Method;

 import java.lang.reflect.Proxy;

 import java.net.ConnectException;

 import java.net.NoRouteToHostException;

 import java.net.UnknownHostException;

 import java.util.ArrayList;

 import java.util.HashSet;

 import java.util.List;

 import java.util.Set;

 import org.apache.commons.httpclient.ConnectTimeoutException;

 import org.apache.commons.httpclient.ConnectionPoolTimeoutException;

 import org.apache.commons.httpclient.NoHttpResponseException;

 import org.apache.log4j.Logger;

 import org.kuali.rice.core.impl.resourceloader.ContextClassLoaderProxy;

 import org.kuali.rice.core.util.ClassLoaderUtils;

 import org.kuali.rice.core.util.reflect.BaseTargetedInvocationHandler;

 import org.kuali.rice.ksb.api.KsbApiServiceLocator;

 import org.kuali.rice.ksb.api.bus.Endpoint;

 import org.kuali.rice.ksb.api.bus.ServiceConfiguration;

 public class BusClientFailureProxy extends BaseTargetedInvocationHandler {

         private static final Logger LOG = Logger.getLogger(BusClientFailureProxy.class);

         private final Object failoverLock = new Object();

         private ServiceConfiguration serviceConfiguration;

         // exceptions that will cause this Proxy to remove the service from the bus

         private static List<Class<?>> serviceRemovalExceptions = new ArrayList<Class<?>>();

         private static List<Integer> serviceRemovalResponseCodes = new ArrayList<Integer>();

         static {

                 serviceRemovalExceptions.add(NoHttpResponseException.class);

                 serviceRemovalExceptions.add(InterruptedIOException.class);

                 serviceRemovalExceptions.add(UnknownHostException.class);

                 serviceRemovalExceptions.add(NoRouteToHostException.class);

                 serviceRemovalExceptions.add(ConnectTimeoutException.class);

                 serviceRemovalExceptions.add(ConnectionPoolTimeoutException.class);

                 serviceRemovalExceptions.add(ConnectException.class);

         }

         static {

             serviceRemovalResponseCodes.add(new Integer(404));

         serviceRemovalResponseCodes.add(new Integer(503));

         }

         private BusClientFailureProxy(Object target, ServiceConfiguration serviceConfiguration) {

                 super(target);

                 this.serviceConfiguration = serviceConfiguration;

         }

         public static Object wrap(Object target, ServiceConfiguration serviceConfiguration) {

                 return Proxy.newProxyInstance(ClassLoaderUtils.getDefaultClassLoader(), ContextClassLoaderProxy.getInterfacesToProxy(target), new BusClientFailureProxy(target, serviceConfiguration));

         }

         protected Object invokeInternal(Object proxyObject, Method method, Object[] params) throws Throwable {

                 Set<ServiceConfiguration> servicesTried = null;

                 do {

                         try {

                                 return method.invoke(getTarget(), params);

                         } catch (Throwable throwable) {                        

                                 if (isServiceRemovalException(throwable)) {

                                         synchronized (failoverLock) {

                                                 LOG.error("Exception caught accessing remote service " + this.serviceConfiguration.getServiceName(), throwable);

                                                 if (servicesTried == null) {

                                                         servicesTried = new HashSet<ServiceConfiguration>();

                                                         servicesTried.add(serviceConfiguration);

                                                 }

                                                 Object failoverService = null;

                                                 List<Endpoint> endpoints = KsbApiServiceLocator.getServiceBus().getEndpoints(serviceConfiguration.getServiceName());

                                                 for (Endpoint endpoint : endpoints) {

                                                         if (!servicesTried.contains(endpoint.getServiceConfiguration())) {

                                                                 failoverService = endpoint.getService();

                                                                 servicesTried.add(endpoint.getServiceConfiguration());

                                                         }

                                                 }                                                                        

                                                 if (failoverService != null) {

                                                         LOG.info("Refetched replacement service for service " + this.serviceConfiguration.getServiceName());

                                                         // as per KULRICE-4287, reassign target to the new service we just fetched, hopefully this one works better!

                                                         setTarget(failoverService);

                                                 } else {

                                                         LOG.error("Didn't find replacement service throwing exception");

                                                         throw throwable;                                        

                                                 }

                                         }

                                 } else {

                                         throw throwable;

                                 }

                         }

                 } while (true);

         }

         private static boolean isServiceRemovalException(Throwable throwable) {

                 LOG.info("Checking for Service Removal Exception: " + throwable.getClass().getName());

                 if (serviceRemovalExceptions.contains(throwable.getClass())) {

                         LOG.info("Found a Service Removal Exception: " + throwable.getClass().getName());

                         return true;

                 } else if (throwable instanceof HttpException) {

                         HttpException httpException = (HttpException)throwable;

                         if (serviceRemovalResponseCodes.contains(httpException.getResponseCode())) {

                                 LOG.info("Found a Service Removal Exception because of a " + httpException.getResponseCode() + " " + throwable.getClass().getName());

                                 return true;

                         }

                 }

                 if (throwable.getCause() != null) {

                         LOG.info("Unwrapping Throwable cause to check for service removal exception from: " + throwable.getClass().getName());

                         return isServiceRemovalException(throwable.getCause());

                 }

                 return false;

         }

 }