/*
    * Copyright 2012 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.student.common.spring;
  
  import java.io.Externalizable;
  import java.io.IOException;
  import java.io.ObjectInput;
  import java.io.ObjectOutput;
  import java.io.Serializable;
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.Method;
  
  import javax.xml.namespace.QName;
  
  import org.kuali.rice.core.api.resourceloader.GlobalResourceLoader;
  import org.springframework.util.ReflectionUtils;
  
  /**
   * 
   * A Serializable Proxy Invokation Handler.  This handler is serializable and knows how to look up the service using the GlobalResourceLocator.
   * 
   * @author Kuali Student Team
   * 
   */
  public class SerializableProxyInvokationHandler implements InvocationHandler, Externalizable {
  
  	/**
  	 * 
  	 */
  	private static final long serialVersionUID = 1L;
  
  	private transient Object serviceDelegate;
  
  	private QName serviceName;
  
  	/**
  	 * 
  	 */
  	public SerializableProxyInvokationHandler() {
  	}
  
  	
  	/**
  	 * @param serviceName the serviceName to set
  	 */
  	public void setServiceName(QName serviceName) {
  		this.serviceName = serviceName;
  	}
  
  
  	/*
  	 * (non-Javadoc)
  	 * 
  	 * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object,
  	 * java.lang.reflect.Method, java.lang.Object[])
  	 */
  	@Override
  	public Object invoke(Object proxy, Method method, Object[] args)
  			throws Throwable {
  
  		if (serviceDelegate == null) {
  			// first time or just after reserialization.
  			try {
  	            serviceDelegate = GlobalResourceLoader.getService(serviceName);
              } catch (Exception e) {
              	
              	if (method.getName().equals("toString")) {
              		// fake toString
              		// spring has an assertion that expects this to work so we will just fake it
              		// once the delegate is resolved the normal toString method will be used.
              		return getClass().getName() + " (serviceName=" + serviceName + ")";
              	}
              	else
              		throw e;
              }
  		}
  
  		// delegate the call to the actual service to fulfill.
  		return ReflectionUtils.invokeMethod(method, serviceDelegate, args);
  	}
  
  	/* (non-Javadoc)
  	 * @see java.io.Externalizable#writeExternal(java.io.ObjectOutput)
  	 */
  	@Override
  	public void writeExternal(ObjectOutput out) throws IOException {
 		
 		QName name = new QName(serviceName.getNamespaceURI(), serviceName.getLocalPart());
 		
 		out.writeObject(name);
 		
 	}
 
 	/* (non-Javadoc)
 	 * @see java.io.Externalizable#readExternal(java.io.ObjectInput)
 	 */
 	@Override
 	public void readExternal(ObjectInput in) throws IOException,
 			ClassNotFoundException {
 		
 		QName name = (QName) in.readObject();
 	
 		this.serviceName = new QName (name.getNamespaceURI(), name.getLocalPart());
 		
 	}
 	
 	
 
 }