/*
    * 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.core.impl.resourceloader;
  
  import org.kuali.rice.core.util.ClassLoaderUtils;
  import org.kuali.rice.core.util.reflect.BaseTargetedInvocationHandler;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Proxy;
  
  /**
   * A Proxy that sets the thread Context ClassLoader before invocation of the
   * proxied object, and resets it back afterwards.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class ContextClassLoaderProxy extends BaseTargetedInvocationHandler {
  
      private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(ContextClassLoaderProxy.class);
  
      /**
       * Convenience method that wraps a specified object with a ContextClassLoaderProxy, with a specified
       * handler classloader and proxy classloader.  If the specified object is null, or the object classloader
       * equals the proxy classloader, the object is returned unwrapped.
       * @param proxiedObject the object to proxy
       * @param proxyClassLoader the classloader OF THE PROXY INSTANCE
       * @param objectClassLoader the classloader to set as the context classloader prior to any invocations on the proxiedObject
       * @return a ContextClassLoaderProxy Proxy for the proxiedObject
       */
      public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy, ClassLoader proxyClassLoader, ClassLoader objectClassLoader) {
          if (proxiedObject == null) {
          	return null;
          }
      	if (proxyClassLoader == null) {
              //proxyClassLoader = Thread.currentThread().getContextClassLoader();
          	proxyClassLoader = proxiedObject.getClass().getClassLoader();
          }
          if (objectClassLoader == null) {
              objectClassLoader = proxiedObject.getClass().getClassLoader();
          }
          if (classesToProxy == null) {
              classesToProxy = getInterfacesToProxy(proxyClassLoader, proxiedObject);
          }
          // this classloader comparison looks fishy
          // it is testing the classloader of the proxy against the intended *context* classloader of the proxiedObject
          // if these are the same the proxiedObject is not wrapped.  However, that implies that if the proxy
          // classloader may equal the intended context class loader, that the context class loader is actually not set,
          // and could theoretically NOT be the intended one in the future
          // somebody who understands this better than me should investigate this, and this method which I have
          // now applied to all prior uses of ContextClassLoaderProxy as a convenience
          //if (proxiedObject != null) { //&& !objectClassLoader.equals(proxyClassLoader)) {
          ContextClassLoaderProxy handler = new ContextClassLoaderProxy(objectClassLoader, proxiedObject);
          LOG.debug("Installed a ContextClassLoaderProxy on object: " + proxiedObject.getClass().getName());
          proxiedObject = Proxy.newProxyInstance(proxyClassLoader, classesToProxy, handler);
          //}
  
          return proxiedObject;
      }
  
      public static Object wrap(Object proxiedObject, ClassLoader proxyClassLoader, ClassLoader objectClassLoader) {
      	return wrap(proxiedObject, null, proxyClassLoader, objectClassLoader);
      }
  
      public static Object wrap(Object proxiedObject, ClassLoader classLoader) {
      	return wrap(proxiedObject, classLoader, classLoader);
      }
  
      public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy) {
      	return wrap(proxiedObject, classesToProxy, null, null);
      }
  
      public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy, ClassLoader classLoader) {
      	return wrap(proxiedObject, classesToProxy, classLoader, classLoader);
      }
  
      public static Object wrap(Object proxiedObject) {
      	return wrap(proxiedObject, null, null, null);
      }
  
      public static Class<?>[] getInterfacesToProxy(Object proxiedObject) {
  	return getInterfacesToProxy(null, proxiedObject);
      }
  
      /**
      * Determines the interfaces which need to be proxied and are visable to the given proxy ClassLoader.
      */
     public static Class<?>[] getInterfacesToProxy(ClassLoader proxyClassLoader, Object proxiedObject) {
     	return ClassLoaderUtils.getInterfacesToProxy(proxiedObject, proxyClassLoader, null);
     }
 
     private ClassLoader classLoader;
 
     public ContextClassLoaderProxy(ClassLoader classLoader, Object target) {
     	super(target);
         this.classLoader = classLoader;
     }
 
     protected Object invokeInternal(Object proxy, Method m, Object[] args) throws Throwable {
         ClassLoader oldCl = Thread.currentThread().getContextClassLoader();
         try {
             Thread.currentThread().setContextClassLoader(this.classLoader);
             return m.invoke(getTarget(), args);
         } catch (InvocationTargetException e) {
         	throw (e.getCause() != null ? e.getCause() : e);
         } finally {
             Thread.currentThread().setContextClassLoader(oldCl);
         }
     }
 }