//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.server.handler;
  
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.List;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.eclipse.jetty.http.HttpStatus;
  import org.eclipse.jetty.server.Handler;
  import org.eclipse.jetty.server.HandlerContainer;
  import org.eclipse.jetty.server.Request;
  import org.eclipse.jetty.server.Server;
  import org.eclipse.jetty.util.annotation.ManagedAttribute;
  import org.eclipse.jetty.util.annotation.ManagedObject;
  import org.eclipse.jetty.util.component.LifeCycle;
  
  /* ------------------------------------------------------------ */
  /** A <code>HandlerWrapper</code> acts as a {@link Handler} but delegates the {@link Handler#handle handle} method and
   * {@link LifeCycle life cycle} events to a delegate. This is primarily used to implement the <i>Decorator</i> pattern.
   *
   */
  @ManagedObject("Handler wrapping another Handler")
  public class HandlerWrapper extends AbstractHandlerContainer
  {
      protected Handler _handler;
  
      /* ------------------------------------------------------------ */
      /**
       *
       */
      public HandlerWrapper()
      {
      }
  
      /* ------------------------------------------------------------ */
      /**
       * @return Returns the handlers.
       */
      @ManagedAttribute(value="Wrapped Handler", readonly=true)
      public Handler getHandler()
      {
          return _handler;
      }
  
      /* ------------------------------------------------------------ */
      /**
       * @return Returns the handlers.
       */
      @Override
      public Handler[] getHandlers()
      {
          if (_handler==null)
              return new Handler[0];
          return new Handler[] {_handler};
      }
  
      /* ------------------------------------------------------------ */
      /**
       * @param handler Set the {@link Handler} which should be wrapped.
       */
      public void setHandler(Handler handler)
      {
          if (isStarted())
              throw new IllegalStateException(STARTED);
  
          // check for loops
          if (handler==this || (handler instanceof HandlerContainer &&
              Arrays.asList(((HandlerContainer)handler).getChildHandlers()).contains(this)))
              throw new IllegalStateException("setHandler loop");
          
          if (handler!=null)
              handler.setServer(getServer());
          
          Handler old=_handler;
          _handler=handler;
          updateBean(old,_handler,true);
      }
  
     /* ------------------------------------------------------------ */
     /** 
      * Replace the current handler with another HandlerWrapper
      * linked to the current handler.  
      * <p>
      * This is equivalent to:
      * <pre>
      *   wrapper.setHandler(getHandler());
      *   setHandler(wrapper);
      * </pre>
      * @param wrapper the wrapper to insert
      */
     public void insertHandler(HandlerWrapper wrapper)
     {
         if (wrapper==null)
             throw new IllegalArgumentException();
         
         HandlerWrapper tail = wrapper;
         while(tail.getHandler() instanceof HandlerWrapper)
             tail=(HandlerWrapper)tail.getHandler();
         if (tail.getHandler()!=null)
             throw new IllegalArgumentException("bad tail of inserted wrapper chain");
         
         Handler next=getHandler();
         setHandler(wrapper);
         tail.setHandler(next);
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
     {
         Handler handler=_handler;
         if (handler!=null)
             handler.handle(target,baseRequest, request, response);
     }
 
     /* ------------------------------------------------------------ */
     @Override
     protected void expandChildren(List<Handler> list, Class<?> byClass)
     {
         expandHandler(_handler,list,byClass);
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void destroy()
     {
         if (!isStopped())
             throw new IllegalStateException("!STOPPED");
         Handler child=getHandler();
         if (child!=null)
         {
             setHandler(null);
             child.destroy();
         }
         super.destroy();
     }
 
 }