// ========================================================================
   // Copyright (c) 1996-2009 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.servlet;
  
  import java.io.IOException;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  
  import org.eclipse.jetty.servlet.api.Registration;
  import javax.servlet.ServletContext;
  import javax.servlet.UnavailableException;
  
  import org.eclipse.jetty.server.handler.ContextHandler;
  import org.eclipse.jetty.util.Loader;
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  import org.eclipse.jetty.util.component.AggregateLifeCycle;
  import org.eclipse.jetty.util.component.Dumpable;
  import org.eclipse.jetty.util.log.Log;
  
  
  /* --------------------------------------------------------------------- */
  /** 
   * 
   */
  public class Holder<T> extends AbstractLifeCycle implements Dumpable
  {
      protected transient Class<? extends T> _class;
      protected final Map<String,String> _initParams=new HashMap<String,String>(3);
      protected String _className;
      protected String _displayName;
      protected boolean _extInstance;
      protected boolean _asyncSupported=true;
  
      /* ---------------------------------------------------------------- */
      protected String _name;
      protected ServletHandler _servletHandler;
  
      /* ---------------------------------------------------------------- */
      protected Holder()
      {
      }
  
      /* ------------------------------------------------------------ */
      /**
       * @return True if this holder was created for a specific instance.
       */
      public boolean isInstance()
      {
          return _extInstance;
      }
      
      /* ------------------------------------------------------------ */
      @SuppressWarnings("unchecked")
      public void doStart()
          throws Exception
      {
          //if no class already loaded and no classname, make servlet permanently unavailable
          if (_class==null && (_className==null || _className.equals("")))
              throw new UnavailableException("No class for Servlet or Filter", -1);
          
          //try to load class
          if (_class==null)
          {
              try
              {
                  _class=Loader.loadClass(Holder.class, _className);
                  if(Log.isDebugEnabled())Log.debug("Holding {}",_class);
              }
              catch (Exception e)
              {
                  Log.warn(e);
                  throw new UnavailableException(e.getMessage(), -1);
              }
          }
      }
      
      /* ------------------------------------------------------------ */
      @Override
      public void doStop()
          throws Exception
      {
          if (!_extInstance)
              _class=null;
      }
     
     /* ------------------------------------------------------------ */
     public String getClassName()
     {
         return _className;
     }
     
     /* ------------------------------------------------------------ */
     public Class<? extends T> getHeldClass()
     {
         return _class;
     }
     
     /* ------------------------------------------------------------ */
     public String getDisplayName()
     {
         return _displayName;
     }
 
     /* ---------------------------------------------------------------- */
     public String getInitParameter(String param)
     {
         if (_initParams==null)
             return null;
         return (String)_initParams.get(param);
     }
     
     /* ------------------------------------------------------------ */
     public Enumeration getInitParameterNames()
     {
         if (_initParams==null)
             return Collections.enumeration(Collections.EMPTY_LIST);
         return Collections.enumeration(_initParams.keySet());
     }
 
     /* ---------------------------------------------------------------- */
     public Map<String,String> getInitParameters()
     {
         return _initParams;
     }
     
     /* ------------------------------------------------------------ */
     public String getName()
     {
         return _name;
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @return Returns the servletHandler.
      */
     public ServletHandler getServletHandler()
     {
         return _servletHandler;
     }
     
     /* ------------------------------------------------------------ */
     public void destroyInstance(Object instance)
     throws Exception
     {
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @param className The className to set.
      */
     public void setClassName(String className)
     {
         _className = className;
         _class=null;
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @param held The class to hold
      */
     public void setHeldClass(Class<? extends T> held)
     {
         _class=held;
         if (held!=null)
         {
             _className=held.getName();
             if (_name==null)
                 _name=held.getName()+"-"+this.hashCode();
         }
     }
     
     /* ------------------------------------------------------------ */
     public void setDisplayName(String name)
     {
         _displayName=name;
     }
     
     /* ------------------------------------------------------------ */
     public void setInitParameter(String param,String value)
     {
         _initParams.put(param,value);
     }
     
     /* ---------------------------------------------------------------- */
     public void setInitParameters(Map<String,String> map)
     {
         _initParams.clear();
         _initParams.putAll(map);
     }
     
     /* ------------------------------------------------------------ */
     /**
      * The name is a primary key for the held object.
      * Ensure that the name is set BEFORE adding a Holder
      * (eg ServletHolder or FilterHolder) to a ServletHandler.
      * @param name The name to set.
      */
     public void setName(String name)
     {
         _name = name;
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @param servletHandler The {@link ServletHandler} that will handle requests dispatched to this servlet.
      */
     public void setServletHandler(ServletHandler servletHandler)
     {
         _servletHandler = servletHandler;
     }
 
     /* ------------------------------------------------------------ */
     public void setAsyncSupported(boolean suspendable)
     {
         _asyncSupported=suspendable;
     }
 
     /* ------------------------------------------------------------ */
     public boolean isAsyncSupported()
     {
         return _asyncSupported;
     }
     
     /* ------------------------------------------------------------ */
     public String toString()
     {
         return _name;
     }
 
     /* ------------------------------------------------------------ */
     protected void illegalStateIfContextStarted()
     {
         if (_servletHandler!=null)
         {
             ContextHandler.Context context=(ContextHandler.Context)_servletHandler.getServletContext();
             if (context!=null && context.getContextHandler().isStarted())
                 throw new IllegalStateException("Started");
         }
     }
 
     /* ------------------------------------------------------------ */
     public void dump(Appendable out, String indent) throws IOException
     {
         out.append(_name).append("==").append(_className).append("\n");
         AggregateLifeCycle.dump(out,indent,_initParams.entrySet());
     }
 
     /* ------------------------------------------------------------ */
     public String dump()
     {
         return AggregateLifeCycle.dump(this);
     }    
     
     /* ------------------------------------------------------------ */
     /* ------------------------------------------------------------ */
     /* ------------------------------------------------------------ */
     protected class HolderConfig 
     {   
         
         /* -------------------------------------------------------- */
         public ServletContext getServletContext()
         {
             return _servletHandler.getServletContext();
         }
 
         /* -------------------------------------------------------- */
         public String getInitParameter(String param)
         {
             return Holder.this.getInitParameter(param);
         }
     
         /* -------------------------------------------------------- */
         public Enumeration getInitParameterNames()
         {
             return Holder.this.getInitParameterNames();
         }
     }
 
     /* -------------------------------------------------------- */
     /* -------------------------------------------------------- */
     /* -------------------------------------------------------- */
     protected class HolderRegistration implements Registration.Dynamic
     {
         public void setAsyncSupported(boolean isAsyncSupported)
         {
             illegalStateIfContextStarted();
             Holder.this.setAsyncSupported(isAsyncSupported);
         }
 
         public void setDescription(String description)
         {
             if (Log.isDebugEnabled())
                 Log.debug(this+" is "+description);
         }
 
         public String getClassName()
         {
             return Holder.this.getClassName();
         }
 
         public String getInitParameter(String name)
         {
             return Holder.this.getInitParameter(name);
         }
 
         public Map<String, String> getInitParameters()
         {
             return Holder.this.getInitParameters();
         }
 
         public String getName()
         {
             return Holder.this.getName();
         }
 
         public boolean setInitParameter(String name, String value)
         {
             illegalStateIfContextStarted();
             if (Holder.this.getInitParameter(name)!=null)
                 return false;
             Holder.this.setInitParameter(name,value);
             return true;
         }
 
         public Set<String> setInitParameters(Map<String, String> initParameters)
         {
             illegalStateIfContextStarted();
             Set<String> clash=null;
             for (String name : initParameters.keySet())
             {
                 if (Holder.this.getInitParameter(name)!=null)
                 {
                     if (clash==null)
                         clash=new HashSet<String>();
                     clash.add(name);
                 }
             }
             if (clash!=null)
                 return clash;
             Holder.this.setInitParameters(initParameters);
             return Collections.emptySet();
         }; 
     }
 }