//
   //  ========================================================================
   //  Copyright (c) 1995-2013 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.jndi;
  
  
  import java.io.IOException;
  import java.util.Hashtable;
  import java.util.Map;
  import java.util.WeakHashMap;
  
  import javax.naming.Context;
  import javax.naming.Name;
  import javax.naming.NameParser;
  import javax.naming.Reference;
  import javax.naming.StringRefAddr;
  import javax.naming.spi.ObjectFactory;
  
  import org.eclipse.jetty.server.handler.ContextHandler;
  import org.eclipse.jetty.util.log.Logger;
  
  
  
  /**
   * ContextFactory.java
   *
   * This is an object factory that produces a jndi naming
   * context based on a classloader.
   *
   *  It is used for the java:comp context.
   *
   *  This object factory is bound at java:comp. When a
   *  lookup arrives for java:comp,  this object factory
   *  is invoked and will return a context specific to
   *  the caller's environment (so producing the java:comp/env
   *  specific to a webapp).
   *
   *  The context selected is based on classloaders. First
   *  we try looking at the thread context classloader if it is set, and walk its
   *  hierarchy, creating a context if none is found. If the thread context classloader
   *  is not set, then we use the classloader associated with the current Context.
   *  
   *  If there is no current context, or no classloader, we return null.
   *
   * Created: Fri Jun 27 09:26:40 2003
   *
   *
   *
   */
  public class ContextFactory implements ObjectFactory
  {
      private static Logger __log = NamingUtil.__log;
  
      /**
       * Map of classloaders to contexts.
       */
      private static final WeakHashMap __contextMap = new WeakHashMap();
  
      /**
       * Threadlocal for injecting a context to use
       * instead of looking up the map.
       */
      private static final ThreadLocal<Context> __threadContext = new ThreadLocal<Context>();
      
      /**
       * Threadlocal for setting a classloader which must be used 
       * when finding the comp context.
       */
      private static final ThreadLocal<ClassLoader> __threadClassLoader = new ThreadLocal<ClassLoader>();
      
  
  
      /**
       * Find or create a context which pertains to a classloader.
       *
       * If the thread context classloader is set, we try to find an already-created naming context
       * for it. If one does not exist, we walk its classloader hierarchy until one is found, or we 
       * run out of parent classloaders. In the latter case, we will create a new naming context associated
       * with the original thread context classloader.
       * 
       * If the thread context classloader is not set, we obtain the classloader from the current 
       * jetty Context, and look for an already-created naming context. 
       * 
       * If there is no current jetty Context, or it has no associated classloader, we 
      * return null.
      * @see javax.naming.spi.ObjectFactory#getObjectInstance(java.lang.Object, javax.naming.Name, javax.naming.Context, java.util.Hashtable)
      */
     public Object getObjectInstance (Object obj,
                                      Name name,
                                      Context nameCtx,
                                      Hashtable env)
         throws Exception
     {
         //First, see if we have had a context injected into us to use.
         Context ctx = (Context)__threadContext.get();
         if (ctx != null)
         {
             if(__log.isDebugEnabled()) __log.debug("Using the Context that is bound on the thread");
             return ctx;
         }
 
         //See if there is a classloader to use for finding the comp context
         //Don't use its parent hierarchy if set.
         ClassLoader loader = (ClassLoader)__threadClassLoader.get();
         if (loader != null)
         {
             if (__log.isDebugEnabled() && loader != null) __log.debug("Using threadlocal classloader");
             ctx = getContextForClassLoader(loader);
             if (ctx == null)
             {
                 ctx = newNamingContext(obj, loader, env, name, nameCtx);
                 __contextMap.put (loader, ctx);
                 if(__log.isDebugEnabled())__log.debug("Made context "+name.get(0)+" for classloader: "+loader);
             }
             return ctx;
         }
        
         //If the thread context classloader is set, then try its hierarchy to find a matching context
         ClassLoader tccl = Thread.currentThread().getContextClassLoader();
         loader = tccl;      
         if (loader != null)
         {
             if (__log.isDebugEnabled() && loader != null) __log.debug("Trying thread context classloader");
             while (ctx == null && loader != null)
             {
                 ctx = getContextForClassLoader(loader);
                 if (ctx == null && loader != null)
                     loader = loader.getParent();
             }
 
             if (ctx == null)
             {
                 ctx = newNamingContext(obj, tccl, env, name, nameCtx);
                 __contextMap.put (tccl, ctx);
                 if(__log.isDebugEnabled())__log.debug("Made context "+name.get(0)+" for classloader: "+tccl);
             }
             return ctx;
         }
 
 
         //If trying thread context classloader hierarchy failed, try the
         //classloader associated with the current context
         if (ContextHandler.getCurrentContext() != null)
         {
             
             if (__log.isDebugEnabled() && loader != null) __log.debug("Trying classloader of current org.eclipse.jetty.server.handler.ContextHandler");
             loader = ContextHandler.getCurrentContext().getContextHandler().getClassLoader();
             ctx = (Context)__contextMap.get(loader);    
 
             if (ctx == null && loader != null)
             {
                 ctx = newNamingContext(obj, loader, env, name, nameCtx);
                 __contextMap.put (loader, ctx);
                 if(__log.isDebugEnabled())__log.debug("Made context "+name.get(0)+" for classloader: "+loader);
             }
 
             return ctx;
         }
         return null;
     }
 
 
     /**
      * Create a new NamingContext.
      * @param obj
      * @param loader
      * @param env
      * @param name
      * @param parentCtx
      * @return
      * @throws Exception
      */
     public NamingContext newNamingContext(Object obj, ClassLoader loader, Hashtable env, Name name, Context parentCtx)
     throws Exception
     {
         Reference ref = (Reference)obj;
         StringRefAddr parserAddr = (StringRefAddr)ref.get("parser");
         String parserClassName = (parserAddr==null?null:(String)parserAddr.getContent());
         NameParser parser = (NameParser)(parserClassName==null?null:loader.loadClass(parserClassName).newInstance());
 
         return new NamingContext (env,
                                   name.get(0),
                                   (NamingContext)parentCtx,
                                   parser);
     }
 
   
     /**
      * Find the naming Context for the given classloader
      * @param loader
      * @return
      */
     public Context getContextForClassLoader(ClassLoader loader)
     {
         if (loader == null)
             return null;
         
         return (Context)__contextMap.get(loader);
     }
 
 
     /**
      * Associate the given Context with the current thread.
      * disassociate method should be called to reset the context.
      * @param ctx the context to associate to the current thread.
      * @return the previous context associated on the thread (can be null)
      */
     public static Context associateContext(final Context ctx)
     {
         Context previous = (Context)__threadContext.get();
         __threadContext.set(ctx);
         return previous;
     }
 
     public static void disassociateContext(final Context ctx)
     {
         __threadContext.remove();
     }
     
     
     public static ClassLoader associateClassLoader(final ClassLoader loader)
     {
         ClassLoader prev = (ClassLoader)__threadClassLoader.get();
         __threadClassLoader.set(loader);
         return prev;
     }
     
     
     public static void disassociateClassLoader ()
     {
         __threadClassLoader.remove();
     }
 
     public static void dump(Appendable out, String indent) throws IOException
     {
         out.append("o.e.j.jndi.ContextFactory@").append(Long.toHexString(__contextMap.hashCode())).append("\n");
         int size=__contextMap.size();
         int i=0;
         for (Map.Entry<ClassLoader,NamingContext> entry : ((Map<ClassLoader,NamingContext>)__contextMap).entrySet())
         {
             boolean last=++i==size;
             ClassLoader loader=entry.getKey();
             out.append(indent).append(" +- ").append(loader.getClass().getSimpleName()).append("@").append(Long.toHexString(loader.hashCode())).append(": ");
 
             NamingContext context = entry.getValue();
             context.dump(out,indent+(last?"    ":" |  "));
         }
     }
 
 }