package org.apache.velocity.context;

/*
 * Copyright 2001,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
 * 
 * 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.
 */

import org.apache.velocity.util.introspection.IntrospectionCacheData;

import org.apache.velocity.app.event.EventCartridge;

import org.apache.velocity.runtime.resource.Resource;

/**
 *  This adapter class is the container for all context types for internal
 *  use.  The AST now uses this class rather than the app-level Context
 *  interface to allow flexibility in the future.
 *
 *  Currently, we have two context interfaces which must be supported :
 *  <ul>
 *  <li> Context : used for application/template data access
 *  <li> InternalHousekeepingContext : used for internal housekeeping and caching
 *  <li> InternalWrapperContext : used for getting root cache context and other
 *       such.
 *  <li> InternalEventContext : for event handling.
 *  </ul>
 *
 *  This class implements the two interfaces to ensure that all methods are 
 *  supported.  When adding to the interfaces, or adding more context 
 *  functionality, the interface is the primary definition, so alter that first
 *  and then all classes as necessary.  As of this writing, this would be 
 *  the only class affected by changes to InternalContext
 *
 *  This class ensures that an InternalContextBase is available for internal
 *  use.  If an application constructs their own Context-implementing
 *  object w/o subclassing AbstractContext, it may be that support for
 *  InternalContext is not available.  Therefore, InternalContextAdapter will
 *  create an InternalContextBase if necessary for this support.  Note that 
 *  if this is necessary, internal information such as node-cache data will be
 *  lost from use to use of the context.  This may or may not be important,
 *  depending upon application.
 * 
 *
 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
 * @version $Id: InternalContextAdapterImpl.java,v 1.8.12.1 2004/03/03 23:22:54 geirm Exp $
 */
public final class InternalContextAdapterImpl implements InternalContextAdapter
{
    /**  
     *  the user data Context that we are wrapping 
     */
    Context context = null;
    
    /** 
     *  the ICB we are wrapping.  We may need to make one
     *  if the user data context implementation doesn't
     *  support one.  The default AbstractContext-derived
     *  VelocityContext does, and it's recommended that 
     *  people derive new contexts from AbstractContext
     *  rather than piecing things together
     */
    InternalHousekeepingContext icb = null;

    /**
     *  The InternalEventContext that we are wrapping.  If
     *  the context passed to us doesn't support it, no
     *  biggie.  We don't make it for them - since its a 
     *  user context thing, nothing gained by making one
     *  for them now
     */
    InternalEventContext iec = null;

    /**
     *  CTOR takes a Context and wraps it, delegating all 'data' calls 
     *  to it.
     * 
     *  For support of internal contexts, it will create an InternalContextBase
     *  if need be.
     */
    public InternalContextAdapterImpl( Context c )
    {
        context = c;

        if ( !( c instanceof InternalHousekeepingContext ))
        {
            icb = new InternalContextBase();
        }
        else
        {
            icb = (InternalHousekeepingContext) context;
        }

        if ( c instanceof InternalEventContext)
        {
            iec = ( InternalEventContext) context;
        }
    }

    /* --- InternalHousekeepingContext interface methods --- */

    public void pushCurrentTemplateName( String s )
    {
        icb.pushCurrentTemplateName( s );
    }

    public void popCurrentTemplateName()
    {
        icb.popCurrentTemplateName();
    }
  
    public String getCurrentTemplateName()
    {
        return icb.getCurrentTemplateName();
    }

    public Object[] getTemplateNameStack()
    {
        return icb.getTemplateNameStack();
    }

    public IntrospectionCacheData icacheGet( Object key )
    {
        return icb.icacheGet( key );
    }
    
    public void icachePut( Object key, IntrospectionCacheData o )
    {
        icb.icachePut( key, o );
    }

   public void setCurrentResource( Resource r )
    {
        icb.setCurrentResource(r);
    }

    public Resource getCurrentResource()
    {
        return icb.getCurrentResource();
    }


    /* ---  Context interface methods --- */

    public Object put(String key, Object value)
    {
        return context.put( key , value );
    }

    public Object get(String key)
    {
        return context.get( key );
    }

    public boolean containsKey(Object key)
    {
        return context.containsKey( key );
    }

    public Object[] getKeys()
    {
        return context.getKeys();
    }

    public Object remove(Object key)
    {
        return context.remove( key );
    }


    /* ---- InternalWrapperContext --- */

    /**
     *  returns the user data context that
     *  we are wrapping
     */
    public Context getInternalUserContext()
    {
        return context;
    }

    /**
     *  Returns the base context that we are 
     *  wrapping. Here, its this, but for other thing
     *  like VM related context contortions, it can
     *  be something else
     */
    public InternalContextAdapter getBaseContext()
    {
        return this;
    }

    /* -----  InternalEventContext ---- */

    public EventCartridge attachEventCartridge( EventCartridge ec )
    {
        if (iec != null)
        {
            return iec.attachEventCartridge( ec );
        }

        return null;
    }

    public EventCartridge getEventCartridge()
    {
        if ( iec != null)
        {
            return iec.getEventCartridge( );
        }

        return null;
    }
}


