// Copyright 2006, 2008, 2009 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.

 package org.apache.tapestry5.internal.services;

 import org.apache.tapestry5.ioc.Resource;

 import org.apache.tapestry5.services.ClasspathAssetAliasManager;

 import org.apache.tapestry5.services.Dispatcher;

 import org.apache.tapestry5.services.Request;

 import org.apache.tapestry5.services.Response;

 import javax.servlet.http.HttpServletResponse;

 import java.io.IOException;

 /**

  * Recognizes requests where the path begins with "/asset/" and delivers the content therein as a bytestream. Also

  * handles requests that are simply polling for a change to the file.

  *

  * @see ResourceStreamer

  * @see ClasspathAssetAliasManager

  * @see ResourceCache

  */

 public class AssetDispatcher implements Dispatcher

 {

     private final ResourceStreamer streamer;

     private final ResourceCache resourceCache;

     private final AssetResourceLocator assetResourceLocator;

     static final String IF_MODIFIED_SINCE_HEADER = "If-Modified-Since";

     public AssetDispatcher(ResourceStreamer streamer,

                            ResourceCache resourceCache,

                            AssetResourceLocator assetResourceLocator)

     {

         this.streamer = streamer;

         this.resourceCache = resourceCache;

         this.assetResourceLocator = assetResourceLocator;

     }

     public boolean dispatch(Request request, Response response) throws IOException

     {

         String path = request.getPath();

         // Remember that the request path does not include the context path, so we can simply start

         // looking for the asset path prefix right off the bat.

         if (!path.startsWith(RequestConstants.ASSET_PATH_PREFIX)) return false;

         // ClassLoaders like their paths to start with a leading slash.

         Resource resource = assetResourceLocator.findResourceForPath(path);

         if (resource == null) return true;

         if (!resource.exists())

         {

             response.sendError(HttpServletResponse.SC_NOT_FOUND, ServicesMessages

                     .assetDoesNotExist(resource));

             return true;

         }

         long ifModifiedSince = 0;

         try

         {

             ifModifiedSince = request.getDateHeader(IF_MODIFIED_SINCE_HEADER);

         }

         catch (IllegalArgumentException ex)

         {

             // Simulate the header being missing if it is poorly formatted.

             ifModifiedSince = -1;

         }

         if (ifModifiedSince > 0)

         {

             long modified = resourceCache.getTimeModified(resource);

             if (ifModifiedSince >= modified)

             {

                 response.sendError(HttpServletResponse.SC_NOT_MODIFIED, "");

                 return true;

             }

         }

         streamer.streamResource(resource);

         return true;

     }

 }