/*
    * Copyright 2004 the original author or authors.
    *
    * 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 com.nordija.tapestry.bayeux.downloads;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hivemind.ApplicationRuntimeException;
  import org.apache.tapestry.IRequestCycle;
  import org.apache.tapestry.engine.IEngineService;
  import org.apache.tapestry.engine.ILink;
  import org.apache.tapestry.services.LinkFactory;
  import org.apache.tapestry.spec.IApplicationSpecification;
  
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * A service which can render links to download resources and accept incoming requests
   * from such links, looking up the download resource and dispatching to the resource.
   * <p/>
   * This service depends on the definition of a tapestry-extension which must point to a
   * implementation of {@link com.nordija.tapestry.bayeux.downloads.DownloadResourceSource}. Please see docs for further info.
   *
   * @author Per Olesen www.nordija.com
   * @version $Id: DownloadService.java 76 2007-05-14 17:12:15Z jeyben $
   */
  public class DownloadService implements IEngineService {
  
      public static final String SERVICE_NAME = "downloads";
  
      public static final String RESOURCE_ID_PARAM_NAME = "resourceId";
      public static final String DOWNLOAD_RESOURCE_SOURCE_EXT_PARAM_NAME = "downloadResourceSourceExtentionName";
      public static final String BAYEUX_DOWNLOADS_EXTENTIONS_PREFIX = "bayeux.downloads.";
      public static final String DEFAULT_RESOURCE_SOURCE_NAME = "resourcesource";
  
      private static final Log LOG = LogFactory.getLog(DownloadService.class);
  
      private HttpServletResponse response;
  
      private LinkFactory linkFactory;
  
      public void setResponse(HttpServletResponse response) {
          this.response = response;
      }
  
      public void setLinkFactory(LinkFactory linkFactory) {
          this.linkFactory = linkFactory;
      }
  
      public String getName() {
          return SERVICE_NAME;
      }
  
      public ILink getLink(boolean post, Object parameter) {
          String resourceId = (String) ((Object[]) parameter)[0];
          String extName = (String) ((Object[]) parameter)[1];
          Map parameters = new HashMap();
          parameters.put("service", getName());
          parameters.put(RESOURCE_ID_PARAM_NAME, resourceId);
          parameters.put(DOWNLOAD_RESOURCE_SOURCE_EXT_PARAM_NAME, extName);
          return linkFactory.constructLink(this, post, parameters, true);
      }
  
      public void service(IRequestCycle cycle) throws IOException {
          // look into the applications ApplicationSpecification to find the extension that
          // enables lookup of resources by their id.
          IApplicationSpecification specification = cycle.getInfrastructure().getApplicationSpecification();
  
          // get the id of the resource from the incoming link
          String downloadResourceSourceExtName = cycle.getParameter(DOWNLOAD_RESOURCE_SOURCE_EXT_PARAM_NAME);
  
          if (downloadResourceSourceExtName == null) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("no '" + DOWNLOAD_RESOURCE_SOURCE_EXT_PARAM_NAME + "' parameter found. Will try to use the default downloadResourceSource '" + DEFAULT_RESOURCE_SOURCE_NAME + "'");
              }
              downloadResourceSourceExtName = DEFAULT_RESOURCE_SOURCE_NAME;
          }
  
          // ask the extension for the resource
          DownloadResourceSource source = (DownloadResourceSource) specification.getExtension(BAYEUX_DOWNLOADS_EXTENTIONS_PREFIX + downloadResourceSourceExtName, DownloadResourceSource.class);
  
          // get the id of the resource from the incoming link
         String resourceId = cycle.getParameter(RESOURCE_ID_PARAM_NAME);
 
         if (resourceId == null) {
             throw new ApplicationRuntimeException("unable to process download link, no '" + RESOURCE_ID_PARAM_NAME + "' parameter found");
         }
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("going to process download resource with id '" + resourceId + "'");
         }
 
         // ask the source for the resource to be downloaded
         DownloadResource downloadResource = source.getDownloadResource(cycle, resourceId);
         if (downloadResource == null) {
             throw new ApplicationRuntimeException("unable to process download link, no resource found on id: '" + resourceId + "'");
         }
 
         streamResource(resourceId, downloadResource);
     }
 
     void streamResource(String resourceId, DownloadResource resource) throws IOException {
         if (LOG.isDebugEnabled()) {
             LOG.debug("streaming resource '" + resourceId + "' with content-type '" + resource.getContentType() + "'");
         }
         response.setContentType(resource.getContentType());
         String contentDisposition = resource.getContentDisposition();
         if (contentDisposition != null) {
             response.setHeader("Content-disposition", contentDisposition);
         }
         OutputStream out = response.getOutputStream();
         InputStream resourceInput = null;
         try {
             resourceInput = resource.getInputStream();
             byte[] buf = new byte[1024];
             int bytesRead;
             while ((bytesRead = resourceInput.read(buf)) != -1) {
                 out.write(buf, 0, bytesRead);
             }
             out.flush();
         } finally {
             if (resourceInput != null) {
                 resourceInput.close();
             }
         }
     }
 }