/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.web.app.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.alfresco.repo.transaction.RetryingTransactionHelper.RetryingTransactionCallback;
import org.alfresco.service.ServiceRegistry;
import org.alfresco.service.cmr.repository.NodeRef;
import org.alfresco.service.transaction.TransactionService;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Servlet responsible for streaming node content from the repo directly to the response stream.
 * The appropriate mimetype is calculated based on filename extension.
 * <p>
 * The URL to the servlet should be generated thus:
 * <pre>/alfresco/download/attach/workspace/SpacesStore/0000-0000-0000-0000/myfile.pdf</pre>
 * or
 * <pre>/alfresco/download/direct/workspace/SpacesStore/0000-0000-0000-0000/myfile.pdf</pre>
 * or
 * <pre>/alfresco/download/[direct|attach]?path=/Company%20Home/MyFolder/myfile.pdf</pre>
 * The protocol, followed by either the store and Id (NodeRef) or instead specify a name based
 * encoded Path to the content, note that the filename element is used for mimetype lookup and
 * as the returning filename for the response stream.
 * <p>
 * The 'attach' or 'direct' element is used to indicate whether to display the stream directly
 * in the browser or download it as a file attachment.
 * <p>
 * By default, the download assumes that the content is on the
 * {@link org.alfresco.model.ContentModel#PROP_CONTENT content property}.<br>
 * To retrieve the content of a specific model property, use a 'property' arg, providing the workspace,
 * node ID AND the qualified name of the property.
 * <p>
 * Like most Alfresco servlets, the URL may be followed by a valid 'ticket' argument for authentication:
 * ?ticket=1234567890
 * <p>
 * And/or also followed by the "?guest=true" argument to force guest access login for the URL. If the 
 * guest=true parameter is used the current session will be logged out and the guest user logged in. 
 * Therefore upon completion of this request the current user will be "guest".
 * <p>
 * If the user attempting the request is not authorised to access the requested node the login page
 * will be redirected to.
 * 
 * @author Kevin Roast
 * @author gavinc
 */
public class DownloadContentServlet extends BaseDownloadContentServlet
{
   private static final long serialVersionUID = -576405943603122206L;

   private static Log logger = LogFactory.getLog(DownloadContentServlet.class);
   
   private static final String DOWNLOAD_URL  = "/d/" + URL_ATTACH + "/{0}/{1}/{2}/{3}";
   private static final String BROWSER_URL   = "/d/" + URL_DIRECT + "/{0}/{1}/{2}/{3}";
   
   @Override
   protected Log getLogger()
   {
      return logger;
   }
   
   /**
    * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
    */
   protected void doGet(final HttpServletRequest req, final HttpServletResponse res)
      throws ServletException, IOException
   {
      if (logger.isDebugEnabled())
      {
         String queryString = req.getQueryString();
         logger.debug("Authenticating request to URL: " + req.getRequestURI() + 
               ((queryString != null && queryString.length() > 0) ? ("?" + queryString) : ""));
      }
      
      AuthenticationStatus status = servletAuthenticate(req, res);
      if (status == AuthenticationStatus.Failure)
      {
         return;
      }
      
      ServiceRegistry serviceRegistry = getServiceRegistry(getServletContext());
      TransactionService transactionService = serviceRegistry.getTransactionService();
      RetryingTransactionCallback<Void> processCallback = new RetryingTransactionCallback<Void>()
      {
         public Void execute() throws Throwable
         {
             processDownloadRequest(req, res, true);
             return null;
         }
      };
      transactionService.getRetryingTransactionHelper().doInTransaction(processCallback, true);
   }
   
   /**
    * Helper to generate a URL to a content node for downloading content from the server.
    * The content is supplied as an HTTP1.1 attachment to the response. This generally means
    * a browser should prompt the user to save the content to specified location.
    * 
    * @param ref     NodeRef of the content node to generate URL for (cannot be null)
    * @param name    File name to return in the URL (cannot be null)
    * 
    * @return URL to download the content from the specified node
    */
   public final static String generateDownloadURL(NodeRef ref, String name)
   {
      return generateUrl(DOWNLOAD_URL, ref, name);
   }
   
   /**
    * Helper to generate a URL to a content node for downloading content from the server.
    * The content is supplied directly in the reponse. This generally means a browser will
    * attempt to open the content directly if possible, else it will prompt to save the file.
    * 
    * @param ref     NodeRef of the content node to generate URL for (cannot be null)
    * @param name    File name to return in the URL (cannot be null)
    * 
    * @return URL to download the content from the specified node
    */
   public final static String generateBrowserURL(NodeRef ref, String name)
   {
      return generateUrl(BROWSER_URL, ref, name);
   }
}