/*
 * Copyright (C) 2005-2007 Alfresco Software Limited.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program 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 General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */
package org.alfresco.web.app.servlet;

import java.io.IOException;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

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

import org.alfresco.error.AlfrescoRuntimeException;
import org.alfresco.model.ContentModel;
import org.alfresco.service.ServiceRegistry;
import org.alfresco.service.cmr.repository.NodeRef;
import org.alfresco.service.cmr.repository.NodeService;
import org.alfresco.service.cmr.repository.StoreRef;
import org.alfresco.service.cmr.repository.TemplateException;
import org.alfresco.service.cmr.repository.TemplateImageResolver;
import org.alfresco.service.cmr.repository.TemplateNode;
import org.alfresco.service.cmr.repository.TemplateService;
import org.alfresco.service.cmr.security.AccessStatus;
import org.alfresco.service.cmr.security.PermissionService;
import org.alfresco.web.ui.common.Utils;
import org.apache.commons.logging.Log;

/**
 * Base class for the template content servlets. Provides common
 * processing for the request.
 * 
 * @see org.alfresco.web.app.servlet.TemplateContentServlet
 * @see org.alfresco.web.app.servlet.GuestTemplateContentServlet
 * 
 * @author Kevin Roast
 * @author gavinc
 */
public abstract class BaseTemplateContentServlet extends BaseServlet
{
   private static final String MIMETYPE_HTML = "text/html;charset=utf-8";

   private static final long serialVersionUID = -4123407921997235977L;

   private static final String ARG_MIMETYPE = "mimetype";
   private static final String ARG_TEMPLATE_PATH = "templatePath";
   private static final String ARG_CONTEXT_PATH  = "contextPath";
   
   /**
    * Gets the logger to use for this request.
    * <p>
    * This will show all debug entries from this class as though they
    * came from the subclass.
    * 
    * @return The logger
    */
   protected abstract Log getLogger();
   
   /**
    * Builds the FreeMarker model
    * 
    * @param services Service Registry instance
    * @param req Http request
    * @param templateRef The node ref of the template to process
    * @return The FreeMarker model
    */
   protected abstract Map<String, Object> buildModel(ServiceRegistry services, 
         HttpServletRequest req, NodeRef templateRef);
   
   /**
    * Processes the template request using the current context i.e. no
    * authentication checks are made, it is presumed they have already
    * been done.
    * 
    * @param req The HTTP request
    * @param res The HTTP response
    * @param redirectToLogin Flag to determine whether to redirect to the login
    *                        page if the user does not have the correct permissions
    */
   protected void processTemplateRequest(HttpServletRequest req, HttpServletResponse res,
         boolean redirectToLogin) throws ServletException, IOException
   {
      Log logger = getLogger();
      String uri = req.getRequestURI();
      
      if (logger.isDebugEnabled())
      {
         String queryString = req.getQueryString();
         logger.debug("Processing URL: " + uri + 
               ((queryString != null && queryString.length() > 0) ? ("?" + queryString) : ""));
      }
      
      uri = uri.substring(req.getContextPath().length());
      StringTokenizer t = new StringTokenizer(uri, "/");
      int tokenCount = t.countTokens();
      
      t.nextToken();    // skip servlet name
      
      NodeRef nodeRef = null;
      NodeRef templateRef = null;
      
      String contentPath = req.getParameter(ARG_CONTEXT_PATH);
      if (contentPath != null && contentPath.length() != 0)
      {
         // process the name based path to resolve the NodeRef
         PathRefInfo pathInfo = resolveNamePath(getServletContext(), contentPath); 
         
         nodeRef = pathInfo.NodeRef;
      }
      else if (tokenCount > 3)
      {
         // get NodeRef to the content from the URL elements
         StoreRef storeRef = new StoreRef(t.nextToken(), t.nextToken());
         nodeRef = new NodeRef(storeRef, t.nextToken());
      }
      
      // get NodeRef to the template if supplied
      String templatePath = req.getParameter(ARG_TEMPLATE_PATH);
      if (templatePath != null && templatePath.length() != 0)
      {
         // process the name based path to resolve the NodeRef
         PathRefInfo pathInfo = resolveNamePath(getServletContext(), templatePath); 
         
         templateRef = pathInfo.NodeRef;
      }
      else if (tokenCount >= 7)
      {
         StoreRef storeRef = new StoreRef(t.nextToken(), t.nextToken());
         templateRef = new NodeRef(storeRef, t.nextToken());
      }
      
      // if no context is specified, use the template itself
      // TODO: should this default to something else?
      if (nodeRef == null && templateRef != null)
      {
         nodeRef = templateRef;
      }
      
      if (nodeRef == null)
      {
         throw new TemplateException("Not enough elements supplied in URL or no 'path' argument specified.");
      }
      
      // get the services we need to retrieve the content
      ServiceRegistry serviceRegistry = getServiceRegistry(getServletContext());
      NodeService nodeService = serviceRegistry.getNodeService();
      TemplateService templateService = serviceRegistry.getTemplateService();
      PermissionService permissionService = serviceRegistry.getPermissionService();
      
      // check that the user has at least READ access on any nodes - else redirect to the login page
      if (permissionService.hasPermission(nodeRef, PermissionService.READ) == AccessStatus.DENIED ||
          (templateRef != null && permissionService.hasPermission(templateRef, PermissionService.READ) == AccessStatus.DENIED))
      {
         if (redirectToLogin)
         {
            if (logger.isDebugEnabled())
               logger.debug("Redirecting to login page...");
            
            redirectToLoginPage(req, res, getServletContext());
         }
         else
         {
            if (logger.isDebugEnabled())
               logger.debug("Returning 403 Forbidden error...");
               
            res.sendError(HttpServletResponse.SC_FORBIDDEN);
         }
         
         return;
      }
      
      String mimetype = MIMETYPE_HTML;
      if (req.getParameter(ARG_MIMETYPE) != null)
      {
         mimetype = req.getParameter(ARG_MIMETYPE);
      }
      res.setContentType(mimetype);
      
      try
      {
         UserTransaction txn = null;
         try
         {
            txn = serviceRegistry.getTransactionService().getUserTransaction(true);
            txn.begin();
            
            // if template not supplied, then use the default against the node
            if (templateRef == null)
            {
               if (nodeService.hasAspect(nodeRef, ContentModel.ASPECT_TEMPLATABLE))
               {
                  templateRef = (NodeRef)nodeService.getProperty(nodeRef, ContentModel.PROP_TEMPLATE);
               }
               if (templateRef == null)
               {
                  throw new TemplateException("Template reference not set against node or not supplied in URL.");
               }
            }
            
            // create the model - put the supplied noderef in as space/document as appropriate
            Object model = getModel(serviceRegistry, req, templateRef, nodeRef);
            
            // process the template against the node content directly to the response output stream
            // assuming the repo is capable of streaming in chunks, this should allow large files
            // to be streamed directly to the browser response stream.
            try
            {
               templateService.processTemplate(
                     null,
                     templateRef.toString(),
                     model,
                     res.getWriter());
               
               // commit the transaction
               txn.commit();
            }
            catch (SocketException e)
            {
               if (e.getMessage().contains("ClientAbortException"))
               {
                  // the client cut the connection - our mission was accomplished apart from a little error message
                  logger.error("Client aborted stream read:\n   node: " + nodeRef + "\n   template: " + templateRef);
                  try { if (txn != null) {txn.rollback();} } catch (Exception tex) {}
               }
               else
               {
                  throw e;
               }
            }
         }
         catch (Throwable txnErr)
         {
            try { if (txn != null) {txn.rollback();} } catch (Exception tex) {}
            throw txnErr;
         }
      }
      catch (Throwable err)
      {
         throw new AlfrescoRuntimeException("Error during template servlet processing: " + err.getMessage(), err);
      }
   }
   
   /**
    * Build the model that to process the template against.
    * <p>
    * The model includes the usual template root objects such as 'companyhome', 'userhome',
    * 'person' and also includes the node specified on the servlet URL as 'space' and 'document'
    *  
    * @param services      ServiceRegistry required for TemplateNode construction
    * @param req           Http request - for accessing Session and url args
    * @param templateRef   NodeRef of the template itself 
    * @param nodeRef       NodeRef of the space/document to process template against
    * 
    * @return an object model ready for executing template against
    */
   @SuppressWarnings("unchecked")
   private Object getModel(ServiceRegistry services, HttpServletRequest req, NodeRef templateRef, NodeRef nodeRef)
   {
      // build FreeMarker default model and merge
      Map<String, Object> root = buildModel(services, req, templateRef);
      
      // put the current NodeRef in as "space" and "document"
      TemplateNode node = new TemplateNode(nodeRef, services, this.imageResolver);
      root.put("space", node);
      root.put("document", node);
      
      // add URL arguments as a map called 'args' to the root of the model
      Map<String, String> args = new HashMap<String, String>(8, 1.0f);
      Enumeration names = req.getParameterNames();
      while (names.hasMoreElements())
      {
         String name = (String)names.nextElement();
         args.put(name, req.getParameter(name));
      }
      root.put("args", args);
      
      return root;
   }
   
   /** Template Image resolver helper */
   protected TemplateImageResolver imageResolver = new TemplateImageResolver()
   {
      public String resolveImagePathForName(String filename, boolean small)
      {
         return Utils.getFileTypeImage(getServletContext(), filename, small);
      }
   };
}