/*
    * Licensed under the GPL License. You may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *   https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
    *
    * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
    * WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
    * PURPOSE.
   */
  package psiprobe.controllers.logs;
  
  import java.io.File;
  import java.util.LinkedList;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.stereotype.Controller;
  import org.springframework.web.bind.ServletRequestUtils;
  import org.springframework.web.bind.annotation.RequestMapping;
  import org.springframework.web.servlet.ModelAndView;
  
  import psiprobe.tools.BackwardsFileStream;
  import psiprobe.tools.BackwardsLineReader;
  import psiprobe.tools.logging.LogDestination;
  
  /**
   * The Class FollowController.
   */
  @Controller
  public class FollowController extends AbstractLogHandlerController {
  
    @RequestMapping(path = "/follow.ajax")
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
        throws Exception {
      return super.handleRequest(request, response);
    }
  
    @Override
    protected ModelAndView handleLogFile(HttpServletRequest request, HttpServletResponse response,
        LogDestination logDest) throws Exception {
  
      ModelAndView mv = new ModelAndView(getViewName());
      File file = logDest.getFile();
  
      if (file.exists()) {
        LinkedList<String> lines = new LinkedList<>();
        long actualLength = file.length();
        long lastKnownLength = ServletRequestUtils.getLongParameter(request, "lastKnownLength", 0);
        long currentLength =
            ServletRequestUtils.getLongParameter(request, "currentLength", actualLength);
        long maxReadLines = ServletRequestUtils.getLongParameter(request, "maxReadLines", 0);
  
        if (lastKnownLength > currentLength || lastKnownLength > actualLength
            || currentLength > actualLength) {
  
          // file length got reset
          lastKnownLength = 0;
          lines.add(" ------------- THE FILE HAS BEEN TRUNCATED --------------");
        }
  
        try (BackwardsFileStream bfs = new BackwardsFileStream(file, currentLength)) {
          BackwardsLineReader br;
          if (logDest.getEncoding() != null) {
            br = new BackwardsLineReader(bfs, logDest.getEncoding());
          } else {
            br = new BackwardsLineReader(bfs);
          }
          long readSize = 0;
          long totalReadSize = currentLength - lastKnownLength;
          String line;
          while (readSize < totalReadSize && (line = br.readLine()) != null) {
            if (!line.isEmpty()) {
              lines.addFirst(line);
              readSize += line.length();
            } else {
              readSize++;
            }
            if (maxReadLines != 0 && lines.size() >= maxReadLines) {
              break;
            }
          }
  
          if (lastKnownLength != 0 && readSize > totalReadSize) {
            lines.removeFirst();
          }
        }
  
        mv.addObject("lines", lines);
      }
      return mv;
    }
  
    @Value("ajax/follow")
    @Override
    public void setViewName(String viewName) {
     super.setViewName(viewName);
   }
 
 }