/*

  *   SONEWS News Server

  *   see AUTHORS for the list of contributors

  *

  *   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 3 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, see <http://www.gnu.org/licenses/>.

  */

 package org.sonews.daemon.command;

 import java.io.IOException;

 import org.sonews.daemon.NNTPConnection;

 import org.sonews.storage.Article;

 import org.sonews.storage.Channel;

 import org.sonews.storage.StorageBackendException;

 /**

  * Class handling the NEXT and LAST command.

  * @author Christian Lins

  * @author Dennis Schwerdel

  * @since n3tpd/0.1

  */

 public class NextPrevCommand implements Command

 {

   @Override

   public String[] getSupportedCommandStrings()

   {

     return new String[]{"NEXT", "PREV"};

   }

   @Override

   public boolean hasFinished()

   {

     return true;

   }

   @Override

   public String impliedCapability()

   {

     return null;

   }

   @Override

   public boolean isStateful()

   {

     return false;

   }

   @Override

   public void processLine(NNTPConnection conn, final String line, byte[] raw)

     throws IOException, StorageBackendException

   {

     final Article currA = conn.getCurrentArticle();

     final Channel currG = conn.getCurrentChannel();

     if (currA == null)

     {

       conn.println("420 no current article has been selected");

       return;

     }

     if (currG == null)

     {

       conn.println("412 no newsgroup selected");

       return;

     }

     final String[] command = line.split(" ");

     if(command[0].equalsIgnoreCase("NEXT"))

     {

       selectNewArticle(conn, currA, currG, 1);

     }

     else if(command[0].equalsIgnoreCase("PREV"))

     {

       selectNewArticle(conn, currA, currG, -1);

     }

     else

     {

       conn.println("500 internal server error");

     }

   }

   private void selectNewArticle(NNTPConnection conn, Article article, Channel grp,

     final int delta)

     throws IOException, StorageBackendException

   {

     assert article != null;

     article = grp.getArticle(grp.getIndexOf(article) + delta);

     if(article == null)

     {

       conn.println("421 no next article in this group");

     }

     else

     {

       conn.setCurrentArticle(article);

       conn.println("223 " + conn.getCurrentChannel().getIndexOf(article)

                     + " " + article.getMessageID()

                     + " article retrieved - request text separately");

     }

   }

 }