/*

 *   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");

    }

  }

}