/*

  *   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.Group;

 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 Group 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, Group 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");

 		}

 	}

 }