/*

  *   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 java.util.List;

 import org.sonews.util.Log;

 import org.sonews.daemon.NNTPConnection;

 import org.sonews.storage.Article;

 import org.sonews.storage.ArticleHead;

 import org.sonews.storage.Headers;

 import org.sonews.storage.StorageBackendException;

 import org.sonews.util.Pair;

 /**

  * Class handling the OVER/XOVER command.

  * 

  * Description of the XOVER command:

  * <pre>

  * XOVER [range]

  *

  * The XOVER command returns information from the overview

  * database for the article(s) specified.

  *

  * The optional range argument may be any of the following:

  *              an article number

  *              an article number followed by a dash to indicate

  *                 all following

  *              an article number followed by a dash followed by

  *                 another article number

  *

  * If no argument is specified, then information from the

  * current article is displayed. Successful responses start

  * with a 224 response followed by the overview information

  * for all matched messages. Once the output is complete, a

  * period is sent on a line by itself. If no argument is

  * specified, the information for the current article is

  * returned.  A news group must have been selected earlier,

  * else a 412 error response is returned. If no articles are

  * in the range specified, a 420 error response is returned

  * by the server. A 502 response will be returned if the

  * client only has permission to transfer articles.

  *

  * Each line of output will be formatted with the article number,

  * followed by each of the headers in the overview database or the

  * article itself (when the data is not available in the overview

  * database) for that article separated by a tab character.  The

  * sequence of fields must be in this order: subject, author,

  * date, message-id, references, byte count, and line count. Other

  * optional fields may follow line count. Other optional fields may

  * follow line count. These fields are specified by examining the

  * response to the LIST OVERVIEW.FMT command. Where no data exists,

  * a null field must be provided (i.e. the output will have two tab

  * characters adjacent to each other). Servers should not output

  * fields for articles that have been removed since the XOVER database

  * was created.

  *

  * The LIST OVERVIEW.FMT command should be implemented if XOVER

  * is implemented. A client can use LIST OVERVIEW.FMT to determine

  * what optional fields  and in which order all fields will be

  * supplied by the XOVER command. 

  *

  * Note that any tab and end-of-line characters in any header

  * data that is returned will be converted to a space character.

  *

  * Responses:

  *

  *   224 Overview information follows

  *   412 No news group current selected

  *   420 No article(s) selected

  *   502 no permission

  *

  * OVER defines additional responses:

  *

  *  First form (message-id specified)

  *    224    Overview information follows (multi-line)

  *    430    No article with that message-id

  *

  *  Second form (range specified)

  *    224    Overview information follows (multi-line)

  *    412    No newsgroup selected

  *    423    No articles in that range

  *

  *  Third form (current article number used)

  *    224    Overview information follows (multi-line)

  *    412    No newsgroup selected

  *    420    Current article number is invalid

  *

  * </pre>

  * @author Christian Lins

  * @since sonews/0.5.0

  */

 public class OverCommand implements Command

 {

 	public static final int MAX_LINES_PER_DBREQUEST = 200;

 	@Override

 	public String[] getSupportedCommandStrings()

 	{

 		return new String[] {"OVER", "XOVER"};

 	}

 	@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

 	{

 		if (conn.getCurrentChannel() == null) {

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

 		} else {

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

 			// If no parameter was specified, show information about

 			// the currently selected article(s)

 			if (command.length == 1) {

 				final Article art = conn.getCurrentArticle();

 				if (art == null) {

 					conn.println("420 no article(s) selected");

 					return;

 				}

 				conn.println(buildOverview(art, -1));

 			} // otherwise print information about the specified range

 			else {

 				long artStart;

 				long artEnd = conn.getCurrentChannel().getLastArticleNumber();

 				String[] nums = command[1].split("-");

 				if (nums.length >= 1) {

 					try {

 						artStart = Integer.parseInt(nums[0]);

 					} catch (NumberFormatException e) {

 						Log.get().info(e.getMessage());

 						artStart = Integer.parseInt(command[1]);

 					}

 				} else {

 					artStart = conn.getCurrentChannel().getFirstArticleNumber();

 				}

 				if (nums.length >= 2) {

 					try {

 						artEnd = Integer.parseInt(nums[1]);

 					} catch (NumberFormatException e) {

 						e.printStackTrace();

 					}

 				}

 				if (artStart > artEnd) {

 					if (command[0].equalsIgnoreCase("OVER")) {

 						conn.println("423 no articles in that range");

 					} else {

 						conn.println("224 (empty) overview information follows:");

 						conn.println(".");

 					}

 				} else {

 					for (long n = artStart; n <= artEnd; n += MAX_LINES_PER_DBREQUEST) {

 						long nEnd = Math.min(n + MAX_LINES_PER_DBREQUEST - 1, artEnd);

 						List<Pair<Long, ArticleHead>> articleHeads = conn.getCurrentChannel().getArticleHeads(n, nEnd);

 						if (articleHeads.isEmpty() && n == artStart

 							&& command[0].equalsIgnoreCase("OVER")) {

 							// This reply is only valid for OVER, not for XOVER command

 							conn.println("423 no articles in that range");

 							return;

 						} else if (n == artStart) {

 							// XOVER replies this although there is no data available

 							conn.println("224 overview information follows");

 						}

 						for (Pair<Long, ArticleHead> article : articleHeads) {

 							String overview = buildOverview(article.getB(), article.getA());

 							conn.println(overview);

 						}

 					} // for

 					conn.println(".");

 				}

 			}

 		}

 	}

 	private String buildOverview(ArticleHead art, long nr)

 	{

 		StringBuilder overview = new StringBuilder();

 		overview.append(nr);

 		overview.append('\t');

 		String subject = art.getHeader(Headers.SUBJECT)[0];

 		if ("".equals(subject)) {

 			subject = "<empty>";

 		}

 		overview.append(escapeString(subject));

 		overview.append('\t');

 		overview.append(escapeString(art.getHeader(Headers.FROM)[0]));

 		overview.append('\t');

 		overview.append(escapeString(art.getHeader(Headers.DATE)[0]));

 		overview.append('\t');

 		overview.append(escapeString(art.getHeader(Headers.MESSAGE_ID)[0]));

 		overview.append('\t');

 		overview.append(escapeString(art.getHeader(Headers.REFERENCES)[0]));

 		overview.append('\t');

 		String bytes = art.getHeader(Headers.BYTES)[0];

 		if ("".equals(bytes)) {

 			bytes = "0";

 		}

 		overview.append(escapeString(bytes));

 		overview.append('\t');

 		String lines = art.getHeader(Headers.LINES)[0];

 		if ("".equals(lines)) {

 			lines = "0";

 		}

 		overview.append(escapeString(lines));

 		overview.append('\t');

 		overview.append(escapeString(art.getHeader(Headers.XREF)[0]));

 		// Remove trailing tabs if some data is empty

 		return overview.toString().trim();

 	}

 	private String escapeString(String str)

 	{

 		String nstr = str.replace("\r", "");

 		nstr = nstr.replace('\n', ' ');

 		nstr = nstr.replace('\t', ' ');

 		return nstr.trim();

 	}

 }