/*

 *   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();

  }

}