/*

  *   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 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.msg(e.getMessage(), true);

             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();

   }

 }