diff -r 6ae5e4f8329b -r c404a87db5b7 src/org/sonews/daemon/command/OverCommand.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/sonews/daemon/command/OverCommand.java	Sun Aug 29 17:43:58 2010 +0200
@@ -0,0 +1,294 @@
+/*
+ *   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();
+  }
+  
+}