/*

 *   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.mlgw;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import javax.mail.Address;

import javax.mail.Authenticator;

import javax.mail.Message;

import javax.mail.MessagingException;

import javax.mail.PasswordAuthentication;

import javax.mail.internet.InternetAddress;

import org.sonews.config.Config;

import org.sonews.storage.Article;

import org.sonews.storage.Group;

import org.sonews.storage.Headers;

import org.sonews.storage.StorageBackendException;

import org.sonews.storage.StorageManager;

import org.sonews.util.Log;

import org.sonews.util.Stats;

/**

 * Dispatches messages from mailing list to newsserver or vice versa.

 * @author Christian Lins

 * @since sonews/0.5.0

 */

public class Dispatcher 

{

  static class PasswordAuthenticator extends Authenticator

  {

    @Override

    public PasswordAuthentication getPasswordAuthentication()

    {

      final String username = 

        Config.inst().get(Config.MLSEND_USER, "user");

      final String password = 

        Config.inst().get(Config.MLSEND_PASSWORD, "mysecret");

      return new PasswordAuthentication(username, password);

    }

  }

  /**

   * Chunks out the email address of the full List-Post header field.

   * @param listPostValue

   * @return The matching email address or null

   */

  private static String chunkListPost(String listPostValue)

  {

    // listPostValue is of form "<mailto:dev@openoffice.org>"

    Pattern mailPattern = Pattern.compile("(\\w+[-|.])*\\w+@(\\w+.)+\\w+");

    Matcher mailMatcher = mailPattern.matcher(listPostValue);

    if(mailMatcher.find())

    {

      return listPostValue.substring(mailMatcher.start(), mailMatcher.end());

    }

    else

    {

      return null;

    }

  }

  /**

   * This method inspects the header of the given message, trying

   * to find the most appropriate recipient.

   * @param msg

   * @param fallback If this is false only List-Post and X-List-Post headers

   *                 are examined.

   * @return null or fitting group name for the given message.

   */

  private static List<String> getGroupFor(final Message msg, final boolean fallback)

    throws MessagingException, StorageBackendException

  {

    List<String> groups = null;

    // Is there a List-Post header?

    String[]        listPost = msg.getHeader(Headers.LIST_POST);

    InternetAddress listPostAddr;

    if(listPost == null || listPost.length == 0 || "".equals(listPost[0]))

    {

      // Is there a X-List-Post header?

      listPost = msg.getHeader(Headers.X_LIST_POST);

    }

    if(listPost != null && listPost.length > 0 

      && !"".equals(listPost[0]) && chunkListPost(listPost[0]) != null)

    {

      // listPost[0] is of form "<mailto:dev@openoffice.org>"

      listPost[0]  = chunkListPost(listPost[0]);

      listPostAddr = new InternetAddress(listPost[0], false);

      groups = StorageManager.current().getGroupsForList(listPostAddr.getAddress());

    }

    else if(fallback)

    {

      Log.get().info("Using fallback recipient discovery for: " + msg.getSubject());

      groups = new ArrayList<String>();

      // Fallback to TO/CC/BCC addresses

      Address[] to = msg.getAllRecipients();

      for(Address toa : to) // Address can have '<' '>' around

      {

        if(toa instanceof InternetAddress)

        {

          List<String> g = StorageManager.current()

            .getGroupsForList(((InternetAddress)toa).getAddress());

          groups.addAll(g);

        }

      }

    }

    return groups;

  }

  /**

   * Posts a message that was received from a mailing list to the 

   * appropriate newsgroup.

   * If the message already exists in the storage, this message checks

   * if it must be posted in an additional group. This can happen for

   * crosspostings in different mailing lists.

   * @param msg

   */

  public static boolean toGroup(final Message msg)

  {

    try

    {

      // Create new Article object

      Article article = new Article(msg);

      boolean posted  = false;

      // Check if this mail is already existing the storage

      boolean updateReq = 

        StorageManager.current().isArticleExisting(article.getMessageID());

      List<String> newsgroups = getGroupFor(msg, !updateReq);

      List<String> oldgroups  = new ArrayList<String>();

      if(updateReq)

      {

        // Check for duplicate entries of the same group

        Article oldArticle = StorageManager.current().getArticle(article.getMessageID());

        List<Group> oldGroups = oldArticle.getGroups();

        for(Group oldGroup : oldGroups)

        {

          if(!newsgroups.contains(oldGroup.getName()))

          {

            oldgroups.add(oldGroup.getName());

          }

        }

      }

      if(newsgroups.size() > 0)

      {

        newsgroups.addAll(oldgroups);

        StringBuilder groups = new StringBuilder();

        for(int n = 0; n < newsgroups.size(); n++)

        {

          groups.append(newsgroups.get(n));

          if (n + 1 != newsgroups.size())

          {

            groups.append(',');

          }

        }

        Log.get().info("Posting to group " + groups.toString());

        article.setGroup(groups.toString());

        //article.removeHeader(Headers.REPLY_TO);

        //article.removeHeader(Headers.TO);

        // Write article to database

        if(updateReq)

        {

          Log.get().info("Updating " + article.getMessageID()

            + " with additional groups");

          StorageManager.current().delete(article.getMessageID());

          StorageManager.current().addArticle(article);

        }

        else

        {

          Log.get().info("Gatewaying " + article.getMessageID() + " to "

            + article.getHeader(Headers.NEWSGROUPS)[0]);

          StorageManager.current().addArticle(article);

          Stats.getInstance().mailGatewayed(

            article.getHeader(Headers.NEWSGROUPS)[0]);

        }

        posted = true;

      }

      else

      {

        StringBuilder buf = new StringBuilder();

        for (Address toa : msg.getAllRecipients())

        {

          buf.append(' ');

          buf.append(toa.toString());

        }

        buf.append(" " + article.getHeader(Headers.LIST_POST)[0]);

        Log.get().warning("No group for" + buf.toString());

      }

      return posted;

    }

    catch(Exception ex)

    {

      ex.printStackTrace();

      return false;

    }

  }

  /**

   * Mails a message received through NNTP to the appropriate mailing list.

   * This method MAY be called several times by PostCommand for the same

   * article.

   */

  public static void toList(Article article, String group)

    throws IOException, MessagingException, StorageBackendException

  {

    // Get mailing lists for the group of this article

    List<String> rcptAddresses = StorageManager.current().getListsForGroup(group);

    if(rcptAddresses == null || rcptAddresses.size() == 0)

    {

      Log.get().warning("No ML-address for " + group + " found.");

      return;

    }

    for(String rcptAddress : rcptAddresses)

    {

      // Compose message and send it via given SMTP-Host

      String smtpHost = Config.inst().get(Config.MLSEND_HOST, "localhost");

      int smtpPort = Config.inst().get(Config.MLSEND_PORT, 25);

      String smtpUser = Config.inst().get(Config.MLSEND_USER, "user");

      String smtpPw = Config.inst().get(Config.MLSEND_PASSWORD, "mysecret");

      String smtpFrom = Config.inst().get(

        Config.MLSEND_ADDRESS, article.getHeader(Headers.FROM)[0]);

      // TODO: Make Article cloneable()

      article.getMessageID(); // Make sure an ID is existing

      article.removeHeader(Headers.NEWSGROUPS);

      article.removeHeader(Headers.PATH);

      article.removeHeader(Headers.LINES);

      article.removeHeader(Headers.BYTES);

      article.setHeader("To", rcptAddress);

      //article.setHeader("Reply-To", listAddress);

      if (Config.inst().get(Config.MLSEND_RW_SENDER, false))

      {

        rewriteSenderAddress(article); // Set the SENDER address

      }

      SMTPTransport smtpTransport = new SMTPTransport(smtpHost, smtpPort);

      smtpTransport.send(article, smtpFrom, rcptAddress);

      smtpTransport.close();

      Stats.getInstance().mailGatewayed(group);

      Log.get().info("MLGateway: Mail " + article.getHeader("Subject")[0]

        + " was delivered to " + rcptAddress + ".");

    }

  }

  /**

   * Sets the SENDER header of the given MimeMessage. This might be necessary

   * for moderated groups that does not allow the "normal" FROM sender.

   * @param msg

   * @throws javax.mail.MessagingException

   */

  private static void rewriteSenderAddress(Article msg)

    throws MessagingException

  {

    String mlAddress = Config.inst().get(Config.MLSEND_ADDRESS, null);

    if(mlAddress != null)

    {

      msg.setHeader(Headers.SENDER, mlAddress);

    }

    else

    {

      throw new MessagingException("Cannot rewrite SENDER header!");

    }

  }

}