/*

 *   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)

	{

		if (msg == null) {

			throw new IllegalArgumentException("Argument 'msg' must not be null!");

		}

		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());

				if (oldArticle != null) {

					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!");

		}

	}

}