/*
 * SMTPTransport.java
 * Copyright(C) 2001 Benjamin A. Speakmon
 * 
 * This file is part of GNU JavaMail, a library.
 * 
 * GNU JavaMail 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 2 of the License, or
 *(at your option) any later version.
 * 
 * GNU JavaMail 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */

package gnu.mail.providers.smtp;

import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import java.util.StringTokenizer;
import javax.mail.Address;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.SendFailedException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.URLName;
import javax.mail.event.TransportEvent;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.net.ssl.TrustManager;

import gnu.inet.smtp.Parameter;
import gnu.inet.smtp.ParameterList;
import gnu.inet.smtp.SMTPConnection;
import gnu.inet.util.BASE64;

/** 
 * This transport handles communications with an SMTP server.
 *
 * @author Andrew Selkirk
 * @author Ben Speakmon
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 * @author Arend Freije
 * @version 2.0
 */
public class SMTPTransport
  extends Transport
{

  /**
   * The connection used to communicate with the server.
   */
  protected SMTPConnection connection;
  
  protected String localHostName;
  
  private List extensions = null;
  private List authenticationMechanisms = null;

  /**
   * Creates a new <code>SMTPTransport</code> instance.
   *
   * @param session a <code>Session</code> value
   * @param urlName an <code>URLName</code> value
   */
  public SMTPTransport(Session session, URLName urlName) 
  {
    super(session, urlName);
   
    // Check for mail.smtp.localhost property
    localHostName = getProperty("localhost");
    if (localHostName == null)
      {
        try
          {
            localHostName = InetAddress.getLocalHost().getHostName();
          }
        catch (UnknownHostException e)
          {
            localHostName = "localhost";
          }
      }
  }

  /**
   * Connects to the SMTP server.
   */
  protected boolean protocolConnect(String host, int port, String username,
                                     String password)
    throws MessagingException 
  {
    if (connection != null)
      {
        return true;
      }
    if (host == null)
      {
        host = getProperty("host");
      }
    if (port < 0)
      {
        port = getIntProperty("port");
      }
    if (username == null)
      {
        username = getProperty("user");
      }
    
    // Check host
    if (host == null)
      {
        host = "localhost";
      }
    
    try
      {	
        int connectionTimeout = getIntProperty("connectiontimeout");
        int timeout = getIntProperty("timeout");
        if (session.getDebug())
          {
            SMTPConnection.logger.setLevel(SMTPConnection.SMTP_TRACE);
          }
        boolean tls = "stmps".equals(url.getProtocol());
        // Locate custom trust manager
        TrustManager tm = null;
        if (tls)
          {
            tm = getTrustManager();
          }
        
        connection = new SMTPConnection(host, port, 
                                        connectionTimeout, timeout,
                                        tls, tm);
    
        // EHLO/HELO
        if (propertyIsFalse("ehlo"))
          {
            if (!connection.helo(localHostName))
              throw new MessagingException("HELO failed: "+
                                           connection.getLastResponse());
          }
        else
          {
            extensions = connection.ehlo(localHostName);
            if (extensions == null)
              {
                if (!connection.helo(localHostName))
                  {
                    throw new MessagingException("HELO failed: "+
                                                 connection.getLastResponse());
                  }
              }
            else
              {
                if (!tls && extensions.contains("STARTTLS"))
                  {
                    if (!propertyIsFalse("tls"))
                      {
                        tm = getTrustManager();
                        if (tm == null)
                          {
                            tls = connection.starttls();
                          }
                        else
                          {
                            tls = connection.starttls(tm);
                          }
                        if (tls)
                          {
                            extensions = connection.ehlo(localHostName);
                          }
                      }
                  }
                if (!tls && "required".equals(getProperty("tls")))
                  {
                    throw new MessagingException("TLS not available");
                  }
                // Populate authenticationMechanisms
                for (Iterator i = extensions.iterator(); i.hasNext(); )
                  {
                    String extension = (String) i.next();
                    if (extension.startsWith("AUTH "))
                      {
                        String m = extension.substring(5);
                        authenticationMechanisms =
                          Collections.list(new StringTokenizer(m));
                      }
                  }
              }
          }
        
        // User authentication
        String auth = getProperty("auth");
        boolean authRequired = "required".equals(auth);
        if (authenticationMechanisms == null ||
            authenticationMechanisms.isEmpty())
          {
            return !authRequired;
          }
        if (authRequired || propertyIsTrue("auth"))
          {
            if (username == null || password == null)
              {
                PasswordAuthentication pa =
                  session.getPasswordAuthentication(url);
                if (pa == null)
                  {
                    InetAddress addr = InetAddress.getByName(host);
                    pa = session.requestPasswordAuthentication(addr,
                                                                port,
                                                                url.getProtocol(),
                                                                null,
                                                                null);
                  }
                if (pa != null)
                  {
                    username = pa.getUserName();
                    password = pa.getPassword();
                  }
              }
            if (username != null && password != null)
              {
                // Discover user ordering preferences for auth mechanisms
                String authPrefs = getProperty("auth.mechanisms");
                Iterator i = null;
                if (authPrefs == null)
                  {
                    i = authenticationMechanisms.iterator();
                  }
                else
                  {
                    List authPrefList =
                      Collections.list(new StringTokenizer(authPrefs, ","));
                    i = authPrefList.iterator();
                  }
                // Try each mechanism in the list in turn
                while (i.hasNext())
                  {
                    String mechanism = (String) i.next();
                    if (authenticationMechanisms.contains(mechanism) &&
                        connection.authenticate(mechanism, username,
                                                 password))
                      {
                        return true;
                      }
                  }
              }
            else
              {
                if (session.getDebug())
                  {
                    debugWarning("server requested AUTH, " +
                                 "but authentication principal " +
                                 "and credentials are not available");
                  }
              }
            return false;
          }
        else
          {
            if (session.getDebug())
              {
                    debugWarning("server requested AUTH, " +
                                 "but authentication is not enabled");
              }
          }
        return !authRequired;
      }
    catch (IOException e)
      {
        throw new MessagingException(e.getMessage(), e);
      }
  }

  private TrustManager getTrustManager() throws MessagingException {
	String tmt = getProperty("trustmanager");
    if (tmt != null)
      {
        try
          {
            Class t = Class.forName(tmt);
            return (TrustManager) t.newInstance();
          } catch (Exception e) {
            throw new MessagingException(e.getMessage(), e);
          }
      }
    return null;
  }

  private void debugWarning(final String warning)
  {
    System.err.println(url.getProtocol() + ": WARNING: " + warning);
  }

  /**
   * Returns the greeting banner.
   */
  public String getGreeting()
    throws MessagingException
  {
    if (!isConnected())
      {
        throw new MessagingException("not connected");
      }
    synchronized (connection)
      {
        return connection.getGreeting();
      }
  }

  /**
   * Send the specified message to the server.
   */
  public void sendMessage(Message message, Address[] addresses)
    throws MessagingException, SendFailedException 
  {
    if (!isConnected())
      {
        throw new MessagingException("not connected");
      }
    if (!(message instanceof MimeMessage))
      {
        throw new SendFailedException("only MimeMessages are supported");
      }
    // Cast message
    MimeMessage mimeMessage = (MimeMessage) message;
      
    int len = addresses.length;
    List sent = new ArrayList(len);
    List unsent = new ArrayList(len);
    List invalid = new ArrayList(len);
    int deliveryStatus = TransportEvent.MESSAGE_NOT_DELIVERED;
    ParameterList params = null; // ESMTP parameters
    
    synchronized (connection)
      {
        try
          {
            // reverse-path
            String from0 = getProperty("from");
            InternetAddress from = null;
            if (from0 != null)
              {
                InternetAddress[] from1 = InternetAddress.parse(from0);
                if (from1 != null && from1.length > 0)
                  {
                    from = from1[0];
                  }
              }
            if (from == null)
              {
                Address[] from2 = mimeMessage.getFrom();
                if (from2 != null && from2.length > 0 &&
                    from2[0] instanceof InternetAddress)
                  {
                    from = (InternetAddress) from2[0];
                  }
              }
            if (from == null)
              {
                from = InternetAddress.getLocalAddress(session);
              }
            String reversePath = from.getAddress();
            // DSN RET
            String dsnRet = getProperty("dsn.ret");
            if (dsnRet != null && extensions != null &&
                extensions.contains("DSN"))
              {
                String FULL = "FULL", HDRS = "HDRS";
                String value = null;
                if (FULL.equalsIgnoreCase(dsnRet))
                  {
                    value = FULL;
                  }
                else if (HDRS.equalsIgnoreCase(dsnRet))
                  {
                    value = HDRS;
                  }
                if (value != null)
                  {
                    if (params == null)
                      params = new ParameterList();
                    params.add(new Parameter("RET", value));
                  }
              }
            // MTRK
            String mtrk = getProperty("mtrk");
            if ("true".equals(mtrk) && extensions != null &&
                extensions.contains("MTRK"))
              {
                int mtrkTimeout = 0;
                String mt = getProperty("mtrk.timeout");
                if (mt != null)
                  mtrkTimeout = Integer.parseInt(mt);
                try
                  {
                    Random r = new Random();
                    byte[] a = new byte[256];
                    r.nextBytes(a);
                    MessageDigest md = MessageDigest.getInstance("SHA-1");
                    md.update(a);
                    byte[] b = md.digest();
                    byte[] certifier = BASE64.encode(b);
                    if (params == null)
                      params = new ParameterList();
                    String value = new String(certifier, "US-ASCII");
                    if (mtrkTimeout > 0)
                      {
                        value += ":" + mtrkTimeout;
                      }
                    params.add(new Parameter("MTRK", value));
                    String envid = mimeMessage.getMessageID();
                    if (envid != null)
                      {
                        int ai = envid.indexOf('@');
                        if (ai != -1)
                          envid = envid.substring(0, ai);
                      }
                    else
                      {
                        envid = "";
                      }
                    envid += Long.toHexString(System.currentTimeMillis());
                    envid += "@";
                    String lha = InetAddress.getLocalHost().getHostAddress();
                    if (envid.length() + lha.length() > 100)
                      {
                        b = lha.getBytes("UTF-8");
                        md.reset();
                        md.update(b);
                        b = md.digest();
                        b = BASE64.encode(b);
                        lha = new String(b, "US-ASCII");
                      }
                    envid += lha;
                    params.add(new Parameter("ENVID", envid));
                  }
                catch (NoSuchAlgorithmException e)
                  {
                    MessagingException e2 =
                      new MessagingException(e.getMessage());
                    e2.initCause(e);
                    throw e2;
                  }
                catch (UnsupportedEncodingException e)
                  {
                    MessagingException e2 =
                      new MessagingException(e.getMessage());
                    e2.initCause(e);
                    throw e2;
                  }
              }
            // MAIL FROM
            if (!connection.mailFrom(reversePath, params))
              {
                throw new SendFailedException(connection.getLastResponse());
              }
            params = null;
            
            // DSN NOTIFY
            String dsnNotify = getProperty("dsn.notify");
            if (dsnNotify != null && extensions != null &&
                extensions.contains("DSN"))
              {
                String NEVER = "NEVER", SUCCESS = "SUCCESS";
                String FAILURE = "FAILURE", DELAY = "DELAY";
                String value = null;
                if (NEVER.equalsIgnoreCase(dsnNotify))
                  {
                    value = NEVER;
                  }
                else
                  {
                    StringBuffer buf = new StringBuffer();
                    StringTokenizer st = new StringTokenizer(dsnNotify, " ,");
                    while (st.hasMoreTokens())
                      {
                        String token = st.nextToken();
                        if (SUCCESS.equalsIgnoreCase(token))
                          {
                            if (buf.length() > 0)
                              {
                                buf.append(',');
                              }
                            buf.append(SUCCESS);
                          }
                        else if (FAILURE.equalsIgnoreCase(token))
                          {
                            if (buf.length() > 0)
                              {
                                buf.append(',');
                              }
                            buf.append(FAILURE);
                          }
                        else if (DELAY.equalsIgnoreCase(token))
                          {
                            if (buf.length() > 0)
                              {
                                buf.append(',');
                              }
                            buf.append(DELAY);
                          }
                      }
                    if (buf.length() > 0)
                      {
                        value = buf.toString();
                      }
                  }
                if (value != null)
                  {
                    params = new ParameterList();
                    params.add(new Parameter("NOTIFY", value));
                  }
              }
            // RCPT TO
            for (int i = 0; i < addresses.length; i++)
              {
                Address address = addresses[i];
                if (address instanceof InternetAddress)
                  {
                    String forwardPath =
                     ((InternetAddress) address).getAddress();
                    if (connection.rcptTo(forwardPath, params))
                      {
                        sent.add(address);
                      }
                    else
                      {
                        invalid.add(address);
                      }
                  }
                else
                  {
                    invalid.add(address);
                  }
              }
          }
        catch (IOException e)
          {
            try
              {
                // Reset connection
                connection.rset();
              }
            catch (IOException e2)
              {
                // Possible transport-level problem
              }
            throw new SendFailedException(e.getMessage());
          }
        
        if (sent.size() > 0)
          {
            try
              {  
                // DATA
                OutputStream dataStream = connection.data();
                if (dataStream == null)
                  {
                    String msg = connection.getLastResponse();
                    throw new MessagingException(msg);
                  }
                mimeMessage.writeTo(dataStream);
                dataStream.flush();
                if (!connection.finishData())
                  {
                    unsent.addAll(sent);
                    sent.clear();
                    deliveryStatus = TransportEvent.MESSAGE_NOT_DELIVERED;
                  }
                else 
                  {
                    deliveryStatus = invalid.isEmpty() ?
                      TransportEvent.MESSAGE_DELIVERED :
                      TransportEvent.MESSAGE_PARTIALLY_DELIVERED;
                  }
              }
            catch (IOException e)
              {
                try
                  {
                    // Attempt to ensure that connection is in control mode
                    if (connection.finishData())
                      {
                        connection.rset();
                      }
                  }
                catch (IOException e2)
                  {
                    // Possible transport-level problem
                  }
                throw new SendFailedException(e.getMessage());
              }
          }
      }
  
    // Notify transport listeners
    Address[] a_sent = new Address[sent.size()];
    sent.toArray(a_sent);
    Address[] a_unsent = new Address[unsent.size()];
    unsent.toArray(a_unsent);
    Address[] a_invalid = new Address[invalid.size()];
    invalid.toArray(a_invalid);
    
    notifyTransportListeners(deliveryStatus, a_sent, a_unsent, a_invalid,
                              mimeMessage);
  }

  /**
   * Close this transport.
   */
  public void close()
    throws MessagingException 
  {
    if (isConnected()) 
      {
        synchronized (connection)
          {
            try 
              {
                connection.quit();
              }
            catch (IOException e) 
              {
                throw new MessagingException(e.getMessage(), e);
              }
            finally
              {
                connection = null;
              }
          }
      }
    super.close();
  }
  
  // -- Utility methods --

  private int getIntProperty(String key)
  {
    String value = getProperty(key);
    if (value != null)
      {
        try
          {
            return Integer.parseInt(value);
          }
        catch (Exception e)
          {
          }
      }
    return -1;
  }
  
  private boolean propertyIsFalse(String key)
  {
    return "false".equals(getProperty(key));
  }
  
  private boolean propertyIsTrue(String key)
  {
    return "true".equals(getProperty(key));
  }
  
  /*
   * Returns the provider-specific or general mail property corresponding to
   * the specified key.
   */
  private String getProperty(String key)
  {
    String value = session.getProperty("mail." + url.getProtocol() + "." + key);
    if (value == null)
      {
        value = session.getProperty("mail." + key);
      }
    return value;
  }
  
}