/************************************************************************
    * Copyright (c) 2000-2006 The Apache Software Foundation.             *
    * All rights reserved.                                                *
    * ------------------------------------------------------------------- *
    * Licensed under the Apache License, Version 2.0 (the "License"); you *
    * may not use this file except in compliance with the License. You    *
    * may obtain a copy of the License at:                                *
    *                                                                     *
    *     http://www.apache.org/licenses/LICENSE-2.0                      *
   *                                                                     *
   * Unless required by applicable law or agreed to in writing, software *
   * distributed under the License is distributed on an "AS IS" BASIS,   *
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or     *
   * implied.  See the License for the specific language governing       *
   * permissions and limitations under the License.                      *
   ***********************************************************************/
  
  package org.apache.james.transport.mailets;
  
  import org.apache.mailet.GenericMailet;
  import org.apache.mailet.Mail;
  import org.apache.mailet.MailAddress;
  
  import javax.mail.MessagingException;
  import javax.mail.internet.InternetAddress;
  import javax.mail.internet.MimeMessage;
  import java.util.Collection;
  import java.util.StringTokenizer;
  import java.util.Vector;
  
  /***
   * <p>Mailet designed to process the recipients from the mail headers rather
   * than the recipients specified in the SMTP message header.  This can be
   * useful if your mail is redirected on-route by a mail server that
   * substitutes a fixed recipient address for the original.</p>
   *
   * <p>To use this, match against the redirection address using the
   * <code>RecipientIs</code> matcher and set the mailet 'class' to
   * <code>UseHeaderRecipients</code>.  This will cause the email to be
   * re-injected into the root process with the recipient substituted
   * by all the recipients in the Mail-For, To and Cc headers
   * of the message.</p>
   *
   * <p>e.g.</p>
   * <pre>
   *    <mailet match="RecipientIs=forwarded@myhost"
   *            class="UseHeaderRecipients">
   *    </mailet>
   * </pre>
   *
   * @version 1.0.0, 24/11/2000
   */
  public class UseHeaderRecipients extends GenericMailet {
  
      /***
       * Controls certain log messages
       */
      private boolean isDebug = false;
  
      /***
       * Initialize the mailet
       *
       * initializes the DEBUG flag
       */
      public void init() {
          isDebug = (getInitParameter("debug") == null) ? false : new Boolean(getInitParameter("debug")).booleanValue();
      }
  
      /***
       * Process an incoming email, removing the currently identified
       * recipients and replacing them with the recipients indicated in
       * the Mail-For, To and Cc headers of the actual email.
       *
       * @param mail incoming email
       */
      public void service(Mail mail) throws MessagingException {
          MimeMessage message = mail.getMessage();
  
          // Utilise features of Set Collections such that they automatically
          // ensure that no two entries are equal using the equality method
          // of the element objects.  MailAddress objects test equality based
          // on equivalent but not necessarily visually identical addresses.
          Collection recipients = mail.getRecipients();
          // Wipe all the exist recipients
          recipients.clear();
          recipients.addAll(getHeaderMailAddresses(message, "Mail-For"));
          if (recipients.isEmpty()) {
              recipients.addAll(getHeaderMailAddresses(message, "To"));
              recipients.addAll(getHeaderMailAddresses(message, "Cc"));
          }
          if (isDebug) {
              log("All recipients = " + recipients.toString());
              log("Reprocessing mail using recipients in message headers");
          }
  
          // Return email to the "root" process.
          getMailetContext().sendMail(mail.getSender(), mail.getRecipients(), mail.getMessage());
          mail.setState(Mail.GHOST);
      }
 
 
     /***
      * Return a string describing this mailet.
      *
      * @return a string describing this mailet
      */
     public String getMailetInfo() {
         return "UseHeaderRecipients Mailet";
     }
 
     /***
      * Work through all the headers of the email with a matching name and
      * extract all the mail addresses as a collection of addresses.
      *
      * @param mail the mail message to read
      * @param name the header name as a String
      * @return the collection of MailAddress objects.
      */
     private Collection getHeaderMailAddresses(MimeMessage message, String name) throws MessagingException {
 
         if (isDebug) {
             StringBuffer logBuffer =
                 new StringBuffer(64)
                         .append("Checking ")
                         .append(name)
                         .append(" headers");
             log(logBuffer.toString());
         }
         Collection addresses = new Vector();
         String[] headers = message.getHeader(name);
         String addressString;
         InternetAddress iAddress;
         if (headers != null) {
             for(int i = 0; i < headers.length; i++) {
                 StringTokenizer st = new StringTokenizer(headers[i], ",", false);
                 while (st.hasMoreTokens()) {
                     addressString = st.nextToken();
                     iAddress = new InternetAddress(addressString);
                     if (isDebug) {
                         log("Address = " + iAddress.toString());
                     }
                     addresses.add(new MailAddress(iAddress));
                 }
             }
         }
         return addresses;
     }
 
 }