content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.camel.component.mail;
  
  import java.util.Enumeration;
  import java.util.UUID;
  
  import jakarta.mail.Header;
  import jakarta.mail.Message;
  import jakarta.mail.MessagingException;
  
  import org.apache.camel.util.ObjectHelper;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class DefaultMailUidGenerator implements MailUidGenerator {
  
      private static final Logger LOG = LoggerFactory.getLogger(DefaultMailUidGenerator.class);
  
      @Override
      public String generateUuid(MailEndpoint mailEndpoint, Message message) {
          String answer = generateMessageIdHeader(message);
          if (answer == null) {
              answer = generateMessageHash(message);
          }
          // fallback and use message number
          if (answer == null || ObjectHelper.isEmpty(answer)) {
              answer = Integer.toString(message.getMessageNumber());
          }
          return answer;
      }
  
      private String generateMessageIdHeader(Message message) {
          LOG.trace("generateMessageIdHeader for msg: {}", message);
  
          // there should be a Message-ID header with the UID
          try {
              String[] values = message.getHeader("Message-ID");
              if (values != null && values.length > 0) {
                  String uid = values[0];
                  LOG.trace("Message-ID header found: {}", uid);
                  return uid;
              }
          } catch (MessagingException e) {
              LOG.warn("Cannot read headers from mail message. This exception will be ignored.", e);
          }
  
          return null;
      }
  
      public String generateMessageHash(Message message) {
          LOG.trace("generateMessageHash for msg: {}", message);
  
          String uid = null;
  
          // create an UID based on message headers on the message, that ought to be unique
          StringBuilder buffer = new StringBuilder();
          try {
              Enumeration<?> it = message.getAllHeaders();
              while (it.hasMoreElements()) {
                  Header header = (Header) it.nextElement();
                  buffer.append(header.getName()).append("=").append(header.getValue()).append("\n");
              }
              if (buffer.length() > 0) {
                  LOG.trace("Generating UID from the following:\n {}", buffer);
                  uid = UUID.nameUUIDFromBytes(buffer.toString().getBytes()).toString();
              }
          } catch (MessagingException e) {
              LOG.warn("Cannot read headers from mail message. This exception will be ignored.", e);
          }
  
          return uid;
      }
  }
  