server/protocols/jmap-draft/src/main/java/org/apache/james/jmap/mailet/ExtractMDNOriginalJMAPMessageId.java

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package org.apache.james.jmap.mailet;

import java.util.Optional;

import javax.inject.Inject;
import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;

import org.apache.james.core.MailAddress;
import org.apache.james.mailbox.MailboxManager;
import org.apache.james.mailbox.MailboxSession;
import org.apache.james.mailbox.model.MessageId;
import org.apache.james.mailbox.model.MultimailboxesSearchQuery;
import org.apache.james.mailbox.model.SearchQuery;
import org.apache.james.mdn.MDN;
import org.apache.james.mdn.MDNReport;
import org.apache.james.mdn.fields.OriginalMessageId;
import org.apache.james.mime4j.message.DefaultMessageBuilder;
import org.apache.james.server.core.MimeMessageInputStream;
import org.apache.james.user.api.UsersRepository;
import org.apache.james.user.api.UsersRepositoryException;
import org.apache.mailet.Mail;
import org.apache.mailet.base.GenericMailet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.Iterables;

import reactor.core.publisher.Flux;

/**
 * This mailet handles MDN messages and define a header X-JAMES-MDN-JMAP-MESSAGE-ID referencing
 * the original message (by its Jmap Id) asking for the recipient to send an MDN.
 */
public class ExtractMDNOriginalJMAPMessageId extends GenericMailet {

    private static final Logger LOGGER = LoggerFactory.getLogger(ExtractMDNOriginalJMAPMessageId.class);

    private static final String X_JAMES_MDN_JMAP_MESSAGE_ID = "X-JAMES-MDN-JMAP-MESSAGE-ID";

    private final MailboxManager mailboxManager;
    private final UsersRepository usersRepository;

    @Inject
    public ExtractMDNOriginalJMAPMessageId(MailboxManager mailboxManager, UsersRepository usersRepository) {
        this.mailboxManager = mailboxManager;
        this.usersRepository = usersRepository;
    }

    @Override
    public void service(Mail mail) throws MessagingException {
        if (mail.getRecipients().size() != 1) {
            LOGGER.warn("MDN should only be sent to a single recipient");
            return;
        }
        MailAddress recipient = Iterables.getOnlyElement(mail.getRecipients());
        MimeMessage mimeMessage = mail.getMessage();

        try {
            var message = new DefaultMessageBuilder().parseMessage(new MimeMessageInputStream(mimeMessage));
            Optional.of(MDN.parse(message))
                .map(MDN::getReport)
                .flatMap(MDNReport::getOriginalMessageIdField)
                .map(OriginalMessageId::getOriginalMessageId)
                .flatMap(messageId -> findMessageIdForRFC822MessageId(messageId, recipient))
                .ifPresent(messageId -> setJmapMessageIdAsHeader(mimeMessage, messageId));
        } catch (Exception e) {
            throw new MessagingException("MDN can't be parse", e);
        }
    }

    private void setJmapMessageIdAsHeader(MimeMessage mimeMessage, MessageId messageId) {
        LOGGER.debug("Adding header {}:{}", X_JAMES_MDN_JMAP_MESSAGE_ID, messageId.serialize());
        try {
            mimeMessage.addHeader(X_JAMES_MDN_JMAP_MESSAGE_ID, messageId.serialize());
        } catch (MessagingException e) {
            LOGGER.error("unable to add " + X_JAMES_MDN_JMAP_MESSAGE_ID + " header to message", e);
        }
    }

    private Optional<MessageId> findMessageIdForRFC822MessageId(String messageId, MailAddress recipient) {
        LOGGER.debug("Searching message {} for recipient {}", messageId, recipient.asPrettyString());
        try {
            MailboxSession session = mailboxManager.createSystemSession(usersRepository.getUsername(recipient));
            int limit = 1;
            MultimailboxesSearchQuery searchByRFC822MessageId = MultimailboxesSearchQuery
                .from(SearchQuery.of(SearchQuery.mimeMessageID(messageId)))
                .build();
            return Flux.from(mailboxManager.search(searchByRFC822MessageId, session, limit)).toStream().findFirst();
        } catch (UsersRepositoryException e) {
            LOGGER.error("unable to find message with Message-Id: " + messageId, e);
        }
        return Optional.empty();
    }

    @Override
    public String getMailetInfo() {
        return "ExtractMDNOriginalJMAPMessageId";
    }

}