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 * 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   *
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 *   http://www.apache.org/licenses/LICENSE-2.0                 *
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 * 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.                                           *
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package org.apache.james.webadmin.service;

import java.util.Optional;
import java.util.function.Consumer;

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

import org.apache.commons.lang3.tuple.Pair;
import org.apache.james.mailrepository.api.MailKey;
import org.apache.james.mailrepository.api.MailRepository;
import org.apache.james.mailrepository.api.MailRepositoryPath;
import org.apache.james.mailrepository.api.MailRepositoryStore;
import org.apache.james.queue.api.MailQueue;
import org.apache.james.queue.api.MailQueueFactory;
import org.apache.james.util.OptionalUtils;
import org.apache.james.util.streams.Iterators;
import org.apache.mailet.Mail;

import com.github.fge.lambdas.Throwing;

public class ReprocessingService {
    public static class MissingKeyException extends RuntimeException {
        MissingKeyException(MailKey key) {
            super(key.asString() + " can not be found");
        }
    }

    static class Reprocessor {
        private final MailQueue mailQueue;
        private final Optional<String> targetProcessor;

        Reprocessor(MailQueue mailQueue, Optional<String> targetProcessor) {
            this.mailQueue = mailQueue;
            this.targetProcessor = targetProcessor;
        }

        private void reprocess(MailRepository repository, Mail mail) {
            try {
                targetProcessor.ifPresent(mail::setState);
                mailQueue.enQueue(mail);
                repository.remove(mail);
            } catch (Exception e) {
                throw new RuntimeException("Error encountered while reprocessing mail " + mail.getName(), e);
            }
        }
    }

    private final MailQueueFactory<?> mailQueueFactory;
    private final MailRepositoryStoreService mailRepositoryStoreService;

    @Inject
    public ReprocessingService(MailQueueFactory<?> mailQueueFactory,
                               MailRepositoryStoreService mailRepositoryStoreService) {
        this.mailQueueFactory = mailQueueFactory;
        this.mailRepositoryStoreService = mailRepositoryStoreService;
    }

    public void reprocessAll(MailRepositoryPath path, Optional<String> targetProcessor, String targetQueue, Consumer<MailKey> keyListener) throws MailRepositoryStore.MailRepositoryStoreException, MessagingException {
        Reprocessor reprocessor = new Reprocessor(getMailQueue(targetQueue), targetProcessor);

        mailRepositoryStoreService
            .getRepositories(path)
            .forEach(Throwing.consumer((MailRepository repository) ->
                Iterators.toStream(repository.list())
                    .peek(keyListener)
                    .map(Throwing.function(key -> Optional.ofNullable(repository.retrieve(key))))
                    .flatMap(OptionalUtils::toStream)
                    .forEach(mail -> reprocessor.reprocess(repository, mail))));
    }

    public void reprocess(MailRepositoryPath path, MailKey key, Optional<String> targetProcessor, String targetQueue) throws MailRepositoryStore.MailRepositoryStoreException, MessagingException {
        Reprocessor reprocessor = new Reprocessor(getMailQueue(targetQueue), targetProcessor);

        Pair<MailRepository, Mail> mailPair = mailRepositoryStoreService
            .getRepositories(path)
            .map(Throwing.function(repository -> Pair.of(repository, Optional.ofNullable(repository.retrieve(key)))))
            .filter(pair -> pair.getRight().isPresent())
            .map(pair -> Pair.of(pair.getLeft(), pair.getRight().get()))
            .findFirst()
            .orElseThrow(() -> new MissingKeyException(key));

        reprocessor.reprocess(mailPair.getKey(), mailPair.getValue());
    }

    private MailQueue getMailQueue(String targetQueue) {
        return mailQueueFactory.getQueue(targetQueue)
            .orElseThrow(() -> new RuntimeException("Can not find queue " + targetQueue));
    }
}
