server/extensions/xep0313-mam/src/main/java/org/apache/vysper/xmpp/modules/extension/xep0313_mam/in_memory/InMemoryArchivedMessagesPage.java

/*
 *  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.vysper.xmpp.modules.extension.xep0313_mam.in_memory;

import java.util.List;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.stream.Collectors;

import org.apache.vysper.xmpp.modules.extension.xep0313_mam.spi.ArchivedMessage;
import org.apache.vysper.xmpp.modules.extension.xep0313_mam.spi.ArchivedMessages;
import org.apache.vysper.xmpp.modules.extension.xep0313_mam.spi.MessagePageRequest;

/**
 * @author Réda Housni Alaoui
 */
public class InMemoryArchivedMessagesPage implements ArchivedMessages {

    private final List<ArchivedMessage> list;

    private final Long firstMessageIndex;

    private final long totalNumberOfMessages;

    public InMemoryArchivedMessagesPage(MessagePageRequest request, List<ArchivedMessage> unlimitedMessages) {
        totalNumberOfMessages = unlimitedMessages.size();

        String firstMessageId = request.firstMessageId().orElse(null);
        String lastMessageId = request.lastMessageId().orElse(null);
        Long pageSize = request.pageSize().orElse(null);

        AtomicBoolean firstMessageFound = new AtomicBoolean(firstMessageId == null);
        AtomicBoolean lastMessageFound = new AtomicBoolean();
        AtomicLong numberOfMessageKept = new AtomicLong();

        list = unlimitedMessages.stream().filter(message -> pageSize == null || numberOfMessageKept.get() < pageSize)
                .peek(message -> lastMessageFound.compareAndSet(false,
                        lastMessageId != null && lastMessageId.equals(message.id())))
                .filter(message -> !lastMessageFound.get())
                .peek(message -> firstMessageFound.compareAndSet(false, message.id().equals(firstMessageId)))
                .filter(message -> firstMessageFound.get() && !message.id().equals(firstMessageId))
                .peek(message -> numberOfMessageKept.incrementAndGet()).collect(Collectors.toList());

        firstMessageIndex = list.stream().findFirst().map(unlimitedMessages::indexOf).map(index -> (long) index)
                .orElse(null);
    }
    
    @Override
    public List<ArchivedMessage> list() {
        return list;
    }

    @Override
    public boolean isEmpty() {
        return list.isEmpty();
    }

    @Override
    public boolean isComplete() {
        return list.size() == totalNumberOfMessages;
    }

    @Override
    public Optional<Long> firstMessageIndex() {
        return Optional.ofNullable(firstMessageIndex);
    }

    @Override
    public Optional<Long> totalNumberOfMessages() {
        return Optional.of(totalNumberOfMessages);
    }
}