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Event capture and querying framework for Java

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/**
 * Copyright (c) 2016, All Contributors (see CONTRIBUTORS file)
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package com.eventsourcing.repository.commands;

import com.eventsourcing.*;
import com.eventsourcing.layout.Layout;
import com.eventsourcing.layout.LayoutConstructor;
import com.eventsourcing.migrations.events.EntityLayoutIntroduced;
import com.googlecode.cqengine.query.Query;
import com.googlecode.cqengine.resultset.ResultSet;
import lombok.SneakyThrows;

import java.util.Optional;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Function;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import static com.eventsourcing.index.EntityQueryFactory.equal;

public class IntroduceEntityLayouts extends StandardCommand {

    private Iterable> entities;

    @LayoutConstructor
    public IntroduceEntityLayouts() {}

    public IntroduceEntityLayouts(Iterable> entities) {this.entities = entities;}

    @Override public EventStream events(Repository repository, LockProvider lockProvider) throws Exception {
        Lock lock = lockProvider.lock(getClass().getName());
        Stream> stream = StreamSupport
                .stream(Spliterators.spliteratorUnknownSize(entities.iterator(), Spliterator.IMMUTABLE), false);
        return EventStream.ofWithState(lock, stream.flatMap(new EntityStreamFunction(repository)));
    }

    @Override public Void result(Lock lock) {
        lock.unlock();
        return null;
    }

    private static class EntityStreamFunction implements Function, Stream> {
        private final Repository repository;

        public EntityStreamFunction(Repository repository) {this.repository = repository;}

        @SneakyThrows
        @Override public Stream apply(Class entity) {
        Layout layout = Layout.forClass(entity);
            byte[] fingerprint = layout.getHash();
            Query> query = equal(EntityLayoutIntroduced.FINGERPRINT, fingerprint);
            try (ResultSet> resultSet = repository
                    .query(EntityLayoutIntroduced.class,
                           query)) {
                if (resultSet.isEmpty()) {
                    return Stream.of(new EntityLayoutIntroduced(fingerprint, Optional.of(layout)));
                } else {
                    return Stream.empty();
                }
            }


        }
    }
}