/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.internal.id;

import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Consumer;
import java.util.function.LongSupplier;
import org.eclipse.collections.api.set.ImmutableSet;
import org.neo4j.configuration.Config;
import org.neo4j.io.pagecache.PageCache;
import org.neo4j.io.pagecache.context.CursorContext;
import org.neo4j.io.pagecache.context.CursorContextFactory;

/**
 * {@link IdGeneratorFactory} that ignores the underlying id file and only uses the provided highIdScanner in
 * {@link IdGeneratorFactory#open(PageCache, Path, IdType, LongSupplier, long, boolean, Config, CursorContextFactory, ImmutableSet,
 * IdSlotDistribution)}, instantiating {@link IdGenerator} that will return that highId and do nothing else.
 * This is of great convenience when migrating between id file formats.
 */
public class ScanOnOpenReadOnlyIdGeneratorFactory implements IdGeneratorFactory {
    private final Map<IdType, ReadOnlyHighIdGenerator> idGenerators = new HashMap<>();

    @Override
    public IdGenerator open(
            PageCache pageCache,
            Path filename,
            IdType idType,
            LongSupplier highIdScanner,
            long maxId,
            boolean readOnly,
            Config config,
            CursorContextFactory contextFactory,
            ImmutableSet<OpenOption> openOptions,
            IdSlotDistribution slotDistribution) {
        long highId = highIdScanner.getAsLong();
        ReadOnlyHighIdGenerator idGenerator = new ReadOnlyHighIdGenerator(highId, idType);
        idGenerators.put(idType, idGenerator);
        return idGenerator;
    }

    @Override
    public IdGenerator create(
            PageCache pageCache,
            Path filename,
            IdType idType,
            long highId,
            boolean throwIfFileExists,
            long maxId,
            boolean readOnly,
            Config config,
            CursorContextFactory contextFactory,
            ImmutableSet<OpenOption> openOptions,
            IdSlotDistribution slotDistribution) {
        return open(
                pageCache,
                filename,
                idType,
                () -> highId,
                maxId,
                readOnly,
                config,
                contextFactory,
                openOptions,
                slotDistribution);
    }

    @Override
    public IdGenerator get(IdType idType) {
        ReadOnlyHighIdGenerator idGenerator = idGenerators.get(idType);
        if (idGenerator == null) {
            throw new IllegalStateException("IdGenerator for " + idType + " not opened");
        }
        return idGenerator;
    }

    @Override
    public void visit(Consumer<IdGenerator> visitor) {
        idGenerators.values().forEach(visitor);
    }

    @Override
    public void clearCache(CursorContext cursorContext) {
        idGenerators.values().forEach(idGenerator -> idGenerator.clearCache(cursorContext));
    }

    @Override
    public Collection<Path> listIdFiles() {
        return Collections.emptyList();
    }
}
