/*
 * 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 static org.neo4j.index.internal.gbptree.RecoveryCleanupWorkCollector.immediate;

import java.io.IOException;
import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.util.function.LongSupplier;
import org.eclipse.collections.api.set.ImmutableSet;
import org.neo4j.configuration.Config;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.pagecache.PageCache;
import org.neo4j.io.pagecache.context.CursorContextFactory;
import org.neo4j.io.pagecache.tracing.PageCacheTracer;

/**
 * A {@link DefaultIdGeneratorFactory} that ignores any existing id file on open and instead replaces it with an id file
 * of the current format with the highId it got from scanning the store on open. I.e. it treats the store as source of truth
 * w/ regards to highId.
 *
 * This is very useful in various id-file migration scenarios, both when migrating from an old format, but also when migrating
 * from a store that has no id files (once upon a time this was accepted).
 */
public class ScanOnOpenOverwritingIdGeneratorFactory extends DefaultIdGeneratorFactory {
    public ScanOnOpenOverwritingIdGeneratorFactory(
            FileSystemAbstraction fs, PageCacheTracer pageCacheTracer, String databaseName) {
        super(fs, immediate(), pageCacheTracer, databaseName);
    }

    @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)
            throws IOException {
        assert !readOnly;
        long highId = highIdScanner.getAsLong();
        return create(
                pageCache,
                filename,
                idType,
                highId,
                true,
                maxId,
                false,
                config,
                contextFactory,
                openOptions,
                slotDistribution);
    }
}
