/*
 * 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.kernel.recovery;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Optional;
import org.neo4j.configuration.Config;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.fs.StoreChannel;
import org.neo4j.io.layout.DatabaseLayout;
import org.neo4j.kernel.impl.transaction.log.CheckpointInfo;
import org.neo4j.kernel.impl.transaction.log.LogPosition;
import org.neo4j.kernel.impl.transaction.log.files.LogFiles;
import org.neo4j.kernel.impl.transaction.log.files.LogFilesBuilder;

public final class RecoveryHelpers {
    private RecoveryHelpers() { // non-constructable
    }

    public static void removeLastCheckpointRecordFromLastLogFile(DatabaseLayout dbLayout, FileSystemAbstraction fs)
            throws IOException {
        LogFiles logFiles = buildLogFiles(dbLayout, fs, null);
        var checkpointFile = logFiles.getCheckpointFile();
        Optional<CheckpointInfo> latestCheckpoint = checkpointFile.findLatestCheckpoint();
        latestCheckpoint.ifPresent(checkpointInfo -> {
            LogPosition entryPosition = checkpointInfo.checkpointEntryPosition();
            try (StoreChannel storeChannel = fs.write(checkpointFile.getCurrentFile())) {
                storeChannel.truncate(entryPosition.getByteOffset());
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        });
    }

    public static boolean logsContainCheckpoint(DatabaseLayout dbLayout, FileSystemAbstraction fs) throws IOException {
        Optional<CheckpointInfo> latestCheckpoint = getLatestCheckpointInfo(dbLayout, fs, null);
        return latestCheckpoint.isPresent();
    }

    public static CheckpointInfo getLatestCheckpoint(DatabaseLayout dbLayout, FileSystemAbstraction fs)
            throws IOException {
        return getLatestCheckpoint(dbLayout, fs, null);
    }

    public static CheckpointInfo getLatestCheckpoint(DatabaseLayout dbLayout, FileSystemAbstraction fs, Config config)
            throws IOException {
        Optional<CheckpointInfo> latestCheckpoint = getLatestCheckpointInfo(dbLayout, fs, config);
        return latestCheckpoint.orElseThrow();
    }

    private static Optional<CheckpointInfo> getLatestCheckpointInfo(
            DatabaseLayout dbLayout, FileSystemAbstraction fs, Config config) throws IOException {
        LogFiles logFiles = buildLogFiles(dbLayout, fs, config);
        var checkpointFile = logFiles.getCheckpointFile();
        return checkpointFile.findLatestCheckpoint();
    }

    private static LogFiles buildLogFiles(DatabaseLayout dbLayout, FileSystemAbstraction fs, Config config)
            throws IOException {
        return LogFilesBuilder.logFilesBasedOnlyBuilder(dbLayout.getTransactionLogsDirectory(), fs)
                .withConfig(config)
                .build();
    }
}
