/*
 * 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.impl.transaction.log.pruning;

import java.io.IOException;

public interface LogPruning {
    /**
     * Prunes logs that have version less than {@code currentVersion}. This is a best effort service and there is no
     * guarantee that any logs will be removed.
     *
     * @param currentVersion The lowest version expected to remain after pruning completes.
     */
    void pruneLogs(long currentVersion) throws IOException;

    /**
     * Check if there might be a desire to prune logs. This could be used as a hint to schedule some log pruning soon,
     * and/or increase the check pointing frequency.
     *
     * @return {@code true} if calling {@link #pruneLogs(long)} now <em>might</em> cause log files to be deleted.
     * Otherwise {@code false} if we are pretty sure that we don't need to prune any logs right now.
     * @param upperVersion check up to this version.
     */
    boolean mightHaveLogsToPrune(long upperVersion);

    /**
     * @return A textual representation of the current log pruning strategy, for logging and debugging purposes.
     */
    String describeCurrentStrategy();

    LogPruning NO_PRUNING = new LogPruning() {
        @Override
        public void pruneLogs(long currentVersion) {}

        @Override
        public boolean mightHaveLogsToPrune(long upperVersion) {
            return false;
        }

        @Override
        public String describeCurrentStrategy() {
            return LogPruneStrategyFactory.NO_PRUNING.toString();
        }
    };
}
