/**
 *    Copyright (C) 2017 MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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 Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include "mongo/db/repl/oplog_entry.h"

namespace mongo {

class OperationContext;

/**
 * An iterator class that can traverse through the oplog entries that are linked via the prevTs
 * field.
 */
class TransactionHistoryIterator {
public:
    /**
     * Creates a new iterator starting with an oplog entry with the given start opTime.
     */
    TransactionHistoryIterator(repl::OpTime startingOpTime);

    /**
     * Returns false if there are no more entries to iterate.
     */
    bool hasNext() const;

    /**
     * Returns the next oplog entry.
     * Should not be called if hasNext is false.
     * Throws if next oplog entry is in a unrecognized format or if it can't find the next oplog
     * entry.
     */
    repl::OplogEntry next(OperationContext* opCtx);

private:
    repl::OpTime _nextOpTime;
};

}  // namespace mongo