/**
 *    Copyright (C) 2014 10gen 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 <set>

#include "mongo/db/storage/record_store.h"
#include "mongo/db/storage/mmap_v1/record_store_v1_base.h"

namespace mongo {

    /**
     * This iterator will go over the collection twice - once going forward (first extent -> last
     * extent) and once backwards in an attempt to salvage potentially corrupted or unreachable 
     * records. It is used by the mongodump --repair option.
     */
    class RecordStoreV1RepairIterator : public RecordIterator {
    public:
        RecordStoreV1RepairIterator(OperationContext* txn,
                                    const RecordStoreV1Base* recordStore);
        virtual ~RecordStoreV1RepairIterator() { }

        virtual bool isEOF();
        virtual DiskLoc getNext();
        virtual DiskLoc curr();

        virtual void invalidate(const DiskLoc& dl);
        virtual void prepareToYield() { }
        virtual bool recoverFromYield() {
            return true;
        }

        virtual RecordData dataFor( const DiskLoc& loc ) const;

    private:

        /**
         * Based on the direction of scan, finds the next valid (un-corrupted) extent in the chain
         * and sets _currExtent to point to that.
         *
         * @return true if valid extent was found (_currExtent will not be null)
         *         false otherwise and _currExtent will be null
         */
        bool _advanceToNextValidExtent();

        // transactional context for read locks. Not owned by us
        OperationContext* _txn;

        // Reference to the owning RecordStore. The store must not be deleted while there are 
        // active iterators on it.
        //
        const RecordStoreV1Base* _recordStore;

        DiskLoc _currExtent;
        DiskLoc _currRecord;

        enum Stage {
            FORWARD_SCAN = 0,
            BACKWARD_SCAN = 1,
            DONE = 2
        };

        Stage _stage;

        // Used to find cycles within an extent. Cleared after each extent has been processed.
        //
        std::set<DiskLoc> _seenInCurrentExtent;
    };

}  // namespace mongo