/**
 *    Copyright (C) 2014 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 <boost/scoped_ptr.hpp>

#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/index/btree_index_cursor.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/record_id.h"
#include "mongo/platform/unordered_set.h"

namespace mongo {

    class IndexAccessMethod;
    class IndexDescriptor;
    class WorkingSet;

    struct CountScanParams {
        CountScanParams() : descriptor(NULL) { }

        // What index are we traversing?
        const IndexDescriptor* descriptor;

        BSONObj startKey;
        bool startKeyInclusive;

        BSONObj endKey;
        bool endKeyInclusive;
    };

    /**
     * Used by the count command.  Scans an index from a start key to an end key.  Does not create
     * any WorkingSetMember(s) for any of the data, instead returning ADVANCED to indicate to the
     * caller that another result should be counted.
     *
     * Only created through the getExecutorCount path, as count is the only operation that doesn't
     * care about its data.
     */
    class CountScan : public PlanStage {
    public:
        CountScan(OperationContext* txn, const CountScanParams& params, WorkingSet* workingSet);
        virtual ~CountScan() { }

        virtual StageState work(WorkingSetID* out);
        virtual bool isEOF();
        virtual void saveState();
        virtual void restoreState(OperationContext* opCtx);
        virtual void invalidate(OperationContext* txn, const DiskLoc& dl, InvalidationType type);

        virtual std::vector<PlanStage*> getChildren() const;

        virtual StageType stageType() const { return STAGE_COUNT_SCAN; }

        virtual PlanStageStats* getStats();

        virtual const CommonStats* getCommonStats();

        virtual const SpecificStats* getSpecificStats();

        static const char* kStageType;

    private:
        /**
         * Initialize the underlying IndexCursor
         */
        void initIndexCursor();

        /**
         * See if we've hit the end yet.
         */
        void checkEnd();

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

        // The WorkingSet we annotate with results.  Not owned by us.
        WorkingSet* _workingSet;

        // Index access.  Both pointers below are owned by Collection -> IndexCatalog.
        const IndexDescriptor* _descriptor;
        const IndexAccessMethod* _iam;

        // Our start cursor is _btreeCursor.
        boost::scoped_ptr<BtreeIndexCursor> _btreeCursor;

        // Our end marker.
        boost::scoped_ptr<BtreeIndexCursor> _endCursor;

        // Could our index have duplicates?  If so, we use _returned to dedup.
        unordered_set<DiskLoc, DiskLoc::Hasher> _returned;

        CountScanParams _params;

        bool _hitEnd;

        bool _shouldDedup;

        CommonStats _commonStats;
        CountScanStats _specificStats;
    };

}  // namespace mongo