/**
 *    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 "mongo/db/jsobj.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/db/record_id.h"

namespace mongo {

    /**
     * This stage outputs its mainChild, and possibly its backup child
     * and also updates the cache.
     *
     * Preconditions: Valid DiskLoc.
     *
     */
    class CachedPlanStage : public PlanStage {
    public:
        /**
         * Takes ownership of 'mainChild', 'mainQs', 'backupChild', and 'backupQs'.
         */
        CachedPlanStage(const Collection* collection,
                        CanonicalQuery* cq,
                        PlanStage* mainChild,
                        QuerySolution* mainQs,
                        PlanStage* backupChild = NULL,
                        QuerySolution* backupQs = NULL);

        virtual ~CachedPlanStage();

        virtual bool isEOF();

        virtual StageState work(WorkingSetID* out);

        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_CACHED_PLAN; }

        virtual PlanStageStats* getStats();

        virtual const CommonStats* getCommonStats();

        virtual const SpecificStats* getSpecificStats();

        static const char* kStageType;

    private:
        PlanStage* getActiveChild() const;
        void updateCache();

        // not owned
        const Collection* _collection;

        // not owned
        CanonicalQuery* _canonicalQuery;

        // Owned by us. Must be deleted after the corresponding PlanStage trees, as
        // those trees point into the query solutions.
        boost::scoped_ptr<QuerySolution> _mainQs;
        boost::scoped_ptr<QuerySolution> _backupQs;

        // Owned by us. Must be deleted before the QuerySolutions above, as these
        // can point into the QuerySolutions.
        boost::scoped_ptr<PlanStage> _mainChildPlan;
        boost::scoped_ptr<PlanStage> _backupChildPlan;

        // True if the main plan errors before producing results
        // and if a backup plan is available (can happen with blocking sorts)
        bool _usingBackupChild;

        // True if the childPlan has produced results yet.
        bool _alreadyProduced;

        // Have we updated the cache with our plan stats yet?
        bool _updatedCache;

        // Stats
        CommonStats _commonStats;
        CachedPlanStats _specificStats;
    };

}  // namespace mongo