/**
 *    Copyright (C) 2013 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 "mongo/db/diskloc.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/s/chunk_version.h"
#include "mongo/s/d_logic.h"
#include "mongo/s/stale_exception.h"

namespace mongo {

    /**
     * This stage drops documents that didn't belong to the shard we're executing on at the time of
     * construction. This matches the contract for sharded cursorids which guarantees that a
     * StaleConfigException will be thrown early or the cursorid for its entire lifetime will return
     * documents matching the shard version set on the connection at the time of cursorid creation.
     *
     * A related system will ensure that the data migrated away from a shard will not be deleted as
     * long as there are active queries from before the migration. Currently, "active queries" is
     * defined by cursorids so it is important that the metadata used in this stage uses the same
     * version as the cursorid. Therefore, you must wrap any Runner using this Stage in a
     * ClientCursor during the same lock grab as constructing the Runner.
     *
     * BEGIN NOTE FROM GREG
     *
     * There are three sharded query contracts:
     *
     * 0) Migration commit takes the db lock - i.e. is serialized with writes and reads.
     * 1) No data should be returned from a query in ranges of migrations that committed after the
     * query started, or from ranges not owned when the query began.
     * 2) No migrated data should be removed from a shard while there are queries that were active
     * before the migration.
     *
     * As implementation details, collection metadata is used to determine the ranges of all data
     * not actively migrated (or orphaned).  CursorIds are currently used to establish "active"
     * queries before migration commit.
     *
     * Combining all this: if a query is started in a db lock and acquires in that (same) lock the
     * collection metadata and a cursorId, the query will return results for exactly the ranges in
     * the metadata (though of arbitrary staleness).  This is the sharded collection query contract.
     *
     * END NOTE FROM GREG
     *
     * Preconditions: Child must be fetched.  TODO: when covering analysis is in just build doc
     * and check that against shard key.  See SERVER-5022.
     */
    class ShardFilterStage : public PlanStage {
    public:
        ShardFilterStage(const CollectionMetadataPtr& metadata, WorkingSet* ws, PlanStage* child);
        virtual ~ShardFilterStage();

        virtual bool isEOF();
        virtual StageState work(WorkingSetID* out);

        virtual void prepareToYield();
        virtual void recoverFromYield();
        virtual void invalidate(const DiskLoc& dl, InvalidationType type);

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

        virtual StageType stageType() const { return STAGE_SHARDING_FILTER; }

        virtual PlanStageStats* getStats();

        virtual const CommonStats* getCommonStats();

        virtual const SpecificStats* getSpecificStats();

        static const char* kStageType;

    private:
        WorkingSet* _ws;
        scoped_ptr<PlanStage> _child;

        // Stats
        CommonStats _commonStats;
        ShardingFilterStats _specificStats;

        // Note: it is important that this is the metadata from the time this stage is constructed.
        // See class comment for details.
        const CollectionMetadataPtr _metadata;
    };

}  // namespace mongo