/**
 *    Copyright (C) 2020-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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/bson/bsonobj.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/query/plan_enumerator_explain_info.h"
#include "mongo/db/query/plan_explainer.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/util/duration.h"

namespace mongo {
/**
 * A PlanExplainer implementation for classic execution plans.
 *
 * For classic execution plans all information required to generate explain output in various
 * formats is stored in the execution tree itself, so having access to the root stage of the
 * execution tree this PlanExplainer should obtain all plan details and execution stats.
 */
class PlanExplainerImpl final : public PlanExplainer {
public:
    PlanExplainerImpl(PlanStage* root, const PlanEnumeratorExplainInfo& explainInfo)
        : PlanExplainer{explainInfo}, _root{root} {}
    PlanExplainerImpl(PlanStage* root) : _root{root} {}
    const ExplainVersion& getVersion() const final;
    bool isMultiPlan() const final;
    std::string getPlanSummary() const final;
    void getSummaryStats(PlanSummaryStats* statsOut) const final;
    PlanStatsDetails getWinningPlanStats(ExplainOptions::Verbosity verbosity) const final;
    PlanStatsDetails getWinningPlanTrialStats() const final;
    std::vector<PlanStatsDetails> getRejectedPlansStats(
        ExplainOptions::Verbosity verbosity) const final;
    std::vector<PlanStatsDetails> getCachedPlanStats(const plan_cache_debug_info::DebugInfo&,
                                                     ExplainOptions::Verbosity) const;

private:
    PlanStage* const _root;
};

/**
 * Retrieves the first stage of a given type from the plan tree, or nullptr if no such stage is
 * found.
 */
PlanStage* getStageByType(PlanStage* root, StageType type);

/**
 * Returns filtered plan stats from the debugInfo object for different verbosity levels.
 */
std::vector<PlanExplainer::PlanStatsDetails> getCachedPlanStats(
    const plan_cache_debug_info::DebugInfo& debugInfo, ExplainOptions::Verbosity verbosity);

/**
 * Adds the path-level multikey information to the explain output in a field called "multiKeyPaths".
 * The value associated with the "multiKeyPaths" field is an object with keys equal to those in the
 * index key pattern and values equal to an array of strings corresponding to paths that cause the
 * index to be multikey.
 *
 * For example, with the index {'a.b': 1, 'a.c': 1} where the paths "a" and "a.b" cause the
 * index to be multikey, we'd have {'multiKeyPaths': {'a.b': ['a', 'a.b'], 'a.c': ['a']}}.
 *
 * This function should only be called if the associated index supports path-level multikey
 * tracking.
 */
void appendMultikeyPaths(const BSONObj& keyPattern,
                         const MultikeyPaths& multikeyPaths,
                         BSONObjBuilder* bob);
}  // namespace mongo