/**
 *    Copyright (C) 2018-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/util/duration.h"
#include <optional>
#include <set>
#include <string>

#include "mongo/util/container_size_helper.h"

namespace mongo {

// The precision of 'executionTime'. Note that 'kNanos' precision requires a precise timer which
// is also slower than the default timer.
enum class QueryExecTimerPrecision { kNoTiming = 0, kNanos, kMillis };

struct QueryExecTime {
    // Precision/unit of 'executionTimeEstimate'.
    QueryExecTimerPrecision precision = QueryExecTimerPrecision::kNoTiming;
    // Time elapsed while executing this plan.
    Nanoseconds executionTimeEstimate{0};
};

/**
 * A container for the summary statistics that the profiler, slow query log, and
 * other non-explain debug mechanisms may want to collect.
 */
struct PlanSummaryStats {

    uint64_t estimateObjectSizeInBytes() const {
        auto strSize = [](const std::string& str) {
            return str.capacity() * sizeof(std::string::value_type);
        };

        return sizeof(*this) +
            container_size_helper::estimateObjectSizeInBytes(
                   indexesUsed, strSize, false /* includeShallowSize */) +
            (replanReason ? strSize(*replanReason) : 0);
    }

    // The number of results returned by the plan.
    size_t nReturned = 0U;

    // The total number of index keys examined by the plan.
    size_t totalKeysExamined = 0U;

    // The total number of documents examined by the plan.
    size_t totalDocsExamined = 0U;

    // The number of collection scans that occur during execution. Note that more than one
    // collection scan may happen during execution (e.g. for $lookup execution).
    long long collectionScans = 0;

    // The number of collection scans that occur during execution which are nontailable. Note that
    // more than one collection scan may happen during execution (e.g. for $lookup execution).
    long long collectionScansNonTailable = 0;

    // Time elapsed while executing this plan.
    QueryExecTime executionTime;

    // Did this plan use an in-memory sort stage?
    bool hasSortStage = false;

    // Did this plan use disk space?
    bool usedDisk = false;

    // The total number of spills to disk from sort stages
    long long sortSpills = 0;

    // The total number of bytes spilled to disk from sort stages
    long long sortSpillBytes = 0;

    // The amount of data we've sorted in bytes
    size_t sortTotalDataSizeBytes = 0;

    // The number of keys that we've sorted.
    long long keysSorted = 0;

    // Did this plan failed during execution?
    bool planFailed = false;

    // The names of each index used by the plan.
    std::set<std::string> indexesUsed;

    // Was this plan a result of using the MultiPlanStage to select a winner among several
    // candidates?
    bool fromMultiPlanner = false;

    // Was this plan recovered from the cache?
    bool fromPlanCache = false;
    // Was a replan triggered during the execution of this query?
    boost::optional<std::string> replanReason;

    // Score calculated for the plan by PlanRanker. Only set if there were multiple candidate plans
    // and allPlansExecution verbosity mode is selected.
    boost::optional<double> score;
};

}  // namespace mongo
