/**
 *    Copyright (C) 2022-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.
 */

#include <benchmark/benchmark.h>

#include "mongo/bson/bsonmisc.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/exec/document_value/document.h"


namespace mongo {
namespace {

/**
 * Generates a linearly-nested (and therefore unbalanced or skewed) BSON object with the given
 * number of non-object (leaf) fields, which is also the depth. For example, for numberOfLeaves = 3,
 * the result is
 * {
 *   "a": "AAA...",
 *   "b": {
 *     "a": "AAA...",
 *     "b": {
 *       "a": "AAA..."
 *     }
 *   }
 * }
 */
BSONObj generateSkewedBsonObj(size_t numberOfLeaves) {
    // Speed-up data generation by re-using previous result.
    static const std::string leafValue(128, 'A');
    static BSONObj result = BSON("a" << leafValue);
    static size_t resultSize = 1;

    invariant(numberOfLeaves >= 1);

    if (resultSize > numberOfLeaves) {
        // Reset if cannot re-use the previous result.
        result = BSON("a" << leafValue);
        resultSize = 1;
    }

    for (; resultSize < numberOfLeaves; ++resultSize) {
        result = BSON("a" << leafValue << "b" << result);
    }
    return result;
}

}  // namespace

/**
 * Benchmarks document's serialization to BSON. The chosen method 'toBson(BSONObjBuilder*, size_t)'
 * by-passes trivial serialization (when document's storage is already in BSON format) and is called
 * by other serialization methods.
 */
void BM_documentToBson(benchmark::State& state) {
    Document doc{generateSkewedBsonObj(state.range(0))};
    for (auto _ : state) {
        BSONObjBuilder bb;
        doc.toBson(&bb);
    }
    state.counters["objsize"] = doc.toBson().objsize();
}

BENCHMARK(BM_documentToBson)->DenseRange(2'000, 10'000, 2'000)->Unit(benchmark::kMicrosecond);

}  // namespace mongo