// Copyright (c) 2021-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <node/minisketchwrapper.h>

#include <logging.h>

#include <util/time.h>

#include <minisketch.h>

#include <algorithm>

#include <cstddef>

#include <cstdint>

#include <optional>

#include <utility>

#include <vector>

namespace node {

namespace {

static constexpr uint32_t BITS = 32;

uint32_t FindBestImplementation()

{

    std::optional<std::pair<SteadyClock::duration, uint32_t>> best;

    uint32_t max_impl = Minisketch::MaxImplementation();

    for (uint32_t impl = 0; impl <= max_impl; ++impl) {

        std::vector<SteadyClock::duration> benches;

        uint64_t offset = 0;

        /* Run a little benchmark with capacity 32, adding 184 entries, and decoding 11 of them once. */

        for (int b = 0; b < 11; ++b) {

            if (!Minisketch::ImplementationSupported(BITS, impl)) break;

            Minisketch sketch(BITS, impl, 32);

            auto start = SteadyClock::now();

            for (uint64_t e = 0; e < 100; ++e) {

                sketch.Add(e*1337 + b*13337 + offset);

            }

            for (uint64_t e = 0; e < 84; ++e) {

                sketch.Add(e*1337 + b*13337 + offset);

            }

            offset += (*sketch.Decode(32))[0];

            auto stop = SteadyClock::now();

            benches.push_back(stop - start);

        }

        /* Remember which implementation has the best median benchmark time. */

        if (!benches.empty()) {

            std::sort(benches.begin(), benches.end());

            if (!best || best->first > benches[5]) {

                best = std::make_pair(benches[5], impl);

            }

        }

    }

    assert(best.has_value());

    LogInfo("Using Minisketch implementation number %i", best->second);

    return best->second;

}

uint32_t Minisketch32Implementation()

{

    // Fast compute-once idiom.

    static uint32_t best = FindBestImplementation();

    return best;

}

} // namespace

Minisketch MakeMinisketch32(size_t capacity)

{

    return Minisketch(BITS, Minisketch32Implementation(), capacity);

}

Minisketch MakeMinisketch32FP(size_t max_elements, uint32_t fpbits)

{

    return Minisketch::CreateFP(BITS, Minisketch32Implementation(), max_elements, fpbits);

}

} // namespace node