// Copyright (c) 2020-2022 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 <blockfilter.h>

#include <serialize.h>

#include <streams.h>

#include <test/fuzz/FuzzedDataProvider.h>

#include <test/fuzz/fuzz.h>

#include <test/fuzz/util.h>

#include <util/bytevectorhash.h>

#include <util/golombrice.h>

#include <algorithm>

#include <cassert>

#include <cstdint>

#include <iosfwd>

#include <unordered_set>

#include <vector>

namespace {

uint64_t HashToRange(const std::vector<uint8_t>& element, const uint64_t f)

{

    const uint64_t hash = CSipHasher(0x0706050403020100ULL, 0x0F0E0D0C0B0A0908ULL)

                              .Write(element)

                              .Finalize();

    return FastRange64(hash, f);

}

std::vector<uint64_t> BuildHashedSet(const std::unordered_set<std::vector<uint8_t>, ByteVectorHash>& elements, const uint64_t f)

{

    std::vector<uint64_t> hashed_elements;

    hashed_elements.reserve(elements.size());

    for (const std::vector<uint8_t>& element : elements) {

        hashed_elements.push_back(HashToRange(element, f));

    }

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

    return hashed_elements;

}

} // namespace

FUZZ_TARGET(golomb_rice)

{

    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());

    std::vector<uint8_t> golomb_rice_data;

    std::vector<uint64_t> encoded_deltas;

    {

        std::unordered_set<std::vector<uint8_t>, ByteVectorHash> elements;

        const int n = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 512);

        for (int i = 0; i < n; ++i) {

            elements.insert(ConsumeRandomLengthByteVector(fuzzed_data_provider, 16));

        }

        VectorWriter stream{golomb_rice_data, 0};

        WriteCompactSize(stream, static_cast<uint32_t>(elements.size()));

        BitStreamWriter bitwriter{stream};

        if (!elements.empty()) {

            uint64_t last_value = 0;

            for (const uint64_t value : BuildHashedSet(elements, static_cast<uint64_t>(elements.size()) * static_cast<uint64_t>(BASIC_FILTER_M))) {

                const uint64_t delta = value - last_value;

                encoded_deltas.push_back(delta);

                GolombRiceEncode(bitwriter, BASIC_FILTER_P, delta);

                last_value = value;

            }

        }

        bitwriter.Flush();

    }

    std::vector<uint64_t> decoded_deltas;

    {

        SpanReader stream{golomb_rice_data};

        BitStreamReader bitreader{stream};

        const uint32_t n = static_cast<uint32_t>(ReadCompactSize(stream));

        for (uint32_t i = 0; i < n; ++i) {

            decoded_deltas.push_back(GolombRiceDecode(bitreader, BASIC_FILTER_P));

        }

    }

    assert(encoded_deltas == decoded_deltas);

    {

        const std::vector<uint8_t> random_bytes = ConsumeRandomLengthByteVector(fuzzed_data_provider, 1024);

        SpanReader stream{random_bytes};

        uint32_t n;

        try {

            n = static_cast<uint32_t>(ReadCompactSize(stream));

        } catch (const std::ios_base::failure&) {

            return;

        }

        BitStreamReader bitreader{stream};

        for (uint32_t i = 0; i < std::min<uint32_t>(n, 1024); ++i) {

            try {

                (void)GolombRiceDecode(bitreader, BASIC_FILTER_P);

            } catch (const std::ios_base::failure&) {

            }

        }

    }

}