// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include <random>
#include <future>
#include <thread>
#include <atomic>
#include <mutex>
#include <condition_variable>
#include <chrono>
#include <vector>
#include <utility>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <catch2/catch_all.hpp>

#include "../image_pusher/TCPStreamPusher.h"
#include "../image_puller/TCPImagePuller.h"
#include "../image_puller/ZMQImagePuller.h"
#include "../common/ImageBuffer.h"
#include "../common/ZeroCopyReturnValue.h"

TEST_CASE("TCPImageCommTest_2Writers_WithAck", "[TCP]") {
    const size_t nframes = 128;
    const int64_t npullers = 2;
    const int64_t images_per_file = 16;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);
    x.RunNumber(567);

    std::mt19937 g1(1387);
    std::uniform_int_distribution<uint16_t> dist;
    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes);
    for (auto &i: image1) i = dist(g1);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", npullers);
    std::vector<std::unique_ptr<TCPImagePuller> > puller;
    for (int i = 0; i < npullers; i++)
        puller.push_back(std::make_unique<TCPImagePuller>(pusher.GetAddress()[0], 64 * 1024 * 1024));

    // Wait for all pullers to connect before starting data collection
    for (int attempt = 0; attempt < 100 && pusher.GetConnectedWriters() < static_cast<size_t>(npullers); ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    REQUIRE(pusher.GetConnectedWriters() == static_cast<size_t>(npullers));

    std::vector<size_t> received(npullers, 0);
    std::vector<size_t> processed(npullers, 0);

    std::thread sender([&] {
        std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
        CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

        StartMessage start{
            .images_per_file = images_per_file,
            .run_number = x.GetRunNumber(),
            .write_master_file = true
        };
        EndMessage end{};

        pusher.StartDataCollection(start);

        for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
            DataMessage data_message;
            data_message.number = i;
            data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                                 x.GetPixelsNum() * sizeof(uint16_t),
                                                 x.GetXPixelsNum(),
                                                 x.GetYPixelsNum(),
                                                 x.GetImageMode(),
                                                 x.GetCompressionAlgorithm());
            serializer.SerializeImage(data_message);
            REQUIRE(pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i));
        }

        REQUIRE(pusher.EndDataCollection(end));
    });

    std::vector<std::thread> receivers;
    receivers.reserve(npullers);

    std::mutex counts_mutex;
    std::vector<size_t> received_by_socket(npullers, 0);
    std::vector<size_t> processed_by_socket(npullers, 0);

    for (int w = 0; w < npullers; w++) {
        receivers.emplace_back([&, w] {
            bool seen_start = false;
            bool seen_end = false;
            std::optional<uint32_t> my_socket_number;

            while (!seen_end) {
                auto out = puller[w]->PollImage(std::chrono::seconds(10));
                REQUIRE(out.has_value());
                REQUIRE(out->cbor != nullptr);
                REQUIRE(out->tcp_msg != nullptr);

                const auto &h = out->tcp_msg->header;

                if (out->cbor->start_message) {
                    my_socket_number = h.socket_number;

                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::START;
                    ack.ok = true;
                    ack.fatal = false;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.image_number = 0;
                    ack.processed_images = 0;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(ack.run_number == x.GetRunNumber());
                    REQUIRE(puller[w]->SendAck(ack));
                    seen_start = true;
                    continue;
                }

                if (out->cbor->data_message) {
                    REQUIRE(seen_start);
                    REQUIRE(my_socket_number.has_value());

                    auto n = out->cbor->data_message->number;
                    REQUIRE(((n / images_per_file) % npullers) == static_cast<int64_t>(*my_socket_number));

                    {
                        std::lock_guard<std::mutex> lg(counts_mutex);
                        received_by_socket.at(*my_socket_number)++;
                        processed_by_socket.at(*my_socket_number)++;
                    }
                    continue;
                }

                if (out->cbor->end_message) {
                    REQUIRE(my_socket_number.has_value());

                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::END;
                    ack.ok = true;
                    ack.fatal = false;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.image_number = 0;
                    {
                        std::lock_guard<std::mutex> lg(counts_mutex);
                        ack.processed_images = processed_by_socket.at(*my_socket_number);
                    }
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    seen_end = true;
                }
            }
        });
    }

    sender.join();
    for (auto &t: receivers) t.join();

    REQUIRE(received_by_socket[0] == nframes / 2);
    REQUIRE(received_by_socket[1] == nframes / 2);

    for (auto &p: puller)
        p->Disconnect();
}

TEST_CASE("TCPImageCommTest_DataFatalAck_PropagatesToPusher", "[TCP]") {
    const size_t nframes = 64;
    const int64_t npullers = 2;
    const int64_t images_per_file = 8;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);

    std::mt19937 g1(42);
    std::uniform_int_distribution<uint16_t> dist;
    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes);
    for (auto &i: image1) i = dist(g1);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", npullers);
    std::vector<std::unique_ptr<TCPImagePuller> > puller;
    for (int i = 0; i < npullers; i++)
        puller.push_back(std::make_unique<TCPImagePuller>(pusher.GetAddress()[0], 64 * 1024 * 1024));


    // Wait for all pullers to connect before starting data collection
    for (int attempt = 0; attempt < 100 && pusher.GetConnectedWriters() < static_cast<size_t>(npullers); ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    REQUIRE(pusher.GetConnectedWriters() == static_cast<size_t>(npullers));

    std::atomic<bool> sent_fatal{false};

    std::thread sender([&] {
        std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
        CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

        StartMessage start{
            .images_per_file = images_per_file,
            .write_master_file = true
        };
        EndMessage end{};

        pusher.StartDataCollection(start);

        for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
            DataMessage data_message;
            data_message.number = i;
            data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                                 x.GetPixelsNum() * sizeof(uint16_t),
                                                 x.GetXPixelsNum(),
                                                 x.GetYPixelsNum(),
                                                 x.GetImageMode(),
                                                 x.GetCompressionAlgorithm());
            serializer.SerializeImage(data_message);
            (void) pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i);
        }

        REQUIRE(pusher.EndDataCollection(end));
        const auto final_msg = pusher.Finalize();
        REQUIRE_THAT(final_msg, Catch::Matchers::ContainsSubstring("quota"));
    });

    std::vector<std::thread> receivers;
    receivers.reserve(npullers);

    for (int w = 0; w < npullers; w++) {
        receivers.emplace_back([&, w] {
            bool seen_end = false;
            bool local_fatal_sent = false;

            while (!seen_end) {
                auto out = puller[w]->PollImage(std::chrono::seconds(2));
                if (!out.has_value()) {
                    // Once this receiver has sent a fatal DATA ACK, no END is guaranteed on this stream.
                    if (local_fatal_sent)
                        break;
                    REQUIRE(out.has_value());
                }

                REQUIRE(out->cbor != nullptr);
                REQUIRE(out->tcp_msg != nullptr);

                const auto &h = out->tcp_msg->header;

                if (out->cbor->start_message) {
                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::START;
                    ack.ok = true;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    continue;
                }

                if (out->cbor->data_message) {
                    if (w == 0 && !sent_fatal.exchange(true)) {
                        PullerAckMessage ack;
                        ack.ack_for = TCPFrameType::DATA;
                        ack.ok = false;
                        ack.fatal = true;
                        ack.run_number = h.run_number;
                        ack.socket_number = h.socket_number;
                        ack.image_number = static_cast<uint64_t>(out->cbor->data_message->number);
                        ack.error_code = TCPAckCode::DiskQuotaExceeded;
                        ack.error_text = "quota exceeded";
                        REQUIRE(puller[w]->SendAck(ack));
                        local_fatal_sent = true;
                    }
                    continue;
                }

                if (out->cbor->end_message) {
                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::END;
                    ack.ok = true;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    seen_end = true;
                }
            }
        });
    }

    sender.join();
    for (auto &t: receivers) t.join();

    for (auto &p: puller)
        p->Disconnect();
}

TEST_CASE("TCPImageCommTest_GetAckProgress_Correct", "[TCP]") {
    const size_t nframes = 64;
    const int64_t npullers = 2;
    const int64_t images_per_file = 8;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);

    std::mt19937 g1(123);
    std::uniform_int_distribution<uint16_t> dist;
    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes);
    for (auto &i: image1) i = dist(g1);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", npullers);
    std::vector<std::unique_ptr<TCPImagePuller> > puller;
    for (int i = 0; i < npullers; i++)
        puller.push_back(std::make_unique<TCPImagePuller>(pusher.GetAddress()[0], 64 * 1024 * 1024));

    // Wait for all pullers to connect before starting data collection
    for (int attempt = 0; attempt < 100 && pusher.GetConnectedWriters() < static_cast<size_t>(npullers); ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    REQUIRE(pusher.GetConnectedWriters() == static_cast<size_t>(npullers));

    std::thread sender([&] {
        std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
        CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

        StartMessage start{
            .images_per_file = images_per_file,
            .write_master_file = true
        };
        EndMessage end{};

        pusher.StartDataCollection(start);

        for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
            DataMessage data_message;
            data_message.number = i;
            data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                                 x.GetPixelsNum() * sizeof(uint16_t),
                                                 x.GetXPixelsNum(),
                                                 x.GetYPixelsNum(),
                                                 x.GetImageMode(),
                                                 x.GetCompressionAlgorithm());
            serializer.SerializeImage(data_message);
            REQUIRE(pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i));
        }

        REQUIRE(pusher.EndDataCollection(end));

        std::this_thread::sleep_for(std::chrono::seconds(5));

        auto progress = pusher.GetImagesWritten();
        REQUIRE(progress.has_value());
        REQUIRE(progress == nframes / 2);
    });

    std::vector<std::thread> receivers;
    receivers.reserve(npullers);

    for (int w = 0; w < npullers; w++) {
        receivers.emplace_back([&, w] {
            bool seen_end = false;
            uint64_t processed = 0;

            while (!seen_end) {
                auto out = puller[w]->PollImage(std::chrono::seconds(10));
                REQUIRE(out.has_value());
                REQUIRE(out->cbor != nullptr);
                REQUIRE(out->tcp_msg != nullptr);

                const auto &h = out->tcp_msg->header;

                if (out->cbor->start_message) {
                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::START;
                    ack.ok = true;
                    ack.fatal = false;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.image_number = 0;
                    ack.processed_images = 0;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    continue;
                }

                if (out->cbor->data_message) {
                    auto number = out->cbor->data_message->number;

                    processed++;
                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::DATA;
                    ack.ok = (number % 2 == 0) ? true : false;
                    ack.fatal = false;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.image_number = number;
                    ack.processed_images = processed;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    continue;
                }

                if (out->cbor->end_message) {
                    PullerAckMessage ack;
                    ack.ack_for = TCPFrameType::END;
                    ack.ok = true;
                    ack.fatal = false;
                    ack.run_number = h.run_number;
                    ack.socket_number = h.socket_number;
                    ack.image_number = 0;
                    ack.processed_images = processed;
                    ack.error_code = TCPAckCode::None;
                    REQUIRE(puller[w]->SendAck(ack));
                    seen_end = true;
                }
            }
        });
    }

    sender.join();
    for (auto &t: receivers) t.join();

    for (auto &p: puller)
        p->Disconnect();
}

TEST_CASE("TCPImageCommTest_AutoPort_StarBind", "[TCP]") {
    const size_t nframes = 8;
    const int64_t images_per_file = 4;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);

    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes, 7u);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", 1);
    TCPImagePuller puller(pusher.GetAddress()[0], 64 * 1024 * 1024);

    std::this_thread::sleep_for(std::chrono::seconds(2));
    REQUIRE(pusher.GetConnectedWriters() == 1);

    std::future<void> receiver = std::async(std::launch::async, [&] {
        bool seen_end = false;
        uint64_t processed = 0;

        while (!seen_end) {
            auto out = puller.PollImage(std::chrono::seconds(10));
            REQUIRE(out.has_value());
            REQUIRE(out->cbor != nullptr);
            REQUIRE(out->tcp_msg != nullptr);

            const auto &h = out->tcp_msg->header;
            if (out->cbor->start_message) {
                PullerAckMessage ack{
                    .ack_for = TCPFrameType::START, .ok = true, .run_number = h.run_number,
                    .socket_number = h.socket_number, .error_code = TCPAckCode::None
                };
                REQUIRE(puller.SendAck(ack));
            } else if (out->cbor->data_message) {
                processed++;
            } else if (out->cbor->end_message) {
                PullerAckMessage ack{
                    .ack_for = TCPFrameType::END, .ok = true, .run_number = h.run_number,
                    .socket_number = h.socket_number, .processed_images = processed, .error_code = TCPAckCode::None
                };
                REQUIRE(puller.SendAck(ack));
                seen_end = true;
            }
        }
    });

    std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
    CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

    StartMessage start{.images_per_file = images_per_file, .write_master_file = true};
    EndMessage end{};
    pusher.StartDataCollection(start);

    for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
        DataMessage data_message;
        data_message.number = i;
        data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                             x.GetPixelsNum() * sizeof(uint16_t),
                                             x.GetXPixelsNum(), x.GetYPixelsNum(),
                                             x.GetImageMode(), x.GetCompressionAlgorithm());
        serializer.SerializeImage(data_message);
        REQUIRE(pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i));
    }

    REQUIRE(pusher.EndDataCollection(end));
    REQUIRE_NOTHROW(receiver.get());
    puller.Disconnect();
}

TEST_CASE("TCPImageCommTest_DisconnectMidWrite_NoHang", "[TCP]") {
    const size_t nframes = 256;
    const int64_t images_per_file = 16;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);

    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes, 11u);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", 1);
    TCPImagePuller puller(pusher.GetAddress()[0], 64 * 1024 * 1024);

    std::thread receiver([&] {
        bool disconnected = false;
        while (!disconnected) {
            auto out = puller.PollImage(std::chrono::seconds(10));
            REQUIRE(out.has_value());
            REQUIRE(out->cbor != nullptr);
            REQUIRE(out->tcp_msg != nullptr);

            const auto &h = out->tcp_msg->header;
            if (out->cbor->start_message) {
                PullerAckMessage ack{
                    .ack_for = TCPFrameType::START, .ok = true, .run_number = h.run_number,
                    .socket_number = h.socket_number, .error_code = TCPAckCode::None
                };
                REQUIRE(puller.SendAck(ack));
            } else if (out->cbor->data_message) {
                puller.Disconnect(); // simulate puller disappearing mid-stream
                disconnected = true;
            }
        }
    });

    auto sender = std::async(std::launch::async, [&] {
        std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
        CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

        StartMessage start{.images_per_file = images_per_file, .write_master_file = true};
        EndMessage end{};

        pusher.StartDataCollection(start);

        for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
            DataMessage data_message;
            data_message.number = i;
            data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                                 x.GetPixelsNum() * sizeof(uint16_t),
                                                 x.GetXPixelsNum(), x.GetYPixelsNum(),
                                                 x.GetImageMode(), x.GetCompressionAlgorithm());
            serializer.SerializeImage(data_message);
            (void) pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i);
        }

        return pusher.EndDataCollection(end);
    });

    REQUIRE(sender.wait_for(std::chrono::seconds(20)) == std::future_status::ready);
    CHECK(sender.get() == false);

    receiver.join();
}

TEST_CASE("TCPImageCommTest_RepubToZMQ", "[TCP][ZeroMQ]") {
    // Chain: TCPStreamPusher --TCP--> TCPImagePuller --ZMQ repub--> ZMQImagePuller
    const size_t nframes = 64;
    const int64_t images_per_file = 8;

    DiffractionExperiment x(DetJF(1));
    x.Raw();
    x.PedestalG0Frames(0).NumTriggers(1).UseInternalPacketGenerator(false).IncidentEnergy_keV(12.4)
            .ImagesPerTrigger(nframes).Compression(CompressionAlgorithm::NO_COMPRESSION);

    std::mt19937 g1(9999);
    std::uniform_int_distribution<uint16_t> dist;
    std::vector<uint16_t> image1(x.GetPixelsNum() * nframes);
    for (auto &i : image1) i = dist(g1);

    // 1. Create TCP pusher on an auto-assigned port
    TCPStreamPusher pusher("tcp://127.0.0.1:*", 1);

    // 2. Create TCP puller with repub over ZMQ (ipc, auto-assigned)
    const std::string repub_addr = "ipc://*";
    // Need to figure out the actual repub endpoint after bind — ZMQ ipc://* picks a temp path.
    // However, ZMQSocket::Bind with "ipc://*" is used in project; the repub socket binds internally,
    // so we need a known address. Use a tcp address instead for testability.
    const std::string repub_bind_addr = "tcp://127.0.0.1:19010";
    TCPImagePuller tcp_puller(pusher.GetAddress()[0], {}, repub_bind_addr);

    // 3. Create ZMQ puller that connects to the repub address
    ZMQImagePuller zmq_puller(repub_bind_addr);

    // Wait for TCP connection
    for (int attempt = 0; attempt < 100 && pusher.GetConnectedWriters() < 1; ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    REQUIRE(pusher.GetConnectedWriters() == 1);

    // Sender thread: push frames over TCP
    std::thread sender([&] {
        std::vector<uint8_t> serialization_buffer(16 * 1024 * 1024);
        CBORStream2Serializer serializer(serialization_buffer.data(), serialization_buffer.size());

        StartMessage start{
            .images_per_file = images_per_file,
            .write_master_file = true
        };
        EndMessage end{};

        pusher.StartDataCollection(start);

        for (int64_t i = 0; i < static_cast<int64_t>(nframes); i++) {
            DataMessage data_message;
            data_message.number = i;
            data_message.image = CompressedImage(image1.data() + i * x.GetPixelsNum(),
                                                 x.GetPixelsNum() * sizeof(uint16_t),
                                                 x.GetXPixelsNum(),
                                                 x.GetYPixelsNum(),
                                                 x.GetImageMode(),
                                                 x.GetCompressionAlgorithm());
            serializer.SerializeImage(data_message);
            REQUIRE(pusher.SendImage(serialization_buffer.data(), serializer.GetBufferSize(), i));
        }

        REQUIRE(pusher.EndDataCollection(end));
    });

    // TCP puller consumer: drains the TCP side (with ACKs) so data keeps flowing
    std::thread tcp_consumer([&] {
        bool seen_end = false;
        while (!seen_end) {
            auto out = tcp_puller.PollImage(std::chrono::seconds(10));
            REQUIRE(out.has_value());
            REQUIRE(out->cbor != nullptr);
            REQUIRE(out->tcp_msg != nullptr);

            const auto &h = out->tcp_msg->header;

            if (out->cbor->start_message) {
                PullerAckMessage ack{};
                ack.ack_for = TCPFrameType::START;
                ack.ok = true;
                ack.run_number = h.run_number;
                ack.socket_number = h.socket_number;
                ack.error_code = TCPAckCode::None;
                REQUIRE(tcp_puller.SendAck(ack));
            } else if (out->cbor->end_message) {
                PullerAckMessage ack{};
                ack.ack_for = TCPFrameType::END;
                ack.ok = true;
                ack.run_number = h.run_number;
                ack.socket_number = h.socket_number;
                ack.error_code = TCPAckCode::None;
                REQUIRE(tcp_puller.SendAck(ack));
                seen_end = true;
            }
            // data frames: no ack needed for this test
        }
    });

    // ZMQ puller consumer: verify the republished stream
    size_t zmq_nimages = 0;
    size_t zmq_errors = 0;
    bool zmq_seen_start = false;
    bool zmq_seen_end = false;

    std::thread zmq_consumer([&] {
        auto timeout = std::chrono::seconds(30);

        // First message should be START
        auto img = zmq_puller.PollImage(timeout);
        if (!img || !img->cbor || !img->cbor->start_message) {
            zmq_errors++;
            return;
        }
        zmq_seen_start = true;

        // Republished START should have writer_notification_zmq_addr cleared
        if (!img->cbor->start_message->writer_notification_zmq_addr.empty()) {
            zmq_errors++;
        }

        // Consume data and END
        img = zmq_puller.PollImage(timeout);
        while (img && img->cbor && !img->cbor->end_message) {
            if (img->cbor->data_message) {
                auto n = img->cbor->data_message->number;
                if (img->cbor->data_message->image.GetCompressedSize() != x.GetPixelsNum() * sizeof(uint16_t))
                    zmq_errors++;
                else if (memcmp(img->cbor->data_message->image.GetCompressed(),
                                image1.data() + n * x.GetPixelsNum(),
                                x.GetPixelsNum() * sizeof(uint16_t)) != 0)
                    zmq_errors++;
                zmq_nimages++;
            }
            img = zmq_puller.PollImage(timeout);
        }
        if (img && img->cbor && img->cbor->end_message)
            zmq_seen_end = true;
    });

    sender.join();
    tcp_consumer.join();
    zmq_consumer.join();

    tcp_puller.Disconnect();
    zmq_puller.Disconnect();

    // The repub uses non-blocking Put for data, so some frames *could* be dropped
    // under extreme back-pressure, but with only 64 frames we expect all of them.
    REQUIRE(zmq_seen_start);
    REQUIRE(zmq_seen_end);
    REQUIRE(zmq_nimages == nframes);
    REQUIRE(zmq_errors == 0);
}

namespace {

// Controllable TCP "writer" peer for backpressure tests. Connects to the pusher, ACKs
// START, then *stalls* (stops draining the socket) until Release() is called, while a
// background thread keeps sending BUSY heartbeats — i.e. a writer that is alive but
// wedged (e.g. on a slow filesystem at high frame rate). Catch2 assertion macros are not
// thread-safe, so the worker threads only touch atomics; the test thread asserts.
class StallableWriterDouble {
public:
    StallableWriterDouble(const std::string &tcp_addr, int rcvbuf_bytes) {
        auto [host, port] = ParseHostPort(tcp_addr);
        fd_ = ::socket(AF_INET, SOCK_STREAM, 0);
        if (fd_ < 0)
            return;
        setsockopt(fd_, SOL_SOCKET, SO_RCVBUF, &rcvbuf_bytes, sizeof(rcvbuf_bytes));
        sockaddr_in sin{};
        sin.sin_family = AF_INET;
        sin.sin_port = htons(port);
        inet_pton(AF_INET, host.c_str(), &sin.sin_addr);
        if (::connect(fd_, reinterpret_cast<sockaddr *>(&sin), sizeof(sin)) != 0) {
            ::close(fd_);
            fd_ = -1;
            return;
        }
        busy_thread_ = std::thread([this] { BusyLoop(); });
        reader_thread_ = std::thread([this] { ReaderLoop(); });
    }

    ~StallableWriterDouble() {
        stop_ = true;
        Release();
        if (fd_ >= 0)
            ::shutdown(fd_, SHUT_RDWR);
        if (reader_thread_.joinable())
            reader_thread_.join();
        if (busy_thread_.joinable())
            busy_thread_.join();
        if (fd_ >= 0)
            ::close(fd_);
    }

    [[nodiscard]] bool Connected() const { return fd_ >= 0; }

    // Stop stalling: let the reader drain DATA and ACK END.
    void Release() {
        {
            std::lock_guard<std::mutex> lg(mtx_);
            released_ = true;
        }
        cv_.notify_all();
    }

    [[nodiscard]] size_t DataFramesReceived() const { return data_frames_.load(); }
    [[nodiscard]] bool EndAcked() const { return end_acked_.load(); }

private:
    static std::pair<std::string, uint16_t> ParseHostPort(const std::string &addr) {
        const std::string prefix = "tcp://";
        const auto hp = addr.substr(prefix.size());
        const auto p = hp.find_last_of(':');
        return {hp.substr(0, p), static_cast<uint16_t>(std::stoi(hp.substr(p + 1)))};
    }

    bool SendHeader(TCPFrameType type, TCPFrameType ack_for, uint64_t run, uint32_t sock, uint32_t flags) {
        TcpFrameHeader h{};
        h.type = static_cast<uint16_t>(type);
        h.ack_for = static_cast<uint16_t>(ack_for);
        h.run_number = run;
        h.socket_number = sock;
        h.flags = flags;
        h.payload_size = 0;
        std::lock_guard<std::mutex> lg(send_mtx_);
        if (fd_ < 0)
            return false;
        return ::send(fd_, &h, sizeof(h), MSG_NOSIGNAL) == static_cast<ssize_t>(sizeof(h));
    }

    bool ReadExact(void *buf, size_t len) {
        auto *p = static_cast<uint8_t *>(buf);
        size_t got = 0;
        while (got < len) {
            const ssize_t rc = ::recv(fd_, p + got, len - got, 0);
            if (rc <= 0)
                return false;
            got += static_cast<size_t>(rc);
        }
        return true;
    }

    void BusyLoop() {
        // Heartbeat keeps the pusher's peer-liveness fresh even while we are not draining.
        while (!stop_) {
            SendHeader(TCPFrameType::BUSY, TCPFrameType::DATA, run_.load(), sock_.load(), 0);
            for (int i = 0; i < 5 && !stop_; i++)
                std::this_thread::sleep_for(std::chrono::milliseconds(50));
        }
    }

    void ReaderLoop() {
        std::vector<uint8_t> discard;
        while (!stop_) {
            TcpFrameHeader h{};
            if (!ReadExact(&h, sizeof(h)))
                return;
            if (h.magic != JFJOCH_TCP_MAGIC || h.version != JFJOCH_TCP_VERSION)
                return;
            if (h.payload_size > 0) {
                discard.resize(h.payload_size);
                if (!ReadExact(discard.data(), discard.size()))
                    return;
            }
            switch (static_cast<TCPFrameType>(h.type)) {
                case TCPFrameType::START:
                    run_.store(h.run_number);
                    sock_.store(h.socket_number);
                    SendHeader(TCPFrameType::ACK, TCPFrameType::START, h.run_number, h.socket_number, TCP_ACK_FLAG_OK);
                    {   // Stall: stop reading until released.
                        std::unique_lock<std::mutex> ul(mtx_);
                        cv_.wait(ul, [this] { return released_ || stop_; });
                    }
                    break;
                case TCPFrameType::DATA:
                    data_frames_.fetch_add(1);
                    break;
                case TCPFrameType::END:
                    SendHeader(TCPFrameType::ACK, TCPFrameType::END, h.run_number, h.socket_number, TCP_ACK_FLAG_OK);
                    end_acked_.store(true);
                    return;
                default:
                    break;  // ignore KEEPALIVE etc.
            }
        }
    }

    int fd_ = -1;
    std::thread reader_thread_;
    std::thread busy_thread_;
    std::atomic<bool> stop_{false};
    std::atomic<uint64_t> run_{0};
    std::atomic<uint32_t> sock_{0};
    std::atomic<size_t> data_frames_{0};
    std::atomic<bool> end_acked_{false};
    std::mutex send_mtx_;
    std::mutex mtx_;
    std::condition_variable cv_;
    bool released_ = false;
};

}  // namespace

TEST_CASE("TCPImageCommTest_StalledWriter_SurvivesViaHeartbeat", "[TCP]") {
    // A writer that is alive (still heartbeating) but has stopped draining — e.g. wedged
    // on a slow filesystem at high frame rate — must NOT be dropped mid-run. The pusher
    // rides out the backpressure on the production zero-copy queue path until the writer
    // recovers. Regression for the queue-path send giving up on a fixed deadline, and for
    // the BUSY heartbeat keeping the connection alive past the peer-liveness window.
    constexpr int64_t N = 1000;                              // > queue depth + socket buffers
    constexpr auto liveness = std::chrono::milliseconds(2000);
    constexpr auto stall = std::chrono::milliseconds(4000);  // > liveness AND > old send deadline

    // Small SO_SNDBUF/SO_RCVBUF so backpressure reaches the queue after few images.
    TCPStreamPusher pusher("tcp://127.0.0.1:*", 1, 16 * 1024);
    pusher.SetPeerLivenessTimeout(liveness);

    StallableWriterDouble writer(pusher.GetAddress()[0], 16 * 1024);
    REQUIRE(writer.Connected());

    for (int attempt = 0; attempt < 200 && pusher.GetConnectedWriters() < 1; ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(25));
    REQUIRE(pusher.GetConnectedWriters() == 1);

    ImageBuffer image_buffer(16 * 1024 * 1024);
    image_buffer.StartMeasurement(static_cast<size_t>(4096));

    StartMessage start{.images_per_file = 1000, .write_master_file = true};
    pusher.StartDataCollection(start);   // writer ACKs START, then stalls (stops reading)

    auto sender = std::async(std::launch::async, [&] {
        for (int64_t i = 0; i < N; i++) {
            ZeroCopyReturnValue *slot = nullptr;
            while ((slot = image_buffer.GetImageSlot()) == nullptr)
                std::this_thread::sleep_for(std::chrono::milliseconds(1));
            std::memset(slot->GetImage(), 0, 256);
            slot->SetImageNumber(i);
            slot->SetImageSize(256);   // arbitrary payload; the writer double discards it
            slot->ReadyToSend();
            pusher.SendImage(*slot);
        }
    });

    // During the stall the queue is full; SendImage must block, not drop the connection.
    std::this_thread::sleep_for(stall);
    CHECK(pusher.GetConnectedWriters() == 1);
    CHECK(sender.wait_for(std::chrono::milliseconds(0)) != std::future_status::ready);

    // Writer recovers and starts draining.
    writer.Release();

    REQUIRE(sender.wait_for(std::chrono::seconds(30)) == std::future_status::ready);
    sender.get();

    // Every image makes it across once the stall clears.
    for (int attempt = 0; attempt < 1200 && writer.DataFramesReceived() < static_cast<size_t>(N); ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(25));
    CHECK(writer.DataFramesReceived() == static_cast<size_t>(N));

    // Queue fully drained: END now hands over cleanly without racing data frames.
    EndMessage end{};
    CHECK(pusher.EndDataCollection(end) == true);

    for (int attempt = 0; attempt < 200 && !writer.EndAcked(); ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(25));
    CHECK(writer.EndAcked());
    CHECK(pusher.GetConnectedWriters() == 1);

    image_buffer.Finalize(std::chrono::seconds(5));
}

TEST_CASE("TCPImageCommTest_WedgedWriter_DroppedByBackpressureCap", "[TCP]") {
    // A writer that keeps heartbeating but never drains (e.g. a permanently wedged
    // filesystem) must not block the run or its finalization forever. The hard
    // backpressure cap tears the connection down even though BUSY keeps arriving, and
    // well before the (longer) peer-liveness timeout that those heartbeats keep at bay.
    constexpr int64_t N = 1000;
    constexpr auto liveness = std::chrono::milliseconds(5000);       // kept fresh by heartbeats
    constexpr auto max_backpressure = std::chrono::milliseconds(1500);

    TCPStreamPusher pusher("tcp://127.0.0.1:*", 1, 16 * 1024);
    pusher.SetPeerLivenessTimeout(liveness);
    pusher.SetMaxBackpressureTimeout(max_backpressure);

    StallableWriterDouble writer(pusher.GetAddress()[0], 16 * 1024);   // never released
    REQUIRE(writer.Connected());

    for (int attempt = 0; attempt < 200 && pusher.GetConnectedWriters() < 1; ++attempt)
        std::this_thread::sleep_for(std::chrono::milliseconds(25));
    REQUIRE(pusher.GetConnectedWriters() == 1);

    ImageBuffer image_buffer(16 * 1024 * 1024);
    image_buffer.StartMeasurement(static_cast<size_t>(4096));

    StartMessage start{.images_per_file = 1000, .write_master_file = true};
    pusher.StartDataCollection(start);   // writer ACKs START, then stalls forever

    auto sender = std::async(std::launch::async, [&] {
        for (int64_t i = 0; i < N; i++) {
            ZeroCopyReturnValue *slot = nullptr;
            while ((slot = image_buffer.GetImageSlot()) == nullptr)
                std::this_thread::sleep_for(std::chrono::milliseconds(1));
            std::memset(slot->GetImage(), 0, 256);
            slot->SetImageNumber(i);
            slot->SetImageSize(256);
            slot->ReadyToSend();
            pusher.SendImage(*slot);
        }
    });

    // The cap must fire and drop the connection despite continuous heartbeats.
    bool dropped = false;
    for (int attempt = 0; attempt < 400 && !dropped; ++attempt) {
        if (pusher.GetConnectedWriters() == 0)
            dropped = true;
        else
            std::this_thread::sleep_for(std::chrono::milliseconds(25));
    }
    CHECK(dropped);

    // Neither the producers nor finalization may hang once the writer is wedged.
    REQUIRE(sender.wait_for(std::chrono::seconds(10)) == std::future_status::ready);
    sender.get();

    EndMessage end{};
    CHECK(pusher.EndDataCollection(end) == false);   // bounded, and reports failure

    image_buffer.Finalize(std::chrono::seconds(5));
}