#include "plc_communication_service.h"

#include "plc_communication_error_classifier.h"
#include "plc_register_repository.h"

#include <QModbusDataUnit>
#include <QModbusDevice>
#include <QModbusReply>
#include <QModbusRtuSerialMaster>
#include <QSerialPort>
#include <QVariant>

#include <algorithm>
#include <utility>

namespace {

constexpr int kRecoveryProbeIntervalMs = 2000;

std::string toUtf8(const QString &value)
{
    const QByteArray bytes = value.toUtf8();
    return std::string(bytes.constData(), static_cast<std::size_t>(bytes.size()));
}

QModbusDataUnit::RegisterType registerType(RegisterArea area)
{
    return area == RegisterArea::M
        ? QModbusDataUnit::Coils : QModbusDataUnit::HoldingRegisters;
}

bool isRecoverableTimeout(PlcCommunicationError error)
{
    return error == PlcCommunicationError::PlcNotResponding
        || error == PlcCommunicationError::CommunicationTimeout;
}

bool isReadingState(PlcConnectionState state)
{
    return state == PlcConnectionState::Connected
        || state == PlcConnectionState::Recovering;
}

bool normalizePollAddresses(
    const std::vector<RegisterAddress> &addresses,
    std::vector<RegisterAddress> *normalized,
    std::string *error)
{
    *normalized = addresses;
    if (std::any_of(
            normalized->cbegin(), normalized->cend(),
            [](const RegisterAddress &address) { return !address.isValid(); }))
    {
        *error = "PLC 轮询地址中包含无效的 M/D 地址";
        return false;
    }
    std::sort(
        normalized->begin(), normalized->end(),
        [](const RegisterAddress &left, const RegisterAddress &right)
        {
            return left.area() == right.area()
                ? left.index() < right.index()
                : left.area() == RegisterArea::M;
        });
    normalized->erase(
        std::unique(normalized->begin(), normalized->end()), normalized->end());
    if (normalized->size() > ProjectLimits::kMaximumPollAddresses)
    {
        *error = "PLC 轮询的去重 M/D 地址最多为 1024 个";
        return false;
    }
    return true;
}

std::size_t pollBlockCount(const std::vector<RegisterAddress> &addresses)
{
    if (addresses.empty())
    {
        return 2U;
    }
    std::size_t blocks = 0U;
    RegisterArea current_area = RegisterArea::M;
    int start_address = 0;
    int count = 0;
    for (const RegisterAddress &address : addresses)
    {
        if (count == 0
            || address.area() != current_area
            || address.index() > start_address + count
            || count >= ProjectLimits::kMaximumModbusReadCount)
        {
            ++blocks;
            current_area = address.area();
            start_address = address.index();
            count = 1;
        }
        else
        {
            count = address.index() - start_address + 1;
        }
    }
    return blocks;
}

} // namespace

PlcCommunicationService::PlcCommunicationService(
    PlcRegisterRepository &repository,
    QObject *parent)
    : QObject(parent),
      repository_(repository),
      master_(std::make_unique<QModbusRtuSerialMaster>())
{
    repository_.setWriteHandlers(
        [this](const RegisterAddress &address, bool value)
        {
            return sendBitWrite(address, value);
        },
        [this](const RegisterAddress &address, std::int16_t value)
        {
            return sendWordWrite(address, value);
        });
    connect(&poll_timer_, &QTimer::timeout, this, &PlcCommunicationService::pollNextBlock);
    recovery_timer_.setSingleShot(true);
    connect(
        &recovery_timer_,
        &QTimer::timeout,
        this,
        &PlcCommunicationService::probeRecovery);
    connect(master_.get(), &QModbusClient::stateChanged,
            this,
            [this](QModbusDevice::State device_state)
            {
                if (device_state == QModbusDevice::ConnectedState)
                {
                    serial_session_opened_ = true;
                    setState(PlcConnectionState::Connected);
                    poll_timer_.start(configuration_.pollIntervalMs);
                    pollNextBlock();
                }
                else if (device_state == QModbusDevice::ConnectingState)
                {
                    serial_session_opened_ = false;
                    setState(PlcConnectionState::Connecting);
                }
                else if (device_state == QModbusDevice::UnconnectedState)
                {
                    if (disconnecting_)
                    {
                        serial_session_opened_ = false;
                    }
                    else if (serial_session_opened_)
                    {
                        handleUnexpectedDisconnect();
                    }
                    else if (state_ != PlcConnectionState::Faulted)
                    {
                        setState(PlcConnectionState::Disconnected);
                    }
                }
            });
    connect(master_.get(), &QModbusClient::errorOccurred,
            this,
            [this](QModbusDevice::Error error)
            {
                if (error != QModbusDevice::NoError)
                {
                    handleModbusError(error);
                }
            });
}

PlcCommunicationService::~PlcCommunicationService() = default;

PlcCommunicationResult PlcCommunicationService::connectDevice(
    const PlcSerialConfiguration &configuration)
{
    const PlcCommunicationResult validation =
        validatePlcSerialConfiguration(configuration);
    if (!validation.succeeded)
    {
        return validation;
    }
    if (state_ == PlcConnectionState::Disconnected
        && master_->state() != QModbusDevice::UnconnectedState)
    {
        closeSerialSession();
    }
    if (master_->state() != QModbusDevice::UnconnectedState)
    {
        return {false, "PLC 连接已经启动，请先断开当前连接"};
    }
    // 每次连接都递增代次；旧连接的异步回复即使晚到也不能污染新缓存
    configuration_ = configuration;
    ++connection_generation_;
    disconnecting_ = false;
    serial_session_opened_ = false;
    received_valid_response_ = false;
    last_error_type_ = PlcCommunicationError::None;
    last_error_.clear();
    master_->setConnectionParameter(
        QModbusDevice::SerialPortNameParameter,
        QString::fromStdString(configuration.portName));
    master_->setConnectionParameter(
        QModbusDevice::SerialBaudRateParameter, configuration.baudRate);
    master_->setConnectionParameter(
        QModbusDevice::SerialDataBitsParameter,
        static_cast<QSerialPort::DataBits>(configuration.dataBits));
    master_->setConnectionParameter(
        QModbusDevice::SerialParityParameter,
        static_cast<QSerialPort::Parity>(configuration.parity));
    master_->setConnectionParameter(
        QModbusDevice::SerialStopBitsParameter,
        static_cast<QSerialPort::StopBits>(configuration.stopBits));
    master_->setTimeout(configuration.responseTimeoutMs);
    master_->setNumberOfRetries(configuration.retries);
    // 新连接必须重新完成完整首读，不能沿用上一条连接的运行资格
    repository_.invalidate();
    updateInitialReadCompleted(false, true);
    rebuildPollBlocks();
    setState(PlcConnectionState::Connecting);
    if (!master_->connectDevice())
    {
        if (last_error_.empty())
        {
            const QModbusDevice::Error error = master_->error() == QModbusDevice::NoError
                ? QModbusDevice::ConnectionError : master_->error();
            handleModbusError(error);
        }
        return {false, last_error_};
    }
    return {true, {}};
}

void PlcCommunicationService::disconnectDevice()
{
    closeSerialSession();
    repository_.invalidate();
    updateInitialReadCompleted(false, true);
    last_error_type_ = PlcCommunicationError::None;
    last_error_.clear();
    setState(PlcConnectionState::Disconnected);
}

PlcCommunicationResult PlcCommunicationService::setPollAddresses(
    const std::vector<RegisterAddress> &addresses)
{
    std::vector<RegisterAddress> normalized;
    std::string error;
    if (!normalizePollAddresses(addresses, &normalized, &error))
    {
        return {false, error};
    }
    if (pollBlockCount(normalized) > ProjectLimits::kMaximumPollBlocks)
    {
        return {false, "PLC 轮询地址拆分后最多允许 64 个读块"};
    }
    // 当前读请求完成前暂存新集合，避免按半旧半新的地址解析回复
    if (pending_reply_ != nullptr)
    {
        pending_poll_addresses_ = std::move(normalized);
        poll_update_pending_ = true;
        return {true, {}};
    }
    applyPollAddresses(normalized);
    return {true, {}};
}

PlcConnectionState PlcCommunicationService::state() const
{
    return state_;
}

bool PlcCommunicationService::initialReadCompleted() const
{
    return initial_read_completed_;
}

PlcCommunicationError PlcCommunicationService::lastErrorType() const
{
    return last_error_type_;
}

const std::string &PlcCommunicationService::lastError() const
{
    return last_error_;
}

const PlcSerialConfiguration &PlcCommunicationService::configuration() const
{
    return configuration_;
}

void PlcCommunicationService::setCallbacks(
    std::function<void()> state_changed,
    std::function<void(bool)> initial_read_changed,
    std::function<void()> cache_updated,
    std::function<void(const std::string &)> error_reported)
{
    state_changed_callback_ = std::move(state_changed);
    initial_read_changed_callback_ = std::move(initial_read_changed);
    cache_updated_callback_ = std::move(cache_updated);
    error_reported_callback_ = std::move(error_reported);
}

void PlcCommunicationService::rebuildPollBlocks()
{
    std::vector<RegisterAddress> addresses = poll_addresses_;
    if (addresses.empty())
    {
        addresses = {
            RegisterAddress{RegisterArea::M, 0},
            RegisterAddress{RegisterArea::D, 0}};
    }
    std::sort(
        addresses.begin(), addresses.end(),
        [](const RegisterAddress &left, const RegisterAddress &right)
        {
            if (left.area() != right.area())
            {
                return left.area() == RegisterArea::M;
            }
            return left.index() < right.index();
        });
    addresses.erase(std::unique(addresses.begin(), addresses.end()), addresses.end());
    // 将相邻地址合并为读块，同时遵守 Modbus 单次读取上限
    poll_blocks_.clear();
    for (const RegisterAddress &address : addresses)
    {
        if (!address.isValid())
        {
            continue;
        }
        if (poll_blocks_.empty()
            || poll_blocks_.back().area != address.area()
            || address.index() > poll_blocks_.back().startAddress
                + poll_blocks_.back().count
            || poll_blocks_.back().count
                >= ProjectLimits::kMaximumModbusReadCount)
        {
            poll_blocks_.push_back({address.area(), address.index(), 1});
        }
        else
        {
            poll_blocks_.back().count = address.index()
                - poll_blocks_.back().startAddress + 1;
        }
    }
    next_poll_block_ = 0;
    if (!initial_read_completed_)
    {
        initial_blocks_read_.assign(poll_blocks_.size(), false);
    }
    else
    {
        initial_blocks_read_.clear();
    }
}

void PlcCommunicationService::applyPollAddresses(
    const std::vector<RegisterAddress> &addresses)
{
    poll_addresses_ = addresses;
    rebuildPollBlocks();
    poll_update_pending_ = false;
    pending_poll_addresses_.clear();
    if (isReadingState(state_) && pending_reply_ == nullptr)
    {
        pollNextBlock();
    }
}

void PlcCommunicationService::pollNextBlock()
{
    if (!isReadingState(state_)
        || pending_reply_ != nullptr || poll_blocks_.empty())
    {
        return;
    }
    // 每次只发一个异步请求，完成回调中再推进到下一个块
    const std::size_t block_index = next_poll_block_;
    const PollBlock block = poll_blocks_.at(block_index);
    next_poll_block_ = (next_poll_block_ + 1U) % poll_blocks_.size();
    QModbusDataUnit request(
        registerType(block.area), block.startAddress, static_cast<quint16>(block.count));
    QModbusReply *reply = master_->sendReadRequest(request, configuration_.serverAddress);
    if (reply == nullptr)
    {
        handleModbusError(master_->error());
        return;
    }
    pending_reply_ = reply;
    const std::uint64_t generation = connection_generation_;
    connect(reply, &QModbusReply::finished,
            this,
            [this, reply, block, block_index, generation]
            {
                // 连接已经重建时，直接丢弃旧回复
                if (generation != connection_generation_)
                {
                    reply->deleteLater();
                    return;
                }
                handleReadFinished(reply, block);
                if (isReadingState(state_)
                    && reply->error() == QModbusDevice::NoError
                    && !poll_update_pending_
                    && block_index < initial_blocks_read_.size())
                {
                    initial_blocks_read_[block_index] = true;
                    const bool completed = std::all_of(
                        initial_blocks_read_.cbegin(),
                        initial_blocks_read_.cend(),
                        [](bool read) { return read; });
                    // 所有轮询块都成功读过，才授予真机运行资格
                    if (completed && !initial_read_completed_)
                    {
                        updateInitialReadCompleted(true);
                        if (state_ == PlcConnectionState::Recovering)
                        {
                            setState(PlcConnectionState::Connected);
                        }
                    }
                }
                if (pending_reply_ == reply)
                {
                    pending_reply_ = nullptr;
                }
                reply->deleteLater();
                if (poll_update_pending_)
                {
                    const std::vector<RegisterAddress> addresses = pending_poll_addresses_;
                    applyPollAddresses(addresses);
                }
            });
}

void PlcCommunicationService::probeRecovery()
{
    if (state_ != PlcConnectionState::Faulted
        || !isRecoverableTimeout(last_error_type_))
    {
        return;
    }
    if (master_->state() != QModbusDevice::ConnectedState)
    {
        return;
    }
    if (pending_reply_ != nullptr)
    {
        recovery_timer_.start(kRecoveryProbeIntervalMs);
        return;
    }
    if (poll_blocks_.empty())
    {
        return;
    }
    const PollBlock block = poll_blocks_.front();
    const QModbusDataUnit request(
        registerType(block.area), block.startAddress, 1);
    QModbusReply *reply = master_->sendReadRequest(request, configuration_.serverAddress);
    if (reply == nullptr)
    {
        handleRecoveryProbeFailure(master_->error());
        return;
    }
    pending_reply_ = reply;
    const std::uint64_t generation = connection_generation_;
    connect(reply, &QModbusReply::finished,
            this,
            [this, reply, generation]
            {
                if (generation != connection_generation_)
                {
                    reply->deleteLater();
                    return;
                }
                if (pending_reply_ == reply)
                {
                    pending_reply_ = nullptr;
                }
                const QModbusDevice::Error error = reply->error();
                reply->deleteLater();
                if (poll_update_pending_)
                {
                    const std::vector<RegisterAddress> addresses = pending_poll_addresses_;
                    applyPollAddresses(addresses);
                }
                if (state_ != PlcConnectionState::Faulted
                    || !isRecoverableTimeout(last_error_type_))
                {
                    return;
                }
                if (error != QModbusDevice::NoError)
                {
                    handleRecoveryProbeFailure(error);
                    return;
                }
                restoreCommunication();
            });
}

void PlcCommunicationService::handleRecoveryProbeFailure(QModbusDevice::Error error)
{
    if (state_ != PlcConnectionState::Faulted
        || !isRecoverableTimeout(last_error_type_))
    {
        return;
    }
    if (error == QModbusDevice::ConnectionError)
    {
        const PlcCommunicationErrorContext context{
            QString::fromStdString(configuration_.portName),
            serial_session_opened_,
            received_valid_response_};
        setError(classifyPlcCommunicationError(error, context));
        return;
    }
    recovery_timer_.start(kRecoveryProbeIntervalMs);
}

void PlcCommunicationService::restoreCommunication()
{
    received_valid_response_ = true;
    last_error_type_ = PlcCommunicationError::None;
    last_error_.clear();
    rebuildPollBlocks();
    setState(PlcConnectionState::Recovering);
    poll_timer_.start(configuration_.pollIntervalMs);
    pollNextBlock();
}

void PlcCommunicationService::handleReadFinished(QModbusReply *reply, PollBlock block)
{
    if (!isReadingState(state_))
    {
        return;
    }
    if (reply->error() != QModbusDevice::NoError)
    {
        handleModbusError(reply->error());
        return;
    }
    // 只有成功回复才能更新 PLC 缓存；写请求不会直接改缓存
    const QModbusDataUnit result = reply->result();
    for (uint index = 0; index < result.valueCount(); ++index)
    {
        const int address = block.startAddress + static_cast<int>(index);
        if (block.area == RegisterArea::M)
        {
            repository_.updateBit(address, result.value(index) != 0U);
        }
        else
        {
            repository_.updateWord(address, static_cast<std::int16_t>(result.value(index)));
        }
    }
    received_valid_response_ = true;
    last_error_type_ = PlcCommunicationError::None;
    last_error_.clear();
    emit cacheUpdated();
    if (cache_updated_callback_)
    {
        cache_updated_callback_();
    }
}

RegisterWriteResult PlcCommunicationService::sendBitWrite(
    const RegisterAddress &address, bool value)
{
    if (state_ != PlcConnectionState::Connected)
    {
        return {false, RegisterError::Unavailable};
    }
    if (pending_write_reply_ != nullptr)
    {
        return {false, RegisterError::WriteRejected};
    }
    QModbusDataUnit unit(QModbusDataUnit::Coils, address.index(), 1);
    unit.setValue(0, value ? 1U : 0U);
    QModbusReply *reply = master_->sendWriteRequest(unit, configuration_.serverAddress);
    if (reply == nullptr)
    {
        handleModbusError(master_->error());
        return {false, RegisterError::WriteRejected};
    }
    pending_write_reply_ = reply;
    connect(reply, &QModbusReply::finished,
            this,
            [this, reply, generation = connection_generation_]
            {
                if (pending_write_reply_ == reply)
                {
                    pending_write_reply_ = nullptr;
                }
                if (generation != connection_generation_)
                {
                    reply->deleteLater();
                    return;
                }
                if (reply->error() != QModbusDevice::NoError)
                {
                    handleModbusError(reply->error());
                }
                reply->deleteLater();
            });
    return {true, RegisterError::None};
}

RegisterWriteResult PlcCommunicationService::sendWordWrite(
    const RegisterAddress &address, std::int16_t value)
{
    if (state_ != PlcConnectionState::Connected)
    {
        return {false, RegisterError::Unavailable};
    }
    if (pending_write_reply_ != nullptr)
    {
        return {false, RegisterError::WriteRejected};
    }
    QModbusDataUnit unit(QModbusDataUnit::HoldingRegisters, address.index(), 1);
    unit.setValue(0, static_cast<quint16>(value));
    QModbusReply *reply = master_->sendWriteRequest(unit, configuration_.serverAddress);
    if (reply == nullptr)
    {
        handleModbusError(master_->error());
        return {false, RegisterError::WriteRejected};
    }
    pending_write_reply_ = reply;
    connect(reply, &QModbusReply::finished,
            this,
            [this, reply, generation = connection_generation_]
            {
                if (pending_write_reply_ == reply)
                {
                    pending_write_reply_ = nullptr;
                }
                if (generation != connection_generation_)
                {
                    reply->deleteLater();
                    return;
                }
                if (reply->error() != QModbusDevice::NoError)
                {
                    handleModbusError(reply->error());
                }
                reply->deleteLater();
            });
    return {true, RegisterError::None};
}

void PlcCommunicationService::updateInitialReadCompleted(
    bool completed, bool force_notification)
{
    if (initial_read_completed_ == completed && !force_notification)
    {
        return;
    }
    initial_read_completed_ = completed;
    emit initialReadCompletedChanged(completed);
    if (initial_read_changed_callback_)
    {
        initial_read_changed_callback_(completed);
    }
}

void PlcCommunicationService::handleUnexpectedDisconnect()
{
    serial_session_opened_ = false;
    const QString port_name = QString::fromStdString(configuration_.portName).trimmed();
    setError({
        PlcCommunicationError::SerialConnectionLost,
        QStringLiteral(
            "PLC 串口 %1 连接已中断；请检查 USB 转串口是否被拔出或已经失效")
            .arg(port_name)});
}

void PlcCommunicationService::handleModbusError(QModbusDevice::Error error)
{
    if (disconnecting_
        || (error == QModbusDevice::ReplyAbortedError
            && state_ == PlcConnectionState::Disconnected)
        || (state_ == PlcConnectionState::Disconnected
            && last_error_type_ == PlcCommunicationError::SerialConnectionLost)
        || state_ == PlcConnectionState::Faulted)
    {
        return;
    }
    const PlcCommunicationErrorContext context{
        QString::fromStdString(configuration_.portName),
        serial_session_opened_,
        received_valid_response_};
    setError(classifyPlcCommunicationError(error, context));
}

void PlcCommunicationService::closeSerialSession()
{
    ++connection_generation_;
    disconnecting_ = true;
    poll_timer_.stop();
    recovery_timer_.stop();
    pending_reply_ = nullptr;
    pending_write_reply_ = nullptr;
    poll_update_pending_ = false;
    pending_poll_addresses_.clear();
    if (master_->state() != QModbusDevice::UnconnectedState)
    {
        master_->disconnectDevice();
    }
    serial_session_opened_ = false;
    received_valid_response_ = false;
    disconnecting_ = false;
}

void PlcCommunicationService::setState(PlcConnectionState state)
{
    if (state_ == state)
    {
        return;
    }
    state_ = state;
    emit stateChanged();
    if (state_changed_callback_)
    {
        state_changed_callback_();
    }
}

void PlcCommunicationService::setError(const PlcCommunicationFailure &failure)
{
    last_error_type_ = failure.type;
    last_error_ = toUtf8(failure.message);
    poll_timer_.stop();
    recovery_timer_.stop();
    // 任意通信故障都会撤销首读资格；恢复后必须重新完整读取
    updateInitialReadCompleted(false);
    const bool disconnected = failure.type == PlcCommunicationError::SerialPortOpenFailed
        || failure.type == PlcCommunicationError::SerialConnectionLost
        || failure.type == PlcCommunicationError::UsbSerialAdapterRemoved;
    if (disconnected)
    {
        closeSerialSession();
    }
    setState(disconnected
        ? PlcConnectionState::Disconnected : PlcConnectionState::Faulted);
    emit communicationError(failure.message);
    if (error_reported_callback_)
    {
        error_reported_callback_(last_error_);
    }
    if (isRecoverableTimeout(failure.type)
        && master_->state() == QModbusDevice::ConnectedState)
    {
        recovery_timer_.start(kRecoveryProbeIntervalMs);
    }
}