// controllerlink.cpp - RemoteClient in its own thread, results as signals (see controllerlink.h)

#include "controllerlink.h"

#include <QElapsedTimer>
#include <QMetaObject>
#include <QMutex>
#include <QMutexLocker>
#include <QQueue>
#include <QThread>
#include <QWaitCondition>

#include <utility>

namespace AdvCtrl {

// Owns the serial port: everything below run() happens in this thread. Results go to the
// ControllerLink as queued calls, so they arrive in the thread of the ControllerLink.
class LinkThread : public QThread
{
public:
    LinkThread(ControllerLink *link, const QString &portName, int baudRate)
        : m_link(link), m_portName(portName), m_baudRate(baudRate)
    {
    }

    void post(const QString &commandLine)
    {
        QMutexLocker lock(&m_mutex);
        m_queue.enqueue(commandLine);
        m_wake.wakeOne();
    }

    void stop()
    {
        requestInterruption();
        QMutexLocker lock(&m_mutex);
        m_wake.wakeOne();
    }

protected:
    void run() override;

private:
    bool takeCommand(QString *commandLine, int waitMs);
    void dropCommands(const QString &why);

    template <typename Function>
    void toLink(Function &&function)
    {
        QMetaObject::invokeMethod(m_link, std::forward<Function>(function), Qt::QueuedConnection);
    }

    void reportError(const QString &message)
    {
        ControllerLink *const link = m_link;
        toLink([link, message] { emit link->error(message); });
    }

    ControllerLink *const m_link;
    const QString m_portName;
    const int m_baudRate;
    QMutex m_mutex;
    QWaitCondition m_wake;
    QQueue<QString> m_queue;
};

void LinkThread::run()
{
    ControllerLink *const link = m_link;
    RemoteClient rc;
    if (!rc.open(m_portName, m_baudRate)) {
        reportError(QStringLiteral("cannot open %1: %2").arg(m_portName, rc.errorString()));
        toLink([link] { link->handleClosed(); });
        return;
    }

    bool detected = false;
    bool ledsSupported = true;
    int failures = 0;                           // consecutive requests without an answer
    QElapsedTimer clock;
    clock.start();
    qint64 nextLeds = 0;
    qint64 nextDetect = 0;

    while (!isInterruptionRequested() && !rc.portFailed()) {
        if (!detected) {
            dropCommands(QStringLiteral("controller not connected"));
            if (clock.elapsed() >= nextDetect) {
                nextDetect = clock.elapsed() + ControllerLink::DetectRetryMs;
                if (rc.detect()) {
                    detected = true;
                    failures = 0;
                    Fields ident;
                    bool known = false;
                    for (int i = 0; i < 3 && !known; ++i) {     // ID; a late PONG may come first
                        known = rc.identify(&ident);
                        if (!known)
                            reportError(QStringLiteral("ID: ") + rc.lastReply().toString());
                        if (rc.portFailed() || isInterruptionRequested())
                            break;
                    }
                    const QString unknown = QStringLiteral("?");
                    const QString firmware = known ? ident.value(QStringLiteral("FW"), unknown) : unknown;
                    const QString cameras = known ? ident.value(QStringLiteral("CAMS"), unknown) : unknown;
                    const QString uid = known ? ident.value(QStringLiteral("UID"), unknown) : unknown;
                    toLink([link, firmware, cameras, uid] { link->handleDetected(firmware, cameras, uid); });
                } else if (!rc.portFailed() && !isInterruptionRequested()) {
                    toLink([link] { link->handleNotDetected(); });
                }
            }
            QThread::msleep(50);
            continue;
        }

        QString commandLine;
        if (takeCommand(&commandLine, 50)) {
            const Reply r = rc.command(commandLine);
            QString result;
            if (r.status == Reply::Ok || r.status == Reply::DeviceError) {
                failures = 0;                           // ERR is an answer, not a link failure
                result = r.toString();
            } else {
                ++failures;
                result = QStringLiteral("!! ") + r.text;
            }
            toLink([link, commandLine, result] { emit link->reply(commandLine, result); });
        } else if (clock.elapsed() >= nextLeds) {
            nextLeds = clock.elapsed() + ControllerLink::LedsPeriodMs;
            if (ledsSupported) {
                quint32 mask = 0;
                if (rc.leds(&mask)) {
                    failures = 0;
                    toLink([link, mask] { emit link->leds(mask); });
                } else if (rc.lastReply().status == Reply::DeviceError) {
                    ledsSupported = false;
                    reportError(QStringLiteral("LEDS not supported by this firmware (%1) - firmware update required")
                                .arg(rc.lastReply().text));
                } else {
                    ++failures;
                    reportError(rc.lastReply().text);
                }
            } else if (rc.ping() || rc.lastReply().status == Reply::Ok
                       || rc.lastReply().status == Reply::DeviceError) {
                failures = 0;                           // old firmware: keep the link check alive
            } else {
                ++failures;
                reportError(rc.lastReply().text);
            }
        }

        if (failures >= ControllerLink::LostAfter) {
            detected = false;                           // back to detection, retried every 2 s
            nextDetect = 0;
            toLink([link] { link->handleLost(); });
        }
    }

    if (rc.portFailed())                                // e.g. the USB adapter was unplugged
        reportError(m_portName + QStringLiteral(": ") + rc.errorString());
    rc.close();
    toLink([link] { link->handleClosed(); });
}

bool LinkThread::takeCommand(QString *commandLine, int waitMs)
{
    QMutexLocker lock(&m_mutex);
    if (m_queue.isEmpty() && !isInterruptionRequested())
        m_wake.wait(&m_mutex, waitMs);
    if (m_queue.isEmpty())
        return false;
    *commandLine = m_queue.dequeue();
    return true;
}

void LinkThread::dropCommands(const QString &why)
{
    QQueue<QString> dropped;
    {
        QMutexLocker lock(&m_mutex);
        dropped.swap(m_queue);
    }
    ControllerLink *const link = m_link;
    const QString result = QStringLiteral("!! ") + why;
    for (const QString &commandLine : std::as_const(dropped))
        toLink([link, commandLine, result] { emit link->reply(commandLine, result); });
}

// ------------------------------------------------------------------ ControllerLink
ControllerLink::ControllerLink(QObject *parent)
    : QObject(parent)
{
}

ControllerLink::~ControllerLink()
{
    if (m_thread) {
        m_thread->stop();
        m_thread->wait();
        delete m_thread;
    }
}

ControllerLink::State ControllerLink::state() const
{
    return m_state;
}

QString ControllerLink::portName() const
{
    return m_portName;
}

void ControllerLink::open(const QString &portName, int baudRate)
{
    if (m_thread)                                       // already open: close() first
        return;
    m_portName = portName;
    m_thread = new LinkThread(this, portName, baudRate);
    m_thread->start();
    setState(NoLink);
}

void ControllerLink::close()
{
    if (m_thread)
        m_thread->stop();
}

void ControllerLink::send(const QString &commandLine)
{
    if (m_thread)
        m_thread->post(commandLine);
}

void ControllerLink::setState(State state)
{
    if (state == m_state)
        return;
    m_state = state;
    emit stateChanged(state);
}

void ControllerLink::handleDetected(const QString &firmware, const QString &cameras, const QString &uid)
{
    if (!m_thread)
        return;
    setState(Link);
    emit detected(firmware, cameras, uid);
}

void ControllerLink::handleNotDetected()
{
    if (!m_thread)
        return;
    setState(NoLink);
    emit notDetected();
}

void ControllerLink::handleLost()
{
    if (!m_thread)
        return;
    setState(NoLink);
    emit lost();
}

void ControllerLink::handleClosed()
{
    if (m_thread) {
        m_thread->wait();
        delete m_thread;
        m_thread = nullptr;
    }
    m_portName.clear();
    setState(Closed);
    emit closed();
}

} // namespace AdvCtrl