#include "controllers/rendering/controllerrenderingengine.h"

#include <QGuiApplication>
#include <QOffscreenSurface>
#include <QOpenGLContext>
#include <QOpenGLFramebufferObject>
#include <QOpenGLFunctions>
#include <QQmlEngine>
#include <QQuickGraphicsDevice>
#include <QQuickRenderControl>
#include <QQuickRenderTarget>
#include <QQuickWindow>
#include <QThread>
#include <QTimer>

#include "controllers/controller.h"
#include "controllers/controllerenginethreadcontrol.h"
#include "controllers/scripting/legacy/controllerscriptenginelegacy.h"
#include "moc_controllerrenderingengine.cpp"
#include "util/cmdlineargs.h"
#include "util/logger.h"
#include "util/thread_affinity.h"
#include "util/timer.h"

// Used in the renderFrame method to properly abort the rendering and terminate the engine.
#define VERIFY_OR_TERMINATE(cond, msg) \
    VERIFY_OR_DEBUG_ASSERT(cond) {     \
        kLogger.warning() << msg;      \
        m_pThread->quit();             \
        return;                        \
    }

namespace {
const mixxx::Logger kLogger("ControllerRenderingEngine");
} // anonymous namespace

using Clock = std::chrono::steady_clock;

ControllerRenderingEngine::ControllerRenderingEngine(
        const LegacyControllerMapping::ScreenInfo& info,
        gsl::not_null<ControllerEngineThreadControl*> engineThreadControl)
        : QObject(),
          m_screenInfo(info),
          m_GLDataFormat(GL_RGBA),
          m_GLDataType(GL_UNSIGNED_BYTE),
          m_isValid(true),
          m_pEngineThreadControl(engineThreadControl) {
    switch (m_screenInfo.pixelFormat) {
    case QImage::Format_RGB16:
        m_GLDataFormat = GL_RGB;
#ifndef QT_OPENGL_ES_2
        if (m_screenInfo.reversedColor) {
            m_GLDataType = GL_UNSIGNED_SHORT_5_6_5_REV;
        } else {
#endif
            m_GLDataType = GL_UNSIGNED_SHORT_5_6_5;
#ifndef QT_OPENGL_ES_2
        }
#endif
        break;
    case QImage::Format_RGB888:
        if (m_screenInfo.reversedColor) {
#ifdef QT_OPENGL_ES_2
            m_isValid = false;
            kLogger.critical() << "Reversed RGB8 format is not supported in OpenGL ES";
#else
            m_GLDataFormat = GL_BGR;
#endif
        } else {
            m_GLDataFormat = GL_RGB;
        }
        m_GLDataType = GL_UNSIGNED_BYTE;
        break;
    case QImage::Format_RGBA8888:
        if (m_screenInfo.reversedColor) {
#ifdef __EMSCRIPTEN__
            m_isValid = false;
            kLogger.critical() << "Reversed RGBA format is not supported in Emscripten/WebAssembly";
#elif !defined(QT_OPENGL_ES_2)
            m_GLDataFormat = GL_BGRA;
#endif
        } else {
            m_GLDataFormat = GL_RGBA;
        }
        m_GLDataType = GL_UNSIGNED_BYTE;
        break;
    default:
        m_isValid = false;
    }

    if (!m_isValid) {
        DEBUG_ASSERT(!"Unsupported format");
        return;
    }

    prepare();
}

void ControllerRenderingEngine::prepare() {
    m_pThread = std::make_unique<QThread>();
    m_pThread->setObjectName("ControllerScreenRenderer");

#if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
    [[maybe_unused]] bool successful = moveToThread(m_pThread.get());
    DEBUG_ASSERT(successful);
#else
    moveToThread(m_pThread.get());
#endif

    // these at first sight weird-looking connections facilitate thread-safe communication.
    connect(this,
            &ControllerRenderingEngine::sendFrameDataRequested,
            this,
            &ControllerRenderingEngine::send);
    connect(m_pThread.get(),
            &QThread::finished,
            this,
            &ControllerRenderingEngine::finish);

    m_pThread->start(QThread::NormalPriority);
}

ControllerRenderingEngine::~ControllerRenderingEngine() {
    DEBUG_ASSERT_THIS_QOBJECT_THREAD_ANTI_AFFINITY();
    m_pThread->wait();
    VERIFY_OR_DEBUG_ASSERT(!m_fbo) {
        kLogger.critical() << "The ControllerEngine is being deleted but hasn't been "
                              "cleaned up. Brace for impact";
    };
}

void ControllerRenderingEngine::start() {
    VERIFY_OR_DEBUG_ASSERT(!thread()->isFinished() && !thread()->isInterruptionRequested()) {
        kLogger.critical() << "Render thread has or is about to terminate. Cannot "
                              "start this render anymore.";
        return;
    }
    QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
}
bool ControllerRenderingEngine::isRunning() const {
    return m_pThread && m_pThread->isRunning();
}

void ControllerRenderingEngine::requestEngineSetup(std::shared_ptr<QQmlEngine> qmlEngine) {
    DEBUG_ASSERT(!m_quickWindow);
    VERIFY_OR_DEBUG_ASSERT(qmlEngine) {
        kLogger.critical() << "No QML engine was passed!";
        return;
    }
    VERIFY_OR_DEBUG_ASSERT_THIS_QOBJECT_THREAD_ANTI_AFFINITY() {
        kLogger.warning() << "Unable to setup OpenGL rendering context from the same "
                             "thread as the render object";
        return;
    }

    QMetaObject::invokeMethod(
            this,
            [this, qmlEngine]() {
                setup(qmlEngine);
            },
            // This invocation will block the current thread!
            Qt::BlockingQueuedConnection);

    if (m_quickWindow) {
        m_renderControl->prepareThread(m_pThread.get());
    }
}

void ControllerRenderingEngine::requestSendingFrameData(
        Controller* controller, const QByteArray& frame) {
    emit sendFrameDataRequested(controller, frame);
}

void ControllerRenderingEngine::setup(std::shared_ptr<QQmlEngine> qmlEngine) {
    VERIFY_OR_DEBUG_ASSERT_THIS_QOBJECT_THREAD_AFFINITY() {
        kLogger.warning() << "The ControllerRenderingEngine setup must be done by its own thread!";
        return;
    }
    if (!m_isValid) {
        DEBUG_ASSERT(!"Trying to setup an invalid engine");
        return;
    }
    QSurfaceFormat format;
    // FIXME multi sampling appears to be unsupported when using offscreen
    // rendering on Wayland QPA:
    //   warning [CtrlScreen_rightdeck] QWaylandGLContext::makeCurrent:
    //   eglError: 0x3009, this: 0x7ffd9c001770 warning [CtrlScreen_rightdeck]
    //   QRhiGles2: Failed to make context current. Expect bad things to happen.
    //   warning [CtrlScreen_rightdeck] Failed to create RHI (backend 2)
    if (QGuiApplication::platformName() != QStringLiteral("wayland")) {
        format.setSamples(m_screenInfo.msaa);
    }
    format.setDepthBufferSize(16);
    format.setStencilBufferSize(8);

    m_context = std::make_unique<QOpenGLContext>();
    m_context->setFormat(format);
    VERIFY_OR_DEBUG_ASSERT(m_context->create()) {
        kLogger.warning() << "Unable to initialize controller screen rendering. Giving up";
        return;
    }
    connect(m_context.get(),
            &QOpenGLContext::aboutToBeDestroyed,
            this,
            &ControllerRenderingEngine::finish);

    m_offscreenSurface = std::make_unique<QOffscreenSurface>();
    m_offscreenSurface->setFormat(m_context->format());

    // offscreen surface needs to be created from application main thread.
    VERIFY_OR_DEBUG_ASSERT(QMetaObject::invokeMethod(
                                   qApp,
                                   [this] {
                                       m_offscreenSurface->create();
                                   },
                                   // This invocation will block the current thread!
                                   Qt::BlockingQueuedConnection) &&
            m_offscreenSurface->isValid()) {
        kLogger.warning() << "Unable to create the OffscreenSurface for controller "
                             "screen rendering. Giving up";
        m_offscreenSurface.reset();
        return;
    }

    m_renderControl = std::make_unique<QQuickRenderControl>(this);
    m_renderControl->setSamples(format.samples());
    m_quickWindow = std::make_unique<QQuickWindow>(m_renderControl.get());

    if (!qmlEngine->incubationController()) {
        qmlEngine->setIncubationController(m_quickWindow->incubationController());
    }

    m_quickWindow->setGeometry(0, 0, m_screenInfo.size.width(), m_screenInfo.size.height());
}

void ControllerRenderingEngine::finish() {
    DEBUG_ASSERT_THIS_QOBJECT_THREAD_AFFINITY();
    emit stopping();

    m_isValid = false;

    if (m_context && m_context->isValid()) {
        disconnect(m_context.get(),
                &QOpenGLContext::aboutToBeDestroyed,
                this,
                &ControllerRenderingEngine::finish);
        m_context->makeCurrent(m_offscreenSurface.get());
        m_renderControl.reset();

        std::shared_ptr<QOffscreenSurface> pOffscreenSurface = std::move(m_offscreenSurface);
        QMetaObject::invokeMethod(
                qApp,
                [pOffscreenSurface] {
                    pOffscreenSurface->destroy();
                });
        m_quickWindow.reset();

        // Free the engine and FBO.
        m_fbo.reset();

        m_context->doneCurrent();
    }
    m_context.reset();
}

void ControllerRenderingEngine::renderFrame() {
    ScopedTimer t(QStringLiteral("ControllerRenderingEngine::renderFrame"));
    if (!m_isValid) {
        DEBUG_ASSERT(!"Trying to render frame on an invalid engine");
        return;
    }

    VERIFY_OR_TERMINATE(m_offscreenSurface->isValid(), "OffscreenSurface isn't valid anymore.");
    VERIFY_OR_TERMINATE(m_context->isValid(), "GLContext isn't valid anymore.");

    if (!m_fbo) {
        VERIFY_OR_TERMINATE(m_context->makeCurrent(m_offscreenSurface.get()),
                "Couldn't make the GLContext current to the OffscreenSurface.");
        ScopedTimer t(QStringLiteral("ControllerRenderingEngine::renderFrame::initFBO"));
        VERIFY_OR_TERMINATE(
                QOpenGLFramebufferObject::hasOpenGLFramebufferObjects(),
                "OpenGL doesn't support FBO");

        m_fbo = std::make_unique<QOpenGLFramebufferObject>(
                m_screenInfo.size, QOpenGLFramebufferObject::CombinedDepthStencil);

        GLenum glError;
        glError = m_context->functions()->glGetError();

        VERIFY_OR_TERMINATE(glError == GL_NO_ERROR, "GLError: " << glError);
        VERIFY_OR_TERMINATE(m_fbo->isValid(), "Failed to initialize FBO");

        m_quickWindow->setGraphicsDevice(QQuickGraphicsDevice::fromOpenGLContext(m_context.get()));

        VERIFY_OR_TERMINATE(m_renderControl->initialize(),
                "Failed to initialize redirected Qt Quick rendering");

        m_quickWindow->setRenderTarget(QQuickRenderTarget::fromOpenGLTexture(m_fbo->texture(),
                m_screenInfo.size));

        m_quickWindow->setGeometry(0, 0, m_screenInfo.size.width(), m_screenInfo.size.height());

        m_context->doneCurrent();
    }

    m_nextFrameStart = Clock::now();

    if (m_pEngineThreadControl) {
        if (!m_pEngineThreadControl->pause()) {
            kLogger.debug() << "Couldn't pause the GUI thread. Rescheduling frame rendering";
            QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
            return;
        }
    }

    m_renderControl->polishItems();

    m_renderControl->beginFrame();

    {
        ScopedTimer t(QStringLiteral("ControllerRenderingEngine::renderFrame::sync"));
        VERIFY_OR_DEBUG_ASSERT(m_renderControl->sync()) {
            kLogger.warning() << "Couldn't sync the render control. Scene may be stuck";
        };
    }

    if (m_pEngineThreadControl) {
        m_pEngineThreadControl->resume();
    }

    VERIFY_OR_TERMINATE(m_offscreenSurface->isValid(), "OffscreenSurface isn't valid anymore.");
    VERIFY_OR_TERMINATE(m_context->makeCurrent(m_offscreenSurface.get()),
            "Couldn't make the GLContext current to the OffscreenSurface.");

#ifdef QT_OPENGL_ES_2
    // OpenGL ES doesn't support extended format and type when reading pixel and
    // only support GL_RGBA/GL_UNSIGNED_BYTE On this platform, we fallback to Qt
    // for the pixel transformation, using QImage conversion capabilities
    QImage fboImage(m_screenInfo.size, QImage::Format_RGBA8888);
#else
    QImage fboImage(m_screenInfo.size, m_screenInfo.pixelFormat);
#endif

    VERIFY_OR_DEBUG_ASSERT(m_fbo->bind()) {
        kLogger.warning() << "Couldn't bind the FBO.";
    }
    GLenum glError;
    // Flush any remaining GL errors.
    while ((glError = m_context->functions()->glGetError()) != GL_NO_ERROR) {
        kLogger.debug() << "Retrieved a previously unhandled GL error: " << glError;
    }
#ifndef QT_OPENGL_ES_2
    m_context->functions()->glFlush();
    glError = m_context->functions()->glGetError();
    VERIFY_OR_TERMINATE(glError == GL_NO_ERROR, "GLError after glFlush: " << glError);
    if (static_cast<std::endian>(m_screenInfo.endian) != std::endian::native) {
        m_context->functions()->glPixelStorei(GL_PACK_SWAP_BYTES, GL_TRUE);
    }
    glError = m_context->functions()->glGetError();
    VERIFY_OR_TERMINATE(glError == GL_NO_ERROR, "GLError after glPixelStorei: " << glError);
#endif

    QDateTime timestamp = QDateTime::currentDateTime();
    m_renderControl->render();
    m_renderControl->endFrame();

    // Flush any remaining GL errors.
    while ((glError = m_context->functions()->glGetError()) != GL_NO_ERROR) {
        kLogger.debug() << "Retrieved a previously unhandled GL error: " << glError;
    }
    {
        ScopedTimer t(QStringLiteral("ControllerRenderingEngine::renderFrame::glReadPixels"));
        m_context->functions()->glReadPixels(0,
                0,
                m_screenInfo.size.width(),
                m_screenInfo.size.height(),
#ifndef QT_OPENGL_ES_2
                m_GLDataFormat,
                m_GLDataType,
#else
                GL_RGBA,
                GL_UNSIGNED_BYTE,
#endif
                fboImage.bits());
    }
    glError = m_context->functions()->glGetError();
    VERIFY_OR_TERMINATE(glError == GL_NO_ERROR, "GLError after glReadPixels: " << glError);
    VERIFY_OR_DEBUG_ASSERT(!fboImage.isNull()) {
        kLogger.warning() << "Screen frame is null!";
    }
    VERIFY_OR_DEBUG_ASSERT(m_fbo->release()) {
        kLogger.debug() << "Couldn't release the FBO.";
    }

    m_context->doneCurrent();

#ifdef QT_OPENGL_ES_2
    fboImage.convertTo(m_screenInfo.pixelFormat);

    // OpenGL ES doesn't support extended reverse format (suffixed with _REV) so
    // we use QImage function for this
    if (static_cast<std::endian>(m_screenInfo.endian) != std::endian::native) {
        fboImage.rgbSwap();
    }

    // OpenGL ES doesn't support explicit endianness (GL_PACK_SWAP_BYTES) se we
    // use Qt helper function to convert the pixel buffer. Only 16 and 32 bit
    // pixel format are supported currently.
    switch (static_cast<std::endian>(m_screenInfo.endian)) {
    case std::endian::big:
        switch (m_screenInfo.pixelFormat) {
        case QImage::Format_RGB16:
            qToBigEndian<quint16>(fboImage.bits(), fboImage.sizeInBytes() / 2, fboImage.bits());
            break;
        case QImage::Format_RGBA8888:
            qToBigEndian<quint32>(fboImage.bits(), fboImage.sizeInBytes() / 4, fboImage.bits());
            break;
        default:
            kLogger.critical()
                    << "Screen endianness mismatches native endianness, but OpenGL "
                       "ES does not let us specify a reverse pixel store order. "
                       "This will likely lead to invalid colors.";
        }
        break;
    case std::endian::little:
        switch (m_screenInfo.pixelFormat) {
        case QImage::Format_RGB16:
            qToLittleEndian<quint16>(fboImage.bits(), fboImage.sizeInBytes(), fboImage.bits());
            break;
        case QImage::Format_RGBA8888:
            qToLittleEndian<quint32>(fboImage.bits(), fboImage.sizeInBytes(), fboImage.bits());
            break;
        default:
            kLogger.critical()
                    << "Screen endianness mismatches native endianness, but OpenGL "
                       "ES does not let us specify a reverse pixel store order. "
                       "This will likely lead to invalid colors.";
        }
        break;
    }
#endif

#if QT_VERSION >= QT_VERSION_CHECK(6, 9, 0)
    fboImage.flip(Qt::Vertical);
#else
    fboImage.mirror(false, true);
#endif

    emit frameRendered(m_screenInfo, fboImage.copy(), timestamp);
}

bool ControllerRenderingEngine::stop() {
    m_pThread->quit();
    return m_pThread->wait();
}

void ControllerRenderingEngine::send(Controller* controller, const QByteArray& frame) {
    DEBUG_ASSERT_THIS_QOBJECT_THREAD_AFFINITY();
    ScopedTimer t(QStringLiteral("ControllerRenderingEngine::send"));
    if (!frame.isEmpty()) {
        VERIFY_OR_TERMINATE(controller->sendBytes(frame), "Unable to send frame to device");
    }

    if (CmdlineArgs::Instance()
                    .getControllerDebug()) {
        auto endOfFrameCycle = Clock::now();
        kLogger.debug()
                << "Frame took "
                << std::chrono::duration_cast<std::chrono::milliseconds>(
                           endOfFrameCycle - m_nextFrameStart)
                           .count()
                << "milliseconds and frame has" << frame.size() << "bytes";
    }

    m_nextFrameStart += std::chrono::microseconds(1000000 / m_screenInfo.target_fps);

    auto durationToWaitBeforeFrame =
            std::chrono::duration_cast<std::chrono::milliseconds>(
                    m_nextFrameStart - Clock::now());

    if (durationToWaitBeforeFrame > std::chrono::milliseconds(0)) {
        if (CmdlineArgs::Instance()
                        .getControllerDebug()) {
            kLogger.debug() << "Waiting for "
                            << durationToWaitBeforeFrame.count()
                            << "milliseconds before rendering next frame";
        }
        QTimer::singleShot(durationToWaitBeforeFrame,
                Qt::PreciseTimer,
                this,
                &ControllerRenderingEngine::renderFrame);
    } else {
        QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
    }
}

bool ControllerRenderingEngine::event(QEvent* event) {
    // In case there is a request for update (e.g using QWindow::requestUpdate),
    // we emit the signal to request rendering using the engine.
    if (event->type() == QEvent::UpdateRequest) {
        renderFrame();
        return true;
    }

    return QObject::event(event);
}