#include "rdp_display_widget.h"

#include <QCursor>
#include <QEvent>
#include <QKeyEvent>
#include <QMouseEvent>
#include <QPainter>
#include <QPixmap>
#include <QResizeEvent>
#include <QTimer>
#include <QWheelEvent>
#include <QtGlobal>

namespace {
QSize sanitizeSize(const QSize& size)
{
    return QSize(qMax(1, size.width()), qMax(1, size.height()));
}

qreal sanitizeDevicePixelRatio(qreal ratio)
{
    if (!(ratio > 0.0)) {
        return 1.0;
    }
    return qBound(1.0, ratio, 4.0);
}

// Windows' virtual-display driver can visibly glitch (stale composited
// content left on screen) when asked to change resolution repeatedly in
// quick succession, which naturally happens as the window's layout settles
// right after creation/connect. Coalescing bursts of resize events into one
// request avoids triggering that.
constexpr int kResizeDebounceMs = 150;
}

RdpDisplayWidget::RdpDisplayWidget(QWidget* parent)
    : QWidget(parent),
      m_remoteSize(1280, 720),
      m_cursorMode(CursorMode::Default),
      m_resizeDebounceTimer(new QTimer(this))
{
    setFocusPolicy(Qt::StrongFocus);
    setMouseTracking(true);
    setAutoFillBackground(false);
    setMinimumSize(320, 200);

    m_resizeDebounceTimer->setSingleShot(true);
    connect(m_resizeDebounceTimer, &QTimer::timeout, this, &RdpDisplayWidget::emitViewportGeometry);

    scheduleViewportGeometryEmit();
}

void RdpDisplayWidget::setFrame(const QImage& frame)
{
    if (frame.isNull()) {
        return;
    }

    m_frame = frame;
    m_remoteSize = sanitizeSize(frame.size());
    update();
}

void RdpDisplayWidget::setRemoteDesktopSize(int width, int height)
{
    if (width < 1 || height < 1) {
        return;
    }

    const QSize nextSize(width, height);
    if (m_remoteSize == nextSize) {
        return;
    }

    m_remoteSize = nextSize;
    // The next actual frame (via setFrame) arrives asynchronously and isn't
    // guaranteed to be sized to match yet. Drawing the old frame stretched
    // to a renderRect() computed from the new m_remoteSize would scale it
    // by the wrong factor for the transition window, producing visibly
    // distorted/duplicated-looking content. Clear it and show the existing
    // "waiting for frame" placeholder until a correctly-sized frame lands.
    m_frame = QImage();
    update();
}

void RdpDisplayWidget::clearFrame()
{
    m_frame = QImage();
    update();
}

void RdpDisplayWidget::setCursorImage(const QImage& image, const QPoint& hotspot)
{
    m_cursorImage = image;
    m_cursorHotspot = hotspot;
    m_cursorMode = CursorMode::Custom;
    applyCursor();
}

void RdpDisplayWidget::setCursorHidden()
{
    m_cursorMode = CursorMode::Hidden;
    applyCursor();
}

void RdpDisplayWidget::setCursorDefault()
{
    m_cursorMode = CursorMode::Default;
    applyCursor();
}

void RdpDisplayWidget::applyCursor()
{
    if (m_cursorMode == CursorMode::Hidden) {
        setCursor(Qt::BlankCursor);
        return;
    }

    if (m_cursorMode == CursorMode::Default || m_cursorImage.isNull()) {
        unsetCursor();
        return;
    }

    const QSize remote = effectiveRemoteSize();
    const QRectF target = renderRect();
    if (remote.isEmpty() || target.isEmpty()) {
        setCursor(QCursor(QPixmap::fromImage(m_cursorImage),
                          m_cursorHotspot.x(),
                          m_cursorHotspot.y()));
        return;
    }

    const qreal scale = target.width() / remote.width();
    QImage scaledImage = m_cursorImage;
    if (!qFuzzyCompare(scale, 1.0)) {
        scaledImage = m_cursorImage.scaled(
            qMax(1, qRound(m_cursorImage.width() * scale)),
            qMax(1, qRound(m_cursorImage.height() * scale)),
            Qt::IgnoreAspectRatio,
            Qt::SmoothTransformation);
    }

    const int hotX = qBound(0, qRound(m_cursorHotspot.x() * scale), scaledImage.width());
    const int hotY = qBound(0, qRound(m_cursorHotspot.y() * scale), scaledImage.height());
    setCursor(QCursor(QPixmap::fromImage(scaledImage), hotX, hotY));
}

void RdpDisplayWidget::paintEvent(QPaintEvent* event)
{
    Q_UNUSED(event);

    QPainter painter(this);
    painter.fillRect(rect(), QColor(QStringLiteral("#101214")));

    const QRectF target = renderRect();
    if (!m_frame.isNull()) {
        painter.drawImage(target, m_frame);
    } else {
        painter.setPen(QColor(QStringLiteral("#b0bec5")));
        painter.drawText(rect(),
                         Qt::AlignCenter,
                         QStringLiteral("Waiting for remote desktop frame..."));
    }
}

void RdpDisplayWidget::resizeEvent(QResizeEvent* event)
{
    QWidget::resizeEvent(event);
    scheduleViewportGeometryEmit();
    applyCursor();
}

bool RdpDisplayWidget::event(QEvent* event)
{
    // Fires when this widget's effective screen changes (e.g. dragged to a
    // different monitor), which is what changes devicePixelRatio(). Newer
    // Qt versions add a more specific QEvent::DevicePixelRatioChange, but
    // this project's Qt 6.2 floor doesn't have it.
    if (event->type() == QEvent::ScreenChangeInternal) {
        scheduleViewportGeometryEmit();
    }
    return QWidget::event(event);
}

void RdpDisplayWidget::scheduleViewportGeometryEmit()
{
    // Restarting an already-running single-shot timer resets its countdown,
    // so a burst of resize events collapses into one emission after things
    // settle, rather than one request per event.
    m_resizeDebounceTimer->start(kResizeDebounceMs);
}

void RdpDisplayWidget::emitViewportGeometry()
{
    const QSize logicalSize = sanitizeSize(this->size());
    const qreal ratio = sanitizeDevicePixelRatio(this->devicePixelRatioF());
    const QSize physicalSize(qRound(logicalSize.width() * ratio), qRound(logicalSize.height() * ratio));
    emit viewportSizeChanged(physicalSize.width(), physicalSize.height());
    emit displayScaleChanged(ratio);
}

void RdpDisplayWidget::keyPressEvent(QKeyEvent* event)
{
    if (event == nullptr) {
        return;
    }

    // Auto-repeat presses must reach the remote server so it can perform
    // its own typematic repeat, exactly as a physical keyboard held down
    // would. Only release events filter out isAutoRepeat() (below), since
    // Qt uses a synthetic release/press pair purely to normalize platform
    // auto-repeat quirks -- forwarding that synthetic release would send a
    // spurious key-up for a key that is still physically held.
    emit keyInput(event->key(),
                  event->nativeScanCode(),
                  event->text(),
                  true,
                  static_cast<int>(event->modifiers()));
    event->accept();
}

void RdpDisplayWidget::keyReleaseEvent(QKeyEvent* event)
{
    if (event == nullptr || event->isAutoRepeat()) {
        return;
    }

    emit keyInput(event->key(),
                  event->nativeScanCode(),
                  event->text(),
                  false,
                  static_cast<int>(event->modifiers()));
    event->accept();
}

bool RdpDisplayWidget::focusNextPrevChild(bool next)
{
    Q_UNUSED(next);
    // Tab/Shift+Tab must reach keyPressEvent() and be forwarded to the
    // remote session instead of moving focus to the next local widget.
    return false;
}

void RdpDisplayWidget::mousePressEvent(QMouseEvent* event)
{
    if (event == nullptr) {
        return;
    }

    setFocus(Qt::MouseFocusReason);
    const QPoint mapped = mapToRemote(event->position());
    emit mouseButtonInput(mapped.x(), mapped.y(), static_cast<int>(event->button()), true);
    event->accept();
}

void RdpDisplayWidget::mouseReleaseEvent(QMouseEvent* event)
{
    if (event == nullptr) {
        return;
    }

    const QPoint mapped = mapToRemote(event->position());
    emit mouseButtonInput(mapped.x(), mapped.y(), static_cast<int>(event->button()), false);
    event->accept();
}

void RdpDisplayWidget::mouseMoveEvent(QMouseEvent* event)
{
    if (event == nullptr) {
        return;
    }

    const QPoint mapped = mapToRemote(event->position());
    emit mouseMoveInput(mapped.x(), mapped.y());
    event->accept();
}

void RdpDisplayWidget::wheelEvent(QWheelEvent* event)
{
    if (event == nullptr) {
        return;
    }

    const QPoint mapped = mapToRemote(event->position());
    const QPoint angle = event->angleDelta();
    emit mouseWheelInput(mapped.x(), mapped.y(), angle.x(), angle.y());
    event->accept();
}

QRectF RdpDisplayWidget::renderRect() const
{
    const QSize remote = effectiveRemoteSize();
    const QRectF area = rect();
    if (area.isEmpty()) {
        return QRectF();
    }

    const qreal scale = qMin(area.width() / remote.width(), area.height() / remote.height());
    const qreal drawWidth = remote.width() * scale;
    const qreal drawHeight = remote.height() * scale;
    const qreal x = area.x() + ((area.width() - drawWidth) * 0.5);
    const qreal y = area.y() + ((area.height() - drawHeight) * 0.5);
    return QRectF(x, y, drawWidth, drawHeight);
}

QPoint RdpDisplayWidget::mapToRemote(const QPointF& pos) const
{
    const QSize remote = effectiveRemoteSize();
    const QRectF target = renderRect();
    if (target.isEmpty()) {
        return QPoint(0, 0);
    }

    const qreal clampedX = qBound(target.left(), pos.x(), target.right());
    const qreal clampedY = qBound(target.top(), pos.y(), target.bottom());

    const qreal normalizedX = (clampedX - target.left()) / qMax(1.0, target.width());
    const qreal normalizedY = (clampedY - target.top()) / qMax(1.0, target.height());

    const int remoteX = qBound(0, static_cast<int>(normalizedX * remote.width()), remote.width() - 1);
    const int remoteY = qBound(0, static_cast<int>(normalizedY * remote.height()), remote.height() - 1);
    return QPoint(remoteX, remoteY);
}

QSize RdpDisplayWidget::effectiveRemoteSize() const
{
    if (m_remoteSize.width() > 0 && m_remoteSize.height() > 0) {
        return m_remoteSize;
    }
    if (!m_frame.isNull()) {
        return sanitizeSize(m_frame.size());
    }
    return QSize(1280, 720);
}