/*
 *  SPDX-FileCopyrightText: 2020 Eoin O 'Neill <eoinoneill1991@gmail.com>
 *  SPDX-FileCopyrightText: 2020 Emmet O 'Neill <emmetoneill.pdx@gmail.com>
 *
 *  SPDX-License-Identifier: GPL-2.0-or-later
 */
#include "kis_zoom_scrollbar.h"

#include "kis_config.h"
#include "kis_global.h"
#include "kis_debug.h"
#include <QMouseEvent>
#include <QTabletEvent>

KisZoomableScrollBar::KisZoomableScrollBar(QWidget *parent)
    : QScrollBar(parent)
    , lastKnownPosition(0,0)
    , accelerationAccumulator(0,0)
    , scrollSubPixelAccumulator(0.0f)
    , zoomThreshold(0.75f)
    , wheelOverscrollSensitivity(1.0f)
    , catchTeleportCorrection(false)
{
    KisConfig config(true);
    zoomEnabled = config.scrollbarZoomEnabled();
}

KisZoomableScrollBar::KisZoomableScrollBar(Qt::Orientation orientation, QWidget *parent)
    : KisZoomableScrollBar(parent)
{
    setOrientation(orientation);
}

KisZoomableScrollBar::~KisZoomableScrollBar()
{
}

QPoint KisZoomableScrollBar::barPosition()
{
    float barPositionNormalized = (float)(value() - minimum()) / (float)(maximum() + pageStep() - minimum());
    QPoint barPosition = orientation() == Qt::Horizontal ?
                QPoint(barPositionNormalized * width() * devicePixelRatio(), 0) :
                QPoint(0, barPositionNormalized * height() * devicePixelRatio());

    return mapToGlobal(QPoint(0,0)) + barPosition;
}

bool KisZoomableScrollBar::catchTeleports(QMouseEvent *event) {
    if (catchTeleportCorrection) {
        catchTeleportCorrection = false;
        event->accept();
        return true;
    }

    return false;
}

void KisZoomableScrollBar::handleWrap( const QPoint &accel, const QPoint &mouseCoord)
{
    QRect windowRect = window()->geometry();
    windowRect = kisGrowRect(windowRect, -2);
    const int windowWidth = windowRect.width();
    const int windowHeight = windowRect.height();
    const int windowX = windowRect.x();
    const int windowY = windowRect.y();
    const bool xWrap = true;
    const bool yWrap = true;

    if (!windowRect.contains(mouseCoord)) {
        int x = mouseCoord.x();
        int y = mouseCoord.y();

        if (x < windowX && xWrap ) {
            x += (windowWidth - 2);
        } else if (x > (windowX + windowWidth) && xWrap ) {
            x -= (windowWidth - 2);
        }

        if (y < windowY && yWrap) {
            y += (windowHeight - 2);
        } else if (y > (windowY + windowHeight) && yWrap) {
            y -= (windowHeight - 2);
        }

        QCursor::setPos(x, y);
        lastKnownPosition = QPoint(x, y) - accel;

        //Important -- teleportation needs to caught to prevent high-acceleration
        //values from QCursor::setPos being read in this event.
        catchTeleportCorrection = true;
    }
}

void KisZoomableScrollBar::handleScroll(const QPoint &accel)
{
    const qreal sliderMovementPix = (orientation() == Qt::Horizontal) ? accel.x() * devicePixelRatio() : accel.y() * devicePixelRatio();
    const qreal zoomMovementPix = (orientation() == Qt::Horizontal) ? -accel.y() : -accel.x();
    const qreal documentLength = maximum() - minimum() + pageStep();
    const qreal widgetLength = (orientation() == Qt::Horizontal) ? width() * devicePixelRatio() : height() * devicePixelRatio();
    const qreal widgetThickness = (orientation() == Qt::Horizontal) ? height() * devicePixelRatio() : width() * devicePixelRatio();

    const QVector2D perpendicularDirection = (orientation() == Qt::Horizontal) ? QVector2D(0, 1) : QVector2D(1, 0);
    const float perpendicularity = QVector2D::dotProduct(perpendicularDirection.normalized(), accelerationAccumulator.normalized());

    if (zoomEnabled && qAbs(perpendicularity) > zoomThreshold && zoomMovementPix != 0) {
        zoom(qreal(zoomMovementPix) / qreal(widgetThickness * 2));
    } else if (sliderMovementPix != 0) {
        const int currentPosition = sliderPosition();
        scrollSubPixelAccumulator += (documentLength) * (sliderMovementPix / widgetLength);

        setSliderPosition(currentPosition + scrollSubPixelAccumulator);
        if (currentPosition + scrollSubPixelAccumulator > maximum() ||
            currentPosition + scrollSubPixelAccumulator <  minimum()) {
            overscroll(scrollSubPixelAccumulator);
        }

        const int sign = (scrollSubPixelAccumulator > 0) - (scrollSubPixelAccumulator < 0);
        scrollSubPixelAccumulator -= floor(abs(scrollSubPixelAccumulator)) * sign;
    }
}

void KisZoomableScrollBar::tabletEvent(QTabletEvent *event) {
    if ( event->type() == QTabletEvent::TabletMove && isSliderDown() ) {
        QPoint globalMouseCoord = mapToGlobal(event->pos());
        QPoint accel = globalMouseCoord - lastKnownPosition;
        accelerationAccumulator += QVector2D(accel);

        if( accelerationAccumulator.length() > 5) {
            accelerationAccumulator = accelerationAccumulator.normalized();
        }

        handleScroll(accel);
        lastKnownPosition = globalMouseCoord;
        event->accept();
    } else {
        if (event->type() == QTabletEvent::TabletPress) {
            QPoint globalMouseCoord = mapToGlobal(event->pos());
            lastKnownPosition = globalMouseCoord;
            setSliderDown(true);
            event->accept();
        } else if(event->type() == QTabletEvent::TabletRelease) {
            setSliderDown(false);
            event->accept();
        } else {
            QScrollBar::tabletEvent(event);
        }
    }
}

void KisZoomableScrollBar::mousePressEvent(QMouseEvent *event)
{
    QScrollBar::mousePressEvent(event);

    lastKnownPosition = mapToGlobal(event->pos());
    accelerationAccumulator = QVector2D(0,0);
    QPoint worldPosition = mapToGlobal(event->pos());
    QPoint barPosition = this->barPosition();
    initialPositionRelativeToBar = worldPosition - barPosition;
    setCursor(Qt::BlankCursor);
}


void KisZoomableScrollBar::mouseMoveEvent(QMouseEvent *event)
{
    QPoint globalMouseCoord = mapToGlobal(event->pos());

    QPoint accel = globalMouseCoord - lastKnownPosition;
    accelerationAccumulator += QVector2D(accel);

    if (catchTeleports(event)) {
        return;
    }

    if (accelerationAccumulator.length() > 5) {
        accelerationAccumulator = accelerationAccumulator.normalized();
    }

    handleScroll(accel);
    lastKnownPosition = globalMouseCoord;
    handleWrap(accel, mapToGlobal(event->pos()));
    event->accept();
}

void KisZoomableScrollBar::mouseReleaseEvent(QMouseEvent *event)
{
    //If there's nowhere for our slider to  go, we should
    //still emit the slider release value.
    if (maximum() == minimum()) {
        emit sliderReleased();
    }
    const QPoint maximumCoordinates = mapToGlobal(QPoint(width() * devicePixelRatio(), height() * devicePixelRatio()));
    const QPoint minimumCoordinates = mapToGlobal(QPoint(0,0));
    const QPoint desiredCoordinates = barPosition() + initialPositionRelativeToBar;
    QPoint cursorPosition = QPoint(
                qMax(minimumCoordinates.x(), qMin(maximumCoordinates.x(), desiredCoordinates.x())),
                qMax(minimumCoordinates.y(), qMin(maximumCoordinates.y(), desiredCoordinates.y()))
                );
    QCursor::setPos(cursorPosition);
    setCursor(Qt::ArrowCursor);
    QScrollBar::mouseReleaseEvent(event);
}

void KisZoomableScrollBar::wheelEvent(QWheelEvent *event) {
    const int delta = (event->angleDelta().y() / 8) * singleStep() * -1;
    const int currentPosition = sliderPosition();

    if (currentPosition + delta > maximum() || currentPosition + delta < minimum()){
        overscroll(delta * wheelOverscrollSensitivity);
    }

    QScrollBar::wheelEvent(event);
}

void KisZoomableScrollBar::setZoomDeadzone(float value)
{
    zoomThreshold = value;
}

void KisZoomableScrollBar::setWheelOverscrollSensitivity(float sensitivity)
{
    wheelOverscrollSensitivity = sensitivity;
}
