#include "graphicsview.h"

#include "graphicsscene.h"

#include <QDebug>
#include <QMouseEvent>
#include <QScrollBar>
#include <QMimeData>
#include <QImageReader>
#include <QStyleOptionGraphicsItem>

// TODO: remove this once we drop older Qt support.
#if QT_VERSION >= QT_VERSION_CHECK(5, 13, 0)
#define COMPAT_CONSTCOLOR constexpr
#else
#define COMPAT_CONSTCOLOR const
#endif

GraphicsView::GraphicsView(QWidget *parent)
    : QGraphicsView (parent)
{
    setDragMode(QGraphicsView::ScrollHandDrag);
    setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setResizeAnchor(QGraphicsView::AnchorUnderMouse);
    setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
    setStyleSheet("background-color: rgba(0, 0, 0, 220);"
                  "border-radius: 3px;");
    setAcceptDrops(true);
    setCheckerboardEnabled(false);

    connect(horizontalScrollBar(), &QScrollBar::valueChanged, this, &GraphicsView::viewportRectChanged);
    connect(verticalScrollBar(), &QScrollBar::valueChanged, this, &GraphicsView::viewportRectChanged);
}

void GraphicsView::showFileFromPath(const QString &filePath, bool doRequestGallery)
{
    emit navigatorViewRequired(false, transform());

    if (filePath.endsWith(".svg")) {
        showSvg(filePath);
    } else {
        QImageReader imageReader(filePath);
        imageReader.setAutoTransform(true);
        imageReader.setDecideFormatFromContent(true);

        // Since if the image format / plugin does not support this feature, imageFormat() will returns an invalid format.
        // So we cannot use imageFormat() and check if it returns QImage::Format_Invalid to detect if we support the file.
        // QImage::Format imageFormat = imageReader.imageFormat();
        if (imageReader.format().isEmpty()) {
            doRequestGallery = false;
            showText(tr("File is not a valid image"));
        } else if (imageReader.supportsAnimation() && imageReader.imageCount() > 1) {
            showAnimated(filePath);
        } else if (!imageReader.canRead()) {
            doRequestGallery = false;
            showText(tr("Image data is invalid or currently unsupported"));
        } else {
            const QPixmap & pixmap = QPixmap::fromImageReader(&imageReader);
            if (pixmap.isNull()) {
                doRequestGallery = false;
                showText(tr("Image data is invalid or currently unsupported"));
            } else {
                showImage(pixmap);
            }
        }
    }

    if (doRequestGallery) {
        emit requestGallery(filePath);
    }
}

void GraphicsView::showImage(const QPixmap &pixmap)
{
    resetTransform();
    scene()->showImage(pixmap);
    checkAndDoFitInView();
}

void GraphicsView::showImage(const QImage &image)
{
    resetTransform();
    scene()->showImage(QPixmap::fromImage(image));
    checkAndDoFitInView();
}

void GraphicsView::showText(const QString &text)
{
    resetTransform();
    scene()->showText(text);
    checkAndDoFitInView();
}

void GraphicsView::showSvg(const QString &filepath)
{
    resetTransform();
    scene()->showSvg(filepath);
    checkAndDoFitInView();
}

void GraphicsView::showAnimated(const QString &filepath)
{
    resetTransform();
    scene()->showAnimated(filepath);
    checkAndDoFitInView();
}

GraphicsScene *GraphicsView::scene() const
{
    return qobject_cast<GraphicsScene*>(QGraphicsView::scene());
}

void GraphicsView::setScene(GraphicsScene *scene)
{
    return QGraphicsView::setScene(scene);
}

qreal GraphicsView::scaleFactor() const
{
    return QStyleOptionGraphicsItem::levelOfDetailFromTransform(transform());
}

void GraphicsView::resetTransform()
{
    QGraphicsView::resetTransform();
}

void GraphicsView::zoomView(qreal scaleFactor)
{
    m_enableFitInView = false;
    scale(scaleFactor, scaleFactor);
    applyTransformationModeByScaleFactor();
    emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
}

// This is always according to user's view.
// the direction of the rotation will NOT be clockwise because the y-axis points downwards.
void GraphicsView::rotateView(bool clockwise)
{
    resetScale();

    QTransform tf(0,                  clockwise ? 1 : -1, 0,
                  clockwise ? -1 : 1, 0,                  0,
                  0,                  0,                  1);
    tf = transform() * tf;
    setTransform(tf);
}

void GraphicsView::flipView(bool horizontal)
{
    QTransform tf(horizontal ? -1 : 1, 0,                   0,
                  0,                   horizontal ? 1 : -1, 0,
                  0,                   0,                   1);
    tf = transform() * tf;
    setTransform(tf);

    // Ensure the navigation view is also flipped.
    emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
}

void GraphicsView::resetScale()
{
    setTransform(resetScale(transform()));
    emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
}

void GraphicsView::fitInView(const QRectF &rect, Qt::AspectRatioMode aspectRadioMode)
{
    QGraphicsView::fitInView(rect, aspectRadioMode);
    applyTransformationModeByScaleFactor();
}

void GraphicsView::checkAndDoFitInView(bool markItOnAnyway)
{
    if (!isThingSmallerThanWindowWith(transform())) {
        m_enableFitInView = true;
        fitInView(sceneRect(), Qt::KeepAspectRatio);
    }

    if (markItOnAnyway) {
        m_enableFitInView = true;
    }
}

inline double zeroOrOne(double number)
{
    return qFuzzyIsNull(number) ? 0 : (number > 0 ? 1 : -1);
}

// Note: this only works if we only have 90 degree based rotation
//       and no shear/translate.
QTransform GraphicsView::resetScale(const QTransform & orig)
{
    return QTransform(zeroOrOne(orig.m11()), zeroOrOne(orig.m12()),
                      zeroOrOne(orig.m21()), zeroOrOne(orig.m22()),
                      orig.dx(),             orig.dy());
}

void GraphicsView::toggleCheckerboard(bool invertCheckerboardColor)
{
    setCheckerboardEnabled(!m_checkerboardEnabled, invertCheckerboardColor);
}

void GraphicsView::mousePressEvent(QMouseEvent *event)
{
    if (shouldIgnoreMousePressMoveEvent(event)) {
        event->ignore();
        // blumia: return here, or the QMouseEvent event transparency won't
        //         work if we set a QGraphicsView::ScrollHandDrag drag mode.
        return;
    }

    return QGraphicsView::mousePressEvent(event);
}

void GraphicsView::mouseMoveEvent(QMouseEvent *event)
{
    if (shouldIgnoreMousePressMoveEvent(event)) {
        event->ignore();
    }

    return QGraphicsView::mouseMoveEvent(event);
}

void GraphicsView::mouseReleaseEvent(QMouseEvent *event)
{
    QGraphicsItem *item = itemAt(event->pos());
    if (!item) {
        event->ignore();
    }

    return QGraphicsView::mouseReleaseEvent(event);
}

void GraphicsView::wheelEvent(QWheelEvent *event)
{
    event->ignore();
    // blumia: no need for calling parent method.
}

void GraphicsView::resizeEvent(QResizeEvent *event)
{
    if (m_enableFitInView) {
        bool originalSizeSmallerThanWindow = isThingSmallerThanWindowWith(resetScale(transform()));
        if (originalSizeSmallerThanWindow && scaleFactor() >= 1) {
            // no longer need to do fitInView()
            // but we leave the m_enableFitInView value unchanged in case
            // user resize down the window again.
        } else if (originalSizeSmallerThanWindow && scaleFactor() < 1) {
            resetScale();
        } else {
            fitInView(sceneRect(), Qt::KeepAspectRatio);
        }
    } else {
        emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
    }
    return QGraphicsView::resizeEvent(event);
}

void GraphicsView::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasUrls() || event->mimeData()->hasImage() || event->mimeData()->hasText()) {
        event->acceptProposedAction();
    } else {
        event->ignore();
    }
//    qDebug() << event->mimeData() << "Drag Enter Event"
//             << event->mimeData()->hasUrls() << event->mimeData()->hasImage()
//             << event->mimeData()->formats() << event->mimeData()->hasFormat("text/uri-list");

    return QGraphicsView::dragEnterEvent(event);
}

void GraphicsView::dragMoveEvent(QDragMoveEvent *event)
{
    Q_UNUSED(event)
    // by default, QGraphicsView/Scene will ignore the action if there are no QGraphicsItem under cursor.
    // We actually doesn't care and would like to keep the drag event as-is, so just do nothing here.
}

void GraphicsView::dropEvent(QDropEvent *event)
{
    event->acceptProposedAction();

    const QMimeData * mimeData = event->mimeData();

    if (mimeData->hasUrls()) {
        const QList<QUrl> &urls = mimeData->urls();
        if (urls.isEmpty()) {
            showText(tr("File url list is empty"));
        } else {
            showFileFromPath(urls.first().toLocalFile(), true);
        }
    } else if (mimeData->hasImage()) {
        QImage img = qvariant_cast<QImage>(mimeData->imageData());
        QPixmap pixmap = QPixmap::fromImage(img);
        if (pixmap.isNull()) {
            showText(tr("Image data is invalid"));
        } else {
            showImage(pixmap);
        }
    } else if (mimeData->hasText()) {
        showText(mimeData->text());
    } else {
        showText(tr("Not supported mimedata: %1").arg(mimeData->formats().first()));
    }
}

bool GraphicsView::isThingSmallerThanWindowWith(const QTransform &transform) const
{
    return rect().size().expandedTo(transform.mapRect(sceneRect()).size().toSize())
            == rect().size();
}

bool GraphicsView::shouldIgnoreMousePressMoveEvent(const QMouseEvent *event) const
{
    if (event->buttons() == Qt::NoButton) {
        return true;
    }

    QGraphicsItem *item = itemAt(event->pos());
    if (!item) {
        return true;
    }

    if (isThingSmallerThanWindowWith(transform())) {
        return true;
    }

    return false;
}

void GraphicsView::setCheckerboardEnabled(bool enabled, bool invertColor)
{
    m_checkerboardEnabled = enabled;
    m_isLastCheckerboardColorInverted = invertColor;
    if (m_checkerboardEnabled) {
        // Prepare background check-board pattern
        QPixmap tilePixmap(0x20, 0x20);
        tilePixmap.fill(invertColor ? QColor(220, 220, 220, 170) : QColor(35, 35, 35, 170));
        QPainter tilePainter(&tilePixmap);
        COMPAT_CONSTCOLOR QColor color(45, 45, 45, 170);
        COMPAT_CONSTCOLOR QColor invertedColor(210, 210, 210, 170);
        tilePainter.fillRect(0, 0, 0x10, 0x10, invertColor ? invertedColor : color);
        tilePainter.fillRect(0x10, 0x10, 0x10, 0x10, invertColor ? invertedColor : color);
        tilePainter.end();

        setBackgroundBrush(tilePixmap);
    } else {
        setBackgroundBrush(Qt::transparent);
    }
}

void GraphicsView::applyTransformationModeByScaleFactor()
{
    if (this->scaleFactor() < 1) {
        scene()->trySetTransformationMode(Qt::SmoothTransformation);
    } else {
        scene()->trySetTransformationMode(Qt::FastTransformation);
    }
}