#ifndef RUNNINGTEXTWIDGET_H
#define RUNNINGTEXTWIDGET_H

#include <QWidget>

enum Direction
{
    North = 0, //上
    South, //下
    West,  //左
    East   //右
};

class RunningTextWidget : public QWidget
{
    Q_OBJECT
public:
    explicit RunningTextWidget(QWidget *parent = nullptr);
    void setText(const QString & newText);
    void setDirection(Direction newDirection);
    void setSpeed(uint newSpeed);

protected:
    void paintEvent(QPaintEvent *event) override final;

private:
    void onTime();
    std::shared_ptr<struct RunningTextWidgetPrivate> d_ptr;
};

#endif // RUNNINGTEXTWIDGET_H

#include "runningtextwidget.h"
#include <QPainter>
#include <QTimer>

struct RunningTextWidgetPrivate
{
    QString text{"飞流直下三千尺，疑是银河落九天"};
    QString drawText;
    QColor textColor{Qt::red};
    int offset{0};
    uint changeOffset{6};//调节变化速度
    RunningTextWidget * p_ptr;
    QSize verticalTextSize;
    Direction direction{Direction::South};
    RunningTextWidget * q_ptr;
    QTimer timer;

    void updateText();
    void updateVerticalTextBoundingSize();
    void move();
};

void RunningTextWidgetPrivate::updateText()
{
    if(direction == Direction::West || direction == Direction::East)
    {
        if(direction == Direction::East)
        {
            drawText.clear();;
            for (auto it = text.rbegin(); it != text.rend(); ++it)
            {
                drawText.append(*it);
            }
        }
        else
        {
            drawText = text;
        }
    }
    else
    {
        if(direction == Direction::South)
        {
            auto temp = text.split("", Qt::SkipEmptyParts).join("\n");
            drawText.clear();
            for (auto it = temp.rbegin(); it != temp.rend(); ++it)
            {
                drawText.append(*it);
            }
        }
        else
        {
            drawText = text.split("", Qt::SkipEmptyParts).join("\n");
        }

        updateVerticalTextBoundingSize();
    }
}

void RunningTextWidgetPrivate::updateVerticalTextBoundingSize()
{
    auto lines = drawText.split("\n");

    int maxWidth = 0;
    int totalHeight = 0;

    auto fontMetrics = q_ptr->fontMetrics();
    for (const auto &line : lines)
    {
        int width = fontMetrics.horizontalAdvance(line);
        if (width > maxWidth)
        {
            maxWidth = width;
        }
        totalHeight += fontMetrics.height();
        totalHeight += fontMetrics.leading();
    }
    totalHeight -= fontMetrics.descent();

    verticalTextSize = QSize(maxWidth, totalHeight);
}

void RunningTextWidgetPrivate::move()
{
    if(direction == Direction::West)
    {
        offset -= changeOffset;
        if(offset < 0 && abs(offset) >= q_ptr->fontMetrics().horizontalAdvance(drawText))
        {
            offset = q_ptr->width();
        }
    }
    else if(direction == Direction::East)
    {
        offset += changeOffset;
        if(offset > q_ptr->width())
        {
            offset = -q_ptr->fontMetrics().horizontalAdvance(drawText);
        }
    }
    else if(direction == Direction::North)
    {
        offset -= changeOffset;
        if(offset < 0 && abs(offset) >= verticalTextSize.height())
        {
            offset = q_ptr->height();
        }
    }
    else if(direction == Direction::South)
    {
        offset += changeOffset;
        if(offset > q_ptr->height())
        {
            offset = -verticalTextSize.height();
        }
    }
}

RunningTextWidget::RunningTextWidget(QWidget *parent)
    : QWidget{parent}
{
    d_ptr = std::make_shared<RunningTextWidgetPrivate>();
    d_ptr->q_ptr = this;
    connect(&d_ptr->timer,&QTimer::timeout,this,&RunningTextWidget::onTime);
    d_ptr->timer.start(40);

    auto font = this->font();
    font.setPixelSize(36);
    font.setBold(true);
    setFont(font);

    d_ptr->updateText();
}

void RunningTextWidget::setText(const QString &newText)
{
    d_ptr->text = newText;
    d_ptr->offset = 0;
    d_ptr->updateText();
    update();
}

void RunningTextWidget::setDirection(Direction newDirection)
{
    d_ptr->direction = newDirection;
    d_ptr->updateText();
}

void RunningTextWidget::setSpeed(uint newSpeed)
{
    d_ptr->changeOffset = newSpeed;
}

void RunningTextWidget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setFont(this->font());
    painter.setPen(d_ptr->textColor);
    auto bRect = painter.boundingRect(rect(),Qt::AlignCenter,d_ptr->drawText);

    if(d_ptr->direction == Direction::West || d_ptr->direction == Direction::East)
    {
        painter.drawText(QRect(d_ptr->offset,bRect.y(),bRect.width(),bRect.height()),d_ptr->drawText);
    }
    else
    {
        painter.drawText(QRect(bRect.x(),d_ptr->offset,bRect.width(),bRect.height()),Qt::AlignCenter,d_ptr->drawText);
    }
}

void RunningTextWidget::onTime()
{
    d_ptr->move();
    update();
}

#include "runningtextwidget.h"
#include <QApplication>
#include <QHBoxLayout>
#include <QRandomGenerator>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget widget;
    auto hb = new QHBoxLayout(&widget);
    for(int i = 0;i < 4;++i)
    {
        auto w = new RunningTextWidget;
        w->setDirection(static_cast<Direction>(i));
        w->setSpeed(QRandomGenerator::global()->bounded(8, 50));
        hb->addWidget(w);
    }
    widget.show();
    return a.exec();
}