#ifndef LINENUMBERAREA_H
#define LINENUMBERAREA_H

#include <QDebug>
#include <QPainter>
#include <QScrollBar>
#include <QWidget>

#include "qmarkdowntextedit.h"

class LineNumArea final : public QWidget {
    Q_OBJECT

   public:
    explicit LineNumArea(QMarkdownTextEdit *parent)
        : QWidget(parent), textEdit(parent) {
        Q_ASSERT(parent);

        _currentLineColor = QColor(QStringLiteral("#eef067"));
        _otherLinesColor = QColor(QStringLiteral("#a6a6a6"));
        setHidden(true);

        // We always use fixed font to avoid "width" issues
        setFont(QFontDatabase::systemFont(QFontDatabase::FixedFont));
    }

    void setCurrentLineColor(QColor color) { _currentLineColor = color; }

    void setOtherLineColor(QColor color) {
        _otherLinesColor = std::move(color);
    }

    int lineNumAreaWidth() const {
        if (!enabled) {
            return 0;
        }

        int digits = 2;
        int max = std::max(1, textEdit->blockCount());
        while (max >= 10) {
            max /= 10;
            ++digits;
        }

#if QT_VERSION >= 0x050B00
        int space =
            13 + textEdit->fontMetrics().horizontalAdvance(u'9') * digits;
#else
        int space =
            13 + textEdit->fontMetrics().width(QLatin1Char('9')) * digits;
#endif

        return space;
    }

    bool isLineNumAreaEnabled() const { return enabled; }

    void setLineNumAreaEnabled(bool e) {
        enabled = e;
        setHidden(!e);
    }

    QSize sizeHint() const override { return {lineNumAreaWidth(), 0}; }

   protected:
    void paintEvent(QPaintEvent *event) override {
        QPainter painter(this);

        painter.fillRect(event->rect(),
                         palette().color(QPalette::Active, QPalette::Window));

        auto block = textEdit->firstVisibleBlock();
        int blockNumber = block.blockNumber();
        qreal top = textEdit->blockBoundingGeometry(block)
                        .translated(textEdit->contentOffset())
                        .top();
        // Maybe the top is not 0?
        top += textEdit->viewportMargins().top();
        qreal bottom = top;

        const QPen currentLine = _currentLineColor;
        const QPen otherLines = _otherLinesColor;
        painter.setFont(font());

        while (block.isValid() && top <= event->rect().bottom()) {
            top = bottom;
            bottom = top + textEdit->blockBoundingRect(block).height();
            if (block.isVisible() && bottom >= event->rect().top()) {
                QString number = QString::number(blockNumber + 1);

                auto isCurrentLine =
                    textEdit->textCursor().blockNumber() == blockNumber;
                painter.setPen(isCurrentLine ? currentLine : otherLines);

                painter.drawText(-5, top, sizeHint().width(),
                                 textEdit->fontMetrics().height(),
                                 Qt::AlignRight, number);
            }

            block = block.next();
            ++blockNumber;
        }
    }

   private:
    bool enabled = false;
    QMarkdownTextEdit *textEdit;
    QColor _currentLineColor;
    QColor _otherLinesColor;
};

#endif    // LINENUMBERAREA_H