// Copyright (C) 2024 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include "codeeditor.h"
#include "linenumberarea.h"

#include <QPainter>
#include <QTextBlock>

CodeEditor::CodeEditor(QWidget *parent)
    : QPlainTextEdit{parent}
    , m_lineNumberArea{new LineNumberArea{this}}
{
    setupConnections();
    updateLineNumberAreaWidth();
    highlightCurrentLine();
}

void CodeEditor::lineNumberAreaPaintEvent(QPaintEvent *event)
{
    const QRect eventRect = event->rect();

    QPainter painter{m_lineNumberArea};
    painter.fillRect(eventRect, palette().color(QPalette::AlternateBase));

    QTextBlock block = firstVisibleBlock();
    int blockNumber = block.blockNumber();
    qreal top = blockBoundingGeometry(block).translated(contentOffset()).top();
    qreal bottom = top + blockBoundingRect(block).height();

    while (block.isVisible() && (top <= eventRect.bottom()) && (blockNumber < blockCount())) {
        if (block.isVisible() && (bottom >= eventRect.top())) {
            const QString number = QString::number(blockNumber + 1);
            painter.setPen(palette().color(QPalette::Text));
            painter.drawText(0, qRound(top), m_lineNumberArea->width() - 5, fontMetrics().height(),
                             Qt::AlignRight, number);
        }

        block = block.next();
        top = bottom;
        bottom = top + blockBoundingRect(block).height();
        ++blockNumber;
    }
}

int CodeEditor::lineNumberAreaWidth() const
{
    int digits = 1;
    int max = qMax(1, blockCount());
    while (max >= 10) {
        max /= 10;
        ++digits;
    }

    const int space = 9 + fontMetrics().horizontalAdvance('9') * digits;
    return space;
}

void CodeEditor::setupConnections()
{
    connect(this, &CodeEditor::blockCountChanged, this, &CodeEditor::updateLineNumberAreaWidth);
    connect(this, &CodeEditor::updateRequest, this, &CodeEditor::updateLineNumberArea);
    connect(this, &CodeEditor::cursorPositionChanged, this, &CodeEditor::highlightCurrentLine);
}

void CodeEditor::resizeEvent(QResizeEvent *event)
{
    QPlainTextEdit::resizeEvent(event);

    const QRect rect = contentsRect();
    m_lineNumberArea->setGeometry(rect.left(), rect.top(), lineNumberAreaWidth(), rect.height());
}

void CodeEditor::updateLineNumberArea(const QRect &rect, int dy)
{
    if (dy)
        m_lineNumberArea->scroll(0, dy);
    else
        m_lineNumberArea->update(0, rect.y(), m_lineNumberArea->width(), rect.height());

    if (rect.contains(viewport()->rect()))
        updateLineNumberAreaWidth();
}

void CodeEditor::updateLineNumberAreaWidth()
{
    setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);
}

void CodeEditor::highlightCurrentLine()
{
    QList<QTextEdit::ExtraSelection> extraSelections;

    if (!isReadOnly()) {
        QTextEdit::ExtraSelection selection;
        selection.format.setBackground(palette().color(QPalette::AlternateBase));
        selection.format.setProperty(QTextFormat::FullWidthSelection, true);
        selection.cursor = textCursor();
        selection.cursor.clearSelection();

        extraSelections.append(selection);
    }

    setExtraSelections(extraSelections);
}