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** Copyright (C) 2016 Petar Perisin <petar.perisin@gmail.com>
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#include "AnsiEscapeCodeHandler.h"

namespace Utils {

/*!
    \class Utils::AnsiEscapeCodeHandler

    \brief The AnsiEscapeCodeHandler class parses text and extracts ANSI escape codes from it.

    In order to preserve color information across text segments, an instance of this class
    must be stored for the lifetime of a stream.
    Also, one instance of this class should not handle multiple streams (at least not
    at the same time).

    Its main function is parseText(), which accepts text and default QTextCharFormat.
    This function is designed to parse text and split colored text to smaller strings,
    with their appropriate formatting information set inside QTextCharFormat.

    Usage:
    \list
    \li Create new instance of AnsiEscapeCodeHandler for a stream.
    \li To add new text, call parseText() with the text and a default QTextCharFormat.
        The result of this function is a list of strings with formats set in appropriate
        QTextCharFormat.
    \endlist
*/

AnsiEscapeCodeHandler::AnsiEscapeCodeHandler() :
    m_previousFormatClosed(true)
{
}

static QColor ansiColor(uint code)
{
    const int red   = code & 1 ? 170 : 0;
    const int green = code & 2 ? 170 : 0;
    const int blue  = code & 4 ? 170 : 0;
    return QColor(red, green, blue);
}

QList<FormattedText> AnsiEscapeCodeHandler::parseText(const FormattedText &input)
{
    enum AnsiEscapeCodes {
        ResetFormat            =  0,
        BoldText               =  1,
        TextColorStart         = 30,
        TextColorEnd           = 37,
        RgbTextColor           = 38,
        DefaultTextColor       = 39,
        BackgroundColorStart   = 40,
        BackgroundColorEnd     = 47,
        RgbBackgroundColor     = 48,
        DefaultBackgroundColor = 49
    };

    const QString escape = QLatin1String("\x1b[");
    const QChar semicolon       = QLatin1Char(';');
    const QChar colorTerminator = QLatin1Char('m');
    const QChar eraseToEol      = QLatin1Char('K');

    QList<FormattedText> outputData;
    QTextCharFormat charFormat = m_previousFormatClosed ? input.format : m_previousFormat;
    QString strippedText;
    if (m_pendingText.isEmpty()) {
        strippedText = input.text;
    } else {
        strippedText = m_pendingText.append(input.text);
        m_pendingText.clear();
    }

    while (!strippedText.isEmpty()) {
        const int escapePos = strippedText.indexOf(escape[0]);
        if (escapePos < 0) {
            outputData << FormattedText(strippedText, charFormat);
            break;
        } else if (escapePos != 0) {
            outputData << FormattedText(strippedText.left(escapePos), charFormat);
            strippedText.remove(0, escapePos);
        }

        while (!strippedText.isEmpty() && escape[0] == strippedText[0]) {
            if (escape.startsWith(strippedText)) {
                // control secquence is not complete
                m_pendingText += strippedText;
                strippedText.clear();
                break;
            }
            if (!strippedText.startsWith(escape)) {
                // not a control sequence
                m_pendingText.clear();
                outputData << FormattedText(strippedText.left(1), charFormat);
                strippedText.remove(0, 1);
                continue;
            }
            m_pendingText += strippedText.mid(0, escape.length());
            strippedText.remove(0, escape.length());

            // \e[K is not supported. Just strip it.
            if (strippedText.startsWith(eraseToEol)) {
                m_pendingText.clear();
                strippedText.remove(0, 1);
                continue;
            }
            // get the number
            QString strNumber;
            QStringList numbers;
            while (!strippedText.isEmpty()) {
                if (strippedText.at(0).isDigit()) {
                    strNumber += strippedText.at(0);
                } else {
                    if (!strNumber.isEmpty())
                        numbers << strNumber;
                    if (strNumber.isEmpty() || strippedText.at(0) != semicolon)
                        break;
                    strNumber.clear();
                }
                m_pendingText += strippedText.mid(0, 1);
                strippedText.remove(0, 1);
            }
            if (strippedText.isEmpty())
                break;

            // remove terminating char
            if (!strippedText.startsWith(colorTerminator)) {
                m_pendingText.clear();
                strippedText.remove(0, 1);
                break;
            }
            // got consistent control sequence, ok to clear pending text
            m_pendingText.clear();
            strippedText.remove(0, 1);

            if (numbers.isEmpty()) {
                charFormat = input.format;
                endFormatScope();
            }

            for (int i = 0; i < numbers.size(); ++i) {
                const int code = numbers.at(i).toInt();

                if (code >= TextColorStart && code <= TextColorEnd) {
                    charFormat.setForeground(ansiColor(code - TextColorStart));
                    setFormatScope(charFormat);
                } else if (code >= BackgroundColorStart && code <= BackgroundColorEnd) {
                    charFormat.setBackground(ansiColor(code - BackgroundColorStart));
                    setFormatScope(charFormat);
                } else {
                    switch (code) {
                    case ResetFormat:
                        charFormat = input.format;
                        endFormatScope();
                        break;
                    case BoldText:
                        charFormat.setFontWeight(QFont::Bold);
                        setFormatScope(charFormat);
                        break;
                    case DefaultTextColor:
                        charFormat.setForeground(input.format.foreground());
                        setFormatScope(charFormat);
                        break;
                    case DefaultBackgroundColor:
                        charFormat.setBackground(input.format.background());
                        setFormatScope(charFormat);
                        break;
                    case RgbTextColor:
                    case RgbBackgroundColor:
                        // See http://en.wikipedia.org/wiki/ANSI_escape_code#Colors
                        if (++i >= numbers.size())
                            break;
                        switch (numbers.at(i).toInt()) {
                        case 2:
                            // RGB set with format: 38;2;<r>;<g>;<b>
                            if ((i + 3) < numbers.size()) {
                                (code == RgbTextColor) ?
                                      charFormat.setForeground(QColor(numbers.at(i + 1).toInt(),
                                                                      numbers.at(i + 2).toInt(),
                                                                      numbers.at(i + 3).toInt())) :
                                      charFormat.setBackground(QColor(numbers.at(i + 1).toInt(),
                                                                      numbers.at(i + 2).toInt(),
                                                                      numbers.at(i + 3).toInt()));
                                setFormatScope(charFormat);
                            }
                            i += 3;
                            break;
                        case 5:
                            // 256 color mode with format: 38;5;<i>
                            uint index = numbers.at(i + 1).toInt();

                            QColor color;
                            if (index < 8) {
                                // The first 8 colors are standard low-intensity ANSI colors.
                                color = ansiColor(index);
                            } else if (index < 16) {
                                // The next 8 colors are standard high-intensity ANSI colors.
                                color = ansiColor(index - 8).lighter(150);
                            } else if (index < 232) {
                                // The next 216 colors are a 6x6x6 RGB cube.
                                uint o = index - 16;
                                color = QColor((o / 36) * 51, ((o / 6) % 6) * 51, (o % 6) * 51);
                            } else {
                                // The last 24 colors are a greyscale gradient.
                                uint grey = (index - 232) * 11;
                                color = QColor(grey, grey, grey);
                            }

                            if (code == RgbTextColor)
                                charFormat.setForeground(color);
                            else
                                charFormat.setBackground(color);

                            setFormatScope(charFormat);
                            ++i;
                            break;
                        }
                        break;
                    default:
                        break;
                    }
                }
            }
        }
    }
    return outputData;
}

void AnsiEscapeCodeHandler::endFormatScope()
{
    m_previousFormatClosed = true;
}

void AnsiEscapeCodeHandler::setFormatScope(const QTextCharFormat &charFormat)
{
    m_previousFormat = charFormat;
    m_previousFormatClosed = false;
}

} // namespace Utils
