/*  This file is part of the KDE libraries

    SPDX-FileCopyrightText: 2000, 2002 Carsten Pfeiffer <pfeiffer@kde.org>

    SPDX-FileCopyrightText: 2000 Malte Starostik <malte@kde.org>

    SPDX-License-Identifier: LGPL-2.0-or-later

*/

#include "textcreator.h"

#include <QFile>

#include <QFontDatabase>

#include <QImage>

#include <QPainter>

#include <QPalette>

#include <QStringDecoder>

#include <QTextDocument>

#include <KDesktopFile>

#include <KPluginFactory>

#include <KSyntaxHighlighting/Definition>

#include <KSyntaxHighlighting/SyntaxHighlighter>

#include <KSyntaxHighlighting/Theme>

// TODO Fix or remove kencodingprober code

// #include <kencodingprober.h>

K_PLUGIN_CLASS_WITH_JSON(TextCreator, "textthumbnail.json")

Unexecuted instantiation: textthumbnail_factory::tr(char const*, char const*, int)

Unexecuted instantiation: textthumbnail_factory::~textthumbnail_factory()

TextCreator::TextCreator(QObject *parent, const QVariantList &args)

    : KIO::ThumbnailCreator(parent, args)

    , m_data(nullptr)

    , m_dataSize(0)

{

}

TextCreator::~TextCreator()

{

    delete[] m_data;

}

static QStringDecoder codecFromContent(const char *data, int dataSize)

{

#if 0 // ### Use this when KEncodingProber does not return junk encoding for UTF-8 data)

    KEncodingProber prober;

    prober.feed(data, dataSize);

    return QStringDecoder(prober.encoding());

#else

    // try to detect UTF text, fall back to locale default (which is usually UTF-8)

    return QStringDecoder(QStringDecoder::encodingForData(QByteArrayView(data, dataSize)).value_or(QStringDecoder::System));

#endif

}

KIO::ThumbnailResult TextCreator::create(const KIO::ThumbnailRequest &request)

{

    const QString path = request.url().toLocalFile();

    // Desktop files, .directory files, and flatpakrefs aren't traditional

    // text files, so their icons should be shown instead

    if (KDesktopFile::isDesktopFile(path) || path.endsWith(QStringLiteral(".directory")) || path.endsWith(QStringLiteral(".flatpakref"))) {

        return KIO::ThumbnailResult::fail();

    }

    bool ok = false;

    // determine some sizes...

    // example: width: 60, height: 64

    const int width = request.targetSize().width();

    const int height = request.targetSize().height();

    const qreal dpr = request.devicePixelRatio();

    QImage img;

    QSize pixmapSize(width, height);

    if (height * 3 > width * 4)

        pixmapSize.setHeight(width * 4 / 3);

    else

        pixmapSize.setWidth(height * 3 / 4);

    if (pixmapSize != m_pixmap.size()) {

        m_pixmap = QPixmap(pixmapSize);

        m_pixmap.setDevicePixelRatio(dpr);

    }

    // one pixel for the rectangle, the rest. whitespace

    int xborder = 1 + pixmapSize.width() / 16 / dpr; // minimum x-border

    int yborder = 1 + pixmapSize.height() / 16 / dpr; // minimum y-border

    // this font is supposed to look good at small sizes

    QFont font = QFontDatabase::systemFont(QFontDatabase::SmallestReadableFont);

    font.setPixelSize(qMax(7.0, qMin(10.0, (pixmapSize.height() / dpr - 2 * yborder) / 16)));

    QFontMetrics fm(font);

    // calculate a better border so that the text is centered

    const QSizeF canvasSize(pixmapSize.width() / dpr - 2 * xborder, pixmapSize.height() / dpr - 2 * yborder);

    const int numLines = (int)(canvasSize.height() / fm.height());

    // assumes an average line length of <= 120 chars

    const int bytesToRead = 120 * numLines;

    // create text-preview

    QFile file(path);

    if (file.open(QIODevice::ReadOnly)) {

        if (!m_data || m_dataSize < bytesToRead + 1) {

            delete[] m_data;

            m_data = new char[bytesToRead + 1];

            m_dataSize = bytesToRead + 1;

        }

        int read = file.read(m_data, bytesToRead);

        if (read > 0) {

            ok = true;

            m_data[read] = '\0';

            QString text = QString(codecFromContent(m_data, read).decode(QByteArrayView(m_data, read))).trimmed();

            if (!text.isValidUtf16()) {

                // See if we are unlucky and the last byte we read was half of a utf16 character

                text.chop(1);

                if (!text.isValidUtf16()) {

                    return KIO::ThumbnailResult::fail();

                }

            }

            // FIXME: maybe strip whitespace and read more?

            // If the text contains tabs or consecutive spaces, it is probably

            // formatted using white space. Use a fixed pitch font in this case.

            const auto textLines = QStringView(text).split(QLatin1Char('\n'));

            for (const auto &line : textLines) {

                const auto trimmedLine = line.trimmed();

                if (trimmedLine.contains('\t') || trimmedLine.contains(QLatin1String("  "))) {

                    font.setFamily(QFontDatabase::systemFont(QFontDatabase::FixedFont).family());

                    break;

                }

            }

            QColor bgColor = QColor(245, 245, 245); // light-grey background

            m_pixmap.fill(bgColor);

            QPainter painter(&m_pixmap);

            QTextDocument textDocument(text);

            // QTextDocument only supports one margin value for all borders,

            // so we do a page-in-page behind its back, and do our own borders

            textDocument.setDocumentMargin(0);

            textDocument.setPageSize(canvasSize);

            textDocument.setDefaultFont(font);

            QTextOption textOption(Qt::AlignTop | Qt::AlignLeft);

            textOption.setTabStopDistance(8 * painter.fontMetrics().horizontalAdvance(QLatin1Char(' ')));

            textOption.setWrapMode(QTextOption::WrapAtWordBoundaryOrAnywhere);

            textDocument.setDefaultTextOption(textOption);

            KSyntaxHighlighting::SyntaxHighlighter syntaxHighlighter;

            syntaxHighlighter.setDefinition(m_highlightingRepository.definitionForFileName(path));

            const auto highlightingTheme = m_highlightingRepository.defaultTheme(KSyntaxHighlighting::Repository::LightTheme);

            syntaxHighlighter.setTheme(highlightingTheme);

            syntaxHighlighter.setDocument(&textDocument);

            syntaxHighlighter.rehighlight();

            // draw page-in-page, with clipping as needed

            painter.translate(xborder, yborder);

            textDocument.drawContents(&painter, QRectF(QPointF(0, 0), canvasSize));

            painter.end();

            img = m_pixmap.toImage();

        }

        file.close();

    }

    return ok ? KIO::ThumbnailResult::pass(img) : KIO::ThumbnailResult::fail();

}

#include "moc_textcreator.cpp"

#include "textcreator.moc"