/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtPDF module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL3$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
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** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPLv3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or later as published by the Free
** Software Foundation and appearing in the file LICENSE.GPL included in
** the packaging of this file. Please review the following information to
** ensure the GNU General Public License version 2.0 requirements will be
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** $QT_END_LICENSE$
**
****************************************************************************/

#include "qpdfdocument.h"
#include "qpdfdocument_p.h"

#include "third_party/pdfium/public/fpdf_doc.h"
#include "third_party/pdfium/public/fpdf_text.h"

#include <QDateTime>
#include <QDebug>
#include <QElapsedTimer>
#include <QFile>
#include <QHash>
#include <QLoggingCategory>
#include <QMutex>
#include <QVector2D>

QT_BEGIN_NAMESPACE

Q_GLOBAL_STATIC(QRecursiveMutex, pdfMutex)
static int libraryRefCount;
static const double CharacterHitTolerance = 16.0;
Q_LOGGING_CATEGORY(qLcDoc, "qt.pdf.document")

QPdfMutexLocker::QPdfMutexLocker()
    : std::unique_lock<QRecursiveMutex>(*pdfMutex())
{
}

QPdfDocumentPrivate::QPdfDocumentPrivate()
    : avail(nullptr)
    , doc(nullptr)
    , loadComplete(false)
    , status(QPdfDocument::Null)
    , lastError(QPdfDocument::NoError)
    , pageCount(0)
{
    asyncBuffer.setData(QByteArray());
    asyncBuffer.open(QIODevice::ReadWrite);

    const QPdfMutexLocker lock;

    if (libraryRefCount == 0)
        FPDF_InitLibrary();
    ++libraryRefCount;

    // FPDF_FILEACCESS setup
    m_Param = this;
    m_GetBlock = fpdf_GetBlock;

    // FX_FILEAVAIL setup
    FX_FILEAVAIL::version = 1;
    IsDataAvail = fpdf_IsDataAvail;

    // FX_DOWNLOADHINTS setup
    FX_DOWNLOADHINTS::version = 1;
    AddSegment = fpdf_AddSegment;
}

QPdfDocumentPrivate::~QPdfDocumentPrivate()
{
    q->close();

    const QPdfMutexLocker lock;

    if (!--libraryRefCount)
        FPDF_DestroyLibrary();
}

void QPdfDocumentPrivate::clear()
{
    QPdfMutexLocker lock;

    if (doc)
        FPDF_CloseDocument(doc);
    doc = nullptr;

    if (avail)
        FPDFAvail_Destroy(avail);
    avail = nullptr;
    lock.unlock();

    if (pageCount != 0) {
        pageCount = 0;
        emit q->pageCountChanged(pageCount);
    }

    loadComplete = false;

    asyncBuffer.close();
    asyncBuffer.setData(QByteArray());
    asyncBuffer.open(QIODevice::ReadWrite);

    if (sequentialSourceDevice)
        sequentialSourceDevice->disconnect(q);
}

void QPdfDocumentPrivate::updateLastError()
{
    if (doc) {
        lastError = QPdfDocument::NoError;
        return;
    }

    QPdfMutexLocker lock;
    const unsigned long error = FPDF_GetLastError();
    lock.unlock();

    switch (error) {
    case FPDF_ERR_SUCCESS: lastError = QPdfDocument::NoError; break;
    case FPDF_ERR_UNKNOWN: lastError = QPdfDocument::UnknownError; break;
    case FPDF_ERR_FILE: lastError = QPdfDocument::FileNotFoundError; break;
    case FPDF_ERR_FORMAT: lastError = QPdfDocument::InvalidFileFormatError; break;
    case FPDF_ERR_PASSWORD: lastError = QPdfDocument::IncorrectPasswordError; break;
    case FPDF_ERR_SECURITY: lastError = QPdfDocument::UnsupportedSecuritySchemeError; break;
    default:
        Q_UNREACHABLE();
    }
}

void QPdfDocumentPrivate::load(QIODevice *newDevice, bool transferDeviceOwnership)
{
    if (transferDeviceOwnership)
        ownDevice.reset(newDevice);
    else
        ownDevice.reset();

    if (newDevice->isSequential()) {
        sequentialSourceDevice = newDevice;
        device = &asyncBuffer;
        QNetworkReply *reply = qobject_cast<QNetworkReply*>(sequentialSourceDevice);

        if (!reply) {
            setStatus(QPdfDocument::Error);
            qWarning() << "QPdfDocument: Loading from sequential devices only supported with QNetworkAccessManager.";
            return;
        }

        if (reply->isFinished() && reply->error() != QNetworkReply::NoError) {
            setStatus(QPdfDocument::Error);
            return;
        }

        QObject::connect(reply, &QNetworkReply::finished, q, [this, reply](){
            if (reply->error() != QNetworkReply::NoError || reply->bytesAvailable() == 0) {
                this->setStatus(QPdfDocument::Error);
            }
        });

        if (reply->header(QNetworkRequest::ContentLengthHeader).isValid())
            _q_tryLoadingWithSizeFromContentHeader();
        else
            QObject::connect(reply, SIGNAL(metaDataChanged()), q, SLOT(_q_tryLoadingWithSizeFromContentHeader()));
    } else {
        device = newDevice;
        initiateAsyncLoadWithTotalSizeKnown(device->size());
        if (!avail) {
            setStatus(QPdfDocument::Error);
            return;
        }

        if (!doc)
            tryLoadDocument();

        if (!doc) {
            updateLastError();
            setStatus(QPdfDocument::Error);
            return;
        }

        QPdfMutexLocker lock;
        const int newPageCount = FPDF_GetPageCount(doc);
        lock.unlock();
        if (newPageCount != pageCount) {
            pageCount = newPageCount;
            emit q->pageCountChanged(pageCount);
        }

        // If it's a local file, and the first couple of pages are available,
        // probably the whole document is available.
        if (checkPageComplete(0) && (pageCount < 2 || checkPageComplete(1))) {
            setStatus(QPdfDocument::Ready);
        } else {
            updateLastError();
            setStatus(QPdfDocument::Error);
        }
    }
}

void QPdfDocumentPrivate::_q_tryLoadingWithSizeFromContentHeader()
{
    if (avail)
        return;

    const QNetworkReply *networkReply = qobject_cast<QNetworkReply*>(sequentialSourceDevice);
    if (!networkReply) {
        setStatus(QPdfDocument::Error);
        return;
    }

    const QVariant contentLength = networkReply->header(QNetworkRequest::ContentLengthHeader);
    if (!contentLength.isValid()) {
        setStatus(QPdfDocument::Error);
        return;
    }

    QObject::connect(sequentialSourceDevice, SIGNAL(readyRead()), q, SLOT(_q_copyFromSequentialSourceDevice()));

    initiateAsyncLoadWithTotalSizeKnown(contentLength.toULongLong());

    if (sequentialSourceDevice->bytesAvailable())
        _q_copyFromSequentialSourceDevice();
}

void QPdfDocumentPrivate::initiateAsyncLoadWithTotalSizeKnown(quint64 totalSize)
{
    // FPDF_FILEACCESS setup
    m_FileLen = totalSize;

    const QPdfMutexLocker lock;

    avail = FPDFAvail_Create(this, this);
}

void QPdfDocumentPrivate::_q_copyFromSequentialSourceDevice()
{
    if (loadComplete)
        return;

    const QByteArray data = sequentialSourceDevice->read(sequentialSourceDevice->bytesAvailable());
    if (data.isEmpty())
        return;

    asyncBuffer.seek(asyncBuffer.size());
    asyncBuffer.write(data);

    checkComplete();
}

void QPdfDocumentPrivate::tryLoadDocument()
{
    QPdfMutexLocker lock;
    switch (FPDFAvail_IsDocAvail(avail, this)) {
        case PDF_DATA_ERROR:
            qCDebug(qLcDoc) << "error loading";
            break;
        case PDF_DATA_NOTAVAIL:
            qCDebug(qLcDoc) << "data not yet available";
            lastError = QPdfDocument::DataNotYetAvailableError;
            setStatus(QPdfDocument::Error);
            break;
        case PDF_DATA_AVAIL:
            // all good
            break;
    }

    Q_ASSERT(!doc);

    doc = FPDFAvail_GetDocument(avail, password);
    lock.unlock();

    updateLastError();

    if (lastError == QPdfDocument::IncorrectPasswordError) {
        FPDF_CloseDocument(doc);
        doc = nullptr;

        setStatus(QPdfDocument::Error);
        emit q->passwordRequired();
    }
}

void QPdfDocumentPrivate::checkComplete()
{
    if (!avail || loadComplete)
        return;

    if (!doc)
        tryLoadDocument();

    if (!doc)
        return;

    loadComplete = true;

    QPdfMutexLocker lock;

    const int newPageCount = FPDF_GetPageCount(doc);
    for (int i = 0; i < newPageCount; ++i) {
        int result = PDF_DATA_NOTAVAIL;
        while (result == PDF_DATA_NOTAVAIL) {
            result = FPDFAvail_IsPageAvail(avail, i, this);
        }

        if (result == PDF_DATA_ERROR)
            loadComplete = false;
    }

    lock.unlock();

    if (loadComplete) {
        if (newPageCount != pageCount) {
            pageCount = newPageCount;
            emit q->pageCountChanged(pageCount);
        }

        setStatus(QPdfDocument::Ready);
    }
}

bool QPdfDocumentPrivate::checkPageComplete(int page)
{
    if (page < 0 || page >= pageCount)
        return false;

    if (loadComplete)
        return true;

    QPdfMutexLocker lock;
    int result = PDF_DATA_NOTAVAIL;
    while (result == PDF_DATA_NOTAVAIL)
        result = FPDFAvail_IsPageAvail(avail, page, this);
    lock.unlock();

    if (result == PDF_DATA_ERROR)
        updateLastError();

    return (result != PDF_DATA_ERROR);
}

void QPdfDocumentPrivate::setStatus(QPdfDocument::Status documentStatus)
{
    if (status == documentStatus)
        return;

    status = documentStatus;
    emit q->statusChanged(status);
}

FPDF_BOOL QPdfDocumentPrivate::fpdf_IsDataAvail(_FX_FILEAVAIL *pThis, size_t offset, size_t size)
{
    QPdfDocumentPrivate *d = static_cast<QPdfDocumentPrivate*>(pThis);
    return offset + size <= static_cast<quint64>(d->device->size());
}

int QPdfDocumentPrivate::fpdf_GetBlock(void *param, unsigned long position, unsigned char *pBuf, unsigned long size)
{
    QPdfDocumentPrivate *d = static_cast<QPdfDocumentPrivate*>(reinterpret_cast<FPDF_FILEACCESS*>(param));
    d->device->seek(position);
    return qMax(qint64(0), d->device->read(reinterpret_cast<char *>(pBuf), size));

}

void QPdfDocumentPrivate::fpdf_AddSegment(_FX_DOWNLOADHINTS *pThis, size_t offset, size_t size)
{
    Q_UNUSED(pThis);
    Q_UNUSED(offset);
    Q_UNUSED(size);
}

QString QPdfDocumentPrivate::getText(FPDF_TEXTPAGE textPage, int startIndex, int count)
{
    QList<ushort> buf(count + 1);
    // TODO is that enough space in case one unicode character is more than one in utf-16?
    int len = FPDFText_GetText(textPage, startIndex, count, buf.data());
    Q_ASSERT(len - 1 <= count); // len is number of characters written, including the terminator
    return QString::fromUtf16(reinterpret_cast<const char16_t *>(buf.constData()), len - 1);
}

QPointF QPdfDocumentPrivate::getCharPosition(FPDF_TEXTPAGE textPage, double pageHeight, int charIndex)
{
    double x, y;
    int count = FPDFText_CountChars(textPage);
    bool ok = FPDFText_GetCharOrigin(textPage, qMin(count - 1, charIndex), &x, &y);
    if (!ok)
        return QPointF();
    return QPointF(x, pageHeight - y);
}

QRectF QPdfDocumentPrivate::getCharBox(FPDF_TEXTPAGE textPage, double pageHeight, int charIndex)
{
    double l, t, r, b;
    bool ok = FPDFText_GetCharBox(textPage, charIndex, &l, &r, &b, &t);
    if (!ok)
        return QRectF();
    return QRectF(l, pageHeight - t, r - l, t - b);
}

QPdfDocumentPrivate::TextPosition QPdfDocumentPrivate::hitTest(int page, QPointF position)
{
    const QPdfMutexLocker lock;

    TextPosition result;
    FPDF_PAGE pdfPage = FPDF_LoadPage(doc, page);
    double pageHeight = FPDF_GetPageHeight(pdfPage);
    FPDF_TEXTPAGE textPage = FPDFText_LoadPage(pdfPage);
    int hitIndex = FPDFText_GetCharIndexAtPos(textPage, position.x(), pageHeight - position.y(),
                                              CharacterHitTolerance, CharacterHitTolerance);
    if (hitIndex >= 0) {
        QPointF charPos = getCharPosition(textPage, pageHeight, hitIndex);
        if (!charPos.isNull()) {
            QRectF charBox = getCharBox(textPage, pageHeight, hitIndex);
            // If the given position is past the end of the line, i.e. if the right edge of the found character's
            // bounding box is closer to it than the left edge is, we say that we "hit" the next character index after
            if (qAbs(charBox.right() - position.x()) < qAbs(charPos.x() - position.x())) {
                charPos.setX(charBox.right());
                ++hitIndex;
            }
            qCDebug(qLcDoc) << "on page" << page << "@" << position << "got char position" << charPos << "index" << hitIndex;
            result =  { charPos, charBox.height(), hitIndex };
        }
    }

    FPDFText_ClosePage(textPage);
    FPDF_ClosePage(pdfPage);

    return result;
}

/*!
    \class QPdfDocument
    \since 5.10
    \inmodule QtPdf

    \brief The QPdfDocument class loads a PDF document and renders pages from it.
*/

/*!
    Constructs a new document with parent object \a parent.
*/
QPdfDocument::QPdfDocument(QObject *parent)
    : QObject(parent)
    , d(new QPdfDocumentPrivate)
{
    d->q = this;
}

/*!
    Destroys the document.
*/
QPdfDocument::~QPdfDocument()
{
}

QPdfDocument::DocumentError QPdfDocument::load(const QString &fileName)
{
    qCDebug(qLcDoc) << "loading" << fileName;

    close();

    d->setStatus(QPdfDocument::Loading);

    QScopedPointer<QFile> f(new QFile(fileName));
    if (!f->open(QIODevice::ReadOnly)) {
        d->lastError = FileNotFoundError;
        d->setStatus(QPdfDocument::Error);
    } else {
        d->load(f.take(), /*transfer ownership*/true);
    }
    return d->lastError;
}

/*!
    \enum QPdfDocument::Status

    This enum describes the current status of the document.

    \value Null The initial status after the document has been created or after it has been closed.
    \value Loading The status after load() has been called and before the document is fully loaded.
    \value Ready The status when the document is fully loaded and its data can be accessed.
    \value Unloading The status after close() has been called on an open document.
                     At this point the document is still valid and all its data can be accessed.
    \value Error The status after Loading, if loading has failed.

    \sa QPdfDocument::status()
*/

/*!
    Returns the current status of the document.
*/
QPdfDocument::Status QPdfDocument::status() const
{
    return d->status;
}

void QPdfDocument::load(QIODevice *device)
{
    close();

    d->setStatus(QPdfDocument::Loading);

    d->load(device, /*transfer ownership*/false);
}

void QPdfDocument::setPassword(const QString &password)
{
    const QByteArray newPassword = password.toUtf8();

    if (d->password == newPassword)
        return;

    d->password = newPassword;
    emit passwordChanged();
}

QString QPdfDocument::password() const
{
    return QString::fromUtf8(d->password);
}

/*!
    \enum QPdfDocument::MetaDataField

    This enum describes the available fields of meta data.

    \value Title The document's title as QString.
    \value Author The name of the person who created the document as QString.
    \value Subject The subject of the document as QString.
    \value Keywords Keywords associated with the document as QString.
    \value Creator If the document was converted to PDF from another format,
                   the name of the conforming product that created the original document
                   from which it was converted as QString.
    \value Producer If the document was converted to PDF from another format,
                    the name of the conforming product that converted it to PDF as QString.
    \value CreationDate The date and time the document was created as QDateTime.
    \value ModificationDate The date and time the document was most recently modified as QDateTime.

    \sa QPdfDocument::metaData()
*/

/*!
    Returns the meta data of the document for the given \a field.
*/
QVariant QPdfDocument::metaData(MetaDataField field) const
{
    if (!d->doc)
        return QString();

    QByteArray fieldName;
    switch (field) {
    case Title:
        fieldName = "Title";
        break;
    case Subject:
        fieldName = "Subject";
        break;
    case Author:
        fieldName = "Author";
        break;
    case Keywords:
        fieldName = "Keywords";
        break;
    case Producer:
        fieldName = "Producer";
        break;
    case Creator:
        fieldName = "Creator";
        break;
    case CreationDate:
        fieldName = "CreationDate";
        break;
    case ModificationDate:
        fieldName = "ModDate";
        break;
    }

    QPdfMutexLocker lock;
    const unsigned long len = FPDF_GetMetaText(d->doc, fieldName.constData(), nullptr, 0);

    QList<ushort> buf(len);
    FPDF_GetMetaText(d->doc, fieldName.constData(), buf.data(), buf.length());
    lock.unlock();

    QString text = QString::fromUtf16(reinterpret_cast<const char16_t *>(buf.data()));

    switch (field) {
    case Title: // fall through
    case Subject:
    case Author:
    case Keywords:
    case Producer:
    case Creator:
        return text;
    case CreationDate: // fall through
    case ModificationDate:
        // convert a "D:YYYYMMDDHHmmSSOHH'mm'" into "YYYY-MM-DDTHH:mm:ss+HH:mm"
        if (text.startsWith(QLatin1String("D:")))
            text = text.mid(2);
        text.insert(4, QLatin1Char('-'));
        text.insert(7, QLatin1Char('-'));
        text.insert(10, QLatin1Char('T'));
        text.insert(13, QLatin1Char(':'));
        text.insert(16, QLatin1Char(':'));
        text.replace(QLatin1Char('\''), QLatin1Char(':'));
        if (text.endsWith(QLatin1Char(':')))
            text.chop(1);

        return QDateTime::fromString(text, Qt::ISODate);
    }

    return QVariant();
}

QPdfDocument::DocumentError QPdfDocument::error() const
{
    return d->lastError;
}

/*!
  Closes the document.
*/
void QPdfDocument::close()
{
    if (!d->doc)
        return;

    d->setStatus(Unloading);

    d->clear();

    if (!d->password.isEmpty()) {
        d->password.clear();
        emit passwordChanged();
    }

    d->setStatus(Null);
}

/*!
  Returns the amount of pages for the loaded document or \c 0 if
  no document is loaded.
*/
int QPdfDocument::pageCount() const
{
    return d->pageCount;
}

QSizeF QPdfDocument::pageSize(int page) const
{
    QSizeF result;
    if (!d->doc || !d->checkPageComplete(page))
        return result;

    const QPdfMutexLocker lock;

    FPDF_GetPageSizeByIndex(d->doc, page, &result.rwidth(), &result.rheight());
    return result;
}

/*!
    Renders the \a page into a QImage of size \a imageSize according to the
    provided \a renderOptions.

    Returns the rendered page or an empty image in case of an error.

    Note: If the \a imageSize does not match the aspect ratio of the page in the
    PDF document, the page is rendered scaled, so that it covers the
    complete \a imageSize.
*/
QImage QPdfDocument::render(int page, QSize imageSize, QPdfDocumentRenderOptions renderOptions)
{
    if (!d->doc || !d->checkPageComplete(page))
        return QImage();

    const QPdfMutexLocker lock;

    QElapsedTimer timer;
    if (Q_UNLIKELY(qLcDoc().isDebugEnabled()))
        timer.start();
    FPDF_PAGE pdfPage = FPDF_LoadPage(d->doc, page);
    if (!pdfPage)
        return QImage();

    QImage result(imageSize, QImage::Format_ARGB32);
    result.fill(Qt::transparent);
    FPDF_BITMAP bitmap = FPDFBitmap_CreateEx(result.width(), result.height(), FPDFBitmap_BGRA, result.bits(), result.bytesPerLine());

    int rotation = 0;
    switch (renderOptions.rotation()) {
    case QPdf::Rotate0:
        rotation = 0;
        break;
    case QPdf::Rotate90:
        rotation = 1;
        break;
    case QPdf::Rotate180:
        rotation = 2;
        break;
    case QPdf::Rotate270:
        rotation = 3;
        break;
    }

    const QPdf::RenderFlags renderFlags = renderOptions.renderFlags();
    int flags = 0;
    if (renderFlags & QPdf::RenderAnnotations)
        flags |= FPDF_ANNOT;
    if (renderFlags & QPdf::RenderOptimizedForLcd)
        flags |= FPDF_LCD_TEXT;
    if (renderFlags & QPdf::RenderGrayscale)
        flags |= FPDF_GRAYSCALE;
    if (renderFlags & QPdf::RenderForceHalftone)
        flags |= FPDF_RENDER_FORCEHALFTONE;
    if (renderFlags & QPdf::RenderTextAliased)
        flags |= FPDF_RENDER_NO_SMOOTHTEXT;
    if (renderFlags & QPdf::RenderImageAliased)
        flags |= FPDF_RENDER_NO_SMOOTHIMAGE;
    if (renderFlags & QPdf::RenderPathAliased)
        flags |= FPDF_RENDER_NO_SMOOTHPATH;

    if (renderOptions.scaledClipRect().isValid()) {
        const QRect &clipRect = renderOptions.scaledClipRect();

        // TODO take rotation into account, like cpdf_page.cpp lines 145-178
        float x0 = clipRect.left();
        float y0 = clipRect.top();
        float x1 = clipRect.left();
        float y1 = clipRect.bottom();
        float x2 = clipRect.right();
        float y2 = clipRect.top();
        QSizeF origSize = pageSize(page);
        QVector2D pageScale(1, 1);
        if (!renderOptions.scaledSize().isNull()) {
            pageScale = QVector2D(renderOptions.scaledSize().width() / float(origSize.width()),
                                  renderOptions.scaledSize().height() / float(origSize.height()));
        }
        FS_MATRIX matrix {(x2 - x0) / result.width() * pageScale.x(),
                          (y2 - y0) / result.width() * pageScale.x(),
                          (x1 - x0) / result.height() * pageScale.y(),
                          (y1 - y0) / result.height() * pageScale.y(), -x0, -y0};

        FS_RECTF clipRectF { 0, 0, float(imageSize.width()), float(imageSize.height()) };

        FPDF_RenderPageBitmapWithMatrix(bitmap, pdfPage, &matrix, &clipRectF, flags);
        qCDebug(qLcDoc) << "matrix" << matrix.a << matrix.b << matrix.c << matrix.d << matrix.e << matrix.f;
        qCDebug(qLcDoc) << "page" << page << "region" << renderOptions.scaledClipRect()
                        << "size" << imageSize << "took" << timer.elapsed() << "ms";
    } else {
        FPDF_RenderPageBitmap(bitmap, pdfPage, 0, 0, result.width(), result.height(), rotation, flags);
        qCDebug(qLcDoc) << "page" << page << "size" << imageSize << "took" << timer.elapsed() << "ms";
    }

    FPDFBitmap_Destroy(bitmap);

    FPDF_ClosePage(pdfPage);
    return result;
}

/*!
    Returns information about the text on the given \a page that can be found
    between the given \a start and \a end points, if any.
*/
QPdfSelection QPdfDocument::getSelection(int page, QPointF start, QPointF end)
{
    const QPdfMutexLocker lock;
    FPDF_PAGE pdfPage = FPDF_LoadPage(d->doc, page);
    double pageHeight = FPDF_GetPageHeight(pdfPage);
    FPDF_TEXTPAGE textPage = FPDFText_LoadPage(pdfPage);
    int startIndex = FPDFText_GetCharIndexAtPos(textPage, start.x(), pageHeight - start.y(),
                                                CharacterHitTolerance, CharacterHitTolerance);
    int endIndex = FPDFText_GetCharIndexAtPos(textPage, end.x(), pageHeight - end.y(),
                                              CharacterHitTolerance, CharacterHitTolerance);

    QPdfSelection result;

    if (startIndex >= 0 && endIndex != startIndex) {
        if (startIndex > endIndex)
            qSwap(startIndex, endIndex);

        // If the given end position is past the end of the line, i.e. if the right edge of the last character's
        // bounding box is closer to it than the left edge is, then extend the char range by one
        QRectF endCharBox = d->getCharBox(textPage, pageHeight, endIndex);
        if (qAbs(endCharBox.right() - end.x()) < qAbs(endCharBox.x() - end.x()))
            ++endIndex;

        int count = endIndex - startIndex;
        QString text = d->getText(textPage, startIndex, count);
        QList<QPolygonF> bounds;
        QRectF hull;
        int rectCount = FPDFText_CountRects(textPage, startIndex, endIndex - startIndex);
        for (int i = 0; i < rectCount; ++i) {
            double l, r, b, t;
            FPDFText_GetRect(textPage, i, &l, &t, &r, &b);
            QRectF rect(l, pageHeight - t, r - l, t - b);
            if (hull.isNull())
                hull = rect;
            else
                hull = hull.united(rect);
            bounds << QPolygonF(rect);
        }
        qCDebug(qLcDoc) << page << start << "->" << end << "found" << startIndex << "->" << endIndex << text;
        result = QPdfSelection(text, bounds, hull, startIndex, endIndex);
    } else {
        qCDebug(qLcDoc) << page << start << "->" << end << "nothing found";
    }

    FPDFText_ClosePage(textPage);
    FPDF_ClosePage(pdfPage);

    return result;
}

/*!
    Returns information about the text on the given \a page that can be found
    beginning at the given \a startIndex with at most \l maxLength characters.
*/
QPdfSelection QPdfDocument::getSelectionAtIndex(int page, int startIndex, int maxLength)
{

    if (page < 0 || startIndex < 0 || maxLength < 0)
        return {};
    const QPdfMutexLocker lock;
    FPDF_PAGE pdfPage = FPDF_LoadPage(d->doc, page);
    double pageHeight = FPDF_GetPageHeight(pdfPage);
    FPDF_TEXTPAGE textPage = FPDFText_LoadPage(pdfPage);
    int pageCount = FPDFText_CountChars(textPage);
    if (startIndex >= pageCount)
        return QPdfSelection();
    QList<QPolygonF> bounds;
    QRectF hull;
    int rectCount = 0;
    QString text;
    if (maxLength > 0) {
        text = d->getText(textPage, startIndex, maxLength);
        rectCount = FPDFText_CountRects(textPage, startIndex, text.length());
        for (int i = 0; i < rectCount; ++i) {
            double l, r, b, t;
            FPDFText_GetRect(textPage, i, &l, &t, &r, &b);
            QRectF rect(l, pageHeight - t, r - l, t - b);
            if (hull.isNull())
                hull = rect;
            else
                hull = hull.united(rect);
            bounds << QPolygonF(rect);
        }
    }
    if (bounds.isEmpty())
        hull = QRectF(d->getCharPosition(textPage, pageHeight, startIndex), QSizeF());
    qCDebug(qLcDoc) << "on page" << page << "at index" << startIndex << "maxLength" << maxLength
                    << "got" << text.length() << "chars," << rectCount << "rects within" << hull;

    FPDFText_ClosePage(textPage);
    FPDF_ClosePage(pdfPage);

    return QPdfSelection(text, bounds, hull, startIndex, startIndex + text.length());
}

/*!
    Returns all the text and its bounds on the given \a page.
*/
QPdfSelection QPdfDocument::getAllText(int page)
{
    const QPdfMutexLocker lock;
    FPDF_PAGE pdfPage = FPDF_LoadPage(d->doc, page);
    double pageHeight = FPDF_GetPageHeight(pdfPage);
    FPDF_TEXTPAGE textPage = FPDFText_LoadPage(pdfPage);
    int count = FPDFText_CountChars(textPage);
    if (count < 1)
        return QPdfSelection();
    QString text = d->getText(textPage, 0, count);
    QList<QPolygonF> bounds;
    QRectF hull;
    int rectCount = FPDFText_CountRects(textPage, 0, count);
    for (int i = 0; i < rectCount; ++i) {
        double l, r, b, t;
        FPDFText_GetRect(textPage, i, &l, &t, &r, &b);
        QRectF rect(l, pageHeight - t, r - l, t - b);
        if (hull.isNull())
            hull = rect;
        else
            hull = hull.united(rect);
        bounds << QPolygonF(rect);
    }
    qCDebug(qLcDoc) << "on page" << page << "got" << count << "chars," << rectCount << "rects within" << hull;

    FPDFText_ClosePage(textPage);
    FPDF_ClosePage(pdfPage);

    return QPdfSelection(text, bounds, hull, 0, count);
}

QT_END_NAMESPACE

#include "moc_qpdfdocument.cpp"