// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qpdfdocument_p.h"
#include "qpdflink.h"
#include "qpdfsearchmodel.h"
#include "qpdfsearchmodel_p.h"

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

#include <QtCore/qelapsedtimer.h>
#include <QtCore/qloggingcategory.h>
#include <QtCore/QMetaEnum>

QT_BEGIN_NAMESPACE

Q_LOGGING_CATEGORY(qLcS, "qt.pdf.search")

static const int UpdateTimerInterval = 100;
static const int ContextChars = 64;

/*!
    \class QPdfSearchModel
    \since 5.15
    \inmodule QtPdf
    \inherits QAbstractListModel

    \brief The QPdfSearchModel class searches for a string in a PDF document
    and holds the results.

    This is used in the \l {Model/View Programming} paradigm to display
    a list of search results, to highlight them on the rendered PDF pages,
    and to iterate through them using the "search forward" / "search backward"
    buttons and shortcuts that would be found in a typical document-viewing UI:

    \image search-results.png
*/

/*!
    \enum QPdfSearchModel::Role

    \value Page The page number where the search result is found (int).
    \value IndexOnPage The index of the search result on the page (int).
    \value Location The position of the search result on the page (QPointF).
    \value ContextBefore The adjacent text on the page, before the search string (QString).
    \value ContextAfter The adjacent text on the page, after the search string (QString).
    \omitvalue NRoles

    \sa QPdfLink
*/

/*!
    Constructs a new search model with parent object \a parent.
*/
QPdfSearchModel::QPdfSearchModel(QObject *parent)
    : QAbstractListModel(*(new QPdfSearchModelPrivate()), parent)
{
    QMetaEnum rolesMetaEnum = metaObject()->enumerator(metaObject()->indexOfEnumerator("Role"));
    for (int r = Qt::UserRole; r < int(Role::NRoles); ++r) {
        QByteArray roleName = QByteArray(rolesMetaEnum.valueToKey(r));
        if (roleName.isEmpty())
            continue;
        roleName[0] = QChar::toLower(roleName[0]);
        m_roleNames.insert(r, roleName);
    }
    connect(this, &QAbstractListModel::dataChanged, this, &QPdfSearchModel::countChanged);
    connect(this, &QAbstractListModel::modelReset, this, &QPdfSearchModel::countChanged);
    connect(this, &QAbstractListModel::rowsRemoved, this, &QPdfSearchModel::countChanged);
    connect(this, &QAbstractListModel::rowsInserted, this, &QPdfSearchModel::countChanged);
}

/*!
    Destroys the model.
*/
QPdfSearchModel::~QPdfSearchModel() {}

/*!
    \reimp
*/
QHash<int, QByteArray> QPdfSearchModel::roleNames() const
{
    return m_roleNames;
}

/*!
    \reimp

    The number of rows in the model is equal to the number of search results found.
*/
int QPdfSearchModel::rowCount(const QModelIndex &parent) const
{
    Q_D(const QPdfSearchModel);
    Q_UNUSED(parent);
    return d->rowCountSoFar;
}

/*!
    \reimp
*/
QVariant QPdfSearchModel::data(const QModelIndex &index, int role) const
{
    Q_D(const QPdfSearchModel);
    const auto pi = const_cast<QPdfSearchModelPrivate*>(d)->pageAndIndexForResult(index.row());
    if (pi.page < 0)
        return QVariant();
    switch (Role(role)) {
    case Role::Page:
        return pi.page;
    case Role::IndexOnPage:
        return pi.index;
    case Role::Location:
        return d->searchResults[pi.page][pi.index].location();
    case Role::ContextBefore:
        return d->searchResults[pi.page][pi.index].contextBefore();
    case Role::ContextAfter:
        return d->searchResults[pi.page][pi.index].contextAfter();
    case Role::NRoles:
        break;
    }
    if (role == Qt::DisplayRole) {
        const QString ret = d->searchResults[pi.page][pi.index].contextBefore() +
                QLatin1String("<b>") + d->searchString + QLatin1String("</b>") +
                d->searchResults[pi.page][pi.index].contextAfter();
        return ret;
    }
    return QVariant();
}

/*!
    \since 6.8
    \property QPdfSearchModel::count
    \brief the number of search results found
*/
int QPdfSearchModel::count() const
{
    return rowCount(QModelIndex());
}

void QPdfSearchModel::updatePage(int page)
{
    Q_D(QPdfSearchModel);
    d->doSearch(page);
}

/*!
    \property QPdfSearchModel::searchString
    \brief the string to search for
*/
QString QPdfSearchModel::searchString() const
{
    Q_D(const QPdfSearchModel);
    return d->searchString;
}

void QPdfSearchModel::setSearchString(const QString &searchString)
{
    Q_D(QPdfSearchModel);
    if (d->searchString == searchString)
        return;

    d->searchString = searchString;
    beginResetModel();
    d->clearResults();
    emit searchStringChanged();
    endResetModel();
}

/*!
    Returns the list of all results found on the given \a page.
*/
QList<QPdfLink> QPdfSearchModel::resultsOnPage(int page) const
{
    Q_D(const QPdfSearchModel);
    const_cast<QPdfSearchModelPrivate *>(d)->doSearch(page);
    if (d->searchResults.size() <= page)
        return {};
    return d->searchResults[page];
}

/*!
    Returns a result found by \a index in the \l document, regardless of the
    page on which it was found.  \a index must be less than \l rowCount.
*/
QPdfLink QPdfSearchModel::resultAtIndex(int index) const
{
    Q_D(const QPdfSearchModel);
    const auto pi = const_cast<QPdfSearchModelPrivate*>(d)->pageAndIndexForResult(index);
    if (pi.page < 0 || index < 0)
        return {};
    return d->searchResults[pi.page][pi.index];
}

/*!
    \property QPdfSearchModel::document
    \brief the document to search
*/
QPdfDocument *QPdfSearchModel::document() const
{
    Q_D(const QPdfSearchModel);
    return d->document;
}

void QPdfSearchModel::setDocument(QPdfDocument *document)
{
    Q_D(QPdfSearchModel);
    if (d->document == document)
        return;

    disconnect(d->documentConnection);
    d->documentConnection = connect(document, &QPdfDocument::pageCountChanged, this,
                                    [this]() { d_func()->clearResults(); });

    d->document = document;
    d->clearResults();
    emit documentChanged();
}

void QPdfSearchModel::timerEvent(QTimerEvent *event)
{
    Q_D(QPdfSearchModel);
    if (event->timerId() != d->updateTimerId)
        return;
    if (!d->document || d->nextPageToUpdate >= d->document->pageCount()) {
        if (d->document)
            qCDebug(qLcS) << "done updating search results on" << d->searchResults.size() << "pages";
        killTimer(d->updateTimerId);
        d->updateTimerId = -1;
    }
    d->doSearch(d->nextPageToUpdate++);
}

QPdfSearchModelPrivate::QPdfSearchModelPrivate() : QAbstractItemModelPrivate()
{
}

void QPdfSearchModelPrivate::clearResults()
{
    Q_Q(QPdfSearchModel);
    rowCountSoFar = 0;
    searchResults.clear();
    pagesSearched.clear();
    if (document) {
        searchResults.resize(document->pageCount());
        pagesSearched.resize(document->pageCount());
    }
    nextPageToUpdate = 0;
    updateTimerId = q->startTimer(UpdateTimerInterval);
}

bool QPdfSearchModelPrivate::doSearch(int page)
{
    if (page < 0 || page >= pagesSearched.size() || searchString.isEmpty())
        return false;
    if (pagesSearched[page])
        return true;
    Q_Q(QPdfSearchModel);

    const QPdfMutexLocker lock;
    QElapsedTimer timer;
    timer.start();
    FPDF_PAGE pdfPage = FPDF_LoadPage(document->d->doc, page);
    if (!pdfPage) {
        qWarning() << "failed to load page" << page;
        return false;
    }
    FPDF_TEXTPAGE textPage = FPDFText_LoadPage(pdfPage);
    if (!textPage) {
        qWarning() << "failed to load text of page" << page;
        FPDF_ClosePage(pdfPage);
        return false;
    }
    FPDF_SCHHANDLE sh = FPDFText_FindStart(textPage, searchString.utf16(), 0, 0);
    QList<QPdfLink> newSearchResults;
    constexpr double CharacterHitTolerance = 6.0;
    while (FPDFText_FindNext(sh)) {
        int idx = FPDFText_GetSchResultIndex(sh);
        int count = FPDFText_GetSchCount(sh);
        int rectCount = FPDFText_CountRects(textPage, idx, count);
        QList<QRectF> rects;
        int startIndex = -1;
        int endIndex = -1;
        for (int r = 0; r < rectCount; ++r) {
            // get bounding box of search result in page coordinates
            double left, top, right, bottom;
            FPDFText_GetRect(textPage, r, &left, &top, &right, &bottom);
            // deal with any internal PDF transforms and
            // convert to the 1x (pixels = points) 4th-quadrant coordinate system
            rects << document->d->mapPageToView(pdfPage, left, top, right, bottom);
            if (r == 0) {
                startIndex = FPDFText_GetCharIndexAtPos(textPage, left, top,
                        CharacterHitTolerance, CharacterHitTolerance);
            }
            if (r == rectCount - 1) {
                endIndex = FPDFText_GetCharIndexAtPos(textPage, right, top,
                        CharacterHitTolerance, CharacterHitTolerance);
            }
            qCDebug(qLcS) << rects.last() << "char idx" << startIndex << "->" << endIndex
                          << "from page rect" << left << top << right << bottom;
        }
        QString contextBefore, contextAfter;
        if (startIndex >= 0 || endIndex >= 0) {
            startIndex = qMax(0, startIndex - ContextChars);
            endIndex += ContextChars;
            int count = endIndex - startIndex + 1;
            if (count > 0) {
                QList<ushort> buf(count + 1);
                int len = FPDFText_GetText(textPage, startIndex, count, buf.data());
                Q_ASSERT(len - 1 <= count); // len is number of characters written, including the terminator
                QString context = QString::fromUtf16(
                        reinterpret_cast<const char16_t *>(buf.constData()), len - 1);
                context = context.replace(QLatin1Char('\n'), QStringLiteral("\u23CE"));
                context = context.remove(QLatin1Char('\r'));
                // try to find the search string near the middle of the context if possible
                int si = context.indexOf(searchString, ContextChars - 5, Qt::CaseInsensitive);
                if (si < 0)
                    si = context.indexOf(searchString, Qt::CaseInsensitive);
                if (si < 0)
                    qWarning() << "search string" << searchString << "not found in context" << context;
                contextBefore = context.mid(0, si);
                contextAfter = context.mid(si + searchString.size());
            }
        }
        if (!rects.isEmpty())
            newSearchResults << QPdfLink(page, rects, contextBefore, contextAfter);
    }
    FPDFText_FindClose(sh);
    FPDFText_ClosePage(textPage);
    FPDF_ClosePage(pdfPage);
    qCDebug(qLcS) << searchString << "took" << timer.elapsed() << "ms to find"
                  << newSearchResults.size() << "results on page" << page;

    pagesSearched[page] = true;
    searchResults[page] = newSearchResults;
    if (newSearchResults.size() > 0) {
        int rowsBefore = rowsBeforePage(page);
        qCDebug(qLcS) << "from row" << rowsBefore << "rowCount" << rowCountSoFar << "increasing by" << newSearchResults.size();
        rowCountSoFar += newSearchResults.size();
        q->beginInsertRows(QModelIndex(), rowsBefore, rowsBefore + newSearchResults.size() - 1);
        q->endInsertRows();
    }
    return true;
}

QPdfSearchModelPrivate::PageAndIndex QPdfSearchModelPrivate::pageAndIndexForResult(int resultIndex)
{
    if (pagesSearched.isEmpty())
        return {-1, -1};
    const int pageCount = document->pageCount();
    int totalSoFar = 0;
    int previousTotalSoFar = 0;
    for (int page = 0; page < pageCount; ++page) {
        if (!pagesSearched[page])
            doSearch(page);
        totalSoFar += searchResults[page].size();
        if (totalSoFar > resultIndex)
            return {page, resultIndex - previousTotalSoFar};
        previousTotalSoFar = totalSoFar;
    }
    return {-1, -1};
}

int QPdfSearchModelPrivate::rowsBeforePage(int page)
{
    int ret = 0;
    for (int i = 0; i < page; ++i)
        ret += searchResults[i].size();
    return ret;
}

QT_END_NAMESPACE

#include "moc_qpdfsearchmodel.cpp"