/*
    SPDX-FileCopyrightText: 2014 Eike Hein <hein@kde.org>

    SPDX-License-Identifier: GPL-2.0-or-later
*/

#include "positioner.h"
#include "foldermodel.h"

#include <cstdlib>
#include <ranges>

#include <QJsonArray>
#include <QJsonDocument>
#include <QJsonObject>
#include <QTimer>

using namespace Qt::StringLiterals;

namespace PositionsConstants
{
// Stripes and items per stripe
constexpr qsizetype headerSize = 2;

// filename, stripe, pos
constexpr qsizetype bucketSize = 3;

// Offsets in bucket
constexpr qsizetype filenameOffset = 0;
constexpr qsizetype stripeOffset = 1;
constexpr qsizetype posOffset = 2;
}

Positioner::Positioner(QObject *parent)
    : QAbstractItemModel(parent)
    , m_enabled(false)
    , m_folderModel(nullptr)
    , m_perStripe(0)
    , m_ignoreNextTransaction(false)
    , m_deferApplyPositions(false)
{
}

Positioner::~Positioner()
{
}

bool Positioner::enabled() const
{
    return m_enabled;
}

void Positioner::setEnabled(bool enabled)
{
    if (m_enabled != enabled) {
        m_enabled = enabled;

        beginResetModel();

        if (enabled && m_folderModel) {
            initMaps();
        }

        endResetModel();

        Q_EMIT enabledChanged();

        setPerStripe(m_perStripe);
    }
}

FolderModel *Positioner::folderModel() const
{
    return m_folderModel;
}

void Positioner::setFolderModel(QObject *folderModel)
{
    if (m_folderModel != folderModel) {
        beginResetModel();

        if (m_folderModel) {
            disconnectSignals(m_folderModel);
        }

        m_folderModel = qobject_cast<FolderModel *>(folderModel);

        if (m_folderModel) {
            connectSignals(m_folderModel);
            if (m_enabled) {
                initMaps();
            }
        }

        endResetModel();

        Q_EMIT folderModelChanged();

        setPerStripe(m_perStripe);
    }
}

int Positioner::perStripe() const
{
    return m_perStripe;
}

void Positioner::setPerStripe(int perStripe)
{
    // Make sure we have screen in use before perStripe update
    // to make sure we update correct positions
    if (perStripe > 0 && screenInUse()) {
        const bool perStripeUpdated = m_perStripe != perStripe;
        const bool resolutionUpdated = updateResolution();
        const int prevPerStripe = m_perStripe;
        if (perStripeUpdated) {
            m_perStripe = perStripe;
            Q_EMIT perStripeChanged();
        }
        const bool unsortedModeOnDrop = m_folderModel->unsortedModeOnDrop();
        if (m_enabled && (perStripeUpdated || resolutionUpdated) && !unsortedModeOnDrop) {
            const bool existingResolution = configurationHasResolution(m_resolution);
            if (existingResolution) {
                loadAndApplyPositionsConfig();
            } else if (m_applet && m_positions.isEmpty()) {
                // We don't have any positions yet, restore them from last used resolution
                const QString lastResolution = m_applet->config().group(QStringLiteral("General")).readEntry(QStringLiteral("lastResolution"));
                if (configurationHasResolution(lastResolution)) {
                    loadAndApplyPositionsConfig(lastResolution);
                }
            }
            // If no longer deferring positions, update them
            if (!m_deferApplyPositions) {
                // If it's a new resolution, preserve icon positions by using previous "perStripe" (if available)
                const bool prevPositionsEmpty = m_positions.empty();
                updatePositionsList(existingResolution ? 0 : prevPerStripe);
                const bool currPositionsEmpty = m_positions.empty();
                if (!currPositionsEmpty) {
                    maybeRestoreAndApplyChangedPositions(!existingResolution);
                } else if (!prevPositionsEmpty) {
                    m_deferRestoreChangedPositions = true;
                }
            } else {
                m_deferRestoreChangedPositions = true;
            }
        } else if (m_enabled && unsortedModeOnDrop) {
            // If we performed drag and drop operation on sorted mode - remove config for all resolutions
            // "savePositionsConfig()" will be called soon, so don't save here
            m_changedPositions.clear();
            m_applet->config().group(u"General"_s).deleteEntry(u"positions"_s);
        }
        if (resolutionUpdated && m_resolution.isEmpty()) {
            // When the resolution disappears, we load icons from the last used resolution and wait for it to be delivered
            // This happens when changing the primary screen when the screens have different resolutions
            connect(
                m_folderModel,
                &FolderModel::screenGeometryChanged,
                this,
                [this] {
                    setPerStripe(m_perStripe);
                },
                Qt::SingleShotConnection);
        }
    }
}

QStringList Positioner::positions() const
{
    QStringList positions;

    if (m_positionsHeader.has_value()) {
        positions.reserve(PositionsConstants::headerSize + m_positions.size() * PositionsConstants::bucketSize);
        positions.append(QString::number(m_positionsHeader->numStripes));
        positions.append(QString::number(m_positionsHeader->perStripe));
        for (auto &&[filename, gridPos] : std::as_const(m_positions).asKeyValueRange()) {
            positions.append(filename);
            positions.append(QString::number(gridPos.stripe));
            positions.append(QString::number(gridPos.pos));
        }
    }

    return positions;
}

int Positioner::map(int row) const
{
    if (m_enabled && m_folderModel) {
        return m_proxyToSource.value(row, -1);
    }

    return row;
}

int Positioner::nearestItem(int currentIndex, Qt::ArrowType direction)
{
    if (!m_enabled || currentIndex >= rowCount()) {
        return -1;
    }

    if (currentIndex < 0) {
        return firstRow();
    }

    int hDirection = 0;
    int vDirection = 0;

    switch (direction) {
    case Qt::LeftArrow:
        hDirection = -1;
        break;
    case Qt::RightArrow:
        hDirection = 1;
        break;
    case Qt::UpArrow:
        vDirection = -1;
        break;
    case Qt::DownArrow:
        vDirection = 1;
        break;
    default:
        return -1;
    }

    QList<int> rows(m_proxyToSource.keys());
    std::sort(rows.begin(), rows.end());

    int nearestItem = -1;
    const QPoint currentPos(currentIndex % m_perStripe, currentIndex / m_perStripe);
    int lastDistance = -1;
    int distance = 0;

    for (const int row : std::as_const(rows)) {
        const QPoint pos(row % m_perStripe, row / m_perStripe);

        if (row == currentIndex) {
            continue;
        }

        if (hDirection == 0) {
            if (vDirection * pos.y() > vDirection * currentPos.y()) {
                distance = (pos - currentPos).manhattanLength();

                if (nearestItem == -1 || distance < lastDistance || (distance == lastDistance && pos.x() == currentPos.x())) {
                    nearestItem = row;
                    lastDistance = distance;
                }
            }
        } else if (vDirection == 0) {
            if (hDirection * pos.x() > hDirection * currentPos.x()) {
                distance = (pos - currentPos).manhattanLength();

                if (nearestItem == -1 || distance < lastDistance || (distance == lastDistance && pos.y() == currentPos.y())) {
                    nearestItem = row;
                    lastDistance = distance;
                }
            }
        }
    }

    return nearestItem;
}

bool Positioner::isBlank(int row) const
{
    if (!m_enabled && m_folderModel) {
        return m_folderModel->isBlank(row);
    }

    if (m_proxyToSource.contains(row) && m_folderModel && !m_folderModel->isBlank(m_proxyToSource.value(row))) {
        return false;
    }

    return true;
}

int Positioner::indexForUrl(const QUrl &url) const
{
    if (!m_folderModel) {
        return -1;
    }

    const QString &name = url.fileName();

    int sourceIndex = -1;

    // TODO Optimize.
    for (int i = 0; i < m_folderModel->rowCount(); ++i) {
        if (m_folderModel->data(m_folderModel->index(i, 0), FolderModel::FileNameRole).toString() == name) {
            sourceIndex = i;

            break;
        }
    }

    return m_sourceToProxy.value(sourceIndex, -1);
}

void Positioner::setRangeSelected(int anchor, int to)
{
    if (!m_folderModel) {
        return;
    }

    if (m_enabled) {
        QVariantList indices;

        for (int i = qMin(anchor, to); i <= qMax(anchor, to); ++i) {
            if (m_proxyToSource.contains(i)) {
                indices.append(m_proxyToSource.value(i));
            }
        }

        if (!indices.isEmpty()) {
            m_folderModel->updateSelection(indices, false);
        }
    } else {
        m_folderModel->setRangeSelected(anchor, to);
    }
}

QHash<int, QByteArray> Positioner::roleNames() const
{
    return FolderModel::staticRoleNames();
}

QModelIndex Positioner::index(int row, int column, const QModelIndex &parent) const
{
    if (parent.isValid()) {
        return QModelIndex();
    }

    return createIndex(row, column);
}

QModelIndex Positioner::parent(const QModelIndex &index) const
{
    if (m_folderModel) {
        m_folderModel->parent(index);
    }

    return QModelIndex();
}

QVariant Positioner::data(const QModelIndex &index, int role) const
{
    if (!index.isValid()) {
        return QVariant();
    }

    if (m_folderModel) {
        if (m_enabled) {
            if (m_proxyToSource.contains(index.row())) {
                return m_folderModel->data(m_folderModel->index(m_proxyToSource.value(index.row()), 0), role);
            } else if (role == FolderModel::BlankRole) {
                return true;
            }
        } else {
            return m_folderModel->data(m_folderModel->index(index.row(), 0), role);
        }
    }

    return QVariant();
}

int Positioner::rowCount(const QModelIndex &parent) const
{
    if (m_folderModel) {
        if (m_enabled) {
            if (parent.isValid()) {
                return 0;
            } else {
                return lastRow() + 1;
            }
        } else {
            return m_folderModel->rowCount(parent);
        }
    }

    return 0;
}

int Positioner::columnCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent)

    if (m_folderModel) {
        return 1;
    }

    return 0;
}

void Positioner::reset()
{
    beginResetModel();

    initMaps();

    endResetModel();

    m_positions.clear();
    updatePositionsList();
    savePositionsConfig();
}

int Positioner::move(const QVariantList &moves, bool save)
{
    struct RowMove {
        int from;
        int to;
        int sourceRow;
    };

    // Don't allow moves while listing.
    if (m_folderModel->status() == FolderModel::Listing) {
        m_deferMovePositions.append(moves);
        return -1;
    }

    QList<int> fromIndices;
    QList<int> toIndices;
    QVariantList sourceRows;
    QList<RowMove> actualMoves;

    for (int i = 0; i < moves.count(); ++i) {
        const int isFrom = (i % 2 == 0);
        int v = moves[i].toInt();

        if (isFrom) {
            if (m_proxyToSource.contains(v)) {
                sourceRows.append(m_proxyToSource.value(v));
            } else {
                sourceRows.append(-1);
            }
            fromIndices.append(v);
        } else {
            // if the to position is taken by something different than ourself, take a new to position
            while (toIndices.contains(v) && moves[i - 1].toInt() != v) {
                ++v;
            }
            toIndices.append(v);
        }
    }

    const int oldCount = rowCount();
    int newEnd = oldCount - 1;
    int maxTo = -1;
    QSet<int> toBeRemoved;

    // NOTE: this is the same code repeated twice: first it "tries" the move to see what the final count would look like to know if there would be rows
    // insertions or removals. then do it for real enclosed in beginRemoveRows/endRemoveRows or beginInsertRows/endRemoveRows
    for (int i = 0; i < fromIndices.count(); ++i) {
        const int from = fromIndices[i];
        int to = toIndices[i];
        const int sourceRow = sourceRows[i].toInt();

        if (sourceRow == -1 || from == to) {
            continue;
        }

        if (to == -1) {
            to = firstFreeRow();

            if (to == -1) {
                to = lastRow() + 1;
            }
        }

        if (!fromIndices.contains(to) && !isBlank(to)) {
            /* find the next blank space
             * we won't be happy if we're moving two icons to the same place
             */
            while ((!isBlank(to) && from != to) || toIndices.contains(to)) {
                to++;
            }
        }

        toIndices[i] = to;

        if (toBeRemoved.contains(to)) {
            toBeRemoved.remove(to);
        }

        if (from == newEnd) {
            for (int i = oldCount - 1; i >= 0 && (isBlank(i) || toBeRemoved.contains(i)); --i) {
                newEnd = i;
            }
            toBeRemoved.insert(newEnd);
        }
        maxTo = std::max(maxTo, to);
        newEnd = std::max(newEnd, maxTo);
        actualMoves.append({from, to, sourceRow});
    }

    if (newEnd < oldCount - 1) {
        beginRemoveRows(QModelIndex(), newEnd + 1, oldCount - 1);
    } else if (newEnd > oldCount - 1 && !m_beginInsertRowsCalled) {
        beginInsertRows(QModelIndex(), oldCount, newEnd);
    }

    for (const RowMove &move : std::as_const(actualMoves)) {
        if (!toIndices.contains(move.from)) {
            m_proxyToSource.remove(move.from);
        }

        updateMaps(move.to, move.sourceRow);

        const QModelIndex &fromIdx = index(move.from, 0);
        Q_EMIT dataChanged(fromIdx, fromIdx);

        if (move.to < oldCount) {
            const QModelIndex &toIdx = index(move.to, 0);
            Q_EMIT dataChanged(toIdx, toIdx);
        }

        // Start tracking moved file
        m_changedPositions[m_folderModel->data(m_folderModel->index(move.sourceRow, 0), FolderModel::UrlRole).toString()] = std::nullopt;
    }

    if (newEnd < oldCount - 1) {
        endRemoveRows();
    } else if (newEnd > oldCount - 1) {
        endInsertRows();
        m_beginInsertRowsCalled = false;
    }

    m_folderModel->updateSelection(sourceRows, true);

    updatePositionsList();
    if (save) {
        savePositionsConfig();
    }

    return toIndices.constFirst();
}

void Positioner::updatePositionsList(int perStripeForPositions)
{
    if (m_enabled && screenInUse() && m_perStripe > 0) {
        if (perStripeForPositions <= 0)
            perStripeForPositions = m_perStripe;

        m_positionsHeader.emplace(PositionsHeader{.numStripes = 1 + ((rowCount() - 1) / m_perStripe), .perStripe = m_perStripe});

        QHashIterator<int, int> it(m_proxyToSource);

        while (it.hasNext()) {
            it.next();

            const QString &name = m_folderModel->data(m_folderModel->index(it.value(), 0), FolderModel::UrlRole).toString();

            if (name.isEmpty()) {
                return;
            }

            m_positions[name] = {
                .stripe = qMax(0, it.key() / perStripeForPositions),
                .pos = qMax(0, it.key() % perStripeForPositions),
            };
        }
    }
}

void Positioner::sourceStatusChanged()
{
    if (m_deferApplyPositions && m_folderModel->status() != FolderModel::Listing) {
        convertFolderModelData();
        // If no longer deferring positions, update them
        if (!m_deferApplyPositions) {
            updatePositionsList();
            if (m_deferRestoreChangedPositions) {
                maybeRestoreAndApplyChangedPositions(false);
                m_skipSaveOnListingCompleted = (m_folderModel->status() == FolderModel::Ready);
            }
        }
    }

    // When deferring moves, skip saving if screen is not in use
    // If screen is in use, this is likely because user created new file
    // so we want to move that file to the spot of creation
    if (m_deferMovePositions.count() > 0 && m_folderModel->status() != FolderModel::Listing) {
        move(m_deferMovePositions, screenInUse());
        m_deferMovePositions.clear();
        // Load the configuration to make sure any of the moved items that are in the configuration
        // are in their correct place after deferred movements
        loadAndApplyPositionsConfig();
    }
}

void Positioner::sourceDataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QList<int> &roles)
{
    if (m_enabled) {
        int start = topLeft.row();
        int end = bottomRight.row();

        for (int i = start; i <= end; ++i) {
            if (m_sourceToProxy.contains(i)) {
                const QModelIndex &idx = index(m_sourceToProxy.value(i), 0);
                Q_EMIT dataChanged(idx, idx);
            }
        }
    } else {
        Q_EMIT dataChanged(topLeft, bottomRight, roles);
    }
}

void Positioner::sourceModelAboutToBeReset()
{
    beginResetModel();
}

void Positioner::sourceModelReset()
{
    if (m_enabled) {
        initMaps();
    }

    endResetModel();
}

void Positioner::sourceRowsAboutToBeInserted(const QModelIndex &parent, int start, int end)
{
    if (m_enabled) {
        // Don't insert yet if we're waiting for listing to complete to apply
        // initial positions;
        if (m_deferApplyPositions) {
            return;
        } else if (m_proxyToSource.isEmpty()) {
            beginInsertRows(parent, start, end);
            m_beginInsertRowsCalled = true;

            initMaps(end + 1);

            return;
        }

        // When new rows are inserted, they might go in the beginning or in the middle.
        // In this case we must update first the existing proxy->source and source->proxy
        // mapping, otherwise the proxy items will point to the wrong source item.
        int count = end - start + 1;
        m_sourceToProxy.clear();
        for (auto it = m_proxyToSource.begin(); it != m_proxyToSource.end(); ++it) {
            int sourceIdx = *it;
            if (sourceIdx >= start) {
                *it += count;
            }
            m_sourceToProxy[*it] = it.key();
        }

        int free = -1;
        int rest = -1;

        for (int i = start; i <= end; ++i) {
            free = firstFreeRow();

            if (free != -1) {
                updateMaps(free, i);
                m_pendingChanges << createIndex(free, 0);
            } else {
                rest = i;
                break;
            }
        }

        if (rest != -1) {
            int firstNew = lastRow() + 1;
            int remainder = (end - rest);

            beginInsertRows(parent, firstNew, firstNew + remainder);
            m_beginInsertRowsCalled = true;

            for (int i = 0; i <= remainder; ++i) {
                updateMaps(firstNew + i, rest + i);
            }
        } else {
            m_ignoreNextTransaction = true;
        }
    } else {
        beginInsertRows(parent, start, end);
        m_beginInsertRowsCalled = true;
    }
}

void Positioner::sourceRowsAboutToBeMoved(const QModelIndex &sourceParent,
                                          int sourceStart,
                                          int sourceEnd,
                                          const QModelIndex &destinationParent,
                                          int destinationRow)
{
    beginMoveRows(sourceParent, sourceStart, sourceEnd, destinationParent, destinationRow);
}

void Positioner::sourceRowsAboutToBeRemoved(const QModelIndex &parent, int first, int last)
{
    if (m_enabled) {
        int oldLast = lastRow();

        for (int i = first; i <= last; ++i) {
            int proxyRow = m_sourceToProxy.take(i);
            // Don't touch m_proxyToSource yet, as beginRemoveRows was not emitted yet
            m_pendingChanges << createIndex(proxyRow, 0);
        }

        QHash<int, int> newProxyToSource;
        QHash<int, int> newSourceToProxy;
        QHashIterator<int, int> it(m_sourceToProxy);
        int delta = std::abs(first - last) + 1;

        while (it.hasNext()) {
            it.next();

            if (it.key() > last) {
                newProxyToSource.insert(it.value(), it.key() - delta);
                newSourceToProxy.insert(it.key() - delta, it.value());
            } else {
                newProxyToSource.insert(it.value(), it.key());
                newSourceToProxy.insert(it.key(), it.value());
            }
        }

        int newLast = 0;
        // Duplicate lastRow instead of assigning m_proxyToSource now as rowCount() can't be changed before beginRemoveRows
        if (!newProxyToSource.isEmpty()) {
            QList<int> keys(newProxyToSource.keys());
            std::sort(keys.begin(), keys.end());
            newLast = keys.last();
        }

        if (oldLast > newLast) {
            int diff = oldLast - newLast;
            beginRemoveRows(QModelIndex(), ((oldLast - diff) + 1), oldLast);
        } else {
            m_ignoreNextTransaction = true;
        }

        m_proxyToSource = newProxyToSource;
        m_sourceToProxy = newSourceToProxy;
    } else {
        beginRemoveRows(parent, first, last);
    }
}

void Positioner::sourceLayoutAboutToBeChanged(const QList<QPersistentModelIndex> &parents, QAbstractItemModel::LayoutChangeHint hint)
{
    Q_UNUSED(parents)

    Q_EMIT layoutAboutToBeChanged(QList<QPersistentModelIndex>(), hint);
}

void Positioner::sourceRowsInserted(const QModelIndex &parent, int first, int last)
{
    Q_UNUSED(parent)
    Q_UNUSED(first)
    Q_UNUSED(last)

    if (!m_ignoreNextTransaction) {
        if (m_beginInsertRowsCalled) {
            endInsertRows();
            m_beginInsertRowsCalled = false;
        }
    } else {
        m_ignoreNextTransaction = false;
    }

    flushPendingChanges(true);

    // Don't generate new positions data if we're waiting for listing to
    // complete to apply initial positions.
    if (!m_deferApplyPositions && screenInUse()) {
        // Load current config
        loadAndApplyPositionsConfig();
        // Update positions to append the missing items
        updatePositionsList();
        if (m_deferRestoreChangedPositions) {
            maybeRestoreAndApplyChangedPositions(false);
        }
    }
}

void Positioner::sourceRowsMoved(const QModelIndex &sourceParent, int sourceStart, int sourceEnd, const QModelIndex &destinationParent, int destinationRow)
{
    Q_UNUSED(sourceParent)
    Q_UNUSED(sourceStart)
    Q_UNUSED(sourceEnd)
    Q_UNUSED(destinationParent)
    Q_UNUSED(destinationRow)

    endMoveRows();
}

void Positioner::sourceRowsRemoved(const QModelIndex &parent, int first, int last)
{
    Q_UNUSED(parent)
    Q_UNUSED(first)
    Q_UNUSED(last)

    if (!m_ignoreNextTransaction) {
        Q_EMIT endRemoveRows();
    } else {
        m_ignoreNextTransaction = false;
    }

    flushPendingChanges(false);

    if (screenInUse()) {
        // Load current config
        loadAndApplyPositionsConfig();
        // Update positions to remove the missing items
        // We do not wait for defer here since we want this to happen instantly
        // due to this being user action
        updatePositionsList();
    }
}

void Positioner::sourceLayoutChanged(const QList<QPersistentModelIndex> &parents, QAbstractItemModel::LayoutChangeHint hint)
{
    Q_UNUSED(parents)

    // Only reinitialize maps when in sorted mode. In unsorted mode, we want to preserve
    // manual icon positions even after layout changes (e.g., after drag and drop).
    if (m_enabled && m_folderModel->sortMode() != -1) {
        initMaps();
    }

    Q_EMIT layoutChanged(QList<QPersistentModelIndex>(), hint);
}

void Positioner::initMaps(int size)
{
    m_proxyToSource.clear();
    m_sourceToProxy.clear();

    if (size == -1) {
        size = m_folderModel->rowCount();
    }

    if (!size) {
        return;
    }

    for (int i = 0; i < size; ++i) {
        updateMaps(i, i);
    }
}

void Positioner::updateMaps(int proxyIndex, int sourceIndex)
{
    m_proxyToSource.insert(proxyIndex, sourceIndex);
    m_sourceToProxy.insert(sourceIndex, proxyIndex);
}

int Positioner::firstRow() const
{
    if (!m_proxyToSource.isEmpty()) {
        QList<int> keys(m_proxyToSource.keys());
        std::sort(keys.begin(), keys.end());

        return keys.first();
    }

    return -1;
}

int Positioner::lastRow() const
{
    if (!m_proxyToSource.isEmpty()) {
        QList<int> keys(m_proxyToSource.keys());
        std::sort(keys.begin(), keys.end());
        return keys.last();
    }

    return 0;
}

int Positioner::firstFreeRow() const
{
    if (!m_proxyToSource.isEmpty()) {
        int last = lastRow();

        for (int i = 0; i <= last; ++i) {
            if (!m_proxyToSource.contains(i)) {
                return i;
            }
        }
    }

    return -1;
}

void Positioner::convertFolderModelData()
{
    // Check if we need to defer
    m_deferApplyPositions = (m_folderModel->status() == FolderModel::Listing);

    // If no screen or no positions, we have nothing to convert
    if (!screenInUse() || m_positions.isEmpty() || m_deferApplyPositions) {
        return;
    }

    // Do not allow saving during this operation
    beginResetModel();

    m_proxyToSource.clear();
    m_sourceToProxy.clear();

    const int folderModelRowCount = m_folderModel->rowCount();

    QHash<QString, int> sourceIndices;
    sourceIndices.reserve(folderModelRowCount);

    for (int i = 0; i < folderModelRowCount; ++i) {
        sourceIndices.insert(m_folderModel->data(m_folderModel->index(i, 0), FolderModel::UrlRole).toString(), i);
    }

    // Restore positions for items that still fit.
    for (auto &&[name, gridPos] : std::as_const(m_positions).asKeyValueRange()) {
        if (gridPos.pos < m_perStripe) {
            if (!sourceIndices.contains(name)) {
                continue;
            }

            const int sourceIndex = sourceIndices.value(name);

            const int index = (gridPos.stripe * m_perStripe) + gridPos.pos;

            if (m_proxyToSource.contains(index)) {
                continue;
            }

            updateMaps(index, sourceIndex);
            sourceIndices.remove(name);
        }
    }

    // Find new positions for items that didn't fit.
    for (auto &&[name, gridPos] : std::as_const(m_positions).asKeyValueRange()) {
        if (gridPos.pos >= m_perStripe) {
            if (!sourceIndices.contains(name)) {
                continue;
            }

            const int sourceIndex = sourceIndices.take(name);

            int index = firstFreeRow();

            if (index == -1) {
                index = lastRow() + 1;
            }

            updateMaps(index, sourceIndex);
        }
    }

    QHashIterator<QString, int> it(sourceIndices);

    // Find positions for new source items we don't have records for.
    while (it.hasNext()) {
        it.next();

        int index = firstFreeRow();

        if (index == -1) {
            index = lastRow() + 1;
        }

        updateMaps(index, it.value());
    }

    endResetModel();
}

void Positioner::flushPendingChanges(bool inserted)
{
    if (m_pendingChanges.isEmpty()) {
        return;
    }

    int last = lastRow();

    for (const QModelIndex &index : std::as_const(m_pendingChanges)) {
        if (index.row() <= last) {
            if (inserted) {
                // Start tracking a new file
                m_changedPositions[data(index, FolderModel::UrlRole).toString()] = std::nullopt;
            }
            Q_EMIT dataChanged(index, index);
        }
    }

    m_pendingChanges.clear();
}

Plasma::Applet *Positioner::applet() const
{
    return m_applet;
}

void Positioner::setApplet(Plasma::Applet *applet)
{
    if (m_applet != applet) {
        Q_ASSERT(!m_applet);
        m_applet = applet;

        loadChangedPositions();

        Q_EMIT appletChanged();
    }
}

bool Positioner::screenInUse() const
{
    if (!m_folderModel) {
        return false;
    }
    return m_folderModel->screenUsed();
}

void Positioner::loadAndApplyPositionsConfig(const QString &resolution)
{
    const QString &resolutionToLoad = resolution.isEmpty() ? m_resolution : resolution;
    if (m_applet && m_enabled && screenInUse() && !resolutionToLoad.isEmpty()) {
        // The old configuration has commas with escape characters, so clean up those from the config
        auto confdata = loadConfigData();
        const QJsonDocument doc = QJsonDocument::fromJson(confdata.toUtf8());

        const auto positions = doc[resolutionToLoad].toVariant().toStringList();
        m_positionsHeader.reset();
        m_positions.clear();
        if (positions.size() >= PositionsConstants::headerSize && (positions.size() - PositionsConstants::headerSize) % PositionsConstants::bucketSize == 0) {
            bool okNumStripes = false;
            bool okPerStripe = false;
            m_positionsHeader = {.numStripes = positions[0].toInt(&okNumStripes), .perStripe = positions[1].toInt(&okPerStripe)};
            if (okNumStripes && okPerStripe) {
                for (qsizetype offset = PositionsConstants::headerSize; offset < positions.size(); offset += PositionsConstants::bucketSize) {
                    bool okStripe = false;
                    bool okPos = false;
                    const auto name = positions[offset + PositionsConstants::filenameOffset];
                    const auto stripe = positions[offset + PositionsConstants::stripeOffset].toInt(&okStripe);
                    const auto pos = positions[offset + PositionsConstants::posOffset].toInt(&okPos);
                    if (!name.isEmpty() && okStripe && okPos) {
                        m_positions[name] = {
                            .stripe = stripe,
                            .pos = pos,
                        };
                    }
                }
            } else {
                m_positionsHeader.reset();
            }
        }

        if (!m_positions.empty()) {
            convertFolderModelData();
        }
    }
}

void Positioner::savePositionsConfig()
{
    if (m_applet && m_enabled && screenInUse() && !m_resolution.isEmpty()) {
        auto confdata = loadConfigData();
        auto doc = QJsonDocument::fromJson(confdata.toUtf8());
        QJsonObject root;
        // Iterate over the old data
        // Positions are serialized like this: [stripes, itemsPerStripe, filename, stripe, position]
        const auto currentPositions = positions();
        for (const auto &[resolution, itemList] : doc.toVariant().toMap().asKeyValueRange()) {
            if (resolution != m_resolution) {
                QStringList newPositions;
                const QStringList positions = itemList.toStringList();
                if (positions.size() >= PositionsConstants::headerSize
                    && (positions.size() - PositionsConstants::headerSize) % PositionsConstants::bucketSize == 0) {
                    newPositions.append(positions[0]);
                    newPositions.append(positions[1]);

                    for (qsizetype offset = PositionsConstants::headerSize; offset < positions.size(); offset += PositionsConstants::bucketSize) {
                        const auto name = positions[offset + PositionsConstants::filenameOffset];
                        const auto stripe = positions[offset + PositionsConstants::stripeOffset];
                        const auto pos = positions[offset + PositionsConstants::posOffset];
                        if (currentPositions.contains(name)) {
                            newPositions.append(name);
                            newPositions.append(stripe);
                            newPositions.append(pos);
                        }
                    }
                }
                root.insert(resolution, QJsonValue::fromVariant(newPositions));
            }
        }
        // Append our new item
        root.insert(m_resolution, QJsonArray::fromStringList(currentPositions));

        const QByteArray data = QJsonDocument(root).toJson(QJsonDocument::Compact);
        auto config = m_applet->config().group(QStringLiteral("General"));
        config.writeEntry(QStringLiteral("lastResolution"), m_resolution);
        config.writeEntry(QStringLiteral("positions"), data);
        config.writeEntry(u"changedPositions"_s, prepareAndGetChangedPositionsJson());
        Q_EMIT m_applet->configNeedsSaving();
    }
}

bool Positioner::updateResolution()
{
    const QString prevResolution = m_resolution;
    QSize size;
    if (m_enabled && screenInUse()) {
        Q_ASSERT(m_folderModel);
        const QSizeF sizeF = m_folderModel->screenGeometry().size();
        size = QSize(std::floor(sizeF.width()), std::floor(sizeF.height()));
    }
    if (size.isEmpty()) {
        m_resolution.clear();
    } else {
        m_resolution = QStringLiteral("%1x%2").arg(size.width()).arg(size.height());
    }
    return m_resolution != prevResolution;
}

bool Positioner::configurationHasResolution(const QString &resolution) const
{
    if (resolution.isEmpty()) {
        return false;
    }
    auto confdata = loadConfigData();
    if (confdata.isEmpty()) {
        return false;
    }
    const QJsonDocument doc = QJsonDocument::fromJson(confdata.toUtf8());
    return doc.object().contains(resolution);
}

QString Positioner::loadConfigData() const
{
    QString confdata;
    if (m_applet) {
        confdata =
            m_applet->config().group(QStringLiteral("General")).readEntry(QStringLiteral("positions")).replace(QStringLiteral("\\,"), QStringLiteral(","));
    }
    return confdata;
}

void Positioner::loadChangedPositions()
{
    const auto jsonArr = QJsonDocument::fromJson(m_applet->config().group(u"General"_s).readEntry(u"changedPositions"_s).toUtf8()).object();

    m_changedPositions.clear();
    m_changedPositions.reserve(jsonArr.size());

    for (const auto &key : jsonArr.keys()) {
        const auto filename = key;

        if (filename.isEmpty()) {
            continue;
        }

        const auto values = jsonArr[key].toVariant().toStringList();
        if (values.size() != 3) {
            continue;
        }

        const auto visitedResolutions = values[0].split(','_L1, Qt::SkipEmptyParts);
        bool okStripeOffset = false;
        bool okPosOffset = false;
        ChangedPosition changedPosition{
            .visitedResolutions = {visitedResolutions.constBegin(), visitedResolutions.constEnd()},
            .gridPosition = {.stripe = values[1].toInt(&okStripeOffset), .pos = values[2].toInt(&okPosOffset)},
        };
        if (!okStripeOffset || !okPosOffset) {
            continue;
        }

        m_changedPositions[filename] = std::move(changedPosition);
    }
}

QByteArray Positioner::prepareAndGetChangedPositionsJson()
{
    // This method must be called with up-to-date "m_positions" list

    QJsonObject jsonObj;
    QStringList toRemove;

    for (auto &&[filename, changedPosition] : m_changedPositions.asKeyValueRange()) {
        if (auto positionsIt = m_positions.constFind(filename); positionsIt != m_positions.constEnd()) {
            if (!changedPosition.has_value()) {
                // Fill empty changed positions slot with current data (it means it started to be tracked recently)
                changedPosition.emplace(ChangedPosition{
                    .visitedResolutions = {m_resolution},
                    .gridPosition = positionsIt.value(),
                });
            }

            jsonObj[filename] = QJsonArray::fromStringList({
                QStringList(changedPosition->visitedResolutions.constBegin(), changedPosition->visitedResolutions.constEnd()).join(','_L1),
                QString::number(changedPosition->gridPosition.stripe),
                QString::number(changedPosition->gridPosition.pos),
            });
        } else {
            toRemove.push_back(filename);
        }
    }

    // Remove all disappeared files from changed positions
    for (auto &&filename : std::as_const(toRemove)) {
        m_changedPositions.remove(filename);
    }

    return QJsonDocument(jsonObj).toJson(QJsonDocument::Compact);
}

QPair<bool, bool> Positioner::restoreChangedPositions()
{
    bool visited = false;
    bool restored = false;

    auto positionsContains = [this](const GridPosition &otherGridPos) {
        return std::ranges::any_of(std::as_const(m_positions), [otherGridPos](auto &&gridPos) {
            return gridPos == otherGridPos;
        });
    };

    auto getOptimalStripes = [this] {
        // Optimal number of stripes to prevent scroll bar if we don't have it yet
        return qMax(m_optimalStripes, m_positionsHeader.value_or(PositionsHeader()).numStripes);
    };

    auto canUpdateGridPos = [&, optimalStripes = getOptimalStripes()](const GridPosition currGridPos, GridPosition &newGridPos) {
        if (currGridPos == newGridPos) {
            // Position has not been changed
            return false;
        }

        bool checkAgain = false;

        if (newGridPos.pos >= m_perStripe) {
            // Icon will be repositioned automatically, so clip to maximum position
            newGridPos.pos = m_perStripe > 0 ? m_perStripe - 1 : currGridPos.pos;
            checkAgain = true;
        }

        if (newGridPos.stripe >= optimalStripes) {
            // Scroll bar will appear, so use maximum possible stripe
            newGridPos.stripe = optimalStripes > 0 ? optimalStripes - 1 : currGridPos.stripe;
            checkAgain = true;
        }

        if (checkAgain && currGridPos == newGridPos) {
            // Position has not been changed
            return false;
        }

        if (positionsContains(newGridPos)) {
            // Ignore position changes which overlaps existing position
            return false;
        }

        return true;
    };

    for (auto &&[filename, changedPosition] : m_changedPositions.asKeyValueRange()) {
        if (!changedPosition.has_value() || changedPosition->visitedResolutions.contains(m_resolution)) {
            continue;
        }

        if (auto positionsIt = m_positions.find(filename); positionsIt != m_positions.end()) {
            auto newGridPos = changedPosition->gridPosition;
            if (canUpdateGridPos(positionsIt.value(), newGridPos)) {
                positionsIt.value() = newGridPos;
                restored = true;
            }
        }

        // Mark current resolution as visited (we don't want to attempt to restore it again)
        changedPosition->visitedResolutions.insert(m_resolution);
        visited = true;
    }

    return {visited, restored};
}

void Positioner::maybeRestoreAndApplyChangedPositions(bool forceConvertAndSave)
{
    // Restore positions which has been changed by the user at different resolution
    const auto [visited, restored] = restoreChangedPositions();
    if (forceConvertAndSave || restored) {
        convertFolderModelData();
        savePositionsConfig();
    } else if (visited) {
        savePositionsConfig();
    }
    m_deferRestoreChangedPositions = false;
}

void Positioner::onItemRenamed(const QString &filename, const QString &newFilename)
{
    updatePositionsList();
    if (filename != newFilename) {
        // Restore item position after rename
        if (auto positionsIt = m_positions.find(filename); positionsIt != m_positions.end()) {
            m_positions[newFilename] = {
                .stripe = qMax(0, positionsIt->stripe),
                .pos = qMax(0, positionsIt->pos),
            };
        }
    }
    m_positions.remove(filename);
    m_changedPositions[newFilename] = std::nullopt;
    convertFolderModelData();
    savePositionsConfig();
}

void Positioner::onItemDeleted(const QUrl &url)
{
    updatePositionsList();
    m_positions.remove(url.toString());
    convertFolderModelData();
    savePositionsConfig();
}

void Positioner::onListingCompleted(const QList<QUrl> &urls)
{
    QHash<QString, GridPosition> newPositions;

    for (const auto &url : urls) {
        if (m_positions.contains(url.toString())) {
            newPositions[url.toString()] = m_positions[url.toString()];
        }
    }

    m_positions = newPositions;

    if (m_skipSaveOnListingCompleted) {
        m_skipSaveOnListingCompleted = false;
    } else {
        savePositionsConfig();
    }
}

void Positioner::connectSignals(FolderModel *model)
{
    connect(model, &QAbstractItemModel::dataChanged, this, &Positioner::sourceDataChanged, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsAboutToBeInserted, this, &Positioner::sourceRowsAboutToBeInserted, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsAboutToBeMoved, this, &Positioner::sourceRowsAboutToBeMoved, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsAboutToBeRemoved, this, &Positioner::sourceRowsAboutToBeRemoved, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::layoutAboutToBeChanged, this, &Positioner::sourceLayoutAboutToBeChanged, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsInserted, this, &Positioner::sourceRowsInserted, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsMoved, this, &Positioner::sourceRowsMoved, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::rowsRemoved, this, &Positioner::sourceRowsRemoved, Qt::UniqueConnection);
    connect(model, &QAbstractItemModel::layoutChanged, this, &Positioner::sourceLayoutChanged, Qt::UniqueConnection);
    connect(m_folderModel, &FolderModel::urlChanged, this, &Positioner::reset, Qt::UniqueConnection);
    connect(m_folderModel, &FolderModel::statusChanged, this, &Positioner::sourceStatusChanged, Qt::UniqueConnection);
    connect(m_folderModel, &FolderModel::itemRenamed, this, &Positioner::onItemRenamed, Qt::UniqueConnection);
    connect(m_folderModel, &FolderModel::listingCompleted, this, &Positioner::onListingCompleted, Qt::UniqueConnection);
    connect(m_folderModel, &FolderModel::itemDeleted, this, &Positioner::onItemDeleted, Qt::UniqueConnection);
}

void Positioner::disconnectSignals(FolderModel *model)
{
    disconnect(model, &QAbstractItemModel::dataChanged, this, &Positioner::sourceDataChanged);
    disconnect(model, &QAbstractItemModel::rowsAboutToBeInserted, this, &Positioner::sourceRowsAboutToBeInserted);
    disconnect(model, &QAbstractItemModel::rowsAboutToBeMoved, this, &Positioner::sourceRowsAboutToBeMoved);
    disconnect(model, &QAbstractItemModel::rowsAboutToBeRemoved, this, &Positioner::sourceRowsAboutToBeRemoved);
    disconnect(model, &QAbstractItemModel::layoutAboutToBeChanged, this, &Positioner::sourceLayoutAboutToBeChanged);
    disconnect(model, &QAbstractItemModel::rowsInserted, this, &Positioner::sourceRowsInserted);
    disconnect(model, &QAbstractItemModel::rowsMoved, this, &Positioner::sourceRowsMoved);
    disconnect(model, &QAbstractItemModel::rowsRemoved, this, &Positioner::sourceRowsRemoved);
    disconnect(model, &QAbstractItemModel::layoutChanged, this, &Positioner::sourceLayoutChanged);
    disconnect(m_folderModel, &FolderModel::urlChanged, this, &Positioner::reset);
    disconnect(m_folderModel, &FolderModel::statusChanged, this, &Positioner::sourceStatusChanged);
    disconnect(m_folderModel, &FolderModel::itemRenamed, this, &Positioner::onItemRenamed);
    disconnect(m_folderModel, &FolderModel::listingCompleted, this, &Positioner::onListingCompleted);
    disconnect(m_folderModel, &FolderModel::itemDeleted, this, &Positioner::onItemDeleted);
}

#include "moc_positioner.cpp"