/*
 * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
 * SPDX-FileCopyrightText: 2014 ownCloud GmbH
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "syncengine.h"
#include "account.h"
#include "common/filesystembase.h"
#include "common/qtcompat.h"
#include "owncloudpropagator.h"
#include "common/syncjournaldb.h"
#include "common/syncjournalfilerecord.h"
#include "discoveryphase.h"
#include "creds/abstractcredentials.h"
#include "common/syncfilestatus.h"
#include "csync_exclude.h"
#include "filesystem.h"
#include "deletejob.h"
#include "propagatedownload.h"
#include "common/asserts.h"
#include "configfile.h"
#include "discovery.h"
#include "common/vfs.h"
#include "clientsideencryption.h"
#include "clientsideencryptionjobs.h"

#ifdef Q_OS_WIN
#include <windows.h>
#else
#include <unistd.h>
#endif

#include <climits>
#include <cassert>
#include <chrono>

#include <QCoreApplication>
#include <QSslSocket>
#include <QDir>
#include <QLoggingCategory>
#include <QMutexLocker>
#include <QThread>
#include <QStringList>
#include <QTextStream>
#include <QTime>
#include <QUrl>
#include <QSslCertificate>
#include <QProcess>
#include <QElapsedTimer>
#include <QFileInfo>
#include <QStorageInfo>
#include <qtextcodec.h>

namespace OCC {

Q_LOGGING_CATEGORY(lcEngine, "nextcloud.sync.engine", QtInfoMsg)

bool SyncEngine::s_anySyncRunning = false;

/** When the client touches a file, block change notifications for this duration (ms)
 *
 * On Linux and Windows the file watcher can't distinguish a change that originates
 * from the client (like a download during a sync operation) and an external change.
 * To work around that, all files the client touches are recorded and file change
 * notifications for these are blocked for some time. This value controls for how
 * long.
 *
 * Reasons this delay can't be very small:
 * - it takes time for the change notification to arrive and to be processed by the client
 * - some time could pass between the client recording that a file will be touched
 *   and its filesystem operation finishing, triggering the notification
 */
static const std::chrono::milliseconds s_touchedFilesMaxAgeMs(3 * 1000);

// doc in header
std::chrono::milliseconds SyncEngine::minimumFileAgeForUpload(2000);

SyncEngine::SyncEngine(AccountPtr account,
                       const QString &localPath,
                       const SyncOptions &syncOptions,
                       const QString &remotePath,
                       OCC::SyncJournalDb *journal)
    : _account(account)
    , _localPath(localPath)
    , _remotePath(remotePath)
    , _journal(journal)
    , _progressInfo(new ProgressInfo)
    , _syncOptions(syncOptions)
{
    qRegisterMetaType<SyncFileItem>("SyncFileItem");
    qRegisterMetaType<SyncFileItemPtr>("SyncFileItemPtr");
    qRegisterMetaType<SyncFileItem::Status>("SyncFileItem::Status");
    qRegisterMetaType<SyncFileStatus>("SyncFileStatus");
    qRegisterMetaType<SyncFileItemVector>("SyncFileItemVector");
    qRegisterMetaType<SyncFileItem::Direction>("SyncFileItem::Direction");

    // Everything in the SyncEngine expects a trailing slash for the localPath.
    ASSERT(localPath.endsWith(QLatin1Char('/')));

    _excludedFiles.reset(new ExcludedFiles(localPath));

    _syncFileStatusTracker.reset(new SyncFileStatusTracker(this));

    _clearTouchedFilesTimer.setSingleShot(true);
    _clearTouchedFilesTimer.setInterval(30 * 1000);
    connect(&_clearTouchedFilesTimer, &QTimer::timeout, this, &SyncEngine::slotClearTouchedFiles);
    connect(this, &SyncEngine::finished, [this](bool /* finished */) {
        _journal->keyValueStoreSet("last_sync", QDateTime::currentSecsSinceEpoch());
    });
}

SyncEngine::~SyncEngine()
{
    abort();
    _excludedFiles.reset();
}

bool SyncEngine::SingleItemDiscoveryOptions::isValid() const
{
    return !filePathRelative.isEmpty() && !discoveryPath.isEmpty()
        && ((discoveryDirItem && !discoveryDirItem->isEmpty()) || discoveryPath == QStringLiteral("/"));
}

/**
 * Check if the item is in the blacklist.
 * If it should not be sync'ed because of the blacklist, update the item with the error instruction
 * and proper error message, and return true.
 * If the item is not in the blacklist, or the blacklist is stale, return false.
 */
bool SyncEngine::checkErrorBlacklisting(SyncFileItem &item)
{
    if (!_journal) {
        qCCritical(lcEngine) << "Journal is undefined!";
        return false;
    }

    SyncJournalErrorBlacklistRecord entry = _journal->errorBlacklistEntry(item._file);
    item._hasBlacklistEntry = false;

    if (!entry.isValid()) {
        return false;
    }

    item._hasBlacklistEntry = true;

    // If duration has expired, it's not blacklisted anymore
    time_t now = Utility::qDateTimeToTime_t(QDateTime::currentDateTimeUtc());
    if (now >= entry._lastTryTime + entry._ignoreDuration) {
        qCInfo(lcEngine) << "blacklist entry for " << item._file << " has expired!";
        return false;
    }

    // If the file has changed locally or on the server, the blacklist
    // entry no longer applies
    if (item._direction == SyncFileItem::Up) { // check the modtime
        if (item._modtime == 0 || entry._lastTryModtime == 0) {
            return false;
        } else if (item._modtime != entry._lastTryModtime) {
            qCInfo(lcEngine) << item._file << " is blacklisted, but has changed mtime!";
            return false;
        } else if (item._renameTarget != entry._renameTarget) {
            qCInfo(lcEngine) << item._file << " is blacklisted, but rename target changed from" << entry._renameTarget;
            return false;
        }
    } else if (item._direction == SyncFileItem::Down) {
        // download, check the etag.
        if (item._etag.isEmpty() || entry._lastTryEtag.isEmpty()) {
            qCInfo(lcEngine) << item._file << "one ETag is empty, no blacklisting";
            return false;
        } else if (item._etag != entry._lastTryEtag) {
            qCInfo(lcEngine) << item._file << " is blacklisted, but has changed etag!";
            return false;
        }
    }

    qint64 waitSeconds = entry._lastTryTime + entry._ignoreDuration - now;
    qCInfo(lcEngine) << "Item is on blacklist: " << entry._file
                     << "retries:" << entry._retryCount
                     << "for another" << waitSeconds << "s";

    // We need to indicate that we skip this file due to blacklisting
    // for reporting and for making sure we don't update the blacklist
    // entry yet.
    // Classification is this _instruction and _status
    item._instruction = CSYNC_INSTRUCTION_IGNORE;
    item._status = SyncFileItem::BlacklistedError;

    auto waitSecondsStr = Utility::durationToDescriptiveString1(1000 * waitSeconds);
    item._errorString = tr("%1 (skipped due to earlier error, trying again in %2)").arg(entry._errorString, waitSecondsStr);

    if (entry._errorCategory == SyncJournalErrorBlacklistRecord::InsufficientRemoteStorage) {
        slotInsufficientRemoteStorage();
    }

    return true;
}

static bool isFileTransferInstruction(SyncInstructions instruction)
{
    return instruction == CSYNC_INSTRUCTION_CONFLICT
        || instruction == CSYNC_INSTRUCTION_NEW
        || instruction == CSYNC_INSTRUCTION_SYNC
        || instruction == CSYNC_INSTRUCTION_TYPE_CHANGE;
}

void SyncEngine::deleteStaleDownloadInfos(const SyncFileItemVector &syncItems)
{
    // Find all downloadinfo paths that we want to preserve.
    QSet<QString> download_file_paths;
    for (const SyncFileItemPtr &it : syncItems) {
        if (it->_direction == SyncFileItem::Down
            && it->_type == ItemTypeFile
            && isFileTransferInstruction(it->_instruction)) {
            download_file_paths.insert(it->_file);
        }
    }

    // Delete from journal and from filesystem.
    const QVector<SyncJournalDb::DownloadInfo> deleted_infos =
        _journal->getAndDeleteStaleDownloadInfos(download_file_paths);
    for (const SyncJournalDb::DownloadInfo &deleted_info : deleted_infos) {
        const QString tmppath = _propagator->fullLocalPath(deleted_info._tmpfile);
        FileSystem::remove(tmppath);
    }
}

void SyncEngine::deleteStaleUploadInfos(const SyncFileItemVector &syncItems)
{
    // Find all blacklisted paths that we want to preserve.
    QSet<QString> upload_file_paths;
    for (const SyncFileItemPtr &it: syncItems) {
        if (it->_direction == SyncFileItem::Up
            && it->_type == ItemTypeFile
            && isFileTransferInstruction(it->_instruction)) {
            upload_file_paths.insert(it->_file);
        }
    }

    // Delete from journal.
    auto ids = _journal->deleteStaleUploadInfos(upload_file_paths);

    // Delete the stales chunk on the server.
    if (account()->capabilities().chunkingNg()) {
        for (uint transferId : std::as_const(ids)) {
            if (!transferId)
                continue; // Was not a chunked upload
            QUrl url = Utility::concatUrlPath(account()->url(), QLatin1String("remote.php/dav/uploads/") + account()->davUser() + QLatin1Char('/') + QString::number(transferId));
            (new DeleteJob(account(), url, {}, this))->start();
        }
    }
}

void SyncEngine::deleteStaleErrorBlacklistEntries(const SyncFileItemVector &syncItems)
{
    // Find all blacklisted paths that we want to preserve.
    QSet<QString> blacklist_file_paths;
    for (const SyncFileItemPtr &it : syncItems) {
        if (it->_hasBlacklistEntry)
            blacklist_file_paths.insert(it->_file);
    }

    // Delete from journal.
    if (!_journal->deleteStaleErrorBlacklistEntries(blacklist_file_paths)) {
        qCWarning(lcEngine) << "Could not delete StaleErrorBlacklistEntries from DB";
    }
}

void SyncEngine::conflictRecordMaintenance()
{
    // Remove stale conflict entries from the database
    // by checking which files still exist and removing the
    // missing ones.
    const auto conflictRecordPaths = _journal->conflictRecordPaths();
    for (const auto &path : conflictRecordPaths) {
        auto fsPath = _propagator->fullLocalPath(QString::fromUtf8(path));
        if (!FileSystem::fileExists(fsPath)) {
            _journal->deleteConflictRecord(path);
        }
    }

    // Did the sync see any conflict files that don't yet have records?
    // If so, add them now.
    //
    // This happens when the conflicts table is new or when conflict files
    // are downloaded but the server doesn't send conflict headers.
    for (const auto &path : std::as_const(_seenConflictFiles)) {
        ASSERT(Utility::isConflictFile(path));

        auto bapath = path.toUtf8();
        if (!conflictRecordPaths.contains(bapath)) {
            ConflictRecord record;
            record.path = bapath;
            auto basePath = Utility::conflictFileBaseNameFromPattern(bapath);
            record.initialBasePath = basePath;

            // Determine fileid of target file
            SyncJournalFileRecord baseRecord;
            if (_journal->getFileRecord(basePath, &baseRecord) && baseRecord.isValid()) {
                record.baseFileId = baseRecord._fileId;
            }

            _journal->setConflictRecord(record);
        }
    }
}

void SyncEngine::caseClashConflictRecordMaintenance()
{
    // Remove stale conflict entries from the database
    // by checking which files still exist and removing the
    // missing ones.
    const auto conflictRecordPaths = _journal->caseClashConflictRecordPaths();
    for (const auto &path : conflictRecordPaths) {
        const auto fsPath = _propagator->fullLocalPath(QString::fromUtf8(path));
        if (!FileSystem::fileExists(fsPath)) {
            _journal->deleteCaseClashConflictByPathRecord(path);
        }
    }
}


void OCC::SyncEngine::slotItemDiscovered(const OCC::SyncFileItemPtr &item)
{
    emit itemDiscovered(item);

    if (Utility::isConflictFile(item->_file))
        _seenConflictFiles.insert(item->_file);
    if (item->_instruction == CSYNC_INSTRUCTION_UPDATE_METADATA && !item->isDirectory()) {
        // For directories, metadata-only updates will be done after all their files are propagated.

        // Update the database now already:  New remote fileid or Etag or RemotePerm
        // Or for files that were detected as "resolved conflict".
        // Or a local inode/mtime change

        // In case of "resolved conflict": there should have been a conflict because they
        // both were new, or both had their local mtime or remote etag modified, but the
        // size and mtime is the same on the server.  This typically happens when the
        // database is removed. Nothing will be done for those files, but we still need
        // to update the database.

        // This metadata update *could* be a propagation job of its own, but since it's
        // quick to do and we don't want to create a potentially large number of
        // mini-jobs later on, we just update metadata right now.

        if (item->_direction == SyncFileItem::Down) {
            auto modificationHappened = false; // Decides whether or not we modify file metadata
            QString filePath = _localPath + item->_file;

            // If the 'W' remote permission changed, update the local filesystem
            SyncJournalFileRecord prev;
            if (_journal->getFileRecord(item->_file, &prev)
                && prev.isValid()
                && prev._remotePerm.hasPermission(RemotePermissions::CanWrite) != item->_remotePerm.hasPermission(RemotePermissions::CanWrite)) {
                const bool isReadOnly = !item->_remotePerm.isNull() && !item->_remotePerm.hasPermission(RemotePermissions::CanWrite);
                modificationHappened = FileSystem::setFileReadOnlyWeak(filePath, isReadOnly);
            }
            if (item->isPermissionsInvalid) {
                const auto isReadOnly = !item->_remotePerm.isNull() && !item->_remotePerm.hasPermission(RemotePermissions::CanWrite);
                FileSystem::setFileReadOnly(filePath, isReadOnly);
            }

            modificationHappened |= item->_size != prev._fileSize;

            auto rec = item->toSyncJournalFileRecordWithInode(filePath);
            if (rec._checksumHeader.isEmpty())
                rec._checksumHeader = prev._checksumHeader;
            rec._serverHasIgnoredFiles |= prev._serverHasIgnoredFiles;

            // Ensure it's a placeholder file on disk
            if (item->_type == ItemTypeFile && _syncOptions._vfs->mode() != Vfs::Off) {
                const auto result = _syncOptions._vfs->convertToPlaceholder(filePath, *item, {}, Vfs::UpdateMetadataType::DatabaseMetadata);
                if (!result) {
                    item->_status = SyncFileItem::Status::NormalError;
                    item->_instruction = CSYNC_INSTRUCTION_ERROR;
                    item->_errorString = tr("Could not update file: %1").arg(result.error());
                    emit itemCompleted(item, ErrorCategory::GenericError);
                    return;
                }
                modificationHappened = true;
            }

            if (item->_type == CSyncEnums::ItemTypeVirtualFile) {
                const auto lockOwnerTypeToSkipReadonly = _account->capabilities().filesLockTypeAvailable()
                    ? SyncFileItem::LockOwnerType::TokenLock
                    : SyncFileItem::LockOwnerType::UserLock;
                if (item->_locked == SyncFileItem::LockStatus::LockedItem
                    && (item->_lockOwnerType != lockOwnerTypeToSkipReadonly || item->_lockOwnerId != account()->davUser())) {
                    qCDebug(lcEngine()) << filePath << "file is locked: making it read only";
                    FileSystem::setFileReadOnly(filePath, true);
                } else {
                    qCDebug(lcEngine()) << filePath << "file is not locked: making it"
                                        << ((!item->_remotePerm.isNull() && !item->_remotePerm.hasPermission(RemotePermissions::CanWrite)) ? "read only"
                                                                                                                                           : "read write");
                    FileSystem::setFileReadOnlyWeak(filePath, (!item->_remotePerm.isNull() && !item->_remotePerm.hasPermission(RemotePermissions::CanWrite)));
                }
            }

            // Update on-disk virtual file metadata
            if (modificationHappened && item->_type == ItemTypeVirtualFile) {
                auto r = _syncOptions._vfs->updateMetadata(*item, filePath, {});
                if (!r) {
                    item->_status = SyncFileItem::Status::NormalError;
                    item->_instruction = CSYNC_INSTRUCTION_ERROR;
                    item->_errorString = tr("Could not update virtual file metadata: %1").arg(r.error());
                    emit itemCompleted(item, ErrorCategory::GenericError);
                    return;
                }
            } else if (prev._modtime != item->_modtime) {
                if (!FileSystem::setModTime(filePath, item->_modtime)) {
                    item->_instruction = CSYNC_INSTRUCTION_ERROR;
                    item->_errorString = tr("Could not update file metadata: %1").arg(filePath);
                    emit itemCompleted(item, ErrorCategory::GenericError);
                    return;
                }
            }

            // Updating the db happens on success
            if (!_journal->setFileRecord(rec)) {
                item->_status = SyncFileItem::Status::NormalError;
                item->_instruction = CSYNC_INSTRUCTION_ERROR;
                item->_errorString = tr("Could not set file record to local DB: %1").arg(rec.path());
                qCWarning(lcEngine) << "Could not set file record to local DB" << rec.path();
            }

            // This might have changed the shared flag, so we must notify SyncFileStatusTracker for example
            emit itemCompleted(item, ErrorCategory::NoError);
        } else {
            // Update only outdated data from the disk.

            SyncJournalFileLockInfo lockInfo;
            lockInfo._locked = item->_locked == SyncFileItem::LockStatus::LockedItem;
            lockInfo._lockTime = item->_lockTime;
            lockInfo._lockTimeout = item->_lockTimeout;
            lockInfo._lockOwnerId = item->_lockOwnerId;
            lockInfo._lockOwnerType = static_cast<qint64>(item->_lockOwnerType);
            lockInfo._lockOwnerDisplayName = item->_lockOwnerDisplayName;
            lockInfo._lockEditorApp = item->_lockOwnerDisplayName;
            lockInfo._lockToken = item->_lockToken;

            if (!_journal->updateLocalMetadata(item->_file, item->_modtime, item->_size, item->_inode, lockInfo)) {
                qCWarning(lcEngine) << "Could not update local metadata for file" << item->_file;
            }
        }
        _hasNoneFiles = true;
        return;
    } else if (item->_instruction == CSYNC_INSTRUCTION_NONE) {
        _hasNoneFiles = true;
        _syncFileStatusTracker->slotCheckAndRemoveSilentlyExcluded(item->_file);
        if (_account->capabilities().uploadConflictFiles() && Utility::isConflictFile(item->_file)) {
            // For uploaded conflict files, files with no action performed on them should
            // be displayed: but we mustn't overwrite the instruction if something happens
            // to the file!
            item->_errorString = tr("Unresolved conflict.");
            item->_instruction = CSYNC_INSTRUCTION_IGNORE;
            item->_status = SyncFileItem::Conflict;
        }
        return;
    } else if (item->_instruction == CSYNC_INSTRUCTION_REMOVE && !item->_isSelectiveSync) {
        _hasRemoveFile = true;
    } else if (item->_instruction == CSYNC_INSTRUCTION_RENAME) {
        _hasNoneFiles = true; // If a file (or every file) has been renamed, it means not al files where deleted
    } else if (item->_instruction == CSYNC_INSTRUCTION_TYPE_CHANGE
        || item->_instruction == CSYNC_INSTRUCTION_SYNC) {
        if (item->_direction == SyncFileItem::Up) {
            // An upload of an existing file means that the file was left unchanged on the server
            // This counts as a NONE for detecting if all the files on the server were changed
            _hasNoneFiles = true;
        }
    }

    // check for blacklisting of this item.
    // if the item is on blacklist, the instruction was set to ERROR
    checkErrorBlacklisting(*item);
    _needsUpdate = true;

    // Insert sorted
    auto it = std::lower_bound( _syncItems.begin(), _syncItems.end(), item ); // the _syncItems is sorted
    _syncItems.insert( it, item );

    slotNewItem(item);

    if (item->isDirectory()) {
        slotFolderDiscovered(item->_etag.isEmpty(), item->_file);
    }
}

void SyncEngine::startSync()
{
    if (_journal->exists()) {
        QVector<SyncJournalDb::PollInfo> pollInfos = _journal->getPollInfos();
        if (!pollInfos.isEmpty()) {
            qCInfo(lcEngine) << "Finish Poll jobs before starting a sync";
            auto *job = new CleanupPollsJob(_account,
                _journal, _localPath, _syncOptions._vfs, this);
            connect(job, &CleanupPollsJob::finished, this, &SyncEngine::startSync);
            connect(job, &CleanupPollsJob::aborted, this, &SyncEngine::slotCleanPollsJobAborted);
            job->start();
            return;
        }

        const auto e2EeLockedFolders = _journal->e2EeLockedFolders();

        if (!e2EeLockedFolders.isEmpty()) {
            for (const auto &e2EeLockedFolder : e2EeLockedFolders) {
                const auto folderId = e2EeLockedFolder.first;
                qCInfo(lcEngine()) << "start unlock job for folderId:" << folderId;
                const auto folderToken = EncryptionHelper::decryptStringAsymmetric(_account->e2e()->getCertificateInformation(), _account->e2e()->paddingMode(), *_account->e2e(), e2EeLockedFolder.second);
                if (!folderToken) {
                    qCWarning(lcEngine()) << "decrypt failed";
                    return;
                }
                // TODO: We need to rollback changes done to metadata in case we have an active lock, this needs to be implemented on the server first
                const auto unlockJob = new OCC::UnlockEncryptFolderApiJob(_account, folderId, *folderToken, _journal, this);
                unlockJob->setShouldRollbackMetadataChanges(true);
                unlockJob->start();
            }
        }
    }

    if (s_anySyncRunning || _syncRunning) {
        return;
    }
    const auto currentEncryptionStatus = EncryptionStatusEnums::toDbEncryptionStatus(EncryptionStatusEnums::fromEndToEndEncryptionApiVersion(_account->capabilities().clientSideEncryptionVersion()));
    [[maybe_unused]] const auto result = _journal->listAllE2eeFoldersWithEncryptionStatusLessThan(static_cast<int>(currentEncryptionStatus), [this](const SyncJournalFileRecord &record) {
        _journal->schedulePathForRemoteDiscovery(record.path());
    });

    s_anySyncRunning = true;
    _syncRunning = true;
    _anotherSyncNeeded = NoFollowUpSync;
    _clearTouchedFilesTimer.stop();

    _hasNoneFiles = false;
    _hasRemoveFile = false;
    _seenConflictFiles.clear();

    _progressInfo->reset();

    if (!QFileInfo::exists(_localPath)) {
        _anotherSyncNeeded = DelayedFollowUp;
        // No _tr, it should only occur in non-mirall
        Q_EMIT syncError(QStringLiteral("Unable to find local sync folder."), ErrorCategory::GenericError);
        finalize(false);
        return;
    }

    // Check free size on disk first.
    const qint64 minFree = criticalFreeSpaceLimit();
    const qint64 freeBytes = Utility::freeDiskSpace(_localPath);
    if (freeBytes >= 0) {
        if (freeBytes < minFree) {
            qCWarning(lcEngine()) << "Too little space available at" << _localPath << ". Have"
                                  << freeBytes << "bytes and require at least" << minFree << "bytes";
            _anotherSyncNeeded = DelayedFollowUp;
            Q_EMIT syncError(tr("Only %1 are available, need at least %2 to start",
                "Placeholders are postfixed with file sizes using Utility::octetsToString()")
                                 .arg(
                                     Utility::octetsToString(freeBytes),
                                     Utility::octetsToString(minFree)), ErrorCategory::GenericError);
            finalize(false);
            return;
        } else {
            qCInfo(lcEngine) << "There are" << freeBytes << "bytes available at" << _localPath;
        }
    } else {
        qCWarning(lcEngine) << "Could not determine free space available at" << _localPath;
    }

    _syncItems.clear();
    _needsUpdate = false;

    if (!_journal->exists()) {
        qCInfo(lcEngine) << "New sync (no sync journal exists)";
    } else {
        qCInfo(lcEngine) << "Sync with existing sync journal";
    }

    QString verStr("Using Qt ");
    verStr.append(qVersion());

    verStr.append(" SSL library ").append(QSslSocket::sslLibraryVersionString().toUtf8().data());
    verStr.append(" on ").append(Utility::platformName());
    qCInfo(lcEngine) << verStr;

    // This creates the DB if it does not exist yet.
    if (!_journal->open()) {
        qCWarning(lcEngine) << "No way to create a sync journal!";
        Q_EMIT syncError(tr("Unable to open or create the local sync database. Make sure you have write access in the sync folder."), ErrorCategory::GenericError);
        finalize(false);
        return;
        // database creation error!
    }

    // Functionality like selective sync might have set up etag storage
    // filtering via schedulePathForRemoteDiscovery(). This *is* the next sync, so
    // undo the filter to allow this sync to retrieve and store the correct etags.
    _journal->clearEtagStorageFilter();

    _excludedFiles->setExcludeConflictFiles(!_account->capabilities().uploadConflictFiles());

    _lastLocalDiscoveryStyle = _localDiscoveryStyle;

    if (_syncOptions._vfs->mode() == Vfs::WithSuffix && _syncOptions._vfs->fileSuffix().isEmpty()) {
        Q_EMIT syncError(tr("Using virtual files with suffix, but suffix is not set"), ErrorCategory::GenericError);
        finalize(false);
        return;
    }

    bool ok = false;
    auto selectiveSyncBlackList = _journal->getSelectiveSyncList(SyncJournalDb::SelectiveSyncBlackList, &ok);
    if (ok) {
        bool usingSelectiveSync = (!selectiveSyncBlackList.isEmpty());
        qCInfo(lcEngine) << (usingSelectiveSync ? "Using Selective Sync" : "NOT Using Selective Sync");
    } else {
        qCWarning(lcEngine) << "Could not retrieve selective sync list from DB";
        Q_EMIT syncError(tr("Unable to read the blacklist from the local database"), ErrorCategory::GenericError);
        finalize(false);
        return;
    }

    processCaseClashConflictsBeforeDiscovery();

    _stopWatch.start();
    _progressInfo->_status = ProgressInfo::Starting;
    emit transmissionProgress(*_progressInfo);

    qCInfo(lcEngine) << "#### Discovery start ####################################################";
    qCInfo(lcEngine) << "Server" << account()->serverVersion()
                     << (account()->isHttp2Supported() ? "Using HTTP/2" : "");
    _progressInfo->_status = ProgressInfo::Discovery;
    emit transmissionProgress(*_progressInfo);

    _remnantReadOnlyFolders.clear();

    _discoveryPhase = std::make_unique<DiscoveryPhase>();
    _discoveryPhase->_fileSystemReliablePermissions = _filesystemPermissionsReliable;
    _discoveryPhase->_leadingAndTrailingSpacesFilesAllowed = _leadingAndTrailingSpacesFilesAllowed;
    _discoveryPhase->_account = _account;
    _discoveryPhase->_excludes = _excludedFiles.data();
    const QString excludeFilePath = _localPath + QStringLiteral(".sync-exclude.lst");
    if (FileSystem::fileExists(excludeFilePath)) {
        _discoveryPhase->_excludes->addExcludeFilePath(excludeFilePath);
        _discoveryPhase->_excludes->reloadExcludeFiles();
    }
    _discoveryPhase->_statedb = _journal;
    _discoveryPhase->_localDir = Utility::trailingSlashPath(_localPath);
    _discoveryPhase->_remoteFolder = Utility::trailingSlashPath(_remotePath);
    _discoveryPhase->_syncOptions = _syncOptions;
    _discoveryPhase->_shouldDiscoverLocaly = [this](const QString &path) {
        const auto result = shouldDiscoverLocally(path);
        return result;
    };
    _discoveryPhase->setSelectiveSyncBlackList(selectiveSyncBlackList);
    _discoveryPhase->setSelectiveSyncWhiteList(_journal->getSelectiveSyncList(SyncJournalDb::SelectiveSyncWhiteList, &ok));
    if (!ok) {
        qCWarning(lcEngine) << "Unable to read selective sync list, aborting.";
        Q_EMIT syncError(tr("Unable to read from the sync journal."), ErrorCategory::GenericError);
        finalize(false);
        return;
    }

    const auto accountCaps = _account->capabilities();
    const auto forbiddenFilenames = accountCaps.forbiddenFilenames();
    const auto forbiddenBasenames = accountCaps.forbiddenFilenameBasenames();
    const auto forbiddenExtensions = accountCaps.forbiddenFilenameExtensions();
    const auto forbiddenChars = accountCaps.forbiddenFilenameCharacters();

    _discoveryPhase->_forbiddenFilenames = forbiddenFilenames;
    _discoveryPhase->_forbiddenBasenames = forbiddenBasenames;
    _discoveryPhase->_forbiddenExtensions = forbiddenExtensions;
    _discoveryPhase->_forbiddenChars = forbiddenChars;
    if (!forbiddenFilenames.isEmpty() &&
        !forbiddenBasenames.isEmpty() &&
        !forbiddenExtensions.isEmpty() &&
        !forbiddenChars.isEmpty()) {
        _shouldEnforceWindowsFileNameCompatibility = true;
        _discoveryPhase->_shouldEnforceWindowsFileNameCompatibility = _shouldEnforceWindowsFileNameCompatibility;
    }
#if defined Q_OS_WINDOWS
    _shouldEnforceWindowsFileNameCompatibility = true;
    _discoveryPhase->_shouldEnforceWindowsFileNameCompatibility = _shouldEnforceWindowsFileNameCompatibility;
#endif

    // Check for invalid character in old server version
    QString invalidFilenamePattern = _account->capabilities().invalidFilenameRegex();
    if (invalidFilenamePattern.isNull()
        && _account->serverVersionInt() < Account::makeServerVersion(8, 1, 0)) {
        // Server versions older than 8.1 don't support some characters in filenames.
        // If the capability is not set, default to a pattern that avoids uploading
        // files with names that contain these.
        // It's important to respect the capability also for older servers -- the
        // version check doesn't make sense for custom servers.
        invalidFilenamePattern = R"([\\:?*"<>|])";
    }
    if (!invalidFilenamePattern.isEmpty())
        _discoveryPhase->_invalidFilenameRx = QRegularExpression(invalidFilenamePattern);
    _discoveryPhase->_serverBlacklistedFiles = _account->capabilities().blacklistedFiles();
    _discoveryPhase->_ignoreHiddenFiles = ignoreHiddenFiles();

    connect(_discoveryPhase.get(), &DiscoveryPhase::itemDiscovered, this, &SyncEngine::slotItemDiscovered);
    connect(_discoveryPhase.get(), &DiscoveryPhase::newBigFolder, this, &SyncEngine::newBigFolder);
    connect(_discoveryPhase.get(), &DiscoveryPhase::existingFolderNowBig, this, &SyncEngine::existingFolderNowBig);
    connect(_discoveryPhase.get(), &DiscoveryPhase::fatalError, this, [this](const QString &errorString, ErrorCategory errorCategory) {
        Q_EMIT syncError(errorString, errorCategory);
        finalize(false);
    });
    connect(_discoveryPhase.get(), &DiscoveryPhase::finished, this, &SyncEngine::slotDiscoveryFinished);
    connect(_discoveryPhase.get(), &DiscoveryPhase::silentlyExcluded,
        _syncFileStatusTracker.data(), &SyncFileStatusTracker::slotAddSilentlyExcluded);
    connect(_discoveryPhase.get(), &DiscoveryPhase::remnantReadOnlyFolderDiscovered, this, &SyncEngine::remnantReadOnlyFolderDiscovered);
    connect(_discoveryPhase.get(), &DiscoveryPhase::seenLockedFile, this, &SyncEngine::seenLockedFile);

    ProcessDirectoryJob *discoveryJob = nullptr;

    if (singleItemDiscoveryOptions().isValid()) {
        _discoveryPhase->_listExclusiveFiles.clear();
        _discoveryPhase->_listExclusiveFiles.push_back(singleItemDiscoveryOptions().filePathRelative);
    }

    if (singleItemDiscoveryOptions().isValid() && singleItemDiscoveryOptions().discoveryDirItem) {
        const auto databaseFingerprint = _journal->dataFingerprint();
        _discoveryPhase->_dataFingerprint = databaseFingerprint;
        ProcessDirectoryJob::PathTuple path = {};
        path._local = path._original = path._server = path._target = singleItemDiscoveryOptions().discoveryPath;

        SyncJournalFileRecord rec;
        const auto localQueryMode = _journal->getFileRecord(singleItemDiscoveryOptions().discoveryDirItem->_file, &rec) && rec.isValid()
            ? ProcessDirectoryJob::NormalQuery
            : ProcessDirectoryJob::ParentDontExist;

        const auto pinState = [this, &rec]() {
            if (!_syncOptions._vfs || _syncOptions._vfs->mode() == Vfs::Off) {
                return PinState::AlwaysLocal;
            }
            if (!rec.isValid()) {
                return PinState::OnlineOnly;
            }
            const auto pinStateInDb = _journal->internalPinStates().rawForPath(singleItemDiscoveryOptions().discoveryDirItem->_file.toUtf8());
            if (pinStateInDb) {
                return *pinStateInDb;
            }
            return PinState::Unspecified;
        }();

        discoveryJob = new ProcessDirectoryJob(
            _discoveryPhase.get(),
            pinState,
            path,
            singleItemDiscoveryOptions().discoveryDirItem,
            {},
            localQueryMode,
            _journal->keyValueStoreGetInt("last_sync", 0),
            _discoveryPhase.get()
        );
    } else {
        discoveryJob = new ProcessDirectoryJob(
            _discoveryPhase.get(),
            PinState::AlwaysLocal,
            _journal->keyValueStoreGetInt("last_sync", 0),
            _discoveryPhase.get()
        );
    }
    
    _discoveryPhase->startJob(discoveryJob);
    connect(discoveryJob, &ProcessDirectoryJob::etag, this, &SyncEngine::slotRootEtagReceived);
    connect(discoveryJob, &ProcessDirectoryJob::updatedRootFolderQuota, account().data(), &Account::rootFolderQuotaChanged);
    connect(discoveryJob, &ProcessDirectoryJob::rootFileIdReceived, this, &SyncEngine::slotRootFileIdReceived);
    connect(_discoveryPhase.get(), &DiscoveryPhase::addErrorToGui, this, &SyncEngine::addErrorToGui);
}

void SyncEngine::slotFolderDiscovered(bool local, const QString &folder)
{
    // Don't wanna overload the UI
    if (!_lastUpdateProgressCallbackCall.isValid() || _lastUpdateProgressCallbackCall.elapsed() >= 200) {
        _lastUpdateProgressCallbackCall.start(); // first call or enough elapsed time
    } else {
        return;
    }

    if (local) {
        _progressInfo->_currentDiscoveredLocalFolder = folder;
        _progressInfo->_currentDiscoveredRemoteFolder.clear();
    } else {
        _progressInfo->_currentDiscoveredRemoteFolder = folder;
        _progressInfo->_currentDiscoveredLocalFolder.clear();
    }
    emit transmissionProgress(*_progressInfo);
}

void SyncEngine::slotRootEtagReceived(const QByteArray &e, const QDateTime &time)
{
    if (_remoteRootEtag.isEmpty()) {
        qCDebug(lcEngine) << "Root etag:" << e;
        _remoteRootEtag = e;
        emit rootEtag(_remoteRootEtag, time);
    }
}

void SyncEngine::slotRootFileIdReceived(const qint64 fileId)
{
    if (_rootFileIdReceived) {
        return;
    }
    _rootFileId = fileId;
    _rootFileIdReceived = true;
    emit rootFileIdReceived(fileId);
}

void SyncEngine::slotNewItem(const SyncFileItemPtr &item)
{
    _progressInfo->adjustTotalsForFile(*item);
}

void SyncEngine::slotDiscoveryFinished()
{
    if (!_discoveryPhase) {
        // There was an error that was already taken care of
        return;
    }

    qCInfo(lcEngine) << "#### Discovery end #################################################### " << _stopWatch.addLapTime(QLatin1String("Discovery Finished")) << "ms";

    // Sanity check
    if (!_journal->open()) {
        qCWarning(lcEngine) << "Bailing out, DB failure";
        Q_EMIT syncError(tr("Cannot open the sync journal"), ErrorCategory::GenericError);
        finalize(false);
        return;
    } else {
        // Commits a possibly existing (should not though) transaction and starts a new one for the propagate phase
        _journal->commitIfNeededAndStartNewTransaction("Post discovery");
    }

    _progressInfo->_currentDiscoveredRemoteFolder.clear();
    _progressInfo->_currentDiscoveredLocalFolder.clear();
    _progressInfo->_status = ProgressInfo::Reconcile;
    emit transmissionProgress(*_progressInfo);

    if (shouldRestartSync()) {
        // Fail the sync once and try again next time.
        qCInfo(lcEngine) << "Restarting sync as discovery results might be incomplete.";
        _anotherSyncNeeded = DelayedFollowUp;
        _restartedSyncAfterDiscovery = true;
        finalize(false);
        return;
    } else {
        _restartedSyncAfterDiscovery = false;
    }

    if (handleMassDeletion()) {
        return;
    }

    if (!_remnantReadOnlyFolders.isEmpty()) {
        handleRemnantReadOnlyFolders();
    }

    finishSync();
}

void SyncEngine::slotCleanPollsJobAborted(const QString &error, const ErrorCategory errorCategory)
{
    emit syncError(error, errorCategory);
    finalize(false);
}

void SyncEngine::detectFileLock(const SyncFileItemPtr &item)
{
    const auto isNewlyUploadedFile = !item->isDirectory() &&
        item->_instruction == CSYNC_INSTRUCTION_NEW &&
        item->_direction == SyncFileItem::Up && item->_status == SyncFileItem::Success;

    if (isNewlyUploadedFile && item->_locked != SyncFileItem::LockStatus::LockedItem && _account->capabilities().filesLockAvailable() &&
        (FileSystem::isMatchingOfficeFileExtension(item->_file) || FileSystem::isMatchingAutoCADDocumentExtension(item->_file) || FileSystem::isMatchingAdobeDocumentExtension(item->_file) || FileSystem::isMatchingAffinityDocumentExtension(item->_file))) {
        {
            SyncJournalFileRecord rec;
            if (!_journal->getFileRecord(item->_file, &rec) || !rec.isValid()) {
                qCWarning(lcEngine) << "Newly-created office file just uploaded but not in sync journal. Not going to lock it." << item->_file;
                return;
            }
        }
        const auto localFilePath = _propagator->fullLocalPath(item->_file);
        const auto allMatchingLockFiles = FileSystem::findAllLockFilesInDir(QFileInfo(localFilePath).absolutePath());
        for (const auto &lockFilePath : allMatchingLockFiles) {
            const auto checkResult = FileSystem::lockFileTargetFilePath(lockFilePath, FileSystem::filePathLockFilePatternMatch(lockFilePath));
            if (checkResult.type == FileSystem::FileLockingInfo::Type::Locked && checkResult.path == localFilePath) {
                qCInfo(lcEngine) << "Newly-created office file lock detected. Let FolderWatcher take it from here..." << item->_file;
                emit lockFileDetected(lockFilePath);
            }
        }
    }
}

void SyncEngine::setNetworkLimits(int upload, int download)
{
    _uploadLimit = upload;
    _downloadLimit = download;

    if (!_propagator)
        return;

    _propagator->_uploadLimit = upload;
    _propagator->_downloadLimit = download;

    if (upload != 0 || download != 0) {
        qCInfo(lcEngine) << "Network Limits (down/up) " << upload << download;
    }
}

void SyncEngine::slotItemCompleted(const SyncFileItemPtr &item, const ErrorCategory category)
{
    _progressInfo->setProgressComplete(*item);

    emit transmissionProgress(*_progressInfo);
    emit itemCompleted(item, category);

    detectFileLock(item);
}

void SyncEngine::slotPropagationFinished(OCC::SyncFileItem::Status status)
{
    if (_propagator->_anotherSyncNeeded && _anotherSyncNeeded == NoFollowUpSync) {
        _anotherSyncNeeded = ImmediateFollowUp;
    }

    if ((status == SyncFileItem::Success || status == SyncFileItem::BlacklistedError) && _discoveryPhase) {
        _journal->setDataFingerprint(_discoveryPhase->_dataFingerprint);
    }

    conflictRecordMaintenance();
    caseClashConflictRecordMaintenance();

    _journal->deleteStaleFlagsEntries();
    _journal->commit("All Finished.", false);

    // Send final progress information even if no
    // files needed propagation, but clear the lastCompletedItem
    // so we don't count this twice (like Recent Files)
    _progressInfo->_lastCompletedItem = SyncFileItem();
    _progressInfo->_status = ProgressInfo::Done;
    emit transmissionProgress(*_progressInfo);

    finalize(status == SyncFileItem::Success);
}

void SyncEngine::finalize(bool success)
{
    setSingleItemDiscoveryOptions({});

    qCInfo(lcEngine) << "Sync run took " << _stopWatch.addLapTime(QLatin1String("Sync Finished")) << "ms";
    _stopWatch.stop();

    if (_discoveryPhase) {
        _discoveryPhase.release()->deleteLater();
    }
    s_anySyncRunning = false;
    _syncRunning = false;
    emit finished(success);

    if (_account->shouldSkipE2eeMetadataChecksumValidation()) {
        qCDebug(lcEngine) << "shouldSkipE2eeMetadataChecksumValidation was set. Sync is finished, so resetting it...";
        _account->resetShouldSkipE2eeMetadataChecksumValidation();
    }

    // Delete the propagator only after emitting the signal.
    _propagator.clear();
    _seenConflictFiles.clear();
    _uniqueErrors.clear();
    _localDiscoveryPaths.clear();
    _localDiscoveryStyle = LocalDiscoveryStyle::FilesystemOnly;

    _clearTouchedFilesTimer.start();
    _leadingAndTrailingSpacesFilesAllowed.clear();
}

void SyncEngine::processCaseClashConflictsBeforeDiscovery()
{
    QSet<QByteArray> pathsToAppend;
    const auto caseClashConflictPaths = _journal->caseClashConflictRecordPaths();
    for (const auto &caseClashConflictPath : caseClashConflictPaths) {
        auto caseClashPathSplit = caseClashConflictPath.split('/');
        if (caseClashPathSplit.size() > 1) {
            caseClashPathSplit.removeLast();
            pathsToAppend.insert(caseClashPathSplit.join('/'));
        }
    }

    for (const auto &pathToAppend : pathsToAppend) {
        _journal->schedulePathForRemoteDiscovery(pathToAppend);
    }
}

void SyncEngine::slotProgress(const SyncFileItem &item, qint64 current)
{
    _progressInfo->setProgressItem(item, current);
    emit transmissionProgress(*_progressInfo);
}


void SyncEngine::restoreOldFiles(SyncFileItemVector &syncItems)
{
    /* When the server is trying to send us lots of file in the past, this means that a backup
       was restored in the server.  In that case, we should not simply overwrite the newer file
       on the file system with the older file from the backup on the server. Instead, we will
       upload the client file. But we still downloaded the old file in a conflict file just in case
    */

    for (const auto &syncItem : std::as_const(syncItems)) {
        if (syncItem->_direction != SyncFileItem::Down || syncItem->_isSelectiveSync) {
            continue;
        }

        switch (syncItem->_instruction) {
        case CSYNC_INSTRUCTION_SYNC:
            qCWarning(lcEngine) << "restoreOldFiles: RESTORING" << syncItem->_file;
            syncItem->_instruction = CSYNC_INSTRUCTION_CONFLICT;
            break;
        case CSYNC_INSTRUCTION_REMOVE:
            if (syncItem->_type != CSyncEnums::ItemTypeVirtualFile && syncItem->_type != CSyncEnums::ItemTypeVirtualFileDownload) {
                qCWarning(lcEngine) << "restoreOldFiles: RESTORING" << syncItem->_file;
                syncItem->_instruction = CSYNC_INSTRUCTION_NEW;
                syncItem->_direction = SyncFileItem::Up;
            }
            break;
        case CSYNC_INSTRUCTION_RENAME:
        case CSYNC_INSTRUCTION_NEW:
            // Ideally we should try to revert the rename or remove, but this would be dangerous
            // without re-doing the reconcile phase.  So just let it happen.
        default:
            break;
        }
    }
}

void SyncEngine::cancelSyncOrContinue(bool cancel)
{
    if (cancel) {
        qCInfo(lcEngine) << "User aborted sync";
        finalize(false);
    } else {
        finishSync();
    }
}

void SyncEngine::finishSync()
{
    auto databaseFingerprint = _journal->dataFingerprint();
    // If databaseFingerprint is empty, this means that there was no information in the database
    // (for example, upgrading from a previous version, or first sync, or server not supporting fingerprint)
    if (!databaseFingerprint.isEmpty() && _discoveryPhase
        && _discoveryPhase->_dataFingerprint != databaseFingerprint) {
        qCInfo(lcEngine) << "data fingerprint changed, assume restore from backup" << databaseFingerprint << _discoveryPhase->_dataFingerprint;
        restoreOldFiles(_syncItems);
    }

    if (_discoveryPhase && _discoveryPhase->_anotherSyncNeeded && !_discoveryPhase->_filesNeedingScheduledSync.empty()) {
        slotScheduleFilesDelayedSync();
    } else if (_discoveryPhase && _discoveryPhase->_anotherSyncNeeded && _anotherSyncNeeded == NoFollowUpSync) {
        _anotherSyncNeeded = ImmediateFollowUp;
    }

    if (_discoveryPhase && !_discoveryPhase->_filesUnscheduleSync.empty()) {
        slotUnscheduleFilesDelayedSync();
    }

    if (_discoveryPhase && _discoveryPhase->_hasDownloadRemovedItems && _discoveryPhase->_hasUploadErrorItems) {
        for (const auto &item : std::as_const(_syncItems)) {
            if (item->_instruction == CSYNC_INSTRUCTION_ERROR && item->_direction == SyncFileItem::Up) {
                // item->_instruction = CSYNC_INSTRUCTION_IGNORE;
            }
        }
        _anotherSyncNeeded = ImmediateFollowUp;
    }

    Q_ASSERT(std::is_sorted(_syncItems.begin(), _syncItems.end()));

    qCInfo(lcEngine) << "#### Reconcile (aboutToPropagate) #################################################### " << _stopWatch.addLapTime(QStringLiteral("Reconcile (aboutToPropagate)")) << "ms";

    _localDiscoveryPaths.clear();

    // To announce the beginning of the sync
    emit aboutToPropagate(_syncItems);

    qCInfo(lcEngine) << "#### Reconcile (aboutToPropagate OK) #################################################### "<< _stopWatch.addLapTime(QStringLiteral("Reconcile (aboutToPropagate OK)")) << "ms";

    // it's important to do this before ProgressInfo::start(), to announce start of new sync
    _progressInfo->_status = ProgressInfo::Propagation;
    emit transmissionProgress(*_progressInfo);
    _progressInfo->startEstimateUpdates();

    // do a database commit
    _journal->commit(QStringLiteral("post treewalk"));

    _propagator = QSharedPointer<OwncloudPropagator>(
        new OwncloudPropagator(_account, _localPath, _remotePath, _journal, _bulkUploadBlackList));
    _propagator->setSyncOptions(_syncOptions);
    connect(_propagator.data(), &OwncloudPropagator::itemCompleted,
            this, &SyncEngine::slotItemCompleted);
    connect(_propagator.data(), &OwncloudPropagator::progress,
            this, &SyncEngine::slotProgress);
    connect(_propagator.data(), &OwncloudPropagator::finished, this, &SyncEngine::slotPropagationFinished, Qt::QueuedConnection);
    connect(_propagator.data(), &OwncloudPropagator::seenLockedFile, this, &SyncEngine::seenLockedFile);
    connect(_propagator.data(), &OwncloudPropagator::touchedFile, this, &SyncEngine::slotAddTouchedFile);
    connect(_propagator.data(), &OwncloudPropagator::insufficientLocalStorage, this, &SyncEngine::slotInsufficientLocalStorage);
    connect(_propagator.data(), &OwncloudPropagator::insufficientRemoteStorage, this, &SyncEngine::slotInsufficientRemoteStorage);
    connect(_propagator.data(), &OwncloudPropagator::newItem, this, &SyncEngine::slotNewItem);

    // apply the network limits to the propagator
    setNetworkLimits(_uploadLimit, _downloadLimit);

    deleteStaleDownloadInfos(_syncItems);
    deleteStaleUploadInfos(_syncItems);
    deleteStaleErrorBlacklistEntries(_syncItems);
    _journal->commit(QStringLiteral("post stale entry removal"));

    // Emit the started signal only after the propagator has been set up.
    if (_needsUpdate)
        Q_EMIT started();

    _propagator->start(std::move(_syncItems));

    qCInfo(lcEngine) << "#### Post-Reconcile end #################################################### " << _stopWatch.addLapTime(QStringLiteral("Post-Reconcile Finished")) << "ms";
}

bool SyncEngine::shouldRestartSync() const
{
    // On Windows with cfapi enabled it's possible that the discovery phase didn't detect all changed files.
    //
    // There is a disconnect between file system events reported and what the low-level file system APIs
    // return -- it's possible that a folder did not yet contain the changed files on the file system even
    // though these files were already reported by the folder watcher.  This sometimes happens when moving a
    // directory from one place to another; in that case the rename would not be caught during the discovery
    // phase, resulting in a remote delete operation of the folder at the original path.
    //
    // It's better to restart the sync a bit later to ensure we didn't miss anything.

    if (_restartedSyncAfterDiscovery) {
        // This is the second attempt: assume the discovery result is complete.
        return false;
    }

    if (const auto vfs = _syncOptions._vfs; vfs && vfs->mode() != Vfs::WindowsCfApi) {
        // Not using cfapi -- no issue there.
        return false;
    }

    for (const auto &syncItem : _syncItems) {
        // If there's at least one remove instruction to be propagated to the remote: bail out, we might have lost a local rename.
        if (syncItem->_instruction == CSYNC_INSTRUCTION_REMOVE && syncItem->_direction == SyncFileItem::Up) {
            return true;
        }
    }
    return false;
}

bool SyncEngine::handleMassDeletion()
{
    const auto displayDialog = ConfigFile().promptDeleteFiles() && !_syncOptions.isCmd();
    const auto allFilesDeleted = !_hasNoneFiles && _hasRemoveFile;

    auto deletionCounter = 0;
    for (const auto &oneItem : std::as_const(_syncItems)) {
        if (oneItem->_instruction == CSYNC_INSTRUCTION_REMOVE) {
            if (oneItem->isDirectory()) {
                const auto result = _journal->listFilesInPath(oneItem->_file.toUtf8(), [&deletionCounter] (const auto &oneRecord) {
                    if (oneRecord.isFile()) {
                        ++deletionCounter;
                    }
                });
                if (!result) {
                    qCDebug(lcEngine()) << "unable to find the number of files within a deleted folder:" << oneItem->_file;
                }
            } else {
                ++deletionCounter;
            }
        }
    }
    const auto filesDeletedThresholdExceeded = deletionCounter > ConfigFile().deleteFilesThreshold();

    if ((allFilesDeleted || filesDeletedThresholdExceeded) && displayDialog) {
        qCWarning(lcEngine) << "Many files are going to be deleted, asking the user";
        int side = 0; // > 0 means more deleted on the server.  < 0 means more deleted on the client
        for (const auto &it : std::as_const(_syncItems)) {
            if (it->_instruction == CSYNC_INSTRUCTION_REMOVE) {
                side += it->_direction == SyncFileItem::Down ? 1 : -1;
            }
        }

        promptUserBeforePropagation([this, side](auto &&callback){
            emit aboutToRemoveAllFiles(side >= 0 ? SyncFileItem::Down : SyncFileItem::Up, callback);
        });
        return true;
    }
    return false;
}

void SyncEngine::handleRemnantReadOnlyFolders()
{
    auto listOfFolders = QStringList{};
    for (const auto &oneFolder : std::as_const(_remnantReadOnlyFolders)) {
        listOfFolders.push_back(oneFolder->_file);
    }

    qCInfo(lcEngine()) << "will delete invalid read-only folders:" << listOfFolders.join(", ");

    for(const auto &oneFolder : std::as_const(_remnantReadOnlyFolders)) {
        const auto fileInfo = QFileInfo{_localPath + oneFolder->_file};
        const auto parentFolderPath = fileInfo.dir().absolutePath();
        slotAddTouchedFile(parentFolderPath);
        const auto parentPermissionsHandler = FileSystem::FilePermissionsRestore{parentFolderPath, FileSystem::FolderPermissions::ReadWrite};
        slotAddTouchedFile(_localPath + oneFolder->_file);

        if (oneFolder->_type == ItemType::ItemTypeDirectory) {
            const auto deletionCallback = [this] (const QString &deleteItem, bool) {
                slotAddTouchedFile(deleteItem);
            };

            qCInfo(lcEngine()) << "delete" << _localPath + oneFolder->_file;
            FileSystem::removeRecursively(_localPath + oneFolder->_file, deletionCallback, nullptr, deletionCallback);
        } else {
            FileSystem::remove(_localPath + oneFolder->_file);
        }
    }
}

template <typename T>
void SyncEngine::promptUserBeforePropagation(T &&lambda)
{
    QPointer<QObject> guard = new QObject();
    QPointer<QObject> self = this;
    auto callback = [this, self, guard](bool cancel) -> void {
        // use a guard to ensure its only called once...
        // qpointer to self to ensure we still exist
        if (!guard || !self) {
            return;
        }
        guard->deleteLater();

        cancelSyncOrContinue(cancel);
    };

    lambda(callback);
}

void SyncEngine::slotAddTouchedFile(const QString &fn)
{
    QElapsedTimer now;
    now.start();
    QString file = QDir::cleanPath(fn);

    // Iterate from the oldest and remove anything older than 15 seconds.
    while (true) {
        auto first = _touchedFiles.begin();
        if (first == _touchedFiles.end())
            break;
        // Compare to our new QElapsedTimer instead of using elapsed().
        // This avoids querying the current time from the OS for every loop.
        auto elapsed = std::chrono::milliseconds(now.msecsSinceReference() - first.key().msecsSinceReference());
        if (elapsed <= s_touchedFilesMaxAgeMs) {
            // We found the first path younger than the maximum age, keep the rest.
            break;
        }

        _touchedFiles.erase(first);
    }

    // This should be the largest QElapsedTimer yet, use constEnd() as hint.
    _touchedFiles.insert(_touchedFiles.constEnd(), now, file);
}

void SyncEngine::slotClearTouchedFiles()
{
    _touchedFiles.clear();
}

void SyncEngine::addAcceptedInvalidFileName(const QString& filePath)
{
    _leadingAndTrailingSpacesFilesAllowed.append(filePath);
}

void SyncEngine::setLocalDiscoveryEnforceWindowsFileNameCompatibility(bool value)
{
    _shouldEnforceWindowsFileNameCompatibility = value;
}

bool SyncEngine::wasFileTouched(const QString &fn) const
{
    // Start from the end (most recent) and look for our path. Check the time just in case.
    auto begin = _touchedFiles.constBegin();
    for (auto it = _touchedFiles.constEnd(); it != begin; --it) {
        if (const auto prevIt = std::prev(it); prevIt.value() == fn)
            return std::chrono::milliseconds(prevIt.key().elapsed()) <= s_touchedFilesMaxAgeMs;
    }
    return false;
}

void SyncEngine::setLocalDiscoveryOptions(LocalDiscoveryStyle style, std::set<QString> paths)
{
    _localDiscoveryStyle = style;
    _localDiscoveryPaths = std::move(paths);

    if (lcEngine().isDebugEnabled() && !_localDiscoveryPaths.empty()) {
        // only execute if logging is enabled
        auto debug = qDebug(lcEngine);
        debug << "paths to discover locally";
        for (const auto &path : _localDiscoveryPaths) {
            debug << path;
        }
    }

    // Normalize to make sure that no path is a contained in another.
    // Note: for simplicity, this code consider anything less than '/' as a path separator, so for
    // example, this will remove "foo.bar" if "foo" is in the list. This will mean we might have
    // some false positive, but that's Ok.
    // This invariant is used in SyncEngine::shouldDiscoverLocally
    QString prev;
    auto it = _localDiscoveryPaths.begin();
    while(it != _localDiscoveryPaths.end()) {
        if (!prev.isNull() && it->startsWith(prev) && (prev.endsWith('/') || *it == prev || it->at(prev.size()) <= '/')) {
            it = _localDiscoveryPaths.erase(it);
        } else {
            prev = *it;
            ++it;
        }
    }
}

void SyncEngine::setSingleItemDiscoveryOptions(const SingleItemDiscoveryOptions &singleItemDiscoveryOptions)
{
    _singleItemDiscoveryOptions = singleItemDiscoveryOptions;
}

const SyncEngine::SingleItemDiscoveryOptions &SyncEngine::singleItemDiscoveryOptions() const
{
    return _singleItemDiscoveryOptions;
}

void SyncEngine::setFilesystemPermissionsReliable(bool reliable)
{
    _filesystemPermissionsReliable = reliable;
}

bool SyncEngine::shouldDiscoverLocally(const QString &path) const
{
    auto result = false;

    if (_localDiscoveryStyle == LocalDiscoveryStyle::FilesystemOnly) {
        result = true;
        return result;
    }

    // The intention is that if "A/X" is in _localDiscoveryPaths:
    // - parent folders like "/", "A" will be discovered (to make sure the discovery reaches the
    //   point where something new happened)
    // - the folder itself "A/X" will be discovered
    // - subfolders like "A/X/Y" will be discovered (so data inside a new or renamed folder will be
    //   discovered in full)
    // Check out TestLocalDiscovery::testLocalDiscoveryDecision()

    auto it = _localDiscoveryPaths.lower_bound(path);
    if (it == _localDiscoveryPaths.end() || !it->startsWith(path)) {
        // Maybe a subfolder of something in the list?
        if (it != _localDiscoveryPaths.begin() && path.startsWith(*(--it))) {
            result = it->endsWith('/') || (path.size() > it->size() && path.at(it->size()) <= '/');
            if (!result) {
                qCDebug(lcEngine()) << path << "no local discovery needed";
            }
            return result;
        }
        result = false;
        qCDebug(lcEngine()) << path << "no local discovery needed";
        return result;
    }

    // maybe an exact match or an empty path?
    if (it->size() == path.size() || path.isEmpty()) {
        return true;
    }

    // Maybe a parent folder of something in the list?
    // check for a prefix + / match
    forever {
        if (it->size() > path.size() && it->at(path.size()) == '/') {
            result = true;
            return result;
        }

        ++it;
        if (it == _localDiscoveryPaths.end() || !it->startsWith(path)) {
            result = false;
            qCDebug(lcEngine()) << path << "no local discovery needed";
            return result;
        }
    }

    qCDebug(lcEngine()) << path << "no local discovery needed";
    return result;
}

void SyncEngine::wipeVirtualFiles(const QString &localPath, SyncJournalDb &journal, Vfs &vfs)
{
    qCInfo(lcEngine) << "Wiping virtual files inside" << localPath;
    const auto resGetFilesBelowPath = journal.getFilesBelowPath(QByteArray(), [&](const SyncJournalFileRecord &rec) {
        if (rec._type != ItemTypeVirtualFile && rec._type != ItemTypeVirtualFileDownload && rec._type != ItemTypeVirtualDirectory) {
            return;
        }

        qCDebug(lcEngine) << "Removing db record for" << rec.path();
        if (!journal.deleteFileRecord(rec._path)) {
            qCWarning(lcEngine) << "Could not update delete file record" << rec._path;
        }

        // If the local file is a dehydrated placeholder, wipe it too.
        // Otherwise leave it to allow the next sync to have a new-new conflict.
        QString localFile = localPath + rec._path;
        if (FileSystem::fileExists(localFile) && vfs.isDehydratedPlaceholder(localFile)) {
            qCDebug(lcEngine) << "Removing local dehydrated placeholder" << rec.path();
            QFile::remove(localFile);
        }
    });

    if (!resGetFilesBelowPath) {
        qCWarning(lcEngine) << "Failed to get files below path" << localPath;
    }

    journal.forceRemoteDiscoveryNextSync();

    // Postcondition: No ItemTypeVirtualFile / ItemTypeVirtualFileDownload left in the db.
    // But hydrated placeholders may still be around.
}

void SyncEngine::switchToVirtualFiles(const QString &localPath, SyncJournalDb &journal, Vfs &vfs)
{
    qCInfo(lcEngine) << "Convert to virtual files inside" << localPath;
    const auto res = journal.getFilesBelowPath({}, [&](const SyncJournalFileRecord &rec) {
        const auto path = rec.path();
        const auto fileName = QFileInfo(path).fileName();
        if (FileSystem::isExcludeFile(fileName)) {
            return;
        }
        SyncFileItem item;
        QString localFile = localPath + path;
        const auto result = vfs.convertToPlaceholder(localFile, item, localFile);
        if (!result.isValid()) {
            qCWarning(lcEngine) << "Could not convert file to placeholder" << result.error();
        }
    });

    if (!res) {
        qCWarning(lcEngine) << "Failed to get files below path" << localPath;
    }
}

void SyncEngine::abort()
{
    if (_propagator) {
        // If we're already in the propagation phase, aborting that is sufficient
        qCInfo(lcEngine) << "Aborting sync in propagator...";
        _propagator->abort();
    } else if (_discoveryPhase) {
        // Delete the discovery and all child jobs after ensuring
        // it can't finish and start the propagator
        disconnect(_discoveryPhase.get(), nullptr, this, nullptr);
        _discoveryPhase.release()->deleteLater();
        qCInfo(lcEngine) << "Aborting sync in discovery...";
        finalize(false);
    }
}

void SyncEngine::slotSummaryError(const QString &message)
{
    if (_uniqueErrors.contains(message))
        return;

    _uniqueErrors.insert(message);
    emit syncError(message, ErrorCategory::GenericError);
}

void SyncEngine::slotInsufficientLocalStorage()
{
    slotSummaryError(
        tr("Disk space is low: Downloads that would reduce free space "
           "below %1 were skipped.")
            .arg(Utility::octetsToString(freeSpaceLimit())));
}

void SyncEngine::slotInsufficientRemoteStorage()
{
    auto msg = tr("There is insufficient space available on the server for some uploads.");
    if (_uniqueErrors.contains(msg)) {
        return;
    }

    _uniqueErrors.insert(msg);
    emit syncError(msg, ErrorCategory::InsufficientRemoteStorage);
}

void SyncEngine::slotScheduleFilesDelayedSync()
{
    if (!_discoveryPhase || _discoveryPhase->_filesNeedingScheduledSync.empty()) {
        return;
    }

    // The latest sync of the interval bucket is the one that goes through and is used in the timer.
    // By running the sync run as late as possible in the selected interval, we try to strike a
    // balance between updating the needed file in a timely manner while also syncing late enough
    // to cover all the files in the interval bucket.

    static constexpr qint64 intervalSecs = 60;
    const auto scheduledSyncBuckets = groupNeededScheduledSyncRuns(intervalSecs);

    qCDebug(lcEngine) << "Active scheduled sync run timers:" << _scheduledSyncTimers.count();

    for (const auto &[scheduledSyncTimerSecs, filesAffected] : scheduledSyncBuckets) {

        const auto currentSecsSinceEpoch = QDateTime::currentSecsSinceEpoch();
        const auto scheduledSyncTimerTime = QDateTime::fromSecsSinceEpoch(currentSecsSinceEpoch + scheduledSyncTimerSecs);
        const auto scheduledSyncTimerMsecs = std::chrono::milliseconds(scheduledSyncTimerSecs * 1000);

        const auto addFilesToTimerAndScheduledHash = [this, &files = filesAffected] (const QSharedPointer<ScheduledSyncTimer> &timer) {
            for (const auto &file : files) {
                timer->files.insert(file);
                _filesScheduledForLaterSync.insert(file, timer);
            }
        };

        // We want to make sure that this bucket won't schedule a sync near a pre-existing sync run,
        // as we often get, for example, locked file notifications one by one as the user interacts
        // through the web.

        const auto nearbyTimer = nearbyScheduledSyncTimer(scheduledSyncTimerSecs, intervalSecs);

        if (nearbyTimer) {
            addFilesToTimerAndScheduledHash(nearbyTimer);
            qCInfo(lcEngine) << "Using a nearby scheduled sync run at:" << scheduledSyncTimerTime
                             << "for files:" << filesAffected
                             << "this timer is now resoponsible for files:" << nearbyTimer->files;
            continue;
        }

        qCInfo(lcEngine) << "Will have a new sync run in" << scheduledSyncTimerSecs
                         << "seconds, at" << scheduledSyncTimerTime
                         << "for files:" << filesAffected;

        QSharedPointer<ScheduledSyncTimer> newTimer(new ScheduledSyncTimer);
        newTimer->setSingleShot(true);
        newTimer->callOnTimeout(this, [this, newTimer] {
            qCInfo(lcEngine) << "Rescanning now that delayed sync run is scheduled for:" << newTimer->files;

            for (const auto &file : std::as_const(newTimer->files)) {
                this->_filesScheduledForLaterSync.remove(file);
            }

            this->startSync();
            this->slotCleanupScheduledSyncTimers();
        });

        addFilesToTimerAndScheduledHash(newTimer);
        qCDebug(lcEngine) << "automated sync will be fired at" << scheduledSyncTimerMsecs;
        newTimer->start(scheduledSyncTimerMsecs);
        _scheduledSyncTimers.append(newTimer);
    }
}

QHash<qint64, SyncEngine::ScheduledSyncBucket> SyncEngine::groupNeededScheduledSyncRuns(const qint64 interval) const
{
    if (!_discoveryPhase || _discoveryPhase->_filesNeedingScheduledSync.empty()) {
        return {};
    }

    QHash<qint64, ScheduledSyncBucket> intervalSyncBuckets;

    for (auto it = _discoveryPhase->_filesNeedingScheduledSync.cbegin();
         it != _discoveryPhase->_filesNeedingScheduledSync.cend();
         ++it) {

        const auto file = it.key();
        const auto syncScheduledSecs = it.value();

        // We don't want to schedule syncs again for files we have already discovered needing a
        // scheduled sync, unless the files have been re-locked or had their lock expire time
        // extended. So we check the time-out of the already set timer with the time-out we
        // receive from the server entry
        //
        // Since the division here is both of ints, we receive a "floor" of the division, so we
        // are safe from a possible situation where the timer's interval is lower than we need
        // for the file we are possibly scheduling a sync run for

        if (_filesScheduledForLaterSync.contains(file) &&
            _filesScheduledForLaterSync.value(file)->interval() / 1000 >= syncScheduledSecs) {

            continue;
        }

        // Both qint64 so division results in floor-ed result
        const auto intervalBucketKey = syncScheduledSecs / interval;

        if (!intervalSyncBuckets.contains(intervalBucketKey)) {
            intervalSyncBuckets.insert(intervalBucketKey, {syncScheduledSecs, {file}});
            continue;
        }

        auto bucketValue = intervalSyncBuckets.value(intervalBucketKey);
        bucketValue.scheduledSyncTimerSecs = qMax(bucketValue.scheduledSyncTimerSecs, syncScheduledSecs);
        bucketValue.files.append(file);
        intervalSyncBuckets.insert(intervalBucketKey, bucketValue);
    }

    return intervalSyncBuckets;
}

QSharedPointer<SyncEngine::ScheduledSyncTimer> SyncEngine::nearbyScheduledSyncTimer(const qint64 scheduledSyncTimerSecs,
                                                                                    const qint64 intervalSecs) const
{
    const auto scheduledSyncTimerMsecs = scheduledSyncTimerSecs * 1000;
    const auto halfIntervalMsecs = (intervalSecs * 1000) / 2;

    for (const auto &scheduledTimer : _scheduledSyncTimers) {

        const auto timerRemainingMsecs = scheduledTimer->remainingTime();
        const auto differenceMsecs = timerRemainingMsecs - scheduledSyncTimerMsecs;
        const auto nearbyScheduledSync = differenceMsecs > -halfIntervalMsecs &&
                                         differenceMsecs < halfIntervalMsecs;

        // Iterated timer is going to fire slightly before we need it to for the parameter timer, delay it.
        if (differenceMsecs > -halfIntervalMsecs && differenceMsecs < 0) {

            const auto scheduledSyncTimerTimeoutMsecs = std::chrono::milliseconds(scheduledSyncTimerMsecs);
            scheduledTimer->start(scheduledSyncTimerTimeoutMsecs);

            qCDebug(lcEngine) << "Delayed sync timer with remaining time" << timerRemainingMsecs / 1000
                              << "by" << (differenceMsecs * -1) / 1000
                              << "seconds due to nearby new sync run needed.";
        }

        if(nearbyScheduledSync) {
            return scheduledTimer;
        }
    }

    return {};
}

void SyncEngine::slotCleanupScheduledSyncTimers()
{
    qCDebug(lcEngine) << "Beginning scheduled sync timer cleanup.";

    auto it = _scheduledSyncTimers.begin();

    while(it != _scheduledSyncTimers.end()) {
        const auto &timer = *it;
        auto eraseTimer = false;

        if(timer && (timer->files.empty() || !timer->isActive())) {
            qCInfo(lcEngine) << "Stopping and erasing an expired/empty scheduled sync run timer.";
            timer->stop();
            eraseTimer = true;
        } else if (!timer) {
            qCInfo(lcEngine) << "Erasing a null scheduled sync run timer.";
            eraseTimer = true;
        }

        if(eraseTimer) {
            it = _scheduledSyncTimers.erase(it);
        } else {
            ++it;
        }
    }
}

void SyncEngine::remnantReadOnlyFolderDiscovered(const SyncFileItemPtr &item)
{
    _remnantReadOnlyFolders.push_back(item);
}

void SyncEngine::slotUnscheduleFilesDelayedSync()
{
    if (!_discoveryPhase || _discoveryPhase->_filesUnscheduleSync.empty()) {
        return;
    }

    for (const auto &file : std::as_const(_discoveryPhase->_filesUnscheduleSync)) {
        const auto fileSyncRunTimer = _filesScheduledForLaterSync.value(file);

        if (fileSyncRunTimer) {
            fileSyncRunTimer->files.remove(file);

            // Below is only needed for logging
            const auto currentMSecsSinceEpoch = QDateTime::currentMSecsSinceEpoch();
            const auto scheduledSyncTimerMSecs = fileSyncRunTimer->remainingTime();
            const auto timerExpireDate = QDateTime::fromMSecsSinceEpoch(currentMSecsSinceEpoch + scheduledSyncTimerMSecs);
            qCInfo(lcEngine) << "Removed" << file << "from sync run timer elapsing at" << timerExpireDate
                             << "this timer is still running for files:" << fileSyncRunTimer->files;
        }
    }

    slotCleanupScheduledSyncTimers();
}

} // namespace OCC
