/*
 * Copyright (C) by Duncan Mac-Vicar P. <duncan@kde.org>
 * Copyright (C) by Klaas Freitag <freitag@owncloud.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 */

#pragma once

#include <cstdint>

#include <QMutex>
#include <QThread>
#include <QString>
#include <QSet>
#include <QMap>
#include <QStringList>
#include <QSharedPointer>
#include <set>

#include "syncfileitem.h"
#include "progressdispatcher.h"
#include "common/utility.h"
#include "syncfilestatustracker.h"
#include "accountfwd.h"
#include "discoveryphase.h"
#include "common/checksums.h"

class QProcess;

namespace OCC {

class SyncJournalFileRecord;
class SyncJournalDb;
class OwncloudPropagator;
class ProcessDirectoryJob;

enum AnotherSyncNeeded {
    NoFollowUpSync,
    ImmediateFollowUp, // schedule this again immediately (limited amount of times)
    DelayedFollowUp // regularly schedule this folder again (around 1/minute, unlimited)
};

/**
 * @brief The SyncEngine class
 * @ingroup libsync
 */
class OWNCLOUDSYNC_EXPORT SyncEngine : public QObject
{
    Q_OBJECT
public:
    struct OWNCLOUDSYNC_EXPORT SingleItemDiscoveryOptions {
        QString discoveryPath;
        QString filePathRelative;
        SyncFileItemPtr discoveryDirItem;

        [[nodiscard]] bool isValid() const;
    };

    SyncEngine(AccountPtr account,
               const QString &localPath,
               const SyncOptions &syncOptions,
               const QString &remotePath,
               SyncJournalDb *journal);

    ~SyncEngine() override;

    [[nodiscard]] bool isSyncRunning() const { return _syncRunning; }

    [[nodiscard]] SyncOptions syncOptions() const { return _syncOptions; }
    [[nodiscard]] bool ignoreHiddenFiles() const { return _ignore_hidden_files; }

    [[nodiscard]] ExcludedFiles &excludedFiles() const { return *_excludedFiles; }
    [[nodiscard]] SyncFileStatusTracker &syncFileStatusTracker() const { return *_syncFileStatusTracker; }

    /* Returns whether another sync is needed to complete the sync */
    [[nodiscard]] AnotherSyncNeeded isAnotherSyncNeeded() const { return _anotherSyncNeeded; }

    [[nodiscard]] bool wasFileTouched(const QString &fn) const;

    [[nodiscard]] AccountPtr account() const { return _account; };
    [[nodiscard]] SyncJournalDb *journal() const { return _journal; }
    [[nodiscard]] QString localPath() const { return _localPath; }

    /** Duration in ms that uploads should be delayed after a file change
     *
     * In certain situations a file can be written to very regularly over a large
     * amount of time. Copying a large file could take a while. A logfile could be
     * updated every second.
     *
     * In these cases it isn't desirable to attempt to upload the "unfinished" file.
     * To avoid that, uploads of files where the distance between the mtime and the
     * current time is less than this duration are skipped.
     */
    static std::chrono::milliseconds minimumFileAgeForUpload;

    /**
     * Returns whether the given folder-relative path should be locally discovered
     * given the local discovery options.
     *
     * Example: If path is 'foo/bar' and style is DatabaseAndFilesystem and dirs contains
     *     'foo/bar/touched_file', then the result will be true.
     */
    [[nodiscard]] bool shouldDiscoverLocally(const QString &path) const;

    /** Access the last sync run's local discovery style */
    [[nodiscard]] LocalDiscoveryStyle lastLocalDiscoveryStyle() const { return _lastLocalDiscoveryStyle; }

    /** Removes all virtual file db entries and dehydrated local placeholders.
     *
     * Particularly useful when switching off vfs mode or switching to a
     * different kind of vfs.
     *
     * Note that *hydrated* placeholder files might still be left. These will
     * get cleaned up by Vfs::unregisterFolder().
     */
    static void wipeVirtualFiles(const QString &localPath, SyncJournalDb &journal, Vfs &vfs);

    static void switchToVirtualFiles(const QString &localPath, SyncJournalDb &journal, Vfs &vfs);

    [[nodiscard]] QSharedPointer<OwncloudPropagator> getPropagator() const { return _propagator; } // for the test
    [[nodiscard]] const SyncEngine::SingleItemDiscoveryOptions &singleItemDiscoveryOptions() const;

public slots:
    void setSingleItemDiscoveryOptions(const OCC::SyncEngine::SingleItemDiscoveryOptions &singleItemDiscoveryOptions);

    void startSync();

    /* Abort the sync.  Called from the main thread */
    void abort();

    void setNetworkLimits(int upload, int download);
    void setSyncOptions(const OCC::SyncOptions &options) { _syncOptions = options; }
    void setIgnoreHiddenFiles(bool ignore) { _ignore_hidden_files = ignore; }

    /**
     * Control whether local discovery should read from filesystem or db.
     *
     * If style is DatabaseAndFilesystem, paths a set of file paths relative to
     * the synced folder. All the parent directories of these paths will not
     * be read from the db and scanned on the filesystem.
     *
     * Note, the style and paths are only retained for the next sync and
     * revert afterwards. Use _lastLocalDiscoveryStyle to discover the last
     * sync's style.
     */
    void setLocalDiscoveryOptions(OCC::LocalDiscoveryStyle style, std::set<QString> paths = {});
    void addAcceptedInvalidFileName(const QString& filePath);

signals:
    // During update, before reconcile
    void rootEtag(const QByteArray &, const QDateTime &);

    // after the above signals. with the items that actually need propagating
    void aboutToPropagate(OCC::SyncFileItemVector &);

    // after each item completed by a job (successful or not)
    void itemCompleted(const OCC::SyncFileItemPtr &item, const OCC::ErrorCategory category);

    void transmissionProgress(const OCC::ProgressInfo &progress);

    void itemDiscovered(const OCC::SyncFileItemPtr &);

    /// We've produced a new sync error of a type.
    void syncError(const QString &message, const OCC::ErrorCategory category);

    void addErrorToGui(const OCC::SyncFileItem::Status status, const QString &errorMessage, const QString &subject, const OCC::ErrorCategory category);

    void finished(bool success);
    void started();

    /**
     * Emitted when the sync engine detects that all the files have been removed or change.
     * This usually happen when the server was reset or something.
     * Set *cancel to true in a slot connected from this signal to abort the sync.
     */
    void aboutToRemoveAllFiles(OCC::SyncFileItem::Direction direction, std::function<void(bool)> f);

    // A new folder was discovered and was not synced because of the confirmation feature
    void newBigFolder(const QString &folder, bool isExternal);

    /** Emitted when propagation has problems with a locked file.
     *
     * Forwarded from OwncloudPropagator::seenLockedFile.
     */
    void seenLockedFile(const QString &fileName);

private slots:
    void slotFolderDiscovered(bool local, const QString &folder);
    void slotRootEtagReceived(const QByteArray &, const QDateTime &time);

    /** When the discovery phase discovers an item */
    void slotItemDiscovered(const OCC::SyncFileItemPtr &item);

    /** Called when a SyncFileItem gets accepted for a sync.
     *
     * Mostly done in initial creation inside treewalkFile but
     * can also be called via the propagator for items that are
     * created during propagation.
     */
    void slotNewItem(const OCC::SyncFileItemPtr &item);

    void slotItemCompleted(const OCC::SyncFileItemPtr &item, const OCC::ErrorCategory category);
    void slotDiscoveryFinished();
    void slotPropagationFinished(bool success);
    void slotProgress(const OCC::SyncFileItem &item, qint64 current);
    void slotCleanPollsJobAborted(const QString &error, const OCC::ErrorCategory category);

    /** Records that a file was touched by a job. */
    void slotAddTouchedFile(const QString &fn);

    /** Wipes the _touchedFiles hash */
    void slotClearTouchedFiles();

    /** Emit a summary error, unless it was seen before */
    void slotSummaryError(const QString &message);

    void slotInsufficientLocalStorage();
    void slotInsufficientRemoteStorage();

    void slotScheduleFilesDelayedSync();
    void slotUnscheduleFilesDelayedSync();
    void slotCleanupScheduledSyncTimers();

private:
    // Some files need a sync run to be executed at a specified time after
    // their status is scheduled to change (e.g. lock status will expire in
    // 20 minutes.)
    //
    // Rather than execute a sync run for each file that needs one, we want
    // to schedule as few sync runs as possible, trying to have the state of
    // these files updated in a timely manner without scheduling runs too
    // frequently. We can therefore group files into a bucket.
    //
    // A bucket contains a group of files requiring a sync run in close
    // proximity to each other, with an assigned sync timer interval that can
    // be used to schedule a sync run which will update all the files in the
    // bucket at the time their state is scheduled to change.
    //
    // In the pair, first is the actual time at which the bucket is going to
    // have its sync scheduled. Second is the vector of all the (paths of)
    // files that fall into this bucket.
    //
    // See SyncEngine::groupNeededScheduledSyncRuns and
    // SyncEngine::slotScheduleFilesDelayedSync for usage.
    struct ScheduledSyncBucket {
        qint64 scheduledSyncTimerSecs = 0LL;
        QVector<QString> files;
    };

    // Sometimes we schedule a timer for, say, 10 files. But we receive updated
    // data from an earlier sync run and we no longer need a scheduled sync.
    //
    // E.g. we had a scheduled sync timer going for a file with a lock state
    // scheduled to expire, but someone already unlocked the file on the web UI
    //
    // By keeping a counter of the files depending on this timer we can
    // perform "garbage collection", by killing the timer if there are no
    // longer any files depending on the scheduled sync run.
    class ScheduledSyncTimer : public QTimer {
    public:
        QSet<QString> files;
    };

    bool checkErrorBlacklisting(SyncFileItem &item);

    // Cleans up unnecessary downloadinfo entries in the journal as well
    // as their temporary files.
    void deleteStaleDownloadInfos(const SyncFileItemVector &syncItems);

    // Removes stale uploadinfos from the journal.
    void deleteStaleUploadInfos(const SyncFileItemVector &syncItems);

    // Removes stale error blacklist entries from the journal.
    void deleteStaleErrorBlacklistEntries(const SyncFileItemVector &syncItems);

    // Removes stale and adds missing conflict records after sync
    void conflictRecordMaintenance();

    // Removes stale and adds missing conflict records after sync
    void caseClashConflictRecordMaintenance();

    // cleanup and emit the finished signal
    void finalize(bool success);

    void processCaseClashConflictsBeforeDiscovery();

    // Aggregate scheduled sync runs into interval buckets. Can be used to
    // schedule a sync run per bucket instead of per file, reducing load.
    //
    // Bucket classification is done by simply dividing the seconds until
    // scheduled sync time by the interval (note -- integer division!)
    QHash<qint64, ScheduledSyncBucket> groupNeededScheduledSyncRuns(const qint64 interval) const;

    // Checks if there is already a scheduled sync run timer active near the
    // time provided as the parameter.
    //
    // If this timer will expire within the interval provided, the return is
    // true.
    //
    // If this expiration occurs before the scheduled sync run provided as the
    // parameter, it is rescheduled to expire at the time of the parameter.
    QSharedPointer<SyncEngine::ScheduledSyncTimer> nearbyScheduledSyncTimer(const qint64 scheduledSyncTimerSecs,
                                                                            const qint64 intervalSecs) const;

    static bool s_anySyncRunning; //true when one sync is running somewhere (for debugging)

    // Must only be accessed during update and reconcile
    QVector<SyncFileItemPtr> _syncItems;

    AccountPtr _account;
    bool _needsUpdate = false;
    bool _syncRunning = false;
    QString _localPath;
    QString _remotePath;
    QByteArray _remoteRootEtag;
    SyncJournalDb *_journal;
    QScopedPointer<DiscoveryPhase> _discoveryPhase;
    QSharedPointer<OwncloudPropagator> _propagator;

    QSet<QString> _bulkUploadBlackList;

    // List of all files with conflicts
    QSet<QString> _seenConflictFiles;

    QScopedPointer<ProgressInfo> _progressInfo;

    QScopedPointer<ExcludedFiles> _excludedFiles;
    QScopedPointer<SyncFileStatusTracker> _syncFileStatusTracker;
    Utility::StopWatch _stopWatch;

    /**
     * check if we are allowed to propagate everything, and if we are not, adjust the instructions
     * to recover
     */
    void checkForPermission(SyncFileItemVector &syncItems);
    [[nodiscard]] RemotePermissions getPermissions(const QString &file) const;

    /**
     * Instead of downloading files from the server, upload the files to the server
     */
    void restoreOldFiles(SyncFileItemVector &syncItems);

    // true if there is at least one file which was not changed on the server
    bool _hasNoneFiles = false;

    // true if there is at leasr one file with instruction REMOVE
    bool _hasRemoveFile = false;

    // If ignored files should be ignored
    bool _ignore_hidden_files = false;


    int _uploadLimit = 0;
    int _downloadLimit = 0;
    SyncOptions _syncOptions;

    AnotherSyncNeeded _anotherSyncNeeded = NoFollowUpSync;

    /** Stores the time since a job touched a file. */
    QMultiMap<QElapsedTimer, QString> _touchedFiles;

    QElapsedTimer _lastUpdateProgressCallbackCall;

    /** For clearing the _touchedFiles variable after sync finished */
    QTimer _clearTouchedFilesTimer;

    /** List of unique errors that occurred in a sync run. */
    QSet<QString> _uniqueErrors;

    /** The kind of local discovery the last sync run used */
    LocalDiscoveryStyle _lastLocalDiscoveryStyle = LocalDiscoveryStyle::FilesystemOnly;
    LocalDiscoveryStyle _localDiscoveryStyle = LocalDiscoveryStyle::FilesystemOnly;
    std::set<QString> _localDiscoveryPaths;

    QStringList _leadingAndTrailingSpacesFilesAllowed;

    // Hash of files we have scheduled for later sync runs, along with a
    // pointer to the timer which will trigger the sync run for it.
    //
    // NOTE: these sync timers are not unique and will likely be shared
    // between several files
    QHash<QString, QSharedPointer<ScheduledSyncTimer>> _filesScheduledForLaterSync;

    // A vector of all the (unique) scheduled sync timers
    QVector<QSharedPointer<ScheduledSyncTimer>> _scheduledSyncTimers;

    SingleItemDiscoveryOptions _singleItemDiscoveryOptions;
};
}