/*
 * Copyright (C) by Klaas Freitag <freitag@owncloud.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#pragma once

#include "ocsynclib.h"
#include "config.h"

#include <QObject>
#include <QByteArray>
#include <QFutureWatcher>

#include <memory>

class QFile;

namespace OCC {

/**
 * Tags for checksum headers values.
 * They are here for being shared between Upload- and Download Job
 */
static const char checkSumMD5C[] = "MD5";
static const char checkSumSHA1C[] = "SHA1";
static const char checkSumSHA2C[] = "SHA256";
static const char checkSumSHA3C[] = "SHA3-256";
static const char checkSumAdlerC[] = "Adler32";

class SyncJournalDb;

/**
 * Returns the highest-quality checksum in a 'checksums'
 * property retrieved from the server.
 *
 * Example: "ADLER32:1231 SHA1:ab124124 MD5:2131affa21"
 *       -> "SHA1:ab124124"
 */
OCSYNC_EXPORT QByteArray findBestChecksum(const QByteArray &checksums);


/// Creates a checksum header from type and value.
OCSYNC_EXPORT QByteArray makeChecksumHeader(const QByteArray &checksumType, const QByteArray &checksum);

/// Parses a checksum header
OCSYNC_EXPORT bool parseChecksumHeader(const QByteArray &header, QByteArray *type, QByteArray *checksum);

/// Convenience for getting the type from a checksum header, null if none
OCSYNC_EXPORT QByteArray parseChecksumHeaderType(const QByteArray &header);

/// Checks OWNCLOUD_DISABLE_CHECKSUM_UPLOAD
OCSYNC_EXPORT bool uploadChecksumEnabled();

// Exported functions for the tests.
QByteArray OCSYNC_EXPORT calcMd5(QIODevice *device);
QByteArray OCSYNC_EXPORT calcSha1(QIODevice *device);
#ifdef ZLIB_FOUND
QByteArray OCSYNC_EXPORT calcAdler32(QIODevice *device);
#endif

/**
 * Computes the checksum of a file.
 * \ingroup libsync
 */
class OCSYNC_EXPORT ComputeChecksum : public QObject
{
    Q_OBJECT
public:
    explicit ComputeChecksum(QObject *parent = nullptr);
    ~ComputeChecksum();

    /**
     * Sets the checksum type to be used. The default is empty.
     */
    void setChecksumType(const QByteArray &type);

    QByteArray checksumType() const;

    /**
     * Computes the checksum for the given file path.
     *
     * done() is emitted when the calculation finishes.
     */
    void start(const QString &filePath);

    /**
     * Computes the checksum for the given device.
     *
     * done() is emitted when the calculation finishes.
     *
     * The device ownership transfers into the thread that
     * will compute the checksum. It must not have a parent.
     */
    void start(std::unique_ptr<QIODevice> device);

    /**
     * Computes the checksum synchronously.
     */
    static QByteArray computeNow(QIODevice *device, const QByteArray &checksumType);

    /**
     * Computes the checksum synchronously on file. Convenience wrapper for computeNow().
     */
    static QByteArray computeNowOnFile(const QString &filePath, const QByteArray &checksumType);

signals:
    void done(const QByteArray &checksumType, const QByteArray &checksum);

private slots:
    void slotCalculationDone();

private:
    void startImpl(std::unique_ptr<QIODevice> device);

    QByteArray _checksumType;

    // watcher for the checksum calculation thread
    QFutureWatcher<QByteArray> _watcher;
};

/**
 * Checks whether a file's checksum matches the expected value.
 * @ingroup libsync
 */
class OCSYNC_EXPORT ValidateChecksumHeader : public QObject
{
    Q_OBJECT
public:
    explicit ValidateChecksumHeader(QObject *parent = nullptr);

    /**
     * Check a file's actual checksum against the provided checksumHeader
     *
     * If no checksum is there, or if a correct checksum is there, the signal validated()
     * will be emitted. In case of any kind of error, the signal validationFailed() will
     * be emitted.
     */
    void start(const QString &filePath, const QByteArray &checksumHeader);

    /**
     * Check a device's actual checksum against the provided checksumHeader
     *
     * Like the other start() but works on an device.
     *
     * The device ownership transfers into the thread that
     * will compute the checksum. It must not have a parent.
     */
    void start(std::unique_ptr<QIODevice> device, const QByteArray &checksumHeader);

signals:
    void validated(const QByteArray &checksumType, const QByteArray &checksum);
    void validationFailed(const QString &errMsg);

private slots:
    void slotChecksumCalculated(const QByteArray &checksumType, const QByteArray &checksum);

private:
    ComputeChecksum *prepareStart(const QByteArray &checksumHeader);

    QByteArray _expectedChecksumType;
    QByteArray _expectedChecksum;
};

/**
 * Hooks checksum computations into csync.
 * @ingroup libsync
 */
class OCSYNC_EXPORT CSyncChecksumHook : public QObject
{
    Q_OBJECT
public:
    explicit CSyncChecksumHook();

    /**
     * Returns the checksum value for \a path that is comparable to \a otherChecksum.
     *
     * Called from csync, where a instance of CSyncChecksumHook has
     * to be set as userdata.
     * The return value will be owned by csync.
     */
    static QByteArray hook(const QByteArray &path, const QByteArray &otherChecksumHeader, void *this_obj);
};
}