/*
 * Copyright (C) 2020, KylinSoft Co., Ltd.
 *
 * 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 3 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef SINGLE_APPLICATION_H
#define SINGLE_APPLICATION_H

#include <QtCore/QtGlobal>
#include <QtNetwork/QLocalSocket>

#ifndef QAPPLICATION_CLASS
  #define QAPPLICATION_CLASS QCoreApplication
#endif

#include QT_STRINGIFY(QAPPLICATION_CLASS)

class SingleApplicationPrivate;

/**
 * @brief The SingleApplication class handles multipe instances of the same
 * Application
 * @see QCoreApplication
 */
class SingleApplication : public QAPPLICATION_CLASS
{
    Q_OBJECT

    typedef QAPPLICATION_CLASS app_t;

public:
    /**
     * @brief Mode of operation of SingleApplication.
     * Whether the block should be user-wide or system-wide and whether the
     * primary instance should be notified when a secondary instance had been
     * started.
     * @note Operating system can restrict the shared memory blocks to the same
     * user, in which case the User/System modes will have no effect and the
     * block will be user wide.
     * @enum
     */
    enum Mode {
        User                    = 1 << 0,
        System                  = 1 << 1,
        SecondaryNotification   = 1 << 2,
        ExcludeAppVersion       = 1 << 3,
        ExcludeAppPath          = 1 << 4
    };
    Q_DECLARE_FLAGS(Options, Mode)

    /**
     * @brief Intitializes a SingleApplication instance with argc command line
     * arguments in argv
     * @arg {int &} argc - Number of arguments in argv
     * @arg {const char *[]} argv - Supplied command line arguments
     * @arg {bool} allowSecondary - Whether to start the instance as secondary
     * if there is already a primary instance.
     * @arg {Mode} mode - Whether for the SingleApplication block to be applied
     * User wide or System wide.
     * @arg {int} timeout - Timeout to wait in miliseconds.
     * @note argc and argv may be changed as Qt removes arguments that it
     * recognizes
     * @note Mode::SecondaryNotification only works if set on both the primary
     * instance and the secondary instance.
     * @note The timeout is just a hint for the maximum time of blocking
     * operations. It does not guarantee that the SingleApplication
     * initialisation will be completed in given time, though is a good hint.
     * Usually 4*timeout would be the worst case (fail) scenario.
     * @see See the corresponding QAPPLICATION_CLASS constructor for reference
     */
    explicit SingleApplication( int &argc, char *argv[], bool allowSecondary = false, Options options = Mode::User, int timeout = 100 );
    ~SingleApplication();

    /**
     * @brief Returns if the instance is the primary instance
     * @returns {bool}
     */
    bool isPrimary();

    /**
     * @brief Returns if the instance is a secondary instance
     * @returns {bool}
     */
    bool isSecondary();

    /**
     * @brief Returns a unique identifier for the current instance
     * @returns {qint32}
     */
    quint32 instanceId();

    /**
     * @brief Returns the process ID (PID) of the primary instance
     * @returns {qint64}
     */
    qint64 primaryPid();

    /**
     * @brief Sends a message to the primary instance. Returns true on success.
     * @param {int} timeout - Timeout for connecting
     * @returns {bool}
     * @note sendMessage() will return false if invoked from the primary
     * instance.
     */
    bool sendMessage( QByteArray message, int timeout = 100 );

Q_SIGNALS:
    void instanceStarted();
    void receivedMessage( quint32 instanceId, QByteArray message );

private:
    SingleApplicationPrivate *d_ptr;
    Q_DECLARE_PRIVATE(SingleApplication)
};

Q_DECLARE_OPERATORS_FOR_FLAGS(SingleApplication::Options)

#endif // SINGLE_APPLICATION_H
