// Copyright (c) Itay Grudev 2015 - 2023
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// Permission is not granted to use this software or any of the associated files
// as sample data for the purposes of building machine learning models.
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

// V3.4.0
#ifndef SINGLE_APPLICATION_H
#define SINGLE_APPLICATION_H

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

#ifndef QAPPLICATION_CLASS
#define QAPPLICATION_CLASS QApplication
#endif

#include QT_STRINGIFY(QAPPLICATION_CLASS)

class SingleApplicationPrivate;

/**
 * @brief Handles multiple instances of the same
 * Application
 * @see QCoreApplication
 */
class SingleApplication : public QAPPLICATION_CLASS {
	Q_OBJECT

	using app_t = QAPPLICATION_CLASS;

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 Mode {
		/** The `SingleApplication` block should apply user wide
		 * (this adds user specific data to the key used for the shared memory and server name)
		 * */
		User = 1 << 0,
		/**
		 * The `SingleApplication` block applies system-wide.
		 */
		System = 1 << 1,
		/**
		 * Whether to trigger `instanceStarted()` even whenever secondary instances are started
		 */
		SecondaryNotification = 1 << 2,
		/**
		 * Excludes the application version from the server name (and memory block) hash
		 */
		ExcludeAppVersion = 1 << 3,
		/**
		 * Excludes the application path from the server name (and memory block) hash
		 */
		ExcludeAppPath = 1 << 4
	};
	Q_DECLARE_FLAGS(Options, Mode)

	/**
	 * @brief Intitializes a `SingleApplication` instance with argc command line
	 * arguments in argv
	 * @arg argc - Number of arguments in argv
	 * @arg argv - Supplied command line arguments
	 * @arg allowSecondary - Whether to start the instance as secondary
	 * if there is already a primary instance.
	 * @arg mode - Whether for the `SingleApplication` block to be applied
	 * User wide or System wide.
	 * @arg timeout - Timeout to wait in milliseconds.
	 * @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 = 1000,
	                           const QString &userData = {});
	~SingleApplication() override;

	/**
	 * @brief Checks if the instance is primary instance
	 * @returns `true` if the instance is primary
	 */
	bool isPrimary() const;

	/**
	 * @brief Checks if the instance is a secondary instance
	 * @returns `true` if the instance is secondary
	 */
	bool isSecondary() const;

	/**
	 * @brief Returns a unique identifier for the current instance
	 * @returns instance id
	 */
	quint32 instanceId() const;

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

	/**
	 * @brief Returns the username of the user running the primary instance
	 * @returns user name
	 */
	QString primaryUser() const;

	/**
	 * @brief Returns the username of the current user
	 * @returns user name
	 */
	QString currentUser() const;

	/**
	 * @brief Mode of operation of sendMessage.
	 */
	enum SendMode {
		NonBlocking,           /** Do not wait for the primary instance termination and return immediately */
		BlockUntilPrimaryExit, /** Wait until the primary instance is terminated */
	};

	/**
	 * @brief Sends a message to the primary instance
	 * @param message data to send
	 * @param timeout timeout for connecting
	 * @param sendMode - Mode of operation
	 * @returns `true` on success
	 * @note sendMessage() will return false if invoked from the primary instance
	 */
	bool sendMessage(const QByteArray &message, int timeout = 100, SendMode sendMode = NonBlocking);

	/**
	 * @brief Get the set user data.
	 * @returns user data
	 */
	QStringList userData() const;

signals:
	/**
	 * @brief Triggered whenever a new instance had been started,
	 * except for secondary instances if the `Mode::SecondaryNotification` flag is not specified
	 */
	void instanceStarted();

	/**
	 * @brief Triggered whenever there is a message received from a secondary instance
	 */
	void receivedMessage(quint32 instanceId, QByteArray message);

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

Q_DECLARE_OPERATORS_FOR_FLAGS(SingleApplication::Options)

#endif // SINGLE_APPLICATION_H
