// The MIT License (MIT)
//
// Copyright (c) Itay Grudev 2015 - 2018
//
// 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:
//
// 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.

#include <QtCore/QTime>
#include <QtCore/QThread>
#include <QtCore/QDateTime>
#include <QtCore/QByteArray>
#include <QtCore/QSharedMemory>
#if QT_VERSION < QT_VERSION_CHECK(5, 10, 0)	// ### Qt 6: remove
#else
#if TODO_LIST
#pragma message("@TODO remove code for QT 5.10 or later")
#endif
#include <QRandomGenerator>
#endif
#include "singleapplication.h"
#include "singleapplication_p.h"

/**
	@brief Constructor. Checks and fires up LocalServer or closes the program
	if another instance already exists
	@param argc
	@param argv
	@param {bool} allowSecondaryInstances
*/
SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSecondary, Options options, int timeout )
	: app_t( argc, argv ), d_ptr( new SingleApplicationPrivate( this ) )
{
	Q_D(SingleApplication);

#if defined(Q_OS_ANDROID) || defined(Q_OS_IOS)
	// On Android and iOS since the library is not supported fallback to
	// standard QApplication behaviour by simply returning at this point.
	qWarning() << "SingleApplication is not supported on Android and iOS systems.";
	return;
#endif

	// Store the current mode of the program
	d->options = options;

	// Generating an application ID used for identifying the shared memory
	// block and QLocalServer
	d->genBlockServerName();

#ifdef Q_OS_UNIX
	// By explicitly attaching it and then deleting it we make sure that the
	// memory is deleted even after the process has crashed on Unix.
	d->memory = new QSharedMemory( d->blockServerName );
	d->memory->attach();
	delete d->memory;
#endif
	// Guarantee thread safe behaviour with a shared memory block.
	d->memory = new QSharedMemory( d->blockServerName );

	// Create a shared memory block
	if( d->memory->create( sizeof( InstancesInfo ) ) ) {
		// Initialize the shared memory block
		d->memory->lock();
		d->initializeMemoryBlock();
		d->memory->unlock();
	} else {
		// Attempt to attach to the memory segment
		if( ! d->memory->attach() ) {
			qCritical() << "SingleApplication: Unable to attach to shared memory block.";
			qCritical() << d->memory->errorString();
			delete d;
			::exit( EXIT_FAILURE );
		}
	}

	InstancesInfo* inst = static_cast<InstancesInfo*>( d->memory->data() );
	QElapsedTimer time;
	time.start();

	// Make sure the shared memory block is initialised and in consistent state
	while( true ) {
		d->memory->lock();

		if( d->blockChecksum() == inst->checksum ) break;

		if( time.elapsed() > 5000 ) {
			qWarning() << "SingleApplication: Shared memory block has been in an inconsistent state from more than 5s. Assuming primary instance failure.";
			d->initializeMemoryBlock();
		}

		d->memory->unlock();

		// Random sleep here limits the probability of a collision between two racing apps
#if QT_VERSION < QT_VERSION_CHECK(5, 10, 0)	// ### Qt 6: remove
		qsrand( QDateTime::currentMSecsSinceEpoch() % std::numeric_limits<uint>::max() );
		QThread::sleep( 8 + static_cast <unsigned long>( static_cast <float>( qrand() ) / RAND_MAX * 10 ) );
#else
#if TODO_LIST
#pragma message("@TODO remove code for QT 5.10 or later")
#endif
		quint32 value = QRandomGenerator::global()->generate();
		QThread::sleep(8 + static_cast<unsigned long>(value / RAND_MAX * 10));
#endif
	}

	if( inst->primary == false) {
		d->startPrimary();
		d->memory->unlock();
		return;
	}

	// Check if another instance can be started
	if( allowSecondary ) {
		inst->secondary += 1;
		inst->checksum = d->blockChecksum();
		d->instanceNumber = inst->secondary;
		d->startSecondary();
		if( d->options & Mode::SecondaryNotification ) {
			d->connectToPrimary( timeout, SingleApplicationPrivate::SecondaryInstance );
		}
		d->memory->unlock();
		return;
	}

	d->memory->unlock();

	d->connectToPrimary( timeout, SingleApplicationPrivate::NewInstance );

	delete d;

	::exit( EXIT_SUCCESS );
}

/**
	@brief Destructor
*/
SingleApplication::~SingleApplication()
{
	Q_D(SingleApplication);
	delete d;
}

bool SingleApplication::isPrimary()
{
	Q_D(SingleApplication);
	return d->server != nullptr;
}

bool SingleApplication::isSecondary()
{
	Q_D(SingleApplication);
	return d->server == nullptr;
}

quint32 SingleApplication::instanceId()
{
	Q_D(SingleApplication);
	return d->instanceNumber;
}

qint64 SingleApplication::primaryPid()
{
	Q_D(SingleApplication);
	return d->primaryPid();
}

bool SingleApplication::sendMessage( QByteArray message, int timeout )
{
	Q_D(SingleApplication);

	// Nobody to connect to
	if( isPrimary() ) return false;

	// Make sure the socket is connected
	d->connectToPrimary( timeout,  SingleApplicationPrivate::Reconnect );

	d->socket->write( message );
	bool dataWritten = d->socket->waitForBytesWritten( timeout );
	d->socket->flush();
	return dataWritten;
}
