// The MIT License (MIT)
//
// Copyright (c) Itay Grudev 2015 - 2016
//
// 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 <cstdlib>

#include <QMessageBox>
#include <QTimer>
#include <QtCore/QByteArray>
#include <QtCore/QCryptographicHash>
#include <QtCore/QDataStream>
#include <QtCore/QDir>
#include <QtCore/QProcess>
#include <QtCore/QSemaphore>
#include <QtCore/QSharedMemory>
#include <QtCore/QStandardPaths>
#include <QtNetwork/QLocalServer>
#include <QtNetwork/QLocalSocket>

#ifdef Q_OS_UNIX
#include <signal.h>
#include <unistd.h>
#endif

#ifdef Q_OS_WIN
#include <lmcons.h>
#include <windows.h>
#endif

#include "singleapplication.h"
#include "singleapplication_p.h"

SingleApplicationPrivate::SingleApplicationPrivate(SingleApplication* q_ptr)
  : q_ptr(q_ptr)
{
    server = nullptr;
    socket = nullptr;
}

SingleApplicationPrivate::~SingleApplicationPrivate()
{
    if (socket != nullptr) {
        socket->close();
        delete socket;
    }

    memory->lock();
    InstancesInfo* inst = static_cast<InstancesInfo*>(memory->data());
    if (server != nullptr) {
        server->close();
        delete server;
        inst->primary = false;
        inst->primaryPid = -1;
    }
    memory->unlock();

    delete memory;
}

void SingleApplicationPrivate::genBlockServerName(int timeout)
{
    QCryptographicHash appData(QCryptographicHash::Sha256);
    appData.addData("SingleApplication", 17);
    appData.addData(SingleApplication::app_t::applicationName().toUtf8());
    appData.addData(SingleApplication::app_t::organizationName().toUtf8());
    appData.addData(SingleApplication::app_t::organizationDomain().toUtf8());

    if (!(options & SingleApplication::Mode::ExcludeAppVersion)) {
        appData.addData(
          SingleApplication::app_t::applicationVersion().toUtf8());
    }

    if (!(options & SingleApplication::Mode::ExcludeAppPath)) {
#ifdef Q_OS_WIN
        appData.addData(
          SingleApplication::app_t::applicationFilePath().toLower().toUtf8());
#else
        appData.addData(
          SingleApplication::app_t::applicationFilePath().toUtf8());
#endif
    }

    // User level block requires a user specific data in the hash
    if (options & SingleApplication::Mode::User) {
#ifdef Q_OS_WIN
        Q_UNUSED(timeout);
        wchar_t username[UNLEN + 1];
        // Specifies size of the buffer on input
        DWORD usernameLength = UNLEN + 1;
        if (GetUserNameW(username, &usernameLength)) {
            appData.addData(QString::fromWCharArray(username).toUtf8());
        } else {
            appData.addData(
              QStandardPaths::standardLocations(QStandardPaths::HomeLocation)
                .join("")
                .toUtf8());
        }
#endif
#ifdef Q_OS_UNIX
        QProcess process;
        process.start(QStringLiteral("whoami"));
        if (process.waitForFinished(timeout) &&
            process.exitCode() == QProcess::NormalExit) {
            appData.addData(process.readLine());
        } else {
            appData.addData(QDir(QStandardPaths::standardLocations(
                                   QStandardPaths::HomeLocation)
                                   .first())
                              .absolutePath()
                              .toUtf8());
        }
#endif
    }

    // Replace the backslash in RFC 2045 Base64 [a-zA-Z0-9+/=] to comply with
    // server naming requirements.
    blockServerName = appData.result().toBase64().replace("/", "_");
}

void SingleApplicationPrivate::startPrimary(bool resetMemory)
{
    Q_Q(SingleApplication);

#ifdef Q_OS_UNIX
    // Handle any further termination signals to ensure the
    // QSharedMemory block is deleted even if the process crashes
    crashHandler();
#endif
    // Successful creation means that no main process exists
    // So we start a QLocalServer to listen for connections
    QLocalServer::removeServer(blockServerName);
    server = new QLocalServer();

    // Restrict access to the socket according to the
    // SingleApplication::Mode::User flag on User level or no restrictions
    if (options & SingleApplication::Mode::User) {
        server->setSocketOptions(QLocalServer::UserAccessOption);
    } else {
        server->setSocketOptions(QLocalServer::WorldAccessOption);
    }

    server->listen(blockServerName);
    QObject::connect(server,
                     &QLocalServer::newConnection,
                     this,
                     &SingleApplicationPrivate::slotConnectionEstablished);

    // Reset the number of connections
    memory->lock();
    InstancesInfo* inst = static_cast<InstancesInfo*>(memory->data());

    if (resetMemory) {
        inst->secondary = 0;
    }

    inst->primary = true;
    inst->primaryPid = q->applicationPid();

    memory->unlock();

    instanceNumber = 0;
}

void SingleApplicationPrivate::startSecondary()
{
#ifdef Q_OS_UNIX
    // Handle any further termination signals to ensure the
    // QSharedMemory block is deleted even if the process crashes
    crashHandler();
#endif
}

void SingleApplicationPrivate::connectToPrimary(int msecs,
                                                ConnectionType connectionType)
{
    // Connect to the Local Server of the Primary Instance if not already
    // connected.
    if (socket == nullptr) {
        socket = new QLocalSocket();
    }

    // If already connected - we are done;
    if (socket->state() == QLocalSocket::ConnectedState)
        return;

    // If not connect
    if (socket->state() == QLocalSocket::UnconnectedState ||
        socket->state() == QLocalSocket::ClosingState) {
        socket->connectToServer(blockServerName);
    }

    // Wait for being connected
    if (socket->state() == QLocalSocket::ConnectingState) {
        socket->waitForConnected(msecs);
    }

    // Initialisation message according to the SingleApplication protocol
    if (socket->state() == QLocalSocket::ConnectedState) {
        // Notify the parent that a new instance had been started;
        QByteArray initMsg;
        QDataStream writeStream(&initMsg, QIODevice::WriteOnly);
        writeStream.setVersion(QDataStream::Qt_5_2);
        writeStream << blockServerName.toLatin1();
        writeStream << static_cast<quint8>(connectionType);
        writeStream << instanceNumber;
        quint16 checksum = qChecksum(initMsg.constData(),
                                     static_cast<quint32>(initMsg.length()));
        writeStream << checksum;

        socket->write(initMsg);
        socket->flush();
        socket->waitForBytesWritten(msecs);
    }
}

qint64 SingleApplicationPrivate::primaryPid()
{
    qint64 pid;

    memory->lock();
    InstancesInfo* inst = static_cast<InstancesInfo*>(memory->data());
    pid = inst->primaryPid;
    memory->unlock();

    return pid;
}

#ifdef Q_OS_UNIX
void SingleApplicationPrivate::crashHandler()
{
    // Handle any further termination signals to ensure the
    // QSharedMemory block is deleted even if the process crashes
    signal(SIGHUP, SingleApplicationPrivate::terminate);  // 1
    signal(SIGINT, SingleApplicationPrivate::terminate);  // 2
    signal(SIGQUIT, SingleApplicationPrivate::terminate); // 3
    signal(SIGILL, SingleApplicationPrivate::terminate);  // 4
    signal(SIGABRT, SingleApplicationPrivate::terminate); // 6
    signal(SIGFPE, SingleApplicationPrivate::terminate);  // 8
    signal(SIGBUS, SingleApplicationPrivate::terminate);  // 10
    signal(SIGSEGV, SingleApplicationPrivate::terminate); // 11
    signal(SIGSYS, SingleApplicationPrivate::terminate);  // 12
    signal(SIGPIPE, SingleApplicationPrivate::terminate); // 13
    signal(SIGALRM, SingleApplicationPrivate::terminate); // 14
    signal(SIGTERM, SingleApplicationPrivate::terminate); // 15
    signal(SIGXCPU, SingleApplicationPrivate::terminate); // 24
    signal(SIGXFSZ, SingleApplicationPrivate::terminate); // 25
}

void SingleApplicationPrivate::terminate(int signum)
{
    delete ((SingleApplication*)QCoreApplication::instance())->d_ptr;
    ::exit(128 + signum);
}
#endif

/**
 * @brief Executed when a connection has been made to the LocalServer
 */
void SingleApplicationPrivate::slotConnectionEstablished()
{
    Q_Q(SingleApplication);

    QLocalSocket* nextConnSocket = server->nextPendingConnection();

    quint32 instanceId = 0;
    ConnectionType connectionType = InvalidConnection;
    if (nextConnSocket->waitForReadyRead(100)) {
        // read all data from message in same order/format as written
        QByteArray msgBytes =
          nextConnSocket->read(nextConnSocket->bytesAvailable() -
                               static_cast<qint64>(sizeof(quint16)));
        QByteArray checksumBytes = nextConnSocket->read(sizeof(quint16));
        QDataStream readStream(msgBytes);
        readStream.setVersion(QDataStream::Qt_5_2);

        // server name
        QByteArray latin1Name;
        readStream >> latin1Name;
        // connectioon type
        quint8 connType = InvalidConnection;
        readStream >> connType;
        connectionType = static_cast<ConnectionType>(connType);
        // instance id
        readStream >> instanceId;
        // checksum
        quint16 msgChecksum = 0;
        QDataStream checksumStream(checksumBytes);
        checksumStream.setVersion(QDataStream::Qt_5_2);
        checksumStream >> msgChecksum;

        const quint16 actualChecksum = qChecksum(
          msgBytes.constData(), static_cast<quint32>(msgBytes.length()));

        if (readStream.status() != QDataStream::Ok ||
            QLatin1String(latin1Name) != blockServerName ||
            msgChecksum != actualChecksum) {
            connectionType = InvalidConnection;
        }
    }

    if (connectionType == InvalidConnection) {
        nextConnSocket->close();
        delete nextConnSocket;
        return;
    }

    QObject::connect(nextConnSocket,
                     &QLocalSocket::aboutToClose,
                     this,
                     [nextConnSocket, instanceId, this]() {
                         emit this->slotClientConnectionClosed(nextConnSocket,
                                                               instanceId);
                     });

    QObject::connect(nextConnSocket,
                     &QLocalSocket::readyRead,
                     this,
                     [nextConnSocket, instanceId, this]() {
                         emit this->slotDataAvailable(nextConnSocket,
                                                      instanceId);
                     });

    if (connectionType == NewInstance ||
        (connectionType == SecondaryInstance &&
         options & SingleApplication::Mode::SecondaryNotification)) {
        emit q->instanceStarted();
    }

    if (nextConnSocket->bytesAvailable() > 0) {
        emit this->slotDataAvailable(nextConnSocket, instanceId);
    }
}

void SingleApplicationPrivate::slotDataAvailable(QLocalSocket* dataSocket,
                                                 quint32 instanceId)
{
    Q_Q(SingleApplication);
    emit q->receivedMessage(instanceId, dataSocket->readAll());
}

void SingleApplicationPrivate::slotClientConnectionClosed(
  QLocalSocket* closedSocket,
  quint32 instanceId)
{
    if (closedSocket->bytesAvailable() > 0)
        emit slotDataAvailable(closedSocket, instanceId);
    closedSocket->deleteLater();
}

/**
 * @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);

    // 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(timeout);

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

    // Create a shared memory block
    if (d->memory->create(sizeof(InstancesInfo))) {
        d->startPrimary(true);
        return;
    } else {
        // Attempt to attach to the memory segment
        if (d->memory->attach()) {
            d->memory->lock();
            InstancesInfo* inst =
              static_cast<InstancesInfo*>(d->memory->data());

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

            // Check if another instance can be started
            if (allowSecondary) {
                inst->secondary += 1;
                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;

    // show message box with inforation that Flameshot is already launched
    QMessageBox msgBox;
    msgBox.setText(QObject::tr(
      "Hi, I'm already running!\nYou can find me in the system tray."));
    int cnt = 3;
    QTimer cntDown;
    QObject::connect(
      &cntDown, &QTimer::timeout, [&msgBox, &cnt, &cntDown]() -> void {
          if (--cnt < 0) {
              cntDown.stop();
              msgBox.close();
          } else {
              msgBox.setWindowTitle(QString("Flameshot (%1)").arg(cnt + 1));
          }
      });
    cntDown.start(1000);
    msgBox.exec();

    ::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->flush();
    d->socket->waitForBytesWritten(timeout);
    return dataWritten;
}