// xenomorphicd main — headless daemon entry point.
//
// QCoreApplication (NOT QGuiApplication): no windows, no QtGui. Claims the
// single-instance flock, binds the WebSocket server, writes the discovery
// file, and runs the event loop forever. Panes and shells survive the app
// quitting; the daemon exits only on SIGTERM/SIGINT (graceful daemonDown) or
// a fatal startup failure. stdout/stderr land in the daemon log file because
// QProcess::startDetached gives the app no pipe back.
#include "DaemonCore.h"

#include <QCoreApplication>
#include <QSocketNotifier>

#include <array>
#include <csignal>
#include <cstring>
#include <iostream>
#include <unistd.h>
#include <utility>

namespace {

// Self-pipe so the signal handler touches nothing but sig_atomic_t state and
// write(); QCoreApplication is not signal-safe by itself.
std::array<int, 2> g_signalPipe = {-1, -1};

extern "C" void handleSignal(int sig)
{
  (void)sig;
  const char b = 'x';
  ssize_t ignored = ::write(g_signalPipe[1], &b, 1);
  (void)ignored;  // best effort; the handler must not do more
}

}  // namespace

int main(int argc, char* argv[])
{
  QCoreApplication app(argc, argv);
  QCoreApplication::setApplicationName(QStringLiteral("xenomorphicd"));

  if (::pipe(g_signalPipe.data()) != 0) {
    std::cerr << "xenomorphicd: pipe() failed\n";
    return 1;
  }

  // memset-init: {} aggregate init does not satisfy the
  // pro-type-member-init check for the __sigaction_u union on macOS.
  struct sigaction sa;  // NOLINT(cppcoreguidelines-pro-type-member-init)
  std::memset(&sa, 0, sizeof(sa));
  // NOLINTBEGIN(cppcoreguidelines-pro-type-union-access)
#ifdef __APPLE__
  // Darwin stores the handler in a union member. Name it directly: the POSIX
  // sa_handler name is a macro there, and the union access is what clang-tidy
  // sees.
  sa.__sigaction_u.__sa_handler = handleSignal;
#else
  sa.sa_handler = handleSignal;
#endif
  // NOLINTEND(cppcoreguidelines-pro-type-union-access)
  std::memset(&sa.sa_mask, 0, sizeof(sa.sa_mask));
  sa.sa_flags = 0;  // no SA_RESTART: let read/connect paths see EINTR
  ::sigaction(SIGTERM, &sa, nullptr);
  ::sigaction(SIGINT, &sa, nullptr);

  DaemonCore core;

  QString error;
  if (!core.start(&error)) {
    // Lands in the daemon log via stderr redirection, and on the console
    // when run in the foreground.
    std::cerr << "xenomorphicd: " << error.toUtf8().constData() << '\n';
    return 1;
  }

  // Signal thread -> event loop bridge.
  auto* sigNotifier =
      new QSocketNotifier(g_signalPipe[0], QSocketNotifier::Read, &app);
  QObject::connect(sigNotifier, &QSocketNotifier::activated, &app,
                   [&core, sigNotifier](int) {
                     sigNotifier->setEnabled(false);
                     core.shutdown(QStringLiteral("shutdown"));
                     QCoreApplication::exit(0);
                   });

  return QCoreApplication::exec();
}