"""Application entry point for the PyQt GUI."""

from __future__ import annotations

from contextlib import suppress
import os
from pathlib import Path
import signal
import sys

import pyqtgraph as pg
from PyQt6.QtCore import QTimer
from PyQt6.QtWidgets import QApplication

# Ensure imports are resolved when started as a script.
PROJECT_ROOT = Path(__file__).resolve().parents[2]
if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

from python_app.gui.app_window import AppWindow
from python_app.gui.theme import apply_light_theme


def _is_headless() -> bool:
    """Return whether the launcher requested a non-interactive deployment."""
    return os.environ.get("RADAR_SYSTEM_HEADLESS", "").strip().lower() in {
        "1",
        "true",
        "yes",
        "on",
    }


def _install_unix_signal_handlers(app: QApplication, window: AppWindow) -> None:
    """Route SIGINT and SIGTERM through the Qt event loop into a clean shutdown.

    `window.close()` runs `closeEvent`, which aborts any active capture and
    shuts down managed C++ processes; only then does the Qt loop exit. A
    short repeating timer keeps the Python interpreter pinned in the event
    loop just long enough to deliver pending signals.
    """

    def _request_shutdown(*_args: object) -> None:
        window.close()
        app.quit()

    for sig in (signal.SIGINT, signal.SIGTERM):
        signal.signal(sig, _request_shutdown)

    keepalive_timer = QTimer(app)
    keepalive_timer.setInterval(200)
    keepalive_timer.timeout.connect(lambda: None)
    keepalive_timer.start()


def main() -> int:
    """Run Qt event loop and show main radar control window."""
    app = QApplication(sys.argv)
    apply_light_theme(app)
    # PyQtGraph foreground controls axis lines, tick text, labels, and titles.
    pg.setConfigOptions(antialias=True, background="#ffffff", foreground="#ffffff")
    window = AppWindow(PROJECT_ROOT)
    if _is_headless():
        _install_unix_signal_handlers(app, window)
    else:
        window.showMaximized()
    exit_code = app.exec()
    # Release hardware, SHM readers and child processes before exiting so that a
    # systemd restart (after a headless fatal exit) starts from a clean slate.
    with suppress(Exception):
        window.close()
    return exit_code


if __name__ == "__main__":
    raise SystemExit(main())