NexusOS/bin/nexus_window.py

#!/usr/bin/env python3
"""Open the NexusOS UI in a native window.

Uses pywebview, which renders via the WebView2 runtime on Windows (already
present on Win10/11) -- a real app window with no browser chrome and none of the
Edge --app profile cold-start. Blocks until the window is closed; the launcher
waits on this process and stops the services when it exits.

Falls back to the default browser if pywebview/WebView2 is unavailable, staying
alive so the launcher doesn't tear the services down underneath it.
"""
import sys
import time
import urllib.request

URL = "http://localhost:8000"


def _wait_for_backend(timeout: float = 40.0) -> bool:
    """Poll /status until the backend answers, so the window never loads before
    the server is up (which shows a localhost error the webview won't retry)."""
    status_url = URL.rstrip("/") + "/status"
    deadline = time.time() + timeout
    while time.time() < deadline:
        try:
            with urllib.request.urlopen(status_url, timeout=2) as r:
                if r.status == 200:
                    return True
        except Exception:
            time.sleep(1)
    return False


def main() -> int:
    try:
        import webview
    except Exception as e:  # pywebview not installed
        return _browser_fallback(f"pywebview unavailable ({e})")

    if not _wait_for_backend():
        print("[nexus] backend not reachable on :8000 after 40s.", file=sys.stderr)

    try:
        webview.create_window(
            "NexusOS",
            URL,
            width=1200,
            height=800,
            min_size=(900, 600),
        )
        webview.start()  # blocks until the window is closed
        return 0
    except Exception as e:  # no WebView2 runtime / backend failure
        return _browser_fallback(f"native window failed ({e})")


def _browser_fallback(reason: str) -> int:
    import webbrowser

    print(f"[nexus] {reason}; opening default browser instead.", file=sys.stderr)
    webbrowser.open(URL)
    # Stay alive so the launcher keeps the services up. The user stops NexusOS
    # by closing the launcher (or the browser tab, then the services idle out).
    try:
        while True:
            time.sleep(3600)
    except KeyboardInterrupt:
        return 0


if __name__ == "__main__":
    sys.exit(main())