#!/usr/bin/env python3
"""Grab the full screen to a PNG. Used by the arena verification flow to
prove the quad grid actually tiles on screen — without this we only have
DisplayServer's inside-Godot view of its own window state, which is the
kind of circumstantial evidence that burned us earlier.

Uses ffmpeg's x11grab (via XWayland on Wayland sessions). `mss` fails on
pure Wayland because its Linux backend is Xlib-only.

Usage: tools/grab-screen.py <output.png> [WIDTH] [HEIGHT]
"""
from __future__ import annotations

import os
import subprocess
import sys
from pathlib import Path

if len(sys.argv) < 2 or len(sys.argv) > 4:
    print("usage: grab-screen.py <output.png> [WIDTH] [HEIGHT]", file=sys.stderr)
    sys.exit(2)

out = Path(sys.argv[1])
width = int(sys.argv[2]) if len(sys.argv) >= 3 else 3440
height = int(sys.argv[3]) if len(sys.argv) >= 4 else 1440
display = os.environ.get("DISPLAY", ":0")

out.parent.mkdir(parents=True, exist_ok=True)

cmd = [
    "ffmpeg",
    "-hide_banner",
    "-loglevel", "error",
    "-f", "x11grab",
    "-video_size", f"{width}x{height}",
    "-i", display,
    "-frames:v", "1",
    "-update", "1",
    "-y",
    str(out),
]
result = subprocess.run(cmd, check=False, capture_output=True, text=True)
if result.returncode != 0:
    print(f"ffmpeg failed (exit {result.returncode}):", file=sys.stderr)
    print(result.stderr, file=sys.stderr)
    sys.exit(result.returncode)

size = out.stat().st_size
print(f"saved {out} ({width}x{height}, {size} bytes)")