#!/usr/bin/env python3
"""Build a non-production grid placement guide with centered safe envelopes."""

from __future__ import annotations

import argparse
from pathlib import Path

from PIL import Image, ImageDraw


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--rows", type=int, required=True)
    parser.add_argument("--cols", type=int, required=True)
    parser.add_argument("--width", type=int, required=True)
    parser.add_argument("--height", type=int, required=True)
    parser.add_argument("--output", type=Path, required=True)
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    if min(args.rows, args.cols, args.width, args.height) < 1:
        raise SystemExit("all dimensions must be positive")
    image = Image.new("RGB", (args.width, args.height), (0, 255, 0))
    draw = ImageDraw.Draw(image)
    for row in range(args.rows):
        for col in range(args.cols):
            left = round(col * args.width / args.cols)
            right = round((col + 1) * args.width / args.cols)
            top = round(row * args.height / args.rows)
            bottom = round((row + 1) * args.height / args.rows)
            cell_w, cell_h = right - left, bottom - top
            margin_x, margin_y = round(cell_w * 0.23), round(cell_h * 0.23)
            box = (left + margin_x, top + margin_y, right - margin_x, bottom - margin_y)
            draw.rectangle(box, outline=(42, 48, 60), width=6)
            cx, cy = (left + right) // 2, (top + bottom) // 2
            draw.line((cx - 18, cy, cx + 18, cy), fill=(240, 240, 232), width=4)
            draw.line((cx, cy - 18, cx, cy + 18), fill=(240, 240, 232), width=4)
    args.output.parent.mkdir(parents=True, exist_ok=True)
    image.save(args.output, optimize=True)
    print(f"GRID_LAYOUT_GUIDE_OK cells={args.rows * args.cols} output={args.output}")


if __name__ == "__main__":
    main()