"""Build an opaque, desktop-sized WebP exploration background."""

from __future__ import annotations

import argparse
from pathlib import Path

from PIL import Image, ImageOps


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser()
    parser.add_argument("--input", required=True, type=Path)
    parser.add_argument("--output", required=True, type=Path)
    parser.add_argument("--width", type=int, default=1920)
    parser.add_argument("--height", type=int, default=1080)
    parser.add_argument("--quality", type=int, default=88)
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    if args.width <= 0 or args.height <= 0:
        raise ValueError("Output dimensions must be positive.")
    if not 1 <= args.quality <= 100:
        raise ValueError("WebP quality must be between 1 and 100.")

    output_path = args.output.resolve()
    output_path.parent.mkdir(parents=True, exist_ok=True)

    with Image.open(args.input) as source:
        rgb_source = ImageOps.exif_transpose(source).convert("RGB")
        resized = ImageOps.fit(
            rgb_source,
            (args.width, args.height),
            method=Image.Resampling.LANCZOS,
            centering=(0.5, 0.5),
        )
        resized.save(
            output_path,
            format="WEBP",
            quality=args.quality,
            method=6,
            exact=False,
        )

    with Image.open(output_path) as result:
        if result.size != (args.width, args.height) or result.mode != "RGB":
            raise RuntimeError(
                f"Unexpected output: {result.size[0]}x{result.size[1]} {result.mode}"
            )

    print(
        f"Built {output_path} ({args.width}x{args.height}, "
        f"{output_path.stat().st_size} bytes)."
    )


if __name__ == "__main__":
    main()