#!/usr/bin/env python3
"""Downscale and re-encode the raw Playwright captures as WebP.

Called by scripts/screenshots.mjs; not useful on its own.

    python3 scripts/screenshots-encode.py <raw-png-dir> <out-dir>

The captures are taken at 2x (desktop) and 3x (mobile) so text is sampled
cleanly, then halved here. Halving rather than keeping the full capture is
deliberate: a README renders images at roughly 850px wide, so a 2880px-wide PNG
buys nothing but repository weight. WebP at q86 takes the forty-image set from
about 16MB to under 2MB.
"""

from __future__ import annotations

import pathlib
import sys

from PIL import Image

QUALITY = 86


def main() -> int:
    if len(sys.argv) != 3:
        print(__doc__, file=sys.stderr)
        return 2

    src = pathlib.Path(sys.argv[1])
    dst = pathlib.Path(sys.argv[2])
    dst.mkdir(parents=True, exist_ok=True)

    captures = sorted(src.glob("*.png"))
    if not captures:
        print(f"no PNG captures in {src}", file=sys.stderr)
        return 1

    before = after = 0
    for png in captures:
        image = Image.open(png).convert("RGB")
        image = image.resize((image.width // 2, image.height // 2), Image.LANCZOS)
        out = dst / f"{png.stem}.webp"
        image.save(out, "WEBP", quality=QUALITY, method=6)
        before += png.stat().st_size
        after += out.stat().st_size

    print(f"encoded {len(captures)} images: {before / 1e6:.1f}MB PNG -> {after / 1e6:.1f}MB WebP")
    return 0


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