#!/usr/bin/env python3
"""Generate the derivative images the site serves in-page.

Three outputs, all derived from the existing PNGs:

1. `public/banners/<slug>.webp`      article banner, q78  (~42% of the PNG)
2. `public/og/thumb/<name>-800.webp` list thumbnail @2x, q72
3. `public/og/thumb/<name>-400.webp` list thumbnail @1x, q72

Why not JPEG anywhere: this art is flat terminal-style with sharp text edges, and it
measured *larger* as JPEG q85 than as PNG (129%); WebP came out at 42%. The PNGs stay
the source of truth for `og:image` (social scrapers do not reliably render WebP share
cards), and the banner PNG doubles as the <picture> fallback.

Usage:
    uv run --with pillow python scripts/optimize-images.py             # everything
    uv run --with pillow python scripts/optimize-images.py <slug> ...  # one post
"""
import glob, os, sys
from PIL import Image

ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
BANNERS = os.path.join(ROOT, "public", "banners")
OG = os.path.join(ROOT, "public", "og")
THUMBS = os.path.join(OG, "thumb")
BANNER_Q = 78
THUMB_Q = 72

def save_webp(im, path, quality):
    os.makedirs(os.path.dirname(path), exist_ok=True)
    if im.mode not in ("RGB", "RGBA"):
        im = im.convert("RGBA" if "A" in im.mode else "RGB")
    im.save(path, "WEBP", quality=quality, method=6)
    return os.path.getsize(path)

def banner(slug):
    png = os.path.join(BANNERS, slug + ".png")
    if not os.path.exists(png):
        return None
    return os.path.getsize(png), save_webp(Image.open(png), png[:-4] + ".webp", BANNER_Q)

def thumbs(slug):
    png = os.path.join(OG, slug + ".png")
    if not os.path.exists(png):
        return None
    im = Image.open(png)
    src = os.path.getsize(png)
    out = []
    for w in (400, 800):
        h = round(w * 630 / 1200)
        out.append(save_webp(im.resize((w, h), Image.LANCZOS),
                             os.path.join(THUMBS, f"{slug}-{w}.webp"), THUMB_Q))
    return src, out

targets = sys.argv[1:]
slugs = targets or sorted(os.path.basename(p)[:-4] for p in glob.glob(os.path.join(OG, "*.png"))
                          if not p.endswith("og-default.png"))

b_png = b_webp = 0
t_png = t_400 = t_800 = 0
for s in slugs:
    b = banner(s)
    if b:
        b_png += b[0]; b_webp += b[1]
    t = thumbs(s)
    if t:
        t_png += t[0]; t_400 += t[1][0]; t_800 += t[1][1]

n = max(1, len(slugs))
print(f"banners : {len(slugs)} files  {b_png/1024/1024:.2f} MB PNG -> {b_webp/1024/1024:.2f} MB WebP "
      f"({100*b_webp/max(1,b_png):.0f}%)   [{b_webp/n/1024:.1f} KB/file]")
print(f"thumbs  : 400w {t_400/1024:.0f} KB ({t_400/n/1024:.1f} KB/file) + 800w "
      f"{t_800/1024:.0f} KB ({t_800/n/1024:.1f} KB/file)  vs PNG {t_png/1024/1024:.2f} MB "
      f"({100*(t_400+t_800)/max(1,t_png):.0f}% of PNG)")