scripts/build_fonts.py

#!/usr/bin/env python3
"""Self-host the web fonts so the app makes NO Google Fonts call at runtime (fully
local). Downloads the LATIN subset (U+0000-00FF) of each weight used by the UI into
ui/public/fonts/ and writes ui/public/fonts.css. Run once (or to refresh), then
`npm run build`. Devanagari (हेर) uses the OS font, as before — these display fonts
don't ship Devanagari glyphs either way.

  python3 scripts/build_fonts.py
"""
from __future__ import annotations

import os
import re
import urllib.request

UA = {"User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 "
                    "(KHTML, like Gecko) Chrome/124.0 Safari/537.36"}
CSS_URL = ("https://fonts.googleapis.com/css2?family=Chakra+Petch:wght@500;600;700"
           "&family=IBM+Plex+Sans:wght@400;500;600&family=JetBrains+Mono:wght@400;500;600&display=swap")
HERE = os.path.dirname(os.path.abspath(__file__))
PUB = os.path.join(os.path.dirname(HERE), "ui", "public")
FONTS = os.path.join(PUB, "fonts")


def _get(url: str) -> bytes:
    return urllib.request.urlopen(urllib.request.Request(url, headers=UA), timeout=30).read()


def main() -> int:
    os.makedirs(FONTS, exist_ok=True)
    css = _get(CSS_URL).decode("utf-8")
    out, picked = [], set()
    for b in re.findall(r"@font-face\s*\{([^}]*)\}", css):
        fam = re.search(r"font-family:\s*'([^']+)'", b)
        wght = re.search(r"font-weight:\s*(\d+)", b)
        url = re.search(r"url\((https://[^)]+\.woff2)\)", b)
        ur = re.search(r"unicode-range:\s*([^;]+);", b)
        if not (fam and wght and url and ur):
            continue
        if "U+0000-00FF" not in ur.group(1).upper().replace(" ", ""):  # latin subset only
            continue
        fam, wght, url = fam.group(1), wght.group(1), url.group(1)
        if (fam, wght) in picked:
            continue
        picked.add((fam, wght))
        fn = fam.lower().replace(" ", "") + "-" + wght + ".woff2"
        open(os.path.join(FONTS, fn), "wb").write(_get(url))
        out.append(f"@font-face{{font-family:'{fam}';font-style:normal;font-weight:{wght};"
                   f"font-display:swap;src:url('/fonts/{fn}') format('woff2');}}")
        print(f"  {fam} {wght} -> {fn}")
    open(os.path.join(PUB, "fonts.css"), "w").write("\n".join(out) + "\n")
    print(f"wrote ui/public/fonts.css ({len(out)} faces)")
    return 0


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