// Builds small self-hosted variable fonts (Latin + Turkish + symbols used in posts) into public/fonts/.
// Sources: @fontsource-variable/{rubik,inter} (SIL OFL 1.1). Usage: npm run fonts
import { mkdirSync, readFileSync, writeFileSync } from 'node:fs';
import { createRequire } from 'node:module';
import subsetFont from 'subset-font';

const require = createRequire(import.meta.url);

const ranges = [
  [0x20, 0x7e], // Basic Latin
  [0xa0, 0xff], // Latin-1 (ç ö ü · ° × …)
  [0x11e, 0x11f], // Ğ ğ
  [0x130, 0x131], // İ ı
  [0x15e, 0x15f], // Ş ş
  [0x394, 0x394], // Δ
  [0x3a9, 0x3a9], // Ω
  [0x3bb, 0x3bc], // λ μ
  [0x2013, 0x2014], // – —
  [0x2018, 0x201e], // ‘ ’ ‚ “ ” „
  [0x2022, 0x2022], // •
  [0x2026, 0x2026], // …
  [0x2032, 0x2033], // ′ ″
  [0x20ba, 0x20ba], // ₺
  [0x2122, 0x2122], // ™
  [0x2190, 0x2193], // ← ↑ → ↓
  [0x2212, 0x2212], // −
  [0x2248, 0x2248], // ≈
  [0x2264, 0x2265], // ≤ ≥
];
const text = ranges
  .flatMap(([a, b]) => Array.from({ length: b - a + 1 }, (_, i) => String.fromCodePoint(a + i)))
  .join('');

// Fontsource ships each family split by unicode-range (latin / latin-ext). Each part is subset
// on its own and keeps Fontsource's unicode-range, so browsers fetch only the parts a page needs.
const families = [
  { pkg: '@fontsource-variable/rubik', family: 'Rubik Variable', slug: 'rubik', wght: [400, 900] },
  { pkg: '@fontsource-variable/inter', family: 'Inter Variable', slug: 'inter', wght: [400, 700] },
];
const parts = ['latin', 'latin-ext'];

/** unicode-range of one Fontsource part, read from the package's own CSS. */
function unicodeRange(pkg, slug, part) {
  const css = readFileSync(require.resolve(`${pkg}/index.css`), 'utf8');
  const block = css
    .split('@font-face')
    .find((b) => b.includes(`${slug}-${part}-wght-normal.woff2`));
  const m = block?.match(/unicode-range:\s*([^;]+);/);
  if (!m) throw new Error(`unicode-range not found for ${slug} ${part}`);
  return m[1].trim();
}

mkdirSync('public/fonts', { recursive: true });
const faces = [];
for (const f of families) {
  for (const part of parts) {
    const source = readFileSync(
      require.resolve(`${f.pkg}/files/${f.slug}-${part}-wght-normal.woff2`),
    );
    const out = await subsetFont(source, text, {
      targetFormat: 'woff2',
      variationAxes: { wght: { min: f.wght[0], max: f.wght[1] } },
    });
    const file = `${f.slug}-${part}.woff2`;
    writeFileSync(`public/fonts/${file}`, out);
    console.log(`${file}: ${source.length} → ${out.length} bytes`);
    faces.push(`@font-face {
  font-family: '${f.family}';
  font-style: normal;
  font-display: swap;
  font-weight: ${f.wght[0]} ${f.wght[1]};
  src: url('/fonts/${file}') format('woff2-variations');
  unicode-range: ${unicodeRange(f.pkg, f.slug, part)};
}`);
  }
}

writeFileSync(
  'src/styles/fonts.css',
  `/* Generated by scripts/subset-fonts.mjs — do not edit. Fonts: SIL OFL 1.1 (Rubik, Inter). */\n${faces.join('\n')}\n`,
);
console.log('Wrote src/styles/fonts.css');