import { readFileSync, writeFileSync } from 'node:fs';
import { resolve } from 'node:path';
import { Buffer } from 'node:buffer';
import subsetFont from 'subset-font';
import opentype from 'opentype.js';

const sourcePath = resolve('assets/fonts/Roboto-Regular.ttf');
const outputPath = resolve('src/pdf/pdf-font.generated.ts');

const ranges = [
  [0x20, 0x7e], [0xa0, 0x17f], [0x400, 0x52f], [0x2000, 0x206f],
];
const required = new Set(['°', '²', '′', '″', '×', '≈', '€', '₽', '—', '→']);
for (const [start, end] of ranges) {
  for (let code = start; code <= end; code++) required.add(String.fromCodePoint(code));
}
const characters = [...required].join('');

const original = readFileSync(sourcePath);
const subset = Buffer.from(await subsetFont(original, characters, { targetFormat: 'truetype' }));
const arrayBuffer = subset.buffer.slice(subset.byteOffset, subset.byteOffset + subset.byteLength);
const font = opentype.parse(arrayBuffer);
const glyphs = {};
const widths = {};
for (const char of characters) {
  const code = char.codePointAt(0);
  const glyph = font.charToGlyph(char);
  if (!code || glyph.index === 0) continue;
  glyphs[code] = glyph.index;
  widths[glyph.index] = Math.round(glyph.advanceWidth || font.unitsPerEm * 0.5);
}

const generated = `/* Generated by scripts/generate-pdf-font.mjs. DO NOT EDIT. */
export const PDF_FONT_BASE64 = ${JSON.stringify(subset.toString('base64'))};
export const PDF_FONT_UNITS_PER_EM = ${font.unitsPerEm};
export const PDF_FONT_ASCENT = ${Math.round(font.ascender)};
export const PDF_FONT_DESCENT = ${Math.round(font.descender)};
export const PDF_FONT_BBOX = ${JSON.stringify([
  Math.round(font.tables.head.xMin), Math.round(font.tables.head.yMin),
  Math.round(font.tables.head.xMax), Math.round(font.tables.head.yMax),
])} as const;
export const PDF_FONT_GLYPHS: Readonly<Record<number, number>> = ${JSON.stringify(glyphs)};
export const PDF_FONT_WIDTHS: Readonly<Record<number, number>> = ${JSON.stringify(widths)};
`;

if (process.argv.includes('--check')) {
  let current = '';
  try { current = readFileSync(outputPath, 'utf8'); } catch {}
  if (current !== generated) {
    console.error('src/pdf/pdf-font.generated.ts is stale; run npm run pdf-font:generate');
    process.exit(1);
  }
} else {
  writeFileSync(outputPath, generated);
  console.log(`Generated ${outputPath} (${subset.length} bytes)`);
}