#!/usr/bin/env node
/**
 * Regenerate the committed country-flag font subset.
 *
 *   npm run subset-flags       (or: node website/tools/subset-flag-font.mjs)
 *
 * Extracts every flag emoji used in website HTML/locales, subsets
 * assets/TwemojiCountryFlags.woff2 down to exactly those flags via Python
 * fontTools (harfbuzz-based JS subsetters drop the COLR color tables and
 * produce invisible flags), and writes:
 *
 *   assets/TwemojiCountryFlags.subset.woff2   (committed)
 *   assets/TwemojiCountryFlags.subset.json    (committed manifest)
 *
 * The website build (build.cjs) is pure Node: it only validates the
 * manifest and fails when a flag was added without re-running this tool.
 *
 * Requires python3 with fonttools + brotli. Override the interpreter with
 * the PYTHON env var, e.g. PYTHON=.venv/bin/python npm run subset-flags
 */
import { execFileSync } from 'node:child_process';
import crypto from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const websiteDir = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
const { collectFlagSourceFiles, extractUsedFlags, flagToCountryCode } = require(path.join(websiteDir, 'flag-font-utils.cjs'));

const sourceFont = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.woff2');
const outputFont = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.subset.woff2');
const manifestPath = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.subset.json');

const python = process.env.PYTHON || 'python3';
try {
    execFileSync(python, ['-c', 'import fontTools.subset, brotli'], { stdio: 'pipe' });
} catch {
    console.error(`error: ${python} lacks fonttools/brotli.`);
    console.error('Install them (e.g. "pip3 install fonttools brotli") or point PYTHON at an interpreter that has them:');
    console.error('  PYTHON=/path/to/venv/bin/python npm run subset-flags');
    process.exit(1);
}

const flags = extractUsedFlags(collectFlagSourceFiles(websiteDir));
if (flags.length === 0) {
    console.error('error: no flag emoji found in website sources — extraction is broken');
    process.exit(1);
}
const codes = flags.map(flagToCountryCode);
console.log(`Found ${codes.length} flags: ${codes.join(' ')}`);

execFileSync(python, [
    path.join(websiteDir, 'tools', 'subset_flag_font.py'),
    sourceFont,
    outputFont,
    codes.join(',')
], { stdio: 'inherit' });

const sha = buf => crypto.createHash('sha256').update(buf).digest('hex');
const manifest = {
    comment: 'Generated by tools/subset-flag-font.mjs — do not edit. build.cjs fails when site flags and this manifest diverge.',
    flags: codes,
    sourceFontSha256: sha(fs.readFileSync(sourceFont)),
    subsetSha256: sha(fs.readFileSync(outputFont))
};
fs.writeFileSync(manifestPath, JSON.stringify(manifest, null, 2) + '\n');

const before = fs.statSync(sourceFont).size;
const after = fs.statSync(outputFont).size;
console.log(`Wrote ${path.relative(process.cwd(), outputFont)} (${(after / 1024).toFixed(1)} KB, -${((1 - after / before) * 100).toFixed(0)}% vs source) + manifest.`);
console.log('Commit both files.');