// Turns the built web app (dist/) into a C file the payload compiles in.
// Every file is stored gzip-compressed and served that way.
//
//   node scripts/embed-assets.mjs <dist dir> <output .c>

import fs from 'node:fs';
import path from 'node:path';
import zlib from 'node:zlib';
import { fileURLToPath } from 'node:url';

const [distDir, outFile] = process.argv.slice(2);
if (!distDir || !outFile) {
  console.error('usage: embed-assets.mjs <dist dir> <output .c>');
  process.exit(1);
}

const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
const version = JSON.parse(fs.readFileSync(path.join(root, 'package.json'), 'utf8')).version;

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.json': 'application/json; charset=utf-8',
  '.png': 'image/png',
  '.ico': 'image/x-icon',
  '.wasm': 'application/wasm',
};

function walk(dir, prefix = '') {
  const out = [];
  for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
    const rel = `${prefix}/${entry.name}`;
    if (entry.isDirectory()) out.push(...walk(path.join(dir, entry.name), rel));
    else out.push(rel);
  }
  return out.sort();
}

const files = walk(distDir);
if (!files.includes('/index.html')) {
  console.error(`${distDir} has no index.html; run "npm run build" first`);
  process.exit(1);
}

let c = '/* Generated by scripts/embed-assets.mjs. Do not edit. */\n#include "assets.h"\n\n';
c += `const char CS_VERSION[] = ${JSON.stringify(version)};\n\n`;
const rows = [];
let total = 0;
files.forEach((rel, i) => {
  const gz = zlib.gzipSync(fs.readFileSync(path.join(distDir, rel)), { level: 9 });
  total += gz.length;
  const bytes = [];
  for (let o = 0; o < gz.length; o += 20) bytes.push('  ' + [...gz.subarray(o, o + 20)].join(','));
  c += `static const unsigned char asset_${i}[] = {\n${bytes.join(',\n')}\n};\n\n`;
  const mime = MIME[path.extname(rel).toLowerCase()] ?? 'application/octet-stream';
  rows.push(`  {${JSON.stringify(rel)}, ${JSON.stringify(mime)}, asset_${i}, sizeof asset_${i}, ${rel.startsWith('/assets/') ? 1 : 0}}`);
});
c += `const struct asset CS_ASSETS[] = {\n${rows.join(',\n')}\n};\n\nconst int CS_ASSET_COUNT = ${files.length};\n`;

fs.mkdirSync(path.dirname(outFile), { recursive: true });
fs.writeFileSync(outFile, c);
console.log(`Embedded ${files.length} files, ${(total / 1024).toFixed(0)} KB compressed -> ${outFile}`);