import fs from 'node:fs/promises';
import path from 'node:path';
import { brotliCompress, constants, gzip } from 'node:zlib';
import { promisify } from 'node:util';

const gzipAsync = promisify(gzip);
const brotliAsync = promisify(brotliCompress);
const distDir = path.resolve('dist');
const extensions = new Set([
  '.css',
  '.html',
  '.js',
  '.json',
  '.svg',
  '.txt',
  '.ttf',
]);

async function walk(dir) {
  const entries = await fs.readdir(dir, { withFileTypes: true });
  const files = await Promise.all(entries.map(async (entry) => {
    const fullPath = path.join(dir, entry.name);
    if (entry.isDirectory()) return walk(fullPath);
    return fullPath;
  }));
  return files.flat();
}

async function compressFile(filePath) {
  if (!extensions.has(path.extname(filePath))) return;

  const input = await fs.readFile(filePath);
  if (input.length < 1024) return;

  const [gz, br] = await Promise.all([
    gzipAsync(input, { level: 9 }),
    brotliAsync(input, {
      params: {
        [constants.BROTLI_PARAM_QUALITY]: 11,
      },
    }),
  ]);

  await Promise.all([
    fs.writeFile(`${filePath}.gz`, gz),
    fs.writeFile(`${filePath}.br`, br),
  ]);
}

const files = await walk(distDir);
await Promise.all(files.map(compressFile));

console.log(`Precompressed ${files.length} dist files with gzip and Brotli where beneficial.`);