import { readdir, readFile, writeFile } from "node:fs/promises";
import path from "node:path";
import { promisify } from "node:util";
import { fileURLToPath } from "node:url";
import { brotliCompress, constants, gzip } from "node:zlib";

const compressBrotli = promisify(brotliCompress);
const compressGzip = promisify(gzip);
const ELIGIBLE_EXTENSIONS = new Set([".css", ".js", ".json"]);
const MINIMUM_BYTES = 1024;

async function eligibleFiles(root) {
  const files = [];
  async function visit(directory) {
    const entries = await readdir(directory, { withFileTypes: true });
    for (const entry of entries) {
      const filePath = path.join(directory, entry.name);
      if (entry.isDirectory()) await visit(filePath);
      else if (entry.isFile() && ELIGIBLE_EXTENSIONS.has(path.extname(entry.name).toLowerCase())) files.push(filePath);
    }
  }
  await visit(root);
  return files;
}

export async function precompressStatic(root) {
  const files = await eligibleFiles(root);
  let sourceBytes = 0;
  let brotliBytes = 0;
  let gzipBytes = 0;
  let writtenFiles = 0;
  for (const filePath of files) {
    const source = await readFile(filePath);
    if (source.length < MINIMUM_BYTES) continue;
    const [brotli, gzipped] = await Promise.all([
      compressBrotli(source, { params: { [constants.BROTLI_PARAM_QUALITY]: 6 } }),
      compressGzip(source, { level: 9 }),
    ]);
    await Promise.all([
      writeFile(`${filePath}.br`, brotli),
      writeFile(`${filePath}.gz`, gzipped),
    ]);
    sourceBytes += source.length;
    brotliBytes += brotli.length;
    gzipBytes += gzipped.length;
    writtenFiles += 2;
  }
  return { sourceFiles: writtenFiles / 2, writtenFiles, sourceBytes, brotliBytes, gzipBytes };
}

if (process.argv[1] && path.resolve(process.argv[1]) === path.resolve(fileURLToPath(import.meta.url))) {
  const root = path.resolve(process.argv[2] ?? "dist");
  const result = await precompressStatic(root);
  console.log(JSON.stringify({ root, ...result }, null, 2));
}