import { brotliCompressSync, constants } from 'node:zlib';
import { createHash } from 'node:crypto';
import { existsSync, readFileSync, readdirSync, renameSync, writeFileSync } from 'node:fs';
import { basename, extname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { dirname } from 'node:path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);
const buildDir = process.argv[2] ?? join(__dirname, '..', 'build', 'web');
const bootstrapPath = join(buildDir, 'flutter_bootstrap.js');
const hashableEntrypoints = ['main.dart.js', 'main.dart.mjs', 'main.dart.wasm'];
const compressibleExtensions = new Set([
  '.css',
  '.html',
  '.js',
  '.json',
  '.mjs',
  '.svg',
  '.toml',
  '.wasm',
]);

if (!existsSync(bootstrapPath)) {
  throw new Error(`Missing Flutter bootstrap file: ${bootstrapPath}`);
}

let bootstrap = readFileSync(bootstrapPath, 'utf8');

for (const entrypoint of hashableEntrypoints) {
  const sourcePath = join(buildDir, entrypoint);
  if (!existsSync(sourcePath)) {
    continue;
  }

  const content = readFileSync(sourcePath);
  const hash = createHash('sha256').update(content).digest('hex').slice(0, 12);
  const extension = extname(entrypoint);
  const stem = entrypoint.slice(0, -extension.length);
  const hashedName = `${stem}.${hash}${extension}`;
  const targetPath = join(buildDir, hashedName);

  renameSync(sourcePath, targetPath);
  bootstrap = bootstrap.replaceAll(entrypoint, hashedName);
}

writeFileSync(bootstrapPath, bootstrap);

for (const filePath of walk(buildDir)) {
  if (filePath.endsWith('.br')) {
    continue;
  }
  if (!compressibleExtensions.has(extname(filePath))) {
    continue;
  }

  const content = readFileSync(filePath);
  writeFileSync(
    `${filePath}.br`,
    brotliCompressSync(content, {
      params: {
        [constants.BROTLI_PARAM_QUALITY]: 11,
      },
    }),
  );
}

function* walk(directory) {
  for (const entry of readdirSync(directory, { withFileTypes: true })) {
    const entryPath = join(directory, entry.name);
    if (entry.isDirectory()) {
      yield* walk(entryPath);
      continue;
    }
    if (entry.isFile()) {
      yield entryPath;
    }
  }
}

console.log(`[userfront] optimized ${basename(buildDir)} with hashed entrypoints and brotli assets`);