import { copyFile, mkdir, readdir, readFile, rm, stat, writeFile } from 'node:fs/promises';
import { dirname, extname, join, resolve } from 'node:path';
import { transform } from 'esbuild';

const sourceRoot = resolve(import.meta.dirname, '..');
const outputRoot = resolve(sourceRoot, 'dist');
const sourceDirectories = ['public', 'utils'];
const sourceFiles = ['config.js', 'tokens.css'];
const totals = {
  css: { files: 0, sourceBytes: 0, outputBytes: 0 },
  js: { files: 0, sourceBytes: 0, outputBytes: 0 }
};

function shouldMinify(filePath) {
  const extension = extname(filePath).toLowerCase();
  return (extension === '.css' || extension === '.js') && !filePath.toLowerCase().endsWith(`.min${extension}`);
}

async function writeBuildFile(sourcePath, destinationPath) {
  await mkdir(dirname(destinationPath), { recursive: true });
  if (!shouldMinify(sourcePath)) {
    await copyFile(sourcePath, destinationPath);
    return;
  }

  const extension = extname(sourcePath).slice(1).toLowerCase();
  const source = await readFile(sourcePath, 'utf8');
  const result = await transform(source, {
    loader: extension,
    minify: true,
    target: 'es2018',
    charset: 'utf8',
    legalComments: 'inline'
  });
  const output = result.code.trimEnd() + '\n';

  await writeFile(destinationPath, output, 'utf8');
  totals[extension].files += 1;
  totals[extension].sourceBytes += Buffer.byteLength(source);
  totals[extension].outputBytes += Buffer.byteLength(output);
}

async function copyDirectory(sourceDirectory, destinationDirectory) {
  await mkdir(destinationDirectory, { recursive: true });
  for (const entry of await readdir(sourceDirectory, { withFileTypes: true })) {
    const sourcePath = join(sourceDirectory, entry.name);
    const destinationPath = join(destinationDirectory, entry.name);

    if (entry.isDirectory()) await copyDirectory(sourcePath, destinationPath);
    else if (entry.isFile()) await writeBuildFile(sourcePath, destinationPath);
  }
}

function formatSavings(type) {
  const total = totals[type];
  const percent = total.sourceBytes
    ? Math.round((1 - total.outputBytes / total.sourceBytes) * 100)
    : 0;
  return `${type.toUpperCase()}: ${total.files} 个文件，${total.sourceBytes} → ${total.outputBytes} 字节，减少 ${percent}%`;
}

if (outputRoot !== resolve(sourceRoot, 'dist')) {
  throw new Error('拒绝清理预期目录之外的构建输出');
}

await rm(outputRoot, { recursive: true, force: true });
await mkdir(outputRoot, { recursive: true });

for (const entry of await readdir(sourceRoot, { withFileTypes: true })) {
  if (entry.isFile() && entry.name.endsWith('.html')) {
    await copyFile(join(sourceRoot, entry.name), join(outputRoot, entry.name));
  }
}
for (const file of sourceFiles) {
  await writeBuildFile(join(sourceRoot, file), join(outputRoot, file));
}
for (const directory of sourceDirectories) {
  const sourceDirectory = join(sourceRoot, directory);
  if ((await stat(sourceDirectory)).isDirectory()) {
    await copyDirectory(sourceDirectory, join(outputRoot, directory));
  }
}

console.log(`压缩构建已生成：${outputRoot}`);
console.log(formatSavings('css'));
console.log(formatSavings('js'));