/**
 * 打包脚本：压缩并拷贝静态资源到 dist 目录。
 *
 * 压缩策略：
 *   - HTML → html-minifier（移除空白、注释、可省略引号）
 *   - CSS  → clean-css
 *   - JS   → terser
 *   - 图片 → 直接拷贝
 *
 * 排除：token.js、.env*、welfare-config.example.js、隐藏目录、node_modules、docs、scripts
 */

const fs = require('fs');
const path = require('path');

const { minify: minifyHtml } = require('html-minifier');
const CleanCSS = require('clean-css');
const { minify: minifyJs } = require('terser');

const ROOT = path.resolve(__dirname, '..');
const DIST = path.join(ROOT, 'dist');

// ───────────────── 排除规则 ─────────────────
const EXCLUDE_NAMES = new Set(['token.js', '.env', '.env.local', 'welfare-config.example.js']);

function shouldExclude(relativePath) {
  const name = path.basename(relativePath);
  if (EXCLUDE_NAMES.has(name)) return true;

  // 隐藏目录 / 黑名单目录
  for (const part of relativePath.split(path.sep)) {
    if (part.startsWith('.') || ['node_modules', 'docs', 'dist', 'scripts'].includes(part)) return true;
  }
  return false;
}

// ───────────────── 压缩器实例 ─────────────────
const htmlMinifyOpts = {
  collapseWhitespace: true,       // 合并空白
  removeComments: true,           // 删除注释
  removeAttributeQuotes: false,   // 保留引号（避免兼容性问题）
  minifyCSS: true,                // 内联 CSS 也压缩
  minifyJS: false,                // 内联 JS 不压缩（避免变量名冲突）
  removeEmptyAttributes: true,
  keepClosingSlash: false,
};
const cleanCSS = new CleanCSS({ level: 2 });

// ───────────────── 文件处理 ─────────────────
const extHandlers = {
  '.html': handleHtml,
  '.css':  handleCss,
  '.js':   handleJs,
};

function handleHtml(src, dest) {
  const raw = fs.readFileSync(src, 'utf8');
  const result = minifyHtml(raw, htmlMinifyOpts);
  fs.writeFileSync(dest, result, 'utf8');
  logFile(src, dest, raw.length, result.length);
}

async function handleJs(src, dest) {
  const raw = fs.readFileSync(src, 'utf8');
  const result = await minifyJs(raw, {
    compress: { drop_console: false },
    mangle: false,              // 不混淆变量名（i18n key 等动态引用）
    output: { comments: false },
  });
  if (result.code) {
    fs.writeFileSync(dest, result.code, 'utf8');
    logFile(src, dest, raw.length, result.code.length);
  } else {
    // terser 压缩失败时直接拷贝
    fs.copyFileSync(src, dest);
    console.warn('[build] ⚠ terser 跳过: ' + path.relative(ROOT, src));
  }
}

function handleCss(src, dest) {
  const raw = fs.readFileSync(src, 'utf8');
  const output = cleanCSS.minify(raw);
  if (output.styles) {
    fs.writeFileSync(dest, output.styles, 'utf8');
    logFile(src, dest, raw.length, output.styles.length);
  } else {
    fs.copyFileSync(src, dest);
  }
}

function logFile(src, dest, before, after) {
  const name = path.relative(ROOT, src);
  const ratio = before > 0 ? ((1 - after / before) * 100).toFixed(1) : '0.0';
  console.log(`[build]  ${name}  ${(before / 1024).toFixed(1)} KB → ${(after / 1024).toFixed(1)} KB (${ratio}%)`);
}

// ───────────────── 目录拷贝（含压缩） ─────────────────
async function buildDir(srcDir, destDir) {
  if (!fs.existsSync(srcDir)) return;
  const entries = fs.readdirSync(srcDir, { withFileTypes: true });
  for (const entry of entries) {
    const src = path.join(srcDir, entry.name);
    const relative = path.relative(ROOT, src);
    if (shouldExclude(relative)) continue;
    const dest = path.join(DIST, relative);

    if (entry.isDirectory()) {
      fs.mkdirSync(dest, { recursive: true });
      await buildDir(src, dest);
    } else {
      fs.mkdirSync(path.dirname(dest), { recursive: true });
      const handler = extHandlers[path.extname(entry.name)];
      if (handler) {
        await handler(src, dest);
      } else {
        fs.copyFileSync(src, dest);
      }
    }
  }
}

// ───────────────── 统计 ─────────────────
function countFiles(dir) {
  let c = 0;
  if (!fs.existsSync(dir)) return 0;
  for (const e of fs.readdirSync(dir, { withFileTypes: true })) {
    c += e.isDirectory() ? countFiles(path.join(dir, e.name)) : 1;
  }
  return c;
}

// ───────────────── 主流程 ─────────────────
(async () => {
  const start = Date.now();

  // 1. 清理
  console.log('[build] 清理 dist…');
  if (fs.existsSync(DIST)) fs.rmSync(DIST, { recursive: true });
  fs.mkdirSync(DIST, { recursive: true });

  // 2. html/ 子目录（含压缩）
  console.log('[build] 打包 html/…');
  await buildDir(path.join(ROOT, 'html'), path.join(DIST, 'html'));

  // 3. css / js / images
  for (const dir of ['css', 'js', 'images']) {
    console.log('[build] 打包 ' + dir + '/…');
    await buildDir(path.join(ROOT, dir), path.join(DIST, dir));
  }

  // 4. 根目录 *.html（压缩）
  console.log('[build] 打包根目录 HTML…');
  for (const entry of fs.readdirSync(ROOT, { withFileTypes: true })) {
    if (!entry.isFile() || !entry.name.endsWith('.html')) continue;
    const src = path.join(ROOT, entry.name);
    const dest = path.join(DIST, entry.name);
    await handleHtml(src, dest);
  }

  const total = countFiles(DIST);
  const elapsed = ((Date.now() - start) / 1000).toFixed(2);
  console.log('[build] 完成！ ' + total + ' 个文件 → dist/ (' + elapsed + 's)');
})();