const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');

const rootDir = path.resolve(__dirname, '..');
const frontendDir = path.join(rootDir, 'frontend');
const distDir = path.join(frontendDir, 'dist');
const workerDir = path.join(rootDir, 'src', 'worker');
const htmlTsFile = path.join(workerDir, 'html.ts');

function inlineRequiredAsset(html, patterns, replacement, assetType) {
  for (const pattern of patterns) {
    if (pattern.test(html)) {
      return html.replace(pattern, replacement);
    }
  }
  throw new Error(`Unable to find the ${assetType} reference in the generated frontend HTML.`);
}

console.log('Building frontend...');
try {
  execFileSync(process.execPath, ['scripts/sync-theme-editor.js'], { cwd: rootDir, stdio: 'inherit' });
  // Dependencies are installed explicitly by developers/CI. Keeping installs out
  // of the build makes production artifacts deterministic and offline-buildable.
  const executableSuffix = process.platform === 'win32' ? '.cmd' : '';
  execFileSync(path.join(frontendDir, 'node_modules', '.bin', `tsc${executableSuffix}`), [], {
    cwd: frontendDir,
    stdio: 'inherit',
  });
  execFileSync(path.join(frontendDir, 'node_modules', '.bin', `vite${executableSuffix}`), ['build'], {
    cwd: frontendDir,
    stdio: 'inherit',
  });

  console.log('Inlining assets...');
  // 2. Read dist/index.html
  let html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf8');

  // 3. Find assets in dist/assets
  const assetsDir = path.join(distDir, 'assets');
  const files = fs.readdirSync(assetsDir).sort();
  const jsFiles = files.filter((file) => file.endsWith('.js'));
  const cssFiles = files.filter((file) => file.endsWith('.css'));

  if (jsFiles.length !== 1 || cssFiles.length !== 1) {
    throw new Error(
      `Expected exactly one JS and one CSS bundle for Worker inlining, got ${jsFiles.length} JS and ${cssFiles.length} CSS.`
    );
  }

  const jsContent = fs.readFileSync(path.join(assetsDir, jsFiles[0]), 'utf8');
  const cssContent = fs.readFileSync(path.join(assetsDir, cssFiles[0]), 'utf8');

  // 4. Inline favicon.svg as base64 data URL
  const faviconPath = path.join(frontendDir, 'public', 'favicon.svg');
  if (fs.existsSync(faviconPath)) {
    const faviconContent = fs.readFileSync(faviconPath, 'utf8');
    const faviconBase64 = Buffer.from(faviconContent).toString('base64');
    html = html.replace(
      /href=["']\/favicon\.svg["']/i,
      `href="data:image/svg+xml;base64,${faviconBase64}"`
    );
  }

  // 5. Inline CSS (replace <link rel="stylesheet" ...>)
  html = inlineRequiredAsset(html, [
    /<link[^>]*rel=["']stylesheet["'][^>]*href=["']\/assets\/[^"']+["'][^>]*>/i,
    /<link[^>]*rel=["']stylesheet["'][^>]*href=["']\/src\/[^"']+["'][^>]*>/i,
  ], () => `<style>${cssContent}</style>`, 'stylesheet');

  // 6. Inline JS (replace <script type="module" src="/src/main.ts"></script> or similar)
  html = inlineRequiredAsset(html, [
    /<script[^>]*type=["']module["'][^>]*src=["']\/assets\/[^"']+["'][^>]*><\/script>/i,
    /<script[^>]*type=["']module["'][^>]*src=["']\/src\/[^"']+["'][^>]*><\/script>/i,
  ], () => `<script type="module">${jsContent}</script>`, 'module script');

  // 7. Write to src/worker/html.ts
  const escapedHtml = html
    .replace(/\\/g, '\\\\')
    .replace(/`/g, '\\`')
    .replace(/\${/g, '\\${');

  const htmlTsContent = `// Automatically generated by scripts/build-html.js. Do not edit directly.
export const HTML = \`${escapedHtml}\`;
`;

  if (!fs.existsSync(workerDir)) {
    fs.mkdirSync(workerDir, { recursive: true });
  }

  fs.writeFileSync(htmlTsFile, htmlTsContent, 'utf8');
  console.log('Frontend built and inlined successfully to src/worker/html.ts!');
} catch (error) {
  console.error('Failed to build and inline frontend:', error);
  process.exit(1);
}