/**
 * Builds the assets the landing page needs, into docs/.
 *
 * The page is served by GitHub Pages straight from the repository, so everything it loads has
 * to be committed — there is no build step on the hosting side. Everything it loads is also
 * local: the previous page pulled Tailwind, CodeMirror and Babel from three CDNs, and its
 * playground died silently when the unpinned `@babel/standalone` URL rolled over to Babel 8
 * and the plugin list it passed stopped existing. Vendoring the compiler pins it to the
 * version in package.json and to a lockfile.
 */
import { build } from 'esbuild';
import { copyFile, mkdir, readFile, writeFile, stat } from 'node:fs/promises';
import { fileURLToPath } from 'node:url';
import path from 'node:path';
import { collectDiagnostics } from './diagnostics.mjs';

const root = path.dirname(path.dirname(fileURLToPath(import.meta.url)));
const docs = path.join(root, 'docs');
const vendor = path.join(docs, 'vendor');

const size = async (file) => {
  const { size: bytes } = await stat(file);
  return `${(bytes / 1024).toFixed(0)} KB`;
};

await mkdir(vendor, { recursive: true });

const pkg = JSON.parse(await readFile(path.join(root, 'package.json'), 'utf8'));

// 1. The library itself, as a browser global the playground can pull names out of.
await build({
  entryPoints: [path.join(root, 'src/index.ts')],
  bundle: true,
  format: 'iife',
  globalName: 'Cereale',
  minify: true,
  target: 'es2022',
  tsconfigRaw: {
    compilerOptions: { experimentalDecorators: false, useDefineForClassFields: true, target: 'es2022' },
  },
  outfile: path.join(docs, 'cereale.js'),
});

// 2. Facts the page would otherwise hard-code and then get wrong. Everything else it needs —
//    the decorator count, the export list — it derives from the bundle at runtime.
await writeFile(
  path.join(docs, 'meta.js'),
  `// Generated by scripts/build-docs.mjs — do not edit.\n` +
  `window.CEREALE_META = ${JSON.stringify({ version: pkg.version, node: pkg.engines.node }, null, 2)};\n`
);

// 3. The compiler errors the page quotes, produced by actually running the compiler. If a
//    snippet the page calls a compile error ever compiles, this fails the build.
const { byCase, problems } = await collectDiagnostics(root);
if (problems.length > 0) {
  console.error('The landing page makes a claim the compiler does not support:\n' +
    problems.map((p) => `  - ${p}`).join('\n'));
  process.exit(1);
}
await writeFile(
  path.join(docs, 'diagnostics.js'),
  `// Generated by scripts/build-docs.mjs from real tsc output — do not edit.\n` +
  `window.CEREALE_DIAGNOSTICS = ${JSON.stringify(byCase, null, 2)};\n`
);

// 4. The playground's TypeScript compiler, pinned by package.json rather than by a CDN URL.
const babel = path.join(root, 'node_modules/@babel/standalone/babel.min.js');
await copyFile(babel, path.join(vendor, 'babel.min.js'));
await writeFile(
  path.join(vendor, 'README.md'),
  `# Vendored assets\n\n` +
  `Generated by \`npm run build:docs\`. Do not edit by hand.\n\n` +
  `- \`babel.min.js\` — @babel/standalone ${JSON.parse(await readFile(path.join(root, 'node_modules/@babel/standalone/package.json'), 'utf8')).version}, ` +
  `used by the playground to compile TypeScript with standard decorators in the browser. ` +
  `Vendored rather than loaded from a CDN: the previous page referenced an unpinned unpkg URL, ` +
  `which silently began serving Babel 8 and broke the playground.\n`
);

console.log(`docs/cereale.js       ${await size(path.join(docs, 'cereale.js'))}`);
console.log(`docs/meta.js          ${await size(path.join(docs, 'meta.js'))}  (v${pkg.version})`);
console.log(`docs/vendor/babel.min.js  ${await size(path.join(vendor, 'babel.min.js'))}`);