import { cp, mkdir, readFile, writeFile } from 'node:fs/promises';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';

const root = dirname(dirname(fileURLToPath(import.meta.url)));
const dist = join(root, 'dist');
const referenceSource = join(root, 'phase2-unreal', 'ReferenceSource');
const publishedReferenceSource = join(dist, 'phase2-unreal', 'ReferenceSource');

await mkdir(dist, { recursive: true });
await cp(referenceSource, publishedReferenceSource, { recursive: true, force: true });
await copyIfChanged(join(root, 'styles.css'), join(dist, 'styles.css'));
await copyIfChanged(join(root, 'src', 'main.ts'), join(dist, 'main.js'));
for (const moduleName of ['shared.js', 'world-architect.js', 'ui-reality.js']) {
  await copyIfChanged(join(root, 'src', moduleName), join(dist, moduleName));
}

const builtHtml = (await BunlessHtml(await import('node:fs/promises')))
  .replace('./src/main.ts', './main.js');
await writeIfChanged(join(dist, 'index.html'), builtHtml);
console.log(`GitWorld build ready: ${dist}`);

async function copyIfChanged(source, destination) {
  if (await filesMatch(source, destination)) {
    return;
  }
  await cp(source, destination);
}

async function writeIfChanged(destination, contents) {
  try {
    if ((await readFile(destination, 'utf8')) === contents) {
      return;
    }
  } catch {
    // The destination does not exist yet.
  }
  await writeFile(destination, contents, 'utf8');
}

async function filesMatch(left, right) {
  try {
    const [leftContents, rightContents] = await Promise.all([
      readFile(left),
      readFile(right)
    ]);
    return leftContents.equals(rightContents);
  } catch {
    return false;
  }
}

async function BunlessHtml(fs) {
  return fs.readFile(join(root, 'index.html'), 'utf8');
}