import { watch } from 'node:fs';
import { access, constants, copyFile, mkdir } from 'node:fs/promises';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const root = join(__dirname, '..');
const source = join(root, 'dist/phx-frontend-plugin-demo/browser/main.js');
const dest = join(root, 'latest/main.js');

async function copyMainJs() {
  try {
    await access(source, constants.F_OK);
    await mkdir(dirname(dest), { recursive: true });
    await copyFile(source, dest);
    console.log('[latest] Copied main.js');
  } catch (err) {
    if (err.code !== 'ENOENT') {
      console.error('[latest] Copy failed:', err.message);
    }
  }
}

function watchMainJs() {
  let timeout;

  const debouncedCopy = () => {
    clearTimeout(timeout);
    timeout = setTimeout(copyMainJs, 100);
  };

  const tryWatch = () => {
    access(source, constants.F_OK)
      .then(() => {
        copyMainJs();
        watch(source, debouncedCopy);
        console.log('[latest] Watching for main.js changes');
      })
      .catch(() => setTimeout(tryWatch, 500));
  };

  tryWatch();
}

if (process.argv.includes('--watch')) {
  watchMainJs();
} else {
  copyMainJs();
}