import { watch } from 'node:fs';
import { access, constants, copyFile, mkdir, readdir, unlink } 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 sourceDir = join(root, 'dist/phx-frontend-plugin-demo/browser');
const destDir = join(root, 'latest');

async function copyJsFiles() {
  try {
    await access(sourceDir, constants.F_OK);
    await mkdir(destDir, { recursive: true });

    const files = (await readdir(sourceDir)).filter((f) => f.endsWith('.js'));

    for (const file of files) {
      await copyFile(join(sourceDir, file), join(destDir, file));
    }

    const destFiles = (await readdir(destDir)).filter((f) => f.endsWith('.js'));
    for (const file of destFiles) {
      if (!files.includes(file)) {
        await unlink(join(destDir, file));
      }
    }

    console.log(`[latest] Copied ${files.length} JS file(s)`);
  } catch (err) {
    if (err.code !== 'ENOENT') {
      console.error('[latest] Copy failed:', err.message);
    }
  }
}

function watchJsFiles() {
  let timeout;

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

  const tryWatch = () => {
    access(sourceDir, constants.F_OK)
      .then(() => {
        copyJsFiles();
        watch(sourceDir, debouncedCopy);
        console.log('[latest] Watching for JS changes in dist');
      })
      .catch(() => setTimeout(tryWatch, 500));
  };

  tryWatch();
}

if (process.argv.includes('--watch')) {
  watchJsFiles();
} else {
  copyJsFiles();
}