import fs from 'node:fs/promises';
import path from 'node:path';
import vm from 'node:vm';

const root = path.resolve(import.meta.dirname, '..');

export async function loadI18n(context) {
  for (const name of ['texts-de', 'i18n']) {
    const filename = path.join(root, `public/js/${name}.js`);
    vm.runInNewContext(await fs.readFile(filename, 'utf8'), context, { filename });
  }
  return context.Wegwichtel.I18n;
}

const escapeText = value => value.replaceAll('&', '&amp;').replaceAll('<', '&lt;').replaceAll('>', '&gt;');

export async function localizedHtml(source) {
  const i18n = await loadI18n({});
  let result = source.replace(/(<[^>]+\bdata-i18n="([^"]+)"[^>]*>)([^<]*)(<\/)/g,
    (_match, opening, key, _text, closing) => opening + escapeText(i18n.t(key)) + closing);
  result = result.replace(/<[^>]+>/g, opening => {
    let translated = opening;
    for (const attribute of ['title', 'aria-label', 'placeholder', 'alt']) {
      const key = new RegExp(`data-i18n-${attribute}="([^"]+)"`).exec(opening)?.[1];
      if (key) translated = translated.replace(new RegExp(`\\b${attribute}="[^"]*"`), `${attribute}="${escapeText(i18n.t(key)).replaceAll('"', '&quot;')}"`);
    }
    return translated;
  });
  return result.replace(/\sdata-i18n(?:-[\w-]+)?="[^"]*"/g, '');
}

export async function readAppFile(relativePath) {
  const source = await fs.readFile(path.join(root, relativePath), 'utf8');
  if (relativePath === 'public/index.html') return localizedHtml(source);
  if (relativePath.startsWith('public/js/')) {
    // Static text assertions read the centralized wording; runtime tests use the real class.
    return source + '\n' + await fs.readFile(path.join(root, 'public/js/texts-de.js'), 'utf8');
  }
  return source;
}