function setText(node, text) {
  if (node) node.textContent = text;
}

function setHtml(node, html) {
  if (node) node.innerHTML = html;
}

function renderFileProtocolGuidance(doc) {
  setText(doc.querySelector('.loader-subtitle'), 'Serve this world over HTTP to initialize Three.js.');
  const bootMessage = doc.getElementById('boot-message');
  if (bootMessage) {
    bootMessage.style.display = 'block';
    setHtml(
      bootMessage,
      [
        '<strong>Three.js modules cannot boot from <code>file://</code>.</strong>',
        'Serve the Nexus over HTTP, for example:',
        '<code>python3 -m http.server 8888</code>',
      ].join('<br>')
    );
  }
}

function injectModuleBootstrap(doc, src = './bootstrap.mjs') {
  const script = doc.createElement('script');
  script.type = 'module';
  script.src = src;
  doc.body.appendChild(script);
  return script;
}

function bootPage(win = window, doc = document) {
  if (win?.location?.protocol === 'file:') {
    renderFileProtocolGuidance(doc);
    return { mode: 'file' };
  }

  injectModuleBootstrap(doc);
  return { mode: 'module' };
}

if (typeof window !== 'undefined' && typeof document !== 'undefined') {
  bootPage(window, document);
}

if (typeof module !== 'undefined') {
  module.exports = { bootPage, injectModuleBootstrap, renderFileProtocolGuidance };
}