sdnext/javascript/loader.js

const appStartTime = performance.now();

async function preloadImages() {
  const dark = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;
  const imagePromises = [];
  const num = Math.floor(9.99 * Math.random());
  const imageUrls = [
    `file=html/logo-bg-${dark ? 'dark' : 'light'}.jpg`,
    `file=html/logo-bg-${num}.jpg`,
  ];
  for (const url of imageUrls) {
    const img = new Image();
    const promise = new Promise((resolve, reject) => {
      img.onload = resolve;
      img.onerror = reject;
    });
    img.src = url;
    imagePromises.push(promise);
  }
  try {
    await Promise.all(imagePromises);
    return true;
  } catch (err) {
    error(`preloadImages: ${err}`);
    return false;
  }
}

async function removeSplash() {
  const splash = document.getElementById('splash');
  if (splash) splash.remove();
  log('removeSplash');
  const t = Math.round(performance.now() - appStartTime);
  log('startupTime', t);
  xhrPost(`${window.api}/log`, { message: `ready time=${t}` });
}

async function createSplash() {
  const dark = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;
  log('createSplash', { theme: dark ? 'dark' : 'light' });
  const num = Math.floor(9.99 * Math.random());
  const splash = `
    <div id="splash" class="splash" style="background: ${dark ? 'black' : 'white'}">
      <div class="loading"><div class="loader"></div></div>
      <div id="motd" class="motd""></div>
    </div>`;
  document.body.insertAdjacentHTML('beforeend', splash);
  const ok = await preloadImages();
  if (!ok) {
    removeSplash();
    return;
  }
  const imgEl = `<div id="spash-img" class="splash-img" alt="logo" style="background-image: url(file=html/logo-bg-${dark ? 'dark' : 'light'}.jpg), url(file=html/logo-bg-${num}.jpg); background-blend-mode: ${dark ? 'multiply' : 'lighten'}"></div>`;
  document.getElementById('splash').insertAdjacentHTML('afterbegin', imgEl);
  fetch(`${window.api}/motd`)
    .then((res) => res.text())
    .then((text) => {
      const motdEl = document.getElementById('motd');
      if (motdEl) motdEl.innerHTML = text.replace(/["]+/g, '');
    })
    .catch((err) => error(`getMOTD: ${err}`));
}

window.onload = createSplash;