add auto blocking YT and yt embed block

blocks/embed/lite-yt-embed.css

@@ -0,0 +1,90 @@
+/* copied from https://github.com/paulirish/lite-youtube-embed/releases/tag/v0.2.0 */
+/* stylelint-disable */
+
+lite-youtube {
+  background-color: #000;
+  position: relative;
+  display: block;
+  contain: content;
+  background-position: center center;
+  background-size: cover;
+  cursor: pointer;
+  max-width: 720px;
+}
+
+/* gradient */
+lite-youtube::before {
+  content: '';
+  display: block;
+  position: absolute;
+  top: 0;
+  background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAADGCAYAAAAT+OqFAAAAdklEQVQoz42QQQ7AIAgEF/T/D+kbq/RWAlnQyyazA4aoAB4FsBSA/bFjuF1EOL7VbrIrBuusmrt4ZZORfb6ehbWdnRHEIiITaEUKa5EJqUakRSaEYBJSCY2dEstQY7AuxahwXFrvZmWl2rh4JZ07z9dLtesfNj5q0FU3A5ObbwAAAABJRU5ErkJggg==);
+  background-position: top;
+  background-repeat: repeat-x;
+  height: 60px;
+  padding-bottom: 50px;
+  width: 100%;
+  transition: all 0.2s cubic-bezier(0, 0, 0.2, 1);
+}
+
+/* responsive iframe with a 16:9 aspect ratio
+    thanks https://css-tricks.com/responsive-iframes/
+*/
+lite-youtube::after {
+  content: "";
+  display: block;
+  padding-bottom: calc(100% / (16 / 9));
+}
+
+lite-youtube > iframe {
+  width: 100%;
+  height: 100%;
+  position: absolute;
+  top: 0;
+  left: 0;
+  border: 0;
+}
+
+/* play button */
+lite-youtube > .lty-playbtn {
+  width: 68px;
+  height: 48px;
+  position: absolute;
+  cursor: pointer;
+  transform: translate3d(-50%, -50%, 0);
+  top: 50%;
+  left: 50%;
+  z-index: 1;
+  background-color: transparent;
+  /* YT's actual play button svg */
+  background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 68 48"><path fill="%23f00" fill-opacity="0.8" d="M66.52,7.74c-0.78-2.93-2.49-5.41-5.42-6.19C55.79,.13,34,0,34,0S12.21,.13,6.9,1.55 C3.97,2.33,2.27,4.81,1.48,7.74C0.06,13.05,0,24,0,24s0.06,10.95,1.48,16.26c0.78,2.93,2.49,5.41,5.42,6.19 C12.21,47.87,34,48,34,48s21.79-0.13,27.1-1.55c2.93-0.78,4.64-3.26,5.42-6.19C67.94,34.95,68,24,68,24S67.94,13.05,66.52,7.74z"></path><path d="M 45,24 27,14 27,34" fill="%23fff"></path></svg>');
+  filter: grayscale(100%);
+  transition: filter .1s cubic-bezier(0, 0, 0.2, 1);
+  border: none;
+}
+
+lite-youtube:hover > .lty-playbtn,
+lite-youtube .lty-playbtn:focus {
+  filter: none;
+}
+
+/* Post-click styles */
+lite-youtube.lyt-activated {
+  cursor: unset;
+}
+
+lite-youtube.lyt-activated::before,
+lite-youtube.lyt-activated > .lty-playbtn {
+  opacity: 0;
+  pointer-events: none;
+}
+
+.lyt-visually-hidden {
+  clip: rect(0 0 0 0);
+  clip-path: inset(50%);
+  height: 1px;
+  overflow: hidden;
+  position: absolute;
+  white-space: nowrap;
+  width: 1px;
+}

blocks/embed/lite-yt-embed.js

@@ -0,0 +1,127 @@
+// Copied from https://github.com/paulirish/lite-youtube-embed/releases/tag/v0.2.0
+/* eslint-disable */
+/**
+ * A lightweight youtube embed. Still should feel the same to the user, just MUCH faster to initialize and paint.
+ *
+ * Thx to these as the inspiration
+ *   https://storage.googleapis.com/amp-vs-non-amp/youtube-lazy.html
+ *   https://autoplay-youtube-player.glitch.me/
+ *
+ * Once built it, I also found these:
+ *   https://github.com/ampproject/amphtml/blob/master/extensions/amp-youtube (👍👍)
+ *   https://github.com/Daugilas/lazyYT
+ *   https://github.com/vb/lazyframe
+ */
+class LiteYTEmbed extends HTMLElement {
+  connectedCallback() {
+    this.videoId = this.getAttribute('videoid');
+
+    let playBtnEl = this.querySelector('.lty-playbtn');
+    // A label for the button takes priority over a [playlabel] attribute on the custom-element
+    this.playLabel = (playBtnEl && playBtnEl.textContent.trim()) || this.getAttribute('playlabel') || 'Play';
+
+    /**
+     * Lo, the youtube placeholder image!  (aka the thumbnail, poster image, etc)
+     *
+     * See https://github.com/paulirish/lite-youtube-embed/blob/master/youtube-thumbnail-urls.md
+     *
+     * TODO: Do the sddefault->hqdefault fallback
+     *       - When doing this, apply referrerpolicy (https://github.com/ampproject/amphtml/pull/3940)
+     * TODO: Consider using webp if supported, falling back to jpg
+     */
+    if (!this.style.backgroundImage) {
+      this.posterUrl = `https://i.ytimg.com/vi/${this.videoId}/hqdefault.jpg`;
+      // Warm the connection for the poster image
+      LiteYTEmbed.addPrefetch('preload', this.posterUrl, 'image');
+
+      this.style.backgroundImage = `url("${this.posterUrl}")`;
+    }
+
+    // Set up play button, and its visually hidden label
+    if (!playBtnEl) {
+      playBtnEl = document.createElement('button');
+      playBtnEl.type = 'button';
+      playBtnEl.classList.add('lty-playbtn');
+      this.append(playBtnEl);
+    }
+    if (!playBtnEl.textContent) {
+      const playBtnLabelEl = document.createElement('span');
+      playBtnLabelEl.className = 'lyt-visually-hidden';
+      playBtnLabelEl.textContent = this.playLabel;
+      playBtnEl.append(playBtnLabelEl);
+    }
+
+    // On hover (or tap), warm up the TCP connections we're (likely) about to use.
+    this.addEventListener('pointerover', LiteYTEmbed.warmConnections, {once: true});
+
+    // Once the user clicks, add the real iframe and drop our play button
+    // TODO: In the future we could be like amp-youtube and silently swap in the iframe during idle time
+    //   We'd want to only do this for in-viewport or near-viewport ones: https://github.com/ampproject/amphtml/pull/5003
+    this.addEventListener('click', e => this.addIframe());
+  }
+
+  // // TODO: Support the the user changing the [videoid] attribute
+  // attributeChangedCallback() {
+  // }
+
+  /**
+   * Add a <link rel={preload | preconnect} ...> to the head
+   */
+  static addPrefetch(kind, url, as) {
+    const linkEl = document.createElement('link');
+    linkEl.rel = kind;
+    linkEl.href = url;
+    if (as) {
+      linkEl.as = as;
+    }
+    document.head.append(linkEl);
+  }
+
+  /**
+   * Begin pre-connecting to warm up the iframe load
+   * Since the embed's network requests load within its iframe,
+   *   preload/prefetch'ing them outside the iframe will only cause double-downloads.
+   * So, the best we can do is warm up a few connections to origins that are in the critical path.
+   *
+   * Maybe `<link rel=preload as=document>` would work, but it's unsupported: http://crbug.com/593267
+   * But TBH, I don't think it'll happen soon with Site Isolation and split caches adding serious complexity.
+   */
+  static warmConnections() {
+    if (LiteYTEmbed.preconnected) return;
+
+    // The iframe document and most of its subresources come right off youtube.com
+    LiteYTEmbed.addPrefetch('preconnect', 'https://www.youtube-nocookie.com');
+    // The botguard script is fetched off from google.com
+    LiteYTEmbed.addPrefetch('preconnect', 'https://www.google.com');
+
+    // Not certain if these ad related domains are in the critical path. Could verify with domain-specific throttling.
+    LiteYTEmbed.addPrefetch('preconnect', 'https://googleads.g.doubleclick.net');
+    LiteYTEmbed.addPrefetch('preconnect', 'https://static.doubleclick.net');
+
+    LiteYTEmbed.preconnected = true;
+  }
+
+  addIframe() {
+    const params = new URLSearchParams(this.getAttribute('params') || []);
+    params.append('autoplay', '1');
+
+    const iframeEl = document.createElement('iframe');
+    iframeEl.width = 560;
+    iframeEl.height = 315;
+    // No encoding necessary as [title] is safe. https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html#:~:text=Safe%20HTML%20Attributes%20include
+    iframeEl.title = this.playLabel;
+    iframeEl.allow = 'accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture';
+    iframeEl.allowFullscreen = true;
+    // AFAIK, the encoding here isn't necessary for XSS, but we'll do it only because this is a URL
+    // https://stackoverflow.com/q/64959723/89484
+    iframeEl.src = `https://www.youtube-nocookie.com/embed/${encodeURIComponent(this.videoId)}?${params.toString()}`;
+    this.append(iframeEl);
+
+    this.classList.add('lyt-activated');
+
+    // Set focus for a11y
+    this.querySelector('iframe').focus();
+  }
+}
+// Register custom element
+customElements.define('lite-youtube', LiteYTEmbed);

scripts/scripts.js

@@ -113,6 +113,42 @@ function buildLiveByMetadata(main) {
   }
 }
 
+export function getYoutubeVideoId(url) {
+  if (url.includes('youtube.com/watch?v=')) {
+    return new URL(url).searchParams.get('v');
+  }
+  if (url.includes('youtube.com/embed/') || url.includes('youtu.be/')) {
+    return new URL(url).pathname.split('/').pop();
+  }
+  return null;
+}
+
+function decorateVideoLinks(main) {
+  [...main.querySelectorAll('a')]
+    .filter(({ href }) => !!href)
+  // only convert plain links
+    .filter((a) => a.textContent?.trim()?.toLowerCase().startsWith('http'))
+  // don't decorate if already in a block. unless it's `columns`.
+    .filter((a) => {
+      const block = a.closest('div.block');
+      if (!block) return true;
+      return block.classList.contains('columns');
+    })
+    .forEach((link) => {
+      const youtubeVideoId = getYoutubeVideoId(link.href);
+
+      if (youtubeVideoId) {
+        loadCSS('/blocks/embed/lite-yt-embed.css');
+        loadScript('/blocks/embed/lite-yt-embed.js');
+        const video = document.createElement('lite-youtube');
+        video.setAttribute('videoid', youtubeVideoId);
+        video.setAttribute('params', 'rel=0');
+        video.classList.add('youtube-video');
+        link.replaceWith(video);
+      }
+    });
+}
+
 /**
  * Build Floating image block
  * @param {Element} main The container element
@@ -214,6 +250,7 @@ export function decorateMain(main) {
   buildAutoBlocks(main);
   decorateSections(main);
   decorateBlocks(main);
+  decorateVideoLinks(main);
 }
 
 /**