add lite-youtube embeds

package.json

@@ -20,6 +20,7 @@
   },
   "dependencies": {
     "@astrojs/rss": "^4.0.5",
+    "lite-youtube-embed": "^0.3.2",
     "marked": "^4.0.17"
   }
 }

public/assets/lite-yt-embed.css

@@ -0,0 +1,102 @@
+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: attr(data-title);
+  display: block;
+  position: absolute;
+  top: 0;
+  /* Pixel-perfect port of YT's gradient PNG, using https://github.com/bluesmoon/pngtocss plus optimizations */
+  background-image: linear-gradient(
+    180deg,
+    rgb(0 0 0 / 67%) 0%,
+    rgb(0 0 0 / 54%) 14%,
+    rgb(0 0 0 / 15%) 54%,
+    rgb(0 0 0 / 5%) 72%,
+    rgb(0 0 0 / 0%) 94%
+  );
+  height: 99px;
+  width: 100%;
+  font-family: 'YouTube Noto', Roboto, Arial, Helvetica, sans-serif;
+  color: hsl(0deg 0% 93.33%);
+  text-shadow: 0 0 2px rgba(0, 0, 0, 0.5);
+  font-size: 18px;
+  padding: 25px 20px;
+  overflow: hidden;
+  white-space: nowrap;
+  text-overflow: ellipsis;
+  box-sizing: border-box;
+}
+
+lite-youtube:hover::before {
+  color: white;
+}
+
+/* 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 {
+  display: block;
+  /* Make the button element cover the whole area for a large hover/click target… */
+  width: 100%;
+  height: 100%;
+  /* …but visually it's still the same size */
+  background: no-repeat center/68px 48px;
+  /* YT's actual play button svg */
+  background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 68 48"><path d="M66.52 7.74c-.78-2.93-2.49-5.41-5.42-6.19C55.79.13 34 0 34 0S12.21.13 6.9 1.55c-2.93.78-4.63 3.26-5.42 6.19C.06 13.05 0 24 0 24s.06 10.95 1.48 16.26c.78 2.93 2.49 5.41 5.42 6.19C12.21 47.87 34 48 34 48s21.79-.13 27.1-1.55c2.93-.78 4.64-3.26 5.42-6.19C67.94 34.95 68 24 68 24s-.06-10.95-1.48-16.26z" fill="red"/><path d="M45 24 27 14v20" fill="white"/></svg>');
+  position: absolute;
+  cursor: pointer;
+  z-index: 1;
+  filter: grayscale(100%);
+  transition: filter 0.1s cubic-bezier(0, 0, 0.2, 1);
+  border: 0;
+}
+
+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;
+}

public/assets/lite-yt-embed.js

@@ -0,0 +1,241 @@
+/**
+ * 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() {
+    console.log('LiteYTEmbed connected');
+    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';
+
+    this.dataset.title = this.getAttribute('title') || '';
+
+    /**
+     * Lo, the youtube poster image!  (aka the thumbnail, image placeholder, etc)
+     *
+     * See https://github.com/paulirish/lite-youtube-embed/blob/master/youtube-thumbnail-urls.md
+     */
+    if (!this.style.backgroundImage) {
+      this.style.backgroundImage = `url("https://i.ytimg.com/vi/${this.videoId}/hqdefault.jpg")`;
+      this.upgradePosterImage();
+    }
+
+    // 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);
+    }
+
+    this.addNoscriptIframe();
+
+    playBtnEl.removeAttribute('href');
+
+    // 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', this.activate);
+
+    // Chrome & Edge desktop have no problem with the basic YouTube Embed with ?autoplay=1
+    // However Safari desktop and most/all mobile browsers do not successfully track the user gesture of clicking through the creation/loading of the iframe,
+    // so they don't autoplay automatically. Instead we must load an additional 2 sequential JS files (1KB + 165KB) (un-br) for the YT Player API
+    // TODO: Try loading the the YT API in parallel with our iframe and then attaching/playing it. #82
+    this.needsYTApi =
+      this.hasAttribute('js-api') ||
+      navigator.vendor.includes('Apple') ||
+      navigator.userAgent.includes('Mobi');
+  }
+
+  /**
+   * 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;
+  }
+
+  fetchYTPlayerApi() {
+    if (window.YT || (window.YT && window.YT.Player)) return;
+
+    this.ytApiPromise = new Promise((res, rej) => {
+      var el = document.createElement('script');
+      el.src = 'https://www.youtube.com/iframe_api';
+      el.async = true;
+      el.onload = (_) => {
+        YT.ready(res);
+      };
+      el.onerror = rej;
+      this.append(el);
+    });
+  }
+
+  /** Return the YT Player API instance. (Public L-YT-E API) */
+  async getYTPlayer() {
+    if (!this.playerPromise) {
+      await this.activate();
+    }
+
+    return this.playerPromise;
+  }
+
+  async addYTPlayerIframe() {
+    this.fetchYTPlayerApi();
+    await this.ytApiPromise;
+
+    const videoPlaceholderEl = document.createElement('div');
+    this.append(videoPlaceholderEl);
+
+    const paramsObj = Object.fromEntries(this.getParams().entries());
+
+    this.playerPromise = new Promise((resolve) => {
+      let player = new YT.Player(videoPlaceholderEl, {
+        width: '100%',
+        videoId: this.videoId,
+        playerVars: paramsObj,
+        events: {
+          onReady: (event) => {
+            event.target.playVideo();
+            resolve(player);
+          },
+        },
+      });
+    });
+  }
+
+  // Add the iframe within <noscript> for indexability discoverability. See https://github.com/paulirish/lite-youtube-embed/issues/105
+  addNoscriptIframe() {
+    const iframeEl = this.createBasicIframe();
+    const noscriptEl = document.createElement('noscript');
+    // Appending into noscript isn't equivalant for mysterious reasons: https://html.spec.whatwg.org/multipage/scripting.html#the-noscript-element
+    noscriptEl.innerHTML = iframeEl.outerHTML;
+    this.append(noscriptEl);
+  }
+
+  getParams() {
+    const params = new URLSearchParams(this.getAttribute('params') || []);
+    params.append('autoplay', '1');
+    params.append('playsinline', '1');
+    return params;
+  }
+
+  async activate() {
+    if (this.classList.contains('lyt-activated')) return;
+    this.classList.add('lyt-activated');
+
+    if (this.needsYTApi) {
+      return this.addYTPlayerIframe(this.getParams());
+    }
+
+    const iframeEl = this.createBasicIframe();
+    this.append(iframeEl);
+
+    // Set focus for a11y
+    iframeEl.focus();
+  }
+
+  createBasicIframe() {
+    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,
+    )}?${this.getParams().toString()}`;
+    return iframeEl;
+  }
+
+  /**
+   * In the spirit of the `lowsrc` attribute and progressive JPEGs, we'll upgrade the reliable
+   * poster image to a higher resolution one, if it's available.
+   * Interestingly this sddefault webp is often smaller in filesize, but we will still attempt it second
+   * because getting _an_ image in front of the user if our first priority.
+   *
+   * See https://github.com/paulirish/lite-youtube-embed/blob/master/youtube-thumbnail-urls.md for more details
+   */
+  upgradePosterImage() {
+    // Defer to reduce network contention.
+    setTimeout(() => {
+      const webpUrl = `https://i.ytimg.com/vi_webp/${this.videoId}/sddefault.webp`;
+      const img = new Image();
+      img.fetchPriority = 'low'; // low priority to reduce network contention
+      img.referrerpolicy = 'origin'; // Not 100% sure it's needed, but https://github.com/ampproject/amphtml/pull/3940
+      img.src = webpUrl;
+      img.onload = (e) => {
+        // A pretty ugly hack since onerror won't fire on YouTube image 404. This is (probably) due to
+        // Youtube's style of returning data even with a 404 status. That data is a 120x90 placeholder image.
+        // … per "annoying yt 404 behavior" in the .md
+        const noAvailablePoster =
+          e.target.naturalHeight == 90 && e.target.naturalWidth == 120;
+        if (noAvailablePoster) return;
+
+        this.style.backgroundImage = `url("${webpUrl}")`;
+      };
+    }, 100);
+  }
+}
+// Register custom element
+customElements.define('lite-youtube', LiteYTEmbed);