From a55f14b7af65c7eef69a7ea809255601163938de Mon Sep 17 00:00:00 2001
From: reddragon333 <122625570+reddragon333@users.noreply.github.com>
Date: Wed, 15 Mar 2023 19:15:00 +0100
Subject: [PATCH] Add files via upload
---
static/js/lite-yt-embed.js | 166 +++++++++++++++++++++++++++++++++++++
1 file changed, 166 insertions(+)
create mode 100644 static/js/lite-yt-embed.js
diff --git a/static/js/lite-yt-embed.js b/static/js/lite-yt-embed.js
new file mode 100644
index 0000000..43275cf
--- /dev/null
+++ b/static/js/lite-yt-embed.js
@@ -0,0 +1,166 @@
+/**
+ * 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.style.backgroundImage = `url("https://i.ytimg.com/vi/${this.videoId}/hqdefault.jpg")`;
+ }
+
+ // 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);
+ }
+ 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.addIframe);
+
+ // 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.needsYTApiForAutoplay = navigator.vendor.includes('Apple') || navigator.userAgent.includes('Mobi');
+ }
+
+ /**
+ * Add a 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 `` 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);
+ });
+ }
+
+ async addYTPlayerIframe(params) {
+ this.fetchYTPlayerApi();
+ await this.ytApiPromise;
+
+ const videoPlaceholderEl = document.createElement('div')
+ this.append(videoPlaceholderEl);
+
+ const paramsObj = Object.fromEntries(params.entries());
+
+ new YT.Player(videoPlaceholderEl, {
+ width: '100%',
+ videoId: this.videoId,
+ playerVars: paramsObj,
+ events: {
+ 'onReady': event => {
+ event.target.playVideo();
+ }
+ }
+ });
+ }
+
+ async addIframe(){
+ if (this.classList.contains('lyt-activated')) return;
+ this.classList.add('lyt-activated');
+
+ const params = new URLSearchParams(this.getAttribute('params') || []);
+ params.append('autoplay', '1');
+ params.append('playsinline', '1');
+
+ if (this.needsYTApiForAutoplay) {
+ return this.addYTPlayerIframe(params);
+ }
+
+ 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);
+
+ // Set focus for a11y
+ iframeEl.focus();
+ }
+}
+// Register custom element
+customElements.define('lite-youtube', LiteYTEmbed);