// https://github.com/paulirish/lite-youtube-embed/blob/master/src/lite-yt-embed.js

// import canAutoPlay from 'can-autoplay'


/**
 * 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 {
    constructor() {
        // Always call super first in constructor
        super()

        // write element functionality in here

        // console.log('canAutoplay', canAutoplay)

    }

    connectedCallback() {
        this.videoId = this.getAttribute('videoid')

        console.log('canAutoplay from connectedCallback', canAutoplay)

        // 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
window.customElements.define('lite-youtube', LiteYTEmbed)