Rewrite/redirect URLs

youtube2hooktube.user.js

// ==UserScript==
// @name        YouTube2HookTube
// @namespace   https://github.com/olmokramer
// @description Automatically redirect YouTube to HookTube
// @include     *
// @run-at      document-start
// @version     4
// @author      Olmo Kramer
// ==/UserScript==

(function() {
	'use strict';

	const seen_urls = {};

	function rewriteURL(url) {
		if (url in seen_urls) {
			return seen_urls[url];
		}

		url = new URL(url);
		url.host = 'hooktube.com';

		if (url.pathname.slice(0, 7) == '/embed/') {
			return url;
		}

		if (url.pathname.slice(0, 6) != '/watch') {
			const vid_id = url.pathname.slice(1);
			const search = url.search;

			url.pathname = '/watch'
			url.search = `?v=${vid_id}`;

			if (search) {
				url.search += `&${search.slice(1)}`;
			}
		}

		return seen_urls[url] = url.href;
	}

	if (window.location.host.match(/youtu(\.be|be\.com)/)) {
		window.location.href = rewriteURL(window.location);
		return;
	}

	function replaceURLs() {
		const domains = [
			'youtube.com',
			'youtu.be',
			'youtube-nocookie.com',
		];

		const attrs = ['href', 'src'];

		for (let domain of domains) {
			for (let attr of attrs) {
				for (let el of document.querySelectorAll(`[${attr}*="${domain}"]`)) {
					const old_url = el.getAttribute(attr);
					const new_url = rewriteURL(old_url);
					if (new_url != old_url) {
						el.setAttribute(attr, rewriteURL(el.getAttribute(attr)));
					}
				}
			}
		}
	}

	document.addEventListener('DOMContentLoaded', function() {
		new MutationObserver(replaceURLs).observe(document.body, {
			attributes: true,
			childList: true,
			subtree: true,
		});

		replaceURLs();
	});
})();