// ==UserScript==
// @name               deAMP
// @name:zh-TW         deAMP
// @description        AMP sucks, thus no AMP thanks.
// @description:zh-TW  垃圾 AMP，好走不送。
// @author             Jason Kwok
// @namespace          https://jasonhk.dev/
// @version            2.2.1
// @license            MIT
// @match              http*://*/*
// @run-at             document_end
// @grant              GM.getValue
// @grant              GM.setValue
// @require            https://cdn.jsdelivr.net/npm/uuid-random@1.3.2/uuid-random.min.js
// @supportURL         https://greasyfork.org/scripts/450569/feedback
// @downloadURL none
// ==/UserScript==

(async () =>
{
    const SESSION_KEY = await getSessionKey();

    const isAmp = document.documentElement.hasAttribute("⚡") || document.documentElement.hasAttribute("amp");
    const canonical = document.head.querySelector("link[rel=canonical][href]");

    if (isAmp && (canonical !== null))
    {
        const lastVisit = sessionStorage.getItem(SESSION_KEY);

        if (location.href === lastVisit)
        {
            console.debug("[deAMP] Last visited URL is the current URL, abort redirection.");
            sessionStorage.removeItem(SESSION_KEY);
        }
        else if (location.href === canonical.href)
        {
            console.debug("[deAMP] Canonical URL is the current URL, abort redirection.");
            sessionStorage.removeItem(SESSION_KEY);
        }
        else
        {
            console.debug(`[deAMP] Redirecting to canonical URL: ${canonical.href}`);

            sessionStorage.setItem(SESSION_KEY, location.href);
            location.replace(canonical.href);
        }
    }
    else
    {
        console.debug("[deAMP] Not an AMP page.");
        sessionStorage.removeItem(SESSION_KEY);
    }

    async function getSessionKey()
    {
        let key = await GM.getValue("SESSION_KEY");
        if (key) { return key; }

        key = uuid();
        GM.setValue("SESSION_KEY", key);
        return key;
    }
})();