// ==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            2.0.0
// @license            MIT
// @match              http*://*/*
// @run-at             document_end
// @grant              none
// @supportURL         https://greasyfork.org/scripts/450569/feedback
// @downloadURL none
// ==/UserScript==

const SESSION_KEY = getSessionKey();

const isAmp = (document.querySelector("html[⚡], html[amp]") !== null);
const canonical = document.head.querySelector("link[rel=canonical][href]");

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

    if (location.href !== lastVisit)
    {
        sessionStorage.setItem(SESSION_KEY, location.href);
        location.replace(canonical.href);
    }
    else
    {
        sessionStorage.removeItem(SESSION_KEY);
    }
}
else
{
    console.debug("[deAMP] Not a valid AMP page.");

    sessionStorage.removeItem(SESSION_KEY);
}


function getSessionKey()
{
    const SESSION_KEY = "sessionKey";

    let key = GM_getValue(SESSION_KEY);
    if (!key)
    {
        key = generateUuidV4();
        GM_setValue(SESSION_KEY, key);
    }

    return key;


    function generateUuidV4()
    {
        const uuid = new Array(36);
        for (let i = 0; i < 36; i++) { uuid[i] = Math.floor(Math.random() * 16); }
        uuid[14] = 4;
        uuid[19] = uuid[19] &= ~(1 << 2);
        uuid[19] = uuid[19] |= (1 << 3);
        uuid[8] = uuid[13] = uuid[18] = uuid[23] = "-";
        return uuid.map((x) => x.toString(16)).join("");
    }
}