YouTube_layout_config.user.js

// ==UserScript==
// @name          YouTube layout config
// @namespace     https://github.com/UCyborg
// @description   Provides configuration interface for switching between desktop and mobile version of YouTube.
// @version       1.0
// @author        UCyborg
// @downloadURL   https://gist.github.com/UCyborg/754fe319866a7f126ec1d074ed922b37/raw/YouTube_layout_config.user.js
// @include       /https:\/\/(www|m)\.youtube\.com\/(?!embed\/.*$)/
// @run-at        document-start
// @require       https://openuserjs.org/src/libs/sizzle/GM_config.js
// @grant         GM_getValue
// @grant         GM_setValue
// @grant         GM_registerMenuCommand
// ==/UserScript==

'use strict';

function updateYTPrefCookie(includeApp, mobileApp) {

  function recordDefaultYTLayout() {
    const url = new URL(window.location);
    if (url.host.split('.')[0] == 'www') {
      GM_setValue('YTDefaultLayout', 'Desktop');
    } else {
      GM_setValue('YTDefaultLayout', 'Mobile');
    }
  }

  function getYTPrefCookie() {
    const name = 'PREF=';
    const ca = document.cookie.split(';');
    for (let i = 0; i < ca.length; i++) {
      let c = ca[i];
      while (c.charAt(0) == ' ') {
        c = c.substring(1);
      }
      if (c.indexOf(name) == 0) {
        return c.substring(name.length, c.length);
      }
    }
    return '';
  }

  function setYTPrefCookie(cookie) {
    if (cookie != '0') {
      const date = new Date();
      date.setFullYear(cookie == '' ? 1970 : date.getFullYear() + 2);
      document.cookie = 'PREF=' + (cookie == '' ? ';' : cookie) + '; expires=' + date.toGMTString() + '; domain=youtube.com; path=/';
    }
  }

  const newCookiePrefs = [];
  if (includeApp) {
    newCookiePrefs.push(('app=' + (mobileApp ? 'm' : 'desktop')));
  }
  const curCookie = getYTPrefCookie();
  const curCookiePrefs = curCookie.split('&');
  let appEncountered = false;
  for (let i = 0; i < curCookiePrefs.length; i++) {
    if (curCookiePrefs[i].split('=')[0] == 'app') {
      appEncountered = true;
      continue;
    }
    newCookiePrefs.push(curCookiePrefs[i]);
  }
  if (!appEncountered) {
    recordDefaultYTLayout();
  }
  const finalCookie = newCookiePrefs.join('&');
  setYTPrefCookie(finalCookie == curCookie ? '0' : finalCookie);
}

(function() {

  function openYTConfig() {
    GM_config.open();
    YTLayoutConfig.style = 'position: fixed; width: 260px; height: 150px; border: 1px solid #000; z-index: 9999;';
  }

  function reloadYTSite(wantedLayout) {
    const url = new URL(window.location);
    const currentLayout = url.host.split('.')[0] == 'www' ? 'Desktop' : 'Mobile';
    let shouldReloadYT = false;

    if (wantedLayout != 'Default' ||
        (wantedLayout = GM_getValue('YTDefaultLayout')) !== undefined) {
      if (currentLayout != wantedLayout) {
        url.host = wantedLayout == 'Desktop' ? 'www.youtube.com' : 'm.youtube.com';
        shouldReloadYT = true;
      }
    }

    if (url.searchParams.has('app')) {
      url.searchParams.delete('app');
      shouldReloadYT = true;
    }
    if (url.searchParams.has('persist_app')) {
      url.searchParams.delete('persist_app');
      shouldReloadYT = true;
    }

    if (shouldReloadYT) {
      window.location.replace(url);
    }

    return shouldReloadYT;
  }

  GM_config.init(
  {
    id: 'YTLayoutConfig',
    title: 'YouTube layout',
    fields:
    {
      YTLayout:
      {
        type: 'radio',
        options: ['Default', 'Desktop', 'Mobile']
      },
      ReloadOnClose:
      {
         type: 'checkbox',
         label: 'Reload if layout has changed',
         default: true
      }
    },
    events:
    {
      save: function()
      {
        GM_config.close();
        if (GM_config.get('ReloadOnClose')) {
          reloadYTSite(GM_config.get('YTLayout'));
        }
      }
    },
    css: '#YTLayoutConfig { background-color: #de7a7a; } #YTLayoutConfig_field_style { font-size: 13px; height: 6em; } #YTLayoutConfig .config_var { position: relative; top: 6px; text-align: center; } #YTLayoutConfig_buttons_holder { text-align: center; } #YTLayoutConfig_closeBtn { display: none; } #YTLayoutConfig .reset_holder { display: none }'
  });

  const savedYTLayout = GM_config.get('YTLayout');

  switch (savedYTLayout) {
    case 'Desktop':
      updateYTPrefCookie(true, false);
      break;
    case 'Mobile':
      updateYTPrefCookie(true, true);
      break;
    case 'Default':
      updateYTPrefCookie(false);
  }

  if (!reloadYTSite(savedYTLayout)) {
    GM_registerMenuCommand('YouTube layout', openYTConfig);
  }
})();