Add titles to Substack redirect links in Gmail, exposing the target URL
// ==UserScript==
// @name SeeStack
// @version 0.1
// @description Add titles to Substack redirect links in Gmail, exposing the target URL
// @author Kevin Shay
// @namespace https://greasyfork.org/users/154233
// @match https://mail.google.com/*
// @require https://update.greasyfork.org/scripts/472236/1249646/GM%20Fetch.js
// @grant GM_xmlhttpRequest
// @connect substack.com
// ==/UserScript==
/* globals gmFetch */
(function() {
'use strict';
// Handle both the hash navigation format and the standalone "View entire message" page
const INDIVIDUAL_EMAIL_RE = new RegExp('(/[a-z]{32})|(permmsgid=msg-f:\\d+)$', 'i');
const ERROR_LOCATION_RE = new RegExp('Refused to connect to "([^]+)"');
const SUBSTACK_REDIRECT = 'https://substack.com/redirect/';
const SUBSTACK_REDIRECT_RE = new RegExp(`^${SUBSTACK_REDIRECT}`);
function getRedirectPromise(url) {
// GM_xmlhttpRequest is part of the Greasemonkey/Tampermonkey API, allowing HTTP
// requests that bypass normal browser CORS restrictions;
// gmFetch wraps it to emulate the fetch API
return gmFetch(url, {
method: 'HEAD'
}).then((res) => {
console.log(res.url);
return res.url;
}).catch((e) => {
// FIXME: If GM_fetch and GM_xmlhttpRequest could be told not to follow redirects,
// we could look at the first redirect response and wouldn't need to rely on errors.
// (Could also use "@connect *" but that requires the user to adjust settings, and
// at any rate we don't actually want or need to request the redirected locations.)
return e.toString().match(ERROR_LOCATION_RE)[1].trim();
});
}
function checkLinks() {
// Quick heuristic to see if this is even a Substack post at all;
// if not, no need to bother inspecting the links
if (!document.body.innerHTML.includes(SUBSTACK_REDIRECT)) {
return;
}
[...document.getElementsByTagName('a')].forEach((el) => {
if (el.href?.match(SUBSTACK_REDIRECT_RE)) {
getRedirectPromise(el.href).then((location) => {
if (location) {
el.setAttribute('title', location);
}
});
}
});
}
// Alternative that fetches each link on mouseover instead of all at once up front.
// The problem with this seems to be that once the redirect is resolved and the title
// attribute is set, you often need to move the mouse again to get the title tooltip
// to show up, which is annoying and makes it feel like it's not working consistently.
function checkLinks_mouseover() {
[...document.getElementsByTagName('a')].forEach((el) => {
if (el.href?.match(SUBSTACK_REDIRECT_RE)) {
const elListener = (evt) => {
getRedirectPromise(evt.target.href).then((location) => {
if (location) {
evt.target.setAttribute('title', location);
}
});
el.removeEventListener('mouseover', elListener);
};
el.addEventListener('mouseover', elListener);
}
});
}
function checkCurrentPage() {
if (!INDIVIDUAL_EMAIL_RE.test(location.href)) {
return;
}
// FIXME: Use a more robust way of waiting for the page content to be ready
setTimeout(checkLinks, 2000);
}
addEventListener('hashchange', checkCurrentPage);
checkCurrentPage();
})();