background.js

"use strict";

const nitterDefault = "https://nitter.net";

let instance;
let nitterDisabled;

window.browser = window.browser || window.chrome;

browser.storage.sync.get(["nitterDisabled", "instance"], (result) => {
  nitterDisabled = result.nitterDisabled;
  instance = result.instance || nitterDefault;
});

browser.storage.onChanged.addListener(function (changes) {
  if ("instance" in changes) {
    instance = changes.instance.newValue || nitterDefault;
  }
  if ("nitterDisabled" in changes) {
    nitterDisabled = changes.nitterDisabled.newValue;
  }
});

function redirectTwitter(url) {
  if (nitterDisabled) {
    return null;
  }
  if (url.host.split(".")[0] === "pbs") {
    return `${instance}/pic/${encodeURIComponent(url.href)}`;
  } else if (url.host.split(".")[0] === "video") {
    return `${instance}/gif/${encodeURIComponent(url.href)}`;
  } else if (url.pathname.includes("tweets")) {
    return `${instance}${url.pathname.replace("/tweets", "")}${url.search}`;
  } else {
    return `${instance}${url.pathname}${url.search}`;
  }
}

browser.webRequest.onBeforeRequest.addListener(
  (details) => {
    const url = new URL(details.url);
    let redirect;
    redirect = { redirectUrl: redirectTwitter(url) };
    if (redirect && redirect.redirectUrl) {
      console.info(
        "Redirecting",
        `"${url.href}"`,
        "=>",
        `"${redirect.redirectUrl}"`
      );
      console.info("Details", details);
    }
    return redirect;
  },
  {
    urls: [
      "*://twitter.com/*",
      "*://www.twitter.com/*",
      "*://mobile.twitter.com/*",
      "*://pbs.twimg.com/*",
      "*://video.twimg.com/*",
    ],
  },
  ["blocking"]
);