auto-redirect.user.js

// ==UserScript==
// @name     auto redirect
// @author          NOP Thread <nop_thread@nops.red>
// @version         0.0.4
// @include         https://pbs.twimg.com/*
// @include         https://twitter.com/*
// @include         https://mobile.twitter.com/*
// @include         https://ja.m.wikipedia.org/*
// @include         http://d.hatena.ne.jp/*
// @include         https://d.hatena.ne.jp/*
// @include         https://www.google.co.jp/*
// @include         https://www.google.com/*
// @include         https://www.amazon.co.jp/*
// @include         https://datatracker.ietf.org/doc/html/*
// @grant    none
// @run-at   document-start
// ==/UserScript==

'use strict';

class Redirector {
  constructor(l = location) {
    this.protocol = l.protocol;
    this.host = l.host;
    this.pathname = l.pathname;
    this.search = l.search;
    this.hash = l.hash;
  }

  redirect() {
    location.replace(`${this.protocol}//${this.host}${this.pathname}${this.search}${this.hash}`);
  }
  
  with_protocol(protocol) {
    this.protocol = protocol;
    return this;
  }
  with_host(host) {
    this.host = host;
    return this;
  }
  with_pathname(pathname) {
    this.pathname = pathname;
    return this;
  }
  with_search(search) {
    this.search = search;
    return this;
  }
  with_hash(hash) {
    this.hash = hash;
    return this;
  }
}

const host_map = new Map([
  ['ja.m.wikipedia.org', 'ja.wikipedia.org'],
  ['mobile.twitter.com', 'twitter.com'],
]);

(function() {
  if(host_map.has(location.hostname)) {
    location.hostname = host_map.get(location.hostname);
    return;
  }
  
  switch(location.hostname) {
    case 'd.hatena.ne.jp':
      escape_hatena();
      return;
    case 'datatracker.ietf.org':
      redirect_ietf_rfc();
      return;
    case 'pbs.twimg.com':
      redirect_pbs_twimg();
      return;
    case 'twitter.com':
      redirect_twitter();
      return;
    case 'www.amazon.co.jp':
      redirect_amazon();
      return;
    case 'www.google.co.jp':
    case 'www.google.com':
      redirect_google();
      return;
  }
})();

function escape_hatena() {
  const pat = /^(\/[^/]+)\/touch(\/.*)$/;
  const matches = pat.exec(location.pathname);
  if(matches) {
    new Redirector().with_pathname(matches[1] + matches[2]).redirect();
  }
}

function redirect_pbs_twimg() {
	const params = new URL(location).searchParams;
  params.set("name", "orig");
  const params_str = `?${params.toString()}`;
  if(params_str !== location.search && params_str !== '?') {
  	new Redirector().with_search(params_str).redirect();
  }
}

function redirect_google() {
  if(location.pathname === '/url') {
    redirect_google_redirector();
  } else {
    redirect_google_search();
  }
}

function redirect_google_search() {
  // See <http://webos-goodies.jp/archives/50785287.html>.
  const params = new URL(location).searchParams;
  /*
  const whitelist = [
  	// `q`: query.
    "q",
    // `hq`: hidden query.
    "hq",
  	// `tbm`: search target?
    "tbm",
  	// `tbs`: image license.
    "tbs",
  ];
  */
  const blacklist = [
    // Unknown. Display related?
    "dpr",
    // Browser height?
    "bih",
    // Browser width?
    "biw",
    // Unknown.
    "ved",
    // Unknown.
    "sa",
    // How the search is started.
    "source",
    // Unknown. Geolocation?
    "gs_l",
    // Unknown.
    "gs_lcp",
    // Unknown.
    "ei",
    // Old query.
    "oq",
    // Browser (client).
    "client",
    // Unknown.
    "sclient",
  ];
  blacklist.forEach((x) => params.delete(x));
  params.sort();
  const params_str = `?${params.toString()}`;
  if(params_str !== location.search && params_str !== '?') {
  	new Redirector().with_search(params_str).redirect();
  }
}

function redirect_google_redirector() {
  const params = new URL(location).searchParams;
  const target_encoded = params.get("url");
  if(target_encoded) {
    const target = decodeURIComponent(target_encoded.replace('+', ' '));
    location.replace(target);
  }
}

function redirect_amazon() {
  const pat = /\/[^/]+\/dp\/(.*)$/;
  const matches = pat.exec(location.pathname);
  if(matches) {
    new Redirector().with_pathname(`/dp/${matches[1]}`).redirect();
  }
}

function redirect_twitter() {
  const pat = /^\/[^/]+\/status\//;
  const matches = pat.exec(location.pathname);
  if(matches && location.search) {
    new Redirector().with_search("").redirect();
  }
}

function redirect_ietf_rfc() {
  const pat = /^https:\/\/datatracker.ietf.org\/doc\/html\/rfc([0-9]+)/;
  const matches = pat.exec(location.href);
  if(matches) {
    location.replace(`https://www.rfc-editor.org/rfc/rfc${matches[1]}.html`);
  }
}