Redirects non-Australian Amazon domains to amazon.com.au, handles 404 errors, and prevents loops. | Note: This script is solely intended for the use of educational purposes only and not to abuse any website. Use it wisely and do not abuse any website. Click "Raw" to install it on Tampermonkey

AmazonRedirect.user.js

// ==UserScript==
// @name         Amazon AU Redirect
// @namespace    https://gist.github.com/origamiofficial/23203b030d4ecbd219e48d3d41d406d3
// @version      3.0
// @description  Redirects non-Australian Amazon domains to amazon.com.au, handles 404 errors, and prevents loops.
// @author       OrigamiOfficial
// @match        *://*.amazon.*/*
// @grant        none
// @run-at       document-start
// @updateURL    https://gist.githubusercontent.com/origamiofficial/23203b030d4ecbd219e48d3d41d406d3/raw/AmazonRedirect.user.js
// @downloadURL  https://gist.githubusercontent.com/origamiofficial/23203b030d4ecbd219e48d3d41d406d3/raw/AmazonRedirect.user.js
// ==/UserScript==

(function() {
    'use strict';

    // List of non-Australian Amazon domains to redirect from
    const amazonDomains = [
        'amazon.com',
        'amazon.co.uk',
        'amazon.ca',
        'amazon.de',
        'amazon.fr',
        'amazon.it',
        'amazon.es',
        'amazon.co.jp',
        'amazon.in',
        'amazon.com.br',
        'amazon.com.mx',
        'amazon.cn',
        'amazon.nl',
        'amazon.se',
        'amazon.pl',
        'amazon.ae',
        'amazon.sa',
        'amazon.sg',
        'amazon.co.nz'
    ];

    // Target Australian domain
    const targetDomain = 'amazon.com.au';

    // Get current URL components
    const url = new URL(window.location.href);
    const params = url.searchParams;
    const currentHostname = url.hostname;

    // Part 1: Immediate redirection from non-AU to AU
    if (!params.has('tm-redirected') || params.get('tm-redirected') !== '1') {
        if (amazonDomains.includes(currentHostname)) {
            // Store the original domain and redirect to AU
            const originalDomain = currentHostname;
            url.hostname = targetDomain;
            url.searchParams.set('original-domain', originalDomain);
            window.location.href = url.toString();
        }
    }

    // Part 2: Check for 404 on AU site and redirect back if necessary
    if (currentHostname === targetDomain) {
        document.addEventListener('DOMContentLoaded', function() {
            if (is404Page()) {
                const originalDomain = params.get('original-domain');
                if (originalDomain) {
                    // Redirect back to the original domain with a flag to prevent re-redirection
                    url.hostname = originalDomain;
                    url.searchParams.delete('original-domain');
                    url.searchParams.set('tm-redirected', '1');
                    window.location.href = url.toString();
                }
            }
        });
    }

    // Function to detect a 404 page based on the provided HTML
    function is404Page() {
        return document.body && document.body.innerHTML.includes('The Web address you entered is not a functioning page on our site');
    }
})();