404.html

<script src="/firebaseConfig.js"></script>
<script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-firestore.js"></script>

<script>
    localStorage.clear();
    console.clear();

    var fullURL = window.location.href;
    var urlBehindRoot = fullURL.replace(window.location.origin + "/", '');

    firebase.initializeApp(firebaseConfig);
    const db = firebase.firestore();

    db.collection("links").where("name", "==", urlBehindRoot)
        .get()
        .then((querySnapshot) => {
            if (querySnapshot.size > 0) {
                querySnapshot.forEach((doc) => {
                    const url = doc.data().url;
                    let redirect = url;
                    if (!redirect.startsWith("https://")) {
                        redirect = "https://" + redirect;
                        window.location.href = redirect;
                    }
                    if (redirect.includes("http://")) {
                        redirect = redirect.replace("http://", "https://");
                        window.location.href = redirect;
                    }
                    window.location.href = redirect;
                });
            } else {
                console.log("No document found for the given name");
            }
        })
        .catch((error) => {
            console.log("Error getting documents: ", error);
        });
</script>