router.js

---
---

function UrlExists(url, cb) {
    jQuery.ajax({
        url:      url,
        dataType: 'text',
        type:     'GET',
        cache:    false,
        complete:  function(xhr){
            if(typeof cb === 'function')
            cb.apply(this, [xhr.status]);
        }
    });
}

function GetShortcutDestination() {
    var s = window.location.href;
    var pathArray = s.split('?');

    // Cut the query if it exists
    if (pathArray.length > 1) {
        return pathArray[1];
    } else {
        return '';
    }
}

function RedirectTo(newLocation) {
    document.location.replace(newLocation);
}

// Pick the shortcut link destination from URL, like: `category:subcategory:card-name`
var sub = GetShortcutDestination();


// If there's a shortcut to handle
if (sub.length > 0) {
    var externalCardURL = '/external/cards/' + sub;
    var internalCardURL = '/internal/cards/' + sub;

    UrlExists(externalCardURL, function(status){
        if (status == 200) { // The sub-card is external and accessible
            RedirectTo(externalCardURL);
        } else {
            UrlExists(internalCardURL, function(status){
                if (status == 200) { // The sub-card is internal and accessible
                    RedirectTo(internalCardURL);
                } else {
                    // No external, no internal - probably no access
                    RedirectTo('/404.html');
                }
            })
        }
    });
}