var documentLocked = false;

window.addEventListener('load', function() {
    document.getElementById('lookup-submit').addEventListener('click', function(ev) {
        ev.preventDefault();
        whoisLookup(document.getElementById('lookup-input').value);
    });
});

window.addEventListener('popstate', function(ev) {
    if(!ev.state)
        return;
    document.getElementById('lookup-input').value = ev.state.target || '';
    document.getElementById('lookup-result').innerText = ev.state.responseText || 'Enter a domain or IP address!';
});

function lockDocument() {
    if(documentLocked)
        return false;

    document.body.classList.add('locked');
    document.getElementById('lookup-input').disabled = true;
    documentLocked = true;
    return true;
}

function freeDocument() {
    if(!documentLocked)
        return false;

    document.body.classList.remove('locked');
    document.getElementById('lookup-input').disabled = false;
    documentLocked = false;
    return true;
}

function whoisLookup(domain) {
    if(!lockDocument())
        return;

    var xhr = new XMLHttpRequest;
    xhr.addEventListener('readystatechange', function() {
        if(xhr.readyState != 4)
            return;

        var response = JSON.parse(xhr.responseText);

        history.pushState(response, null, location.pathname + '?domain=' + encodeURIComponent(domain));
        document.getElementById('lookup-result').innerText = response.responseText;
        freeDocument();
    });
    xhr.open('GET', whoisUrl + '?ajax=1&domain=' + encodeURIComponent(domain));
    xhr.send();
}