function createXHR() {
    if (window.XMLHttpRequest) {
        return new XMLHttpRequest();
    } else if (window.ActiveXObject) {
        try {
            return new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                return new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }

    return null;
}

function getNowListening(username, cb) {
    var xhr = createXHR();
    xhr.onreadystatechange = function() {
        if (xhr.readyState !== 4)
            return;

        var xml = null;

        if(window.DOMParser) {
            var parser = new DOMParser();
            xml = parser.parseFromString(xhr.responseText, 'text/xml');
        } else {
            xml = new ActiveXObject('Microsoft.XMLDOM');
            xml.async = 'false';
            xml.loadXML(xhr.responseText);
            xml = xml.childNodes[1];
        }

        cb(xml.getElementsByTagName('Track')[0]);
    };
    xhr.open('GET', '/np.php?t=' + (new Date().getTime()) + '&u=' + username, true);
    xhr.send();
}

function getNodeText(node) {
    if (typeof node.textContent === 'undefined') {
        return node.text;
    } else {
        return node.textContent;
    }
}

function setNodeText(node, text) {
    if (typeof node.textContent === 'undefined') {
        node.innerText = text;
    } else {
        node.textContent = text;
    }
}

function setNowListening(track) {
    var cover = document.getElementById('music-cover'),
        title = document.getElementById('music-title'),
        artist = document.getElementById('music-artist'),
        header = document.getElementById('music-header'),
        content = document.getElementById('music'),
        coverUrl = getNodeText(track.getElementsByTagName('Medium')[0]);

    if (content.className.indexOf('hidden') >= 0)
        content.className = content.className.replace('hidden', '');

    setNodeText(header, getNodeText(track.getElementsByTagName('IsPlaying')[0]) != '0' ? 'Listening to' : 'Last listened to');
    cover.src = coverUrl.length < 1 ? '//now.flash.moe/resources/no-cover.png' : coverUrl.replace('/64s/', '/100s/').replace('https:', '');
    setNodeText(title, getNodeText(track.getElementsByTagName('Name')[0]));
    title.href = getNodeText(track.getElementsByTagName('Url')[0]);
    setNodeText(artist, getNodeText(track.getElementsByTagName('Name')[1]));
    artist.href = title.href.substring(0, title.href.indexOf('/_/'));
}

window.onload = function() {
    var lastFmUsername = '',
        lastFmFind = '//www.last.fm/user/';

    var links = document.getElementsByTagName('a');
    for (var i = 0; i < links.length; i++) {
        var indexOf = links[i].href.indexOf(lastFmFind);
        if(indexOf > -1) {
            lastFmUsername = links[i].href.substring(indexOf + lastFmFind.length);
            break;
        }
    }

    if(lastFmUsername) {
        setInterval(function() { getNowListening(lastFmUsername, function(track) { setNowListening(track); }); }, 60000);
        getNowListening(lastFmUsername, function(track) { setNowListening(track); });
    }
};