var songEndpoint = "https://stream.services.nez-cf.net.eu.org:1965/ntv_nowplaying.php";

function fetchSong() {
    return new Promise((resolve, reject) => {
        var xhr = new XMLHttpRequest();
        xhr.addEventListener("load", function() {
            if (this.status == 200) resolve(this.responseText);
            else reject(this);
        });
        xhr.open("GET", songEndpoint);
        xhr.send();
    });
}

function spacePad(i, c = " ", a = 32) {
    var l = 32 - i.length;
    if (l < 0) l = 0;
    return i + c.repeat(l);
}

var scrollIndex = -1;
var scrollText = "";
var scrollElement = "null";
var skipTurns = 0;
var skipTurnsBegin = 5;
function scroller() {
    if (scrollElement == "null") return;
    if (skipTurns > 0) return skipTurns--;
    if (skipTurnsBegin > 0) skipTurnsBegin--;
    scrollIndex++;
    if (scrollIndex > scrollText.length) {
        scrollIndex = -1;
        skipTurnsBegin = 5;
        return skipTurns = 5;
    }
    if (scrollText.length > 32) scrollElement.innerHTML = spacePad(scrollText.substr(skipTurnsBegin > 0 ? 0 : scrollIndex, 32).replace(/ /g, "&nbsp;"));
    else scrollElement.innerHTML = spacePad(scrollText.replace(/ /g, "&nbsp;"));
}

async function updateSongs() {
    var song = await fetchSong();
    song = "now playing: " + song;
    if (scrollText != song) {
        scrollText = song;
        scrollIndex = -1;    
    }
}

document.addEventListener("DOMContentLoaded", function() {
    scrollElement = document.getElementById("song-display");
    setInterval(scroller, 200);
    updateSongs();
    setInterval(updateSongs, 20 * 1000);
});