function update(){
	var xhttp = new XMLHttpRequest();
	xhttp.onreadystatechange = function() {
		if (xhttp.readyState == 4 && xhttp.status == 200) {
			var json_text = xhttp.responseText;
			var json_obj = JSON.parse(json_text);
			var playing = '';
			var first = getFirstPlaying(json_obj);

			if (first == null) {
				playing = 'Mitte munnigi ei mängi prg';
			}
			else if (first.artist != undefined) { 
				playing = first.artist + ' - '; 
				playing += first.title;						
			} else {	
				playing += first.title;
			}
			var nowPlaying = playing;
			update_field('on-air', playing);
			update_listeners(json_obj);
		}
	};
	xhttp.open("GET", "http://kahtlane.eu:8000/status-json.xsl", true);
	xhttp.send();
}

function update_field(field, data){
	document.getElementById(field).innerHTML = data;
	return 'ok';
}

function update_listeners(json_obj){
	var nowPlaying = getFirstPlaying(json_obj);	

	if(nowPlaying != null) {
		update_field('listeners1', nowPlaying.listeners);
	}	
}

function autoupdate(){
	update();
	setInterval(function(){ update(); }, 30000);	
}

function change_bg(id){
	document.body.style.backgroundImage = "url('http://i.imgur.com/" + id + ".jpg')";
}

function reset_bg(){
	document.body.style.backgroundImage = "url('http://i.imgur.com/BkSL2KJ.png')";
}

function getFirstPlaying(jsonObj){
	var sources = jsonObj.icestats.source;
	var masterStreams = [
		'/live',
	]

	for(o=0; o < sources.length; o++) {
		if (sources[o].title != undefined && masterStreams.some(stream=>sources[o].listenurl.endsWith(stream))) { //check if source has a title key AND belongs to masterStreams
			return sources[o];
		} 
	}
	
	return null;
}