var player;
var pos_int;
var analyser;
var audio_data;
var vol_prev;

function init() {
	player = document.querySelector('#player');

	player.addEventListener('ended', nextTrack);
	player.addEventListener('loadedmetadata', display_duration);
	player.addEventListener('timeupdate', update_position);

	navigator.mediaSession.setActionHandler('play', playTrack);
	navigator.mediaSession.setActionHandler('pause', pauseTrack);
	navigator.mediaSession.setActionHandler('stop', stopTrack);
	navigator.mediaSession.setActionHandler('previoustrack', prevTrack);
	navigator.mediaSession.setActionHandler('nexttrack', nextTrack);

	let seek = document.querySelector('#seek-slider');
	seek.addEventListener('input', function(){
		player.currentTime = seek.value;
		display_current_time();
	});

	let vol = document.querySelector('#volume-slider');
	vol.addEventListener('input', function(){
		player.volume = vol.value/100;
		if (vol.value == 0) {
			document.querySelector('#vol-btn').style.display = 'none';
			document.querySelector('#vol-off-btn').style.display = 'initial';
		} else {
			document.querySelector('#vol-btn').style.display = 'initial';
			document.querySelector('#vol-off-btn').style.display = 'none';
		}
	});

	init_analyzer();
}

async function get_rand_track() {
	let res = await fetch("./rand_track/")
	let data = await res.json();
	return data;
}

async function nextTrack() {
	track = await get_rand_track();
	player.src = track.source;
	playTrack();
}

function prevTrack() {
	// TODO: implement a history array
}

async function playTrack() {
	if (!player.src) {
		return nextTrack();
	}
	player.play(); 
	navigator.mediaSession.playbackState = "playing";
	setMediaSession(track);

	document.querySelector("#play-btn").style.display = "none";
	document.querySelector("#pause-btn").style.display = "initial";
}

function pauseTrack() {
	player.pause();
	navigator.mediaSession.playbackState = "paused";

	document.querySelector("#play-btn").style.display = "initial";
	document.querySelector("#pause-btn").style.display = "none";
}

function stopTrack() {
	player.pause();
	player.load();
	navigator.mediaSession.playbackState = "none";

	document.querySelector("#play-btn").style.display = "initial";
	document.querySelector("#pause-btn").style.display = "none";
}

function setMediaSession(track) {
	navigator.mediaSession.metadata = new MediaMetadata({
		title: track.title,
		artist: track.artist,
		album: track.album,
		artwork: track.artwork
	});
}

function update_position() {
	navigator.mediaSession.setPositionState({
		duration: Math.floor(player.duration),
		playbackRate: player.playbackRate,
		position: Math.floor(player.currentTime)
	});

	analyser.getByteTimeDomainData(audio_data);

	document.querySelector('#seek-slider').value = Math.floor(player.currentTime);
	display_current_time();
}

function calculate_time(raw_secs) {
	let mins = Math.floor(raw_secs / 60);
	let secs = Math.round(raw_secs % 60);
	let ret = mins + ':' + String(secs).padStart(2,'0');
	return ret;
}

function display_duration() {
	let dur = document.querySelector('#duration');
	dur.textContent = calculate_time(player.duration);

	document.querySelector('#seek-slider').max = Math.floor(player.duration);
}

function display_current_time() {
	cur = document.querySelector('#current-time');
	cur.textContent = calculate_time(player.currentTime);
}

function volume_off() {
	let vol = document.querySelector('#volume-slider');
	vol_prev = vol.value;
	vol.value = 0;
	player.volume = 0;

	document.querySelector('#vol-btn').style.display = 'none';
	document.querySelector('#vol-off-btn').style.display = 'initial';
}

function volume_restore() {
	let vol = document.querySelector('#volume-slider');
	vol.value = vol_prev;
	player.volume = vol_prev / 100;

	document.querySelector('#vol-btn').style.display = 'initial';
	document.querySelector('#vol-off-btn').style.display = 'none';
}

function init_analyzer() {
	let audioCtx = new AudioContext();
	analyser = audioCtx.createAnalyser();
	let source = audioCtx.createMediaElementSource(player);

	source.connect(analyser);
	source.connect(audioCtx.destination);

	audio_data = new Uint8Array(analyser.frequencyBinCount);
}