background.js

var player;
var port;
var UNSTARTED = -1;
var ENDED = 0;
var PLAYING = 1;
var PAUSED = 2;
var BUFFERING = 3;
var VIDCUED = 5;

function ToggleMusic() {
    //Possible values are unstarted (-1), ended (0), playing (1), paused (2), buffering (3), video cued (5).
    var playerState = player.getPlayerState();
    var toggledOn = true;

    if (playerState == PAUSED || playerState == UNSTARTED || playerState == ENDED) {
        player.playVideo();
    }
    else if (playerState == VIDCUED) {
        var playlist = localStorage.getItem('playlist');
        playlist = JSON.parse(playlist);
        player.loadVideoById(playlist[0].ID);
    }
    else {
        player.pauseVideo();
        toggledOn = false;
    }

    return toggledOn;
}

function ShuffleMusic() {
    var playlist = JSON.parse(localStorage.getItem('playlist'));
    playlist = ShufflePlaylist(playlist);
    localStorage.setItem('playlist', JSON.stringify(playlist));

    //The best way to do this is to load the next two songs so that we've got the next one pre-loaded.
    LoadNext(playlist, 1);
}

function LoadNext(playlist, countToLoad) {
    //Possible values are unstarted (-1), ended (0), playing (1), paused (2), buffering (3), video cued (5).
    var playerState = player.getPlayerState();

    var wasPlayingSong = playerState == 1 || playerState == 3;

    if (playerState != UNSTARTED) {
        player.stopVideo();
        player.clearVideo();
    }

    for (count = 0; count < countToLoad; count++) {
        player.loadVideoById(playlist[count].ID);
    }

    if (!wasPlayingSong) {
        player.pauseVideo();
    }
}

function NextSong() {
    var playlist = JSON.parse(localStorage.getItem('playlist'));

    var nextSong = playlist.shift();
    playlist.push(nextSong); //Move it to the end.

    LoadNext(playlist, 1);

    localStorage.setItem('playlist', JSON.stringify(playlist));
}

function onPlayerStateChange() {
    var playerState = player.getPlayerState();

    if (playerState == BUFFERING) {
        port.postMessage({ playerState: "Buffering" });
    }
    else if (playerState == PLAYING) {
        port.postMessage({ playerState: "Playing" });
    }
    else if (playerState == PAUSED) {
        port.postMessage({ playerState: "Paused" });
    }

    if (playerState == ENDED) {
        NextSong();
    }
}

function Initialize(playlist) {
    port = chrome.extension.connect({ name: "statusPoller" });
    if (!player) {
        YT_ready(function(){
            var frameID = getFrameID("MusicHolder");
            if (frameID) {
                player = new YT.Player(frameID, {
                    events: {
                        "onReady": function() {
                            player.cueVideoById(playlist[0].ID, 0);
                        },
                        "onStateChange": onPlayerStateChange
                    }
                });
            }
        });
    } else {
        // Only reload if the player is not playing. Otherwise, the music
        // stops when re-opening the popup.
        if (player.getPlayerState && player.getPlayerState() != PLAYING) {
            player.cueVideoById(playlist[0].ID, 0);
        }
    }
}

function GetIdFromUrl(url) {
    var regExp = /^.*((youtu.be\/)|(v\/)|(\/u\/\w\/)|(embed\/)|(watch\?))\??v?=?([^#\&\?]*).*/;
    var match = url.match(regExp);
    if (match && match[7].length == 11) {
        return match[7];
    } else {
        alert("Failed to read YouTube URL. Did you enter a valid link?");
    }
}

//shuffles list in-place
function ShufflePlaylist(list) {
    var i, j, t;
    for (i = 1; i < list.length; i++) {
        j = Math.floor(Math.random() * (1 + i));  // choose j in [0..i]
        if (j != i) {
            t = list[i];                        // swap list[i] and list[j]
            list[i] = list[j];
            list[j] = t;
        }
    }

    return list;
}