Boyd audio class

part of LD35;

class Audio {
    static Audio instance;

    AudioContext ctx;
    String extension = "ogg";
    GainNode volumeNode;

    double volume = 1.0;
    bool muted = false;

    RangeInputElement slider;
    DivElement mutebutton;

    Audio() {
        instance = this;
        this.ctx = new AudioContext();

        volumeNode = this.ctx.createGain()..connectNode(ctx.destination);

        AudioElement a = new AudioElement();
        if (a.canPlayType("audio/mpeg;codecs=mp3") != "") {
            extension = "mp3";
        };

        mutebutton = querySelector("#volume");
        slider = querySelector("#volumeslider");

        mutebutton.onClick.listen((Event e) {
            toggleMute();
        });

        slider.onChange.listen((Event e) {
            setVolume(double.parse(slider.value), slider:false);
        });

        setVolume(0.5);
    }

    static void setVolume(num vol, {bool mute : false, bool slider : true}) {
        instance.volume = clamp(vol.toDouble(), 0.0, 1.0);
        instance.volumeNode.gain.value = mute ? 0.0 : instance.volume;
        instance.muted = mute;
        if (slider) {
            instance.slider.value = "${instance.volume}";
        }
        instance.updateMuteElement();
    }

    static void play(String soundname, [String subtitle=null]) {
        if (soundname == null) { return; }
        if (Assets.sounds.containsKey(soundname)) {
            AudioBuffer sound = Assets.sounds[soundname];

            var source = instance.ctx.createBufferSource()
                ..buffer = sound
                ..connectNode(instance.volumeNode)
                ..start(0);

            if (subtitle != null) {

            }
        }
    }

    static void playRandom(List<String> soundnames, [List<String> subtitle=null]) {
        if (soundnames == null || soundnames.isEmpty) { return; }
        int r = rand.nextInt(soundnames.length);
        String sub = subtitle == null ? null : subtitle[r];
        play(soundnames[r], sub);
    }

    static void toggleMute() {
        setVolume(instance.volume, mute:!instance.muted);
    }

    void updateMuteElement() {
        if (this.muted) {
            mutebutton.classes.remove("glyphicon-volume-up");
            mutebutton.classes.add("glyphicon-volume-off");
        } else {
            mutebutton.classes.remove("glyphicon-volume-off");
            mutebutton.classes.add("glyphicon-volume-up");
        }
    }
}