audrey/src/playbin.vala

enum PlaybinState {
    STOPPED,
    PAUSED,
    PLAYING,
}

private class SourceFuncWrapper {
    public SourceFunc inner;

    public SourceFuncWrapper () {
        this.inner = null;
    }
}

class Playbin : GLib.Object {
    private Mpv.Handle mpv = new Mpv.Handle ();

    public PlaybinState state { get; private set; default = PlaybinState.STOPPED; }

    private int _volume = 100;
    public int volume {
        get { return _volume; }
        set {
            _volume = value;
            assert (mpv.set_property_int64 ("volume", value) >= 0);
        }
    }

    public bool _mute = false;
    public bool mute {
        get { return _mute; }
        set {
            _mute = value;
            assert (mpv.set_property_flag ("mute", value) >= 0);
        }
    }

    public uint play_queue_position { get; private set; }
    public Subsonic.Song? song { get; private set; }
    public signal void now_playing ();

    public double position { get; private set; default = 0.0; }
    public double duration { get; private set; default = 0.0; }

    public Subsonic.Client api { get; set; default = null; }

    private ListModel _play_queue = null;
    public ListModel play_queue {
        get { return _play_queue; }
        set {
            assert (_play_queue == null); // only set this once
            _play_queue = value;
            value.items_changed.connect (on_play_queue_items_changed);
        }
    }

    private void on_play_queue_items_changed (ListModel play_queue, uint position, uint removed, uint added) {
        for (uint i = 0; i < removed; i += 1) {
            assert (this.mpv.command ({
                "playlist-remove",
                position.to_string (),
            }) >= 0);
        }

        for (uint i = 0; i < added; i += 1) {
            assert (this.mpv.command ({
                "loadfile",
                this.api.stream_uri (((Subsonic.Song) play_queue.get_item (position+i)).id),
                "insert-at-play",
                (position+i).to_string (),
            }) >= 0);
        }
    }

    public Playbin () {
        assert (this.mpv.initialize () >= 0);
        assert (this.mpv.set_property_string ("user-agent", Audrey.Const.user_agent) >= 0);
        assert (this.mpv.set_property_string ("video", "no") >= 0);
        assert (this.mpv.set_property_string ("prefetch-playlist", "yes") >= 0);
        assert (this.mpv.set_property_string ("gapless-audio", "yes") >= 0);
        assert (this.mpv.observe_property (0, "time-pos", Mpv.Format.DOUBLE) >= 0);
        assert (this.mpv.observe_property (1, "duration", Mpv.Format.DOUBLE) >= 0);
        assert (this.mpv.observe_property (2, "playlist-pos", Mpv.Format.INT64) >= 0);

        this.mpv.wakeup_callback = () => {
            Idle.add (() => {
                while (true) {
                    var event = this.mpv.wait_event (0.0);
                    if (event.event_id == Mpv.EventId.NONE) break;

                    switch (event.event_id) {
                    case Mpv.EventId.PROPERTY_CHANGE:
                        var data = event.parse_property ();
                        switch (event.reply_userdata) {
                        case 0:
                            assert (data.name == "time-pos");
                            if (data.format == Mpv.Format.NONE) {
                                this.position = 0.0;
                            } else {
                                this.position = data.parse_double ();
                            }
                            break;

                        case 1:
                            assert (data.name == "duration");
                            if (data.format == Mpv.Format.NONE) {
                                this.duration = 0.0;
                            } else {
                                this.duration = data.parse_double ();
                            }
                            break;

                        case 2:
                            assert (data.name == "playlist-pos");
                            if (data.format == Mpv.Format.NONE) {
                                this.play_queue_position = 0;
                            } else {
                                this.play_queue_position = (uint) data.parse_int64 ();
                            }
                            break;

                        default:
                            assert (false);
                            break;
                        }
                        break;

                    case Mpv.EventId.FILE_LOADED:
                        this.song = (Subsonic.Song) this.play_queue.get_item (this.play_queue_position);
                        this.now_playing ();
                        break;
                      
                    default:
                        // ignore by default
                        break;
                    }
                }
            
                return false;
            });
        };
    }

    public void seek (double position) {
        this.position = position;
        assert (this.mpv.command ({"seek", position.to_string (), "absolute"}) >= 0);
    }

    // manually changes which track in the play queue to play
    public void select_track (uint position)
            requires (position < this.play_queue.get_n_items ())
    {
        assert (this.mpv.command ({"playlist-play-index", position.to_string ()}) >= 0);
        this.state = PlaybinState.PLAYING;
    }

    public void pause () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PAUSED;
        assert (this.mpv.command ({"pause"}) >= 0);
    }

    public void play () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PLAYING;
        assert (this.mpv.command ({"play"}) >= 0);
    }

    public void next_track () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PLAYING;
        assert (this.mpv.command ({"playlist-next-playlist"}) >= 0);
    }

    public void prev_track () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PLAYING;
        assert (this.mpv.command ({"playlist-prev-playlist"}) >= 0);
    }
}