public enum PlaybinState {
    STOPPED,
    PAUSED,
    PLAYING,
}

public 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 {
            var ret = mpv.set_property_int64 ("volume", value);
            if (ret >= 0) {
                _volume = value;
            } else {
                warning ("failed to set volume: %s", ret.to_string ());
            }
        }
    }

    public bool _mute = false;
    public bool mute {
        get { return _mute; }
        set {
            var ret = mpv.set_property_flag ("mute", value);
            if (ret >= 0) {
                _mute = value;
            } else {
                warning ("failed to set mute status: %s", ret.to_string ());
            }
        }
    }

    // invariant: equal to play queue length iff state is STOPPED
    public uint play_queue_position { get; private set; }

    // signalled when a new track is current
    public signal void new_track ();
    // signalled when the last track is over
    public signal void stopped ();

    // set to false when manually switching tracks
    private bool inc_position;

    // these are mostly synced with mpv
    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; }

    public ListStore _play_queue;
    public ListModel play_queue { get { return this._play_queue; } }

    // try to prevent wait_event to be called twice
    private bool is_handling_event = false;

    public Playbin () {
        this._play_queue = new ListStore (typeof (Subsonic.Song));

        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);
        assert (this.mpv.observe_property (3, "pause", Mpv.Format.FLAG) >= 0);

        this.mpv.wakeup_callback = () => {
            Idle.add (() => {
                if (this.is_handling_event) return false;
                this.is_handling_event = true;

                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:
                            // here as a sanity check
                            // should always match our own play_queu_position/state
                            assert (data.name == "playlist-pos");
                            int64 playlist_pos = data.parse_int64 ();
                            if (playlist_pos < 0) {
                                if (this.state != PlaybinState.STOPPED) {
                                    error ("mpv has no current playlist entry, but we think it's index %u", this.play_queue_position);
                                }
                                assert (this.play_queue_position == this.play_queue.get_n_items ());
                            } else {
                                if (this.state == PlaybinState.STOPPED) {
                                    error ("mpv is at playlist entry %u, but we're stopped", (uint) playlist_pos);
                                }
                                if (this.play_queue_position != (uint) playlist_pos) {
                                    error ("mpv is at playlist entry %u, but we think it's %u", (uint) playlist_pos, this.play_queue_position);
                                }
                            }
                            break;

                        case 3:
                            // also here as a sanity check
                            // should always match our own state
                            assert (data.name == "pause");
                            bool pause = data.parse_flag ();
                            if (pause && this.state != PlaybinState.PAUSED) {
                                error (@"mpv is paused, but we are @(this.state)");
                            }
                            if (!pause && this.state == PlaybinState.PAUSED) {
                                error ("mpv is not paused, but we are paused");
                            }
                            break;

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

                    case Mpv.EventId.START_FILE:
                        debug ("START_FILE received");
                        if (this.inc_position) {
                            this.play_queue_position += 1;
                        } else {
                            this.inc_position = true;
                        }

                        // estimate duration from api data
                        // while mpv doesn't know it
                        this.duration = ((Subsonic.Song) this._play_queue.get_item (this.play_queue_position)).duration;

                        this.new_track ();
                        break;

                    case Mpv.EventId.END_FILE:
                        debug ("END_FILE received");
                        var data = event.parse_end_file ();
                        if (data.error < 0) {
                            warning ("playback of track aborted: %s", data.error.to_string ());
                        }

                        if (this.inc_position && this.play_queue_position+1 == this._play_queue.get_n_items ()) {
                            // reached the end (?)
                            this.play_queue_position += 1;
                            this.state = PlaybinState.STOPPED;
                            this.stopped ();
                        }

                        break;
                      
                    default:
                        // ignore by default
                        break;
                    }
                }
            
                this.is_handling_event = false;
                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;
        this.play_queue_position = position;
        this.inc_position = false;
    }

    public void pause () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PAUSED;
        debug ("setting state to paused");
        // TODO: abstract away this handling around mpv api a bit for auto debug printing
        var ret = this.mpv.set_property_flag("pause", true);
        if (ret != 0) {
            debug (@"failed to set state to paused ($(ret)): $(ret.to_string())");
        }
    }

    public void play () {
        assert (this.state != PlaybinState.STOPPED);
        this.state = PlaybinState.PLAYING;
        debug ("setting state to playing");
        var ret = this.mpv.set_property_flag("pause", false);
        if (ret != 0) {
            debug (@"failed to set state to playing ($(ret)): $(ret.to_string())");
        }
    }

    public void go_to_next_track ()
            requires (this.state != PlaybinState.STOPPED)
    {
        if (this.play_queue_position+1 < this._play_queue.get_n_items ()) {
            this.inc_position = false;
            this.play_queue_position += 1;
            assert (this.mpv.command ({"playlist-next-playlist"}) >= 0);
        } else {
            warning ("tried to skip forward at end of play queue, ignoring");
        }
    }

    public void go_to_prev_track ()
            requires (this.state != PlaybinState.STOPPED)
    {
        if (this.play_queue_position > 0) {
            this.inc_position = false;
            this.play_queue_position -= 1;
            assert (this.mpv.command ({"playlist-prev-playlist"}) >= 0);
        } else {
            warning ("tried to skip to prev track at start of play queue, ignoring");
        }
    }

    public void remove_track (uint position)
            requires (position < this._play_queue.get_n_items ())
    {
        assert (false); // TODO
    }

    public void clear () {
        assert (this.mpv.command({"playlist-clear"}) >= 0);
        if (this.state != PlaybinState.STOPPED) {
            assert (this.mpv.command({"playlist-remove", "current"}) >= 0);
        }
        this.state = PlaybinState.STOPPED;
        this._play_queue.remove_all ();
        this.play_queue_position = 0;

        this.stopped ();
    }

    public void append_track (Subsonic.Song song) {
        assert (this.mpv.command({
            "loadfile",
            this.api.stream_uri (song.id),
            "append",
        }) >= 0);
        if (this.state == STOPPED) this.play_queue_position += 1;
        this._play_queue.append (song);
    }
}