import Toybox.Lang;
import Toybox.Position;
import Toybox.Timer;

// Single-shot GPS acquisition with a hard timeout. Uses both
// enableLocationEvents (fires on real hardware) and a polling
// fallback via Position.getInfo() (works in the simulator where
// "Set Position" doesn't trigger location events).
class GpsService {

    private var _callback as Method(result as Dictionary or Null) as Void;
    private var _timer as Timer.Timer;
    private var _pollTimer as Timer.Timer;
    private var _finished as Boolean = false;
    private var _bestFix as Dictionary or Null = null;

    function initialize(callback as Method(result as Dictionary or Null) as Void) {
        _callback = callback;
        _timer = new Timer.Timer();
        _pollTimer = new Timer.Timer();
    }

    function start() as Void {
        Position.enableLocationEvents(
            Position.LOCATION_CONTINUOUS,
            method(:_onPosition)
        );
        // Poll Position.getInfo() every 500ms as fallback for simulator.
        _pollTimer.start(method(:_poll), 500, true);
        _timer.start(method(:_onTimeout), Config.GPS_TIMEOUT_MS, false);
    }

    function _poll() as Void {
        if (_finished) { return; }
        var info = Position.getInfo();
        if (info != null && info.position != null) {
            _processInfo(info);
        }
    }

    function _onPosition(info as Position.Info) as Void {
        if (_finished) { return; }
        _processInfo(info);
    }

    private function _processInfo(info as Position.Info) as Void {
        if (info == null || info.position == null) { return; }

        var degrees = info.position.toDegrees();
        var quality = (info.accuracy != null) ? info.accuracy : 0;

        // Always keep the best quality fix.
        if (_bestFix == null || quality >= (_bestFix["q"] as Number)) {
            _bestFix = {
                "lat" => degrees[0].toFloat(),
                "lon" => degrees[1].toFloat(),
                "acc" => quality.toFloat(),
                "q"   => quality
            };
        }
    }

    function _onTimeout() as Void {
        _finish(_bestFix);
    }

    function _finish(result as Dictionary or Null) as Void {
        if (_finished) { return; }
        _finished = true;
        _timer.stop();
        _pollTimer.stop();
        Position.enableLocationEvents(Position.LOCATION_DISABLE, method(:_onPosition));
        _callback.invoke(result);
    }
}