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

// Single-shot GPS acquisition with a hard timeout. Caller supplies
// a callback that fires exactly once with either a position fix or
// null (if nothing usable was received before the timeout). Accuracy
// shortcut: if the fix already hits Config.GPS_TARGET_ACCURACY_M we
// stop waiting even if the timeout hasn't expired.
class GpsService {

    private var _callback as Method(result as Dictionary or Null) as Void;
    private var _timer 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();
    }

    function start() as Void {
        Position.enableLocationEvents(
            Position.LOCATION_CONTINUOUS,
            method(:_onPosition)
        );
        _timer.start(method(:_onTimeout), Config.GPS_TIMEOUT_MS, false);
    }

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

        var degrees = info.position.toDegrees();
        var acc = (info.accuracy != null) ? info.accuracy.toFloat() : null;

        _bestFix = {
            "lat" => degrees[0].toFloat(),
            "lon" => degrees[1].toFloat(),
            "acc" => acc
        };

        // Good enough → stop early.
        if (acc != null && acc <= Config.GPS_TARGET_ACCURACY_M) {
            _finish(_bestFix);
        }
    }

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

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