import 'package:flutter/foundation.dart';
import 'package:flutter/scheduler.dart';
class BeamClock extends ChangeNotifier implements ValueListenable<double> {
  BeamClock._();
  static final BeamClock instance = BeamClock._();

  Ticker? _ticker;
  int _attachCount = 0;
  double _base = 0;
  double _value = 0;
  @override
  double get value => _value;

  @visibleForTesting
  bool get isRunning => _ticker != null;

  @visibleForTesting
  int get attachCount => _attachCount;

  void attach() {
    _attachCount++;
    if (_ticker == null) {
      _base = _value;
      _ticker = Ticker(_onTick)..start();
    }
  }

  void detach() {
    if (_attachCount == 0) return;
    _attachCount--;
    if (_attachCount == 0) {
      _ticker?.dispose();
      _ticker = null;
    }
  }

  void _onTick(Duration elapsed) {
    _value = _base + elapsed.inMicroseconds / Duration.microsecondsPerSecond;
    notifyListeners();
  }
}