flame/lib/effects/effects.dart

import 'dart:math';
import '../components/component.dart';

export './move_effect.dart';
export './scale_effect.dart';

abstract class PositionComponentEffect {
  bool _isDisposed = false;
  bool get isDisposed => _isDisposed;

  /// If the animation should first follow the initial curve and then follow the
  /// curve backwards
  bool isAlternating;
  bool isInfinite;
  double percentage;
  double travelTime;
  double _curveTime = 0.0;
  int _curveDirection = 1;

  PositionComponentEffect(this.isInfinite, this.isAlternating);

  void update(double dt) {
    _curveTime += dt * _curveDirection;
    if (isAlternating) {
      _curveDirection = isMax() ? -1 : (isMin() ? 1 : _curveDirection);
    } else if (isInfinite && isMax()){
      percentage = 0.0;
    }
    percentage = min(1.0, max(0.0, _curveTime / travelTime));
  }

  void dispose() => _isDisposed = true;

  PositionComponent component;

  bool hasFinished() =>
      (!isInfinite && !isAlternating && isMax()) ||
          (!isInfinite && isAlternating && isMin()) || isDisposed;
  bool isMax() => percentage == null ? false : percentage == 1.0;
  bool isMin() => percentage == null ? false : percentage == 0.0;
}