FloatValue.java

public class FloatValue {
    public boolean dirty = true;
    public float baseValue;         //before any buffs
    public float value;             //with all buffs
    transient private YSet<FloatAffector> affectors = hs();

    public void recalc() {
        float mul = affectors.reduce(0f, (cur, affector) -> cur + affector.mul);
        float add = affectors.reduce(0f, (cur, affector) -> cur + affector.add);
        value = baseValue * mul + add;
        dirty = false;
    }

    public void addAffect(FloatAffector af) {
        if (affectors.contains(af)) BadException.die("already contains " + af);
        affectors.add(af);
        dirty = true;
    }

    public void removeAffect(FloatAffector af) {
        if (!affectors.contains(af)) BadException.die("trying to remove, but not contained " + af);
        affectors.remove(af);
        dirty = true;
    }

    public static class FloatAffector {
        public float mul;
        public float add;

        public YList<String> valuePath;

        public FloatAffector(float mul, float add) {
            this.mul = mul;
            this.add = add;
        }

        public void addTo(Object o) {
            FloatValue.<FloatValue>get(o, valuePath).addAffect(this);
        }
        public void removeFrom(Object o) {
            FloatValue.<FloatValue>get(o, valuePath).removeAffect(this);
        }
    }

    public static <T> T get(Object target, List<String> path) {
        Object curObj = target;
        for (String fieldName : path) curObj = Reflector.get(curObj, fieldName);
        return (T) curObj;
    }

}