no.arktekk.siren.util.Lens Maven / Gradle / Ivy

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package no.arktekk.siren.util;


import java.util.function.BiFunction;
import java.util.function.Function;

public final class Lens implements Function {

    public final Function fget;
    public final BiFunction fset;

    private Lens(Function fget, BiFunction fset) {
        this.fget = fget;
        this.fset = fset;
    }

    public B get(A a) {
        return fget.apply(a);
    }

    public A set(A a, B b) {
        return fset.apply(a, b);
    }

    @Override
    public B apply(A a) {
        return get(a);
    }

    public A updated(A whole, B part) {
        return set(whole, part);
    }

    public A mod(A a, Function f) {
        return set(a, f.apply(apply(a)));
    }

    public  Lens compose(final Lens that) {
        return new Lens<>(c -> get(that.apply(c)), (c, b) -> that.mod(c, a -> set(a, b)));
    }

    public  Lens andThen(Lens that) {
        return that.compose(this);
    }

    public static  Lens of(Function fget, BiFunction fset) {
        return new Lens<>(fget, fset);
    }
}