package com.github.lokic.javaplus;

import lombok.EqualsAndHashCode;

import lombok.ToString;

import java.io.Serializable;

import java.util.NoSuchElementException;

import java.util.function.Function;

public interface Either<L, R> {

static <L, R> Either<L, R> left(L left) {

return new Left<>(left);

}

static <L, R> Either<L, R> right(R right) {

return new Right<>(right);

}

L getLeft();

R getRight();

boolean isLeft();

boolean isRight();

@SuppressWarnings("unchecked")

default <U> Either<L, U> flatMap(Function<? super R, ? extends Either<L, ? extends U>> mapper) {

if (isRight()) {

return (Either<L, U>) mapper.apply(getRight());

} else {

return (Either<L, U>) this;

}

}

@ToString

@EqualsAndHashCode

final class Left<L, R> implements Either<L, R>, Serializable {

private static final long serialVersionUID = 1L;

private final L value;

private Left(L value) {

this.value = value;

}

@Override

public L getLeft() {

return value;

}

@Override

public R getRight() {

throw new NoSuchElementException("getRight() at Left");

}

@Override

public boolean isLeft() {

return true;

}

@Override

public boolean isRight() {

return false;

}

}

@ToString

@EqualsAndHashCode

final class Right<L, R> implements Either<L, R>, Serializable {

private static final long serialVersionUID = 1L;

private final R value;

private Right(R value) {

this.value = value;

}

@Override

public L getLeft() {

throw new NoSuchElementException("getLeft() at Right");

}

@Override

public R getRight() {

return value;

}

@Override

public boolean isLeft() {

return false;

}

@Override

public boolean isRight() {

return true;

}

}

}