private final Either<Matcher<? super Throwable>, Matcher<? super A>> matcher;

private final AtomicReference<Either<Throwable, A>> resultRef;

private IOMatcher(Either<Matcher<? super Throwable>, Matcher<? super A>> matcher) {

this.matcher = matcher;

resultRef = new AtomicReference<>();

}

@Override

protected boolean matchesSafely(IO<A> io) {

Either<Throwable, A> res = io.safe().unsafePerformIO();

resultRef.set(res);

return res.match(t -> matcher.match(tMatcher -> tMatcher.matches(t),

aMatcher -> false),

a -> matcher.match(tMatcher -> false,

aMatcher -> aMatcher.matches(a)));

}

@Override

public void describeTo(Description description) {

matcher.match(m -> io(() -> m.describeTo(description.appendText("IO throwing exception matching "))),

m -> io(() -> m.describeTo(description.appendText("IO yielding value matching "))))

.unsafePerformIO();

}

@Override

protected void describeMismatchSafely(IO<A> item, Description mismatchDescription) {

resultRef.get().match(t -> io(() -> mismatchDescription.appendText("IO threw " + t)),

a -> io(() -> mismatchDescription.appendText("IO yielded value " + a)))

.unsafePerformIO();

}

public static <A> IOMatcher<A> yieldsValue(Matcher<? super A> matcher) {

return new IOMatcher<>(right(matcher));

}

public static <A> IOMatcher<A> completesNormally() {

return yieldsValue(anything());

}

public static <A> IOMatcher<A> throwsException(Matcher<? super Throwable> throwableMatcher) {

return new IOMatcher<>(left(throwableMatcher));

}