import org.hamcrest.Description;
import org.hamcrest.Factory;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeDiagnosingMatcher;

import java.util.Optional;

import static org.hamcrest.core.IsEqual.equalTo;

public class OptionalWithValue<T> extends TypeSafeDiagnosingMatcher<Optional<? extends T>> {

	@Factory
	public static <T> Matcher<Optional<? extends T>> optionalWithValue(Matcher<? super T> valueMatcher) {
		return new OptionalWithValue<>(valueMatcher);
	}

	@Factory
	public static <T> Matcher<Optional<? extends T>> optionalWithValue(T value) {
		return optionalWithValue(equalTo(value));
	}

	private final Matcher<? super T> subMatcher;

	public OptionalWithValue(Matcher<? super T> subMatcher) {
		this.subMatcher = subMatcher;
	}

	@Override
	protected boolean matchesSafely(Optional<? extends T> item, Description mismatchDescription) {
		if (!item.isPresent()) {
			mismatchDescription.appendText("an empty optional");
			return false;
		}

		boolean matches = subMatcher.matches(item.get());
		if (!matches) {
			subMatcher.describeMismatch(item.get(), mismatchDescription);
		}

		return matches;
	}

	@Override
	public void describeTo(Description description) {
		description.appendText("optional with value ");
		subMatcher.describeTo(description);
	}
}