package at.gv.egiz.moazs.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import java.util.function.Supplier;

import static at.gv.egiz.moazs.MoaZSException.moaZSException;

@Component
public class JAXBClassNotFoundFix {

    private static final Logger log = LoggerFactory.getLogger(JAXBClassNotFoundFix.class);

    private JAXBClassNotFoundFix() {}

    /**
     * Solves JAXB's "ClassNotFoundException: com.sun.xml.internal.bind.v2.ContextFactory" in Java >= 9
     * by running func in a dedicated thread which has its context classloader replaced with a classloader that finds
     * the ContextFactory.
     *
     * See https://sjhannah.com/blog/2018/11/21/jaxb-hell-on-jdk-9/
     * Note: "runInTheadWithClassClassLoader" is not a typo.
     * @param func function that is called in a dedicated thread.
     * @param <A> return value of func.
     * @return
     */
    public static <A> A runInTheadWithClassClassLoader(Supplier<A> func) {

        final Object[] result = new Object[1];
        final Exception[] error = new Exception[1];

        Thread t = new Thread(() -> {
            try {
                result[0] = func.get();
            } catch (Exception ex) {
                error[0] = ex;
            }
        });

        t.setContextClassLoader(JAXBClassNotFoundFix.class.getClassLoader());
        t.start();

        try {
            t.join();
        } catch (InterruptedException ex) {
            log.error("Interrupted. ", ex);
            throw moaZSException("Interrupted. ", ex);
        }

        if (error[0] != null) {
            throw moaZSException("Could not run function.", error[0]);
        }

        return (A)result[0];
    }
}