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Error handling in Functional Programming
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package org.zalando.fauxpas;

import lombok.SneakyThrows;
import org.apiguardian.api.API;

import javax.annotation.Nullable;

import static org.apiguardian.api.API.Status.MAINTAINED;
import static org.apiguardian.api.API.Status.STABLE;

public final class TryWith {

    private TryWith() {

    }

    @API(status = MAINTAINED)
    public static  void tryWith(
            @Nullable final O outer, @Nullable final I inner, final ThrowingBiConsumer consumer) throws X {

        tryWith(outer, a -> {
            tryWith(inner, b -> {
                consumer.tryAccept(a, b);
            });
        });
    }

    @API(status = STABLE)
    public static  void tryWith(@Nullable final R resource,
            final ThrowingConsumer consumer) throws X {

        try {
            consumer.tryAccept(resource);
        } catch (final Throwable e) {
            throw tryClose(resource, TryWith.cast(e));
        }

        tryClose(resource);
    }

    @API(status = MAINTAINED)
    public static  T tryWith(
            @Nullable final O outer, @Nullable final I inner, final ThrowingBiFunction function) throws X {

        // not exactly sure why those explicit type parameters are needed
        return TryWith.tryWith(outer, a ->
                tryWith(inner, b -> {
                    return function.tryApply(a, b);
                }));
    }

    @API(status = STABLE)
    public static  T tryWith(@Nullable final R resource,
            final ThrowingFunction supplier) throws X {

        final T value;

        try {
            value = supplier.tryApply(resource);
        } catch (final Throwable e) {
            throw tryClose(resource, TryWith.cast(e));
        }

        tryClose(resource);

        return value;
    }

    @SneakyThrows
    private static void tryClose(@Nullable final AutoCloseable resource) {
        if (resource == null) {
            return;
        }

        resource.close();
    }

    @SuppressWarnings("unchecked")
    private static  X cast(final Throwable e) {
        return (X) e;
    }

    private static  X tryClose(@Nullable final AutoCloseable closeable, final X e) {
        if (closeable == null) {
            return e;
        }

        try {
            closeable.close();
        } catch (final Throwable inner) {
            e.addSuppressed(inner);
        }

        return e;
    }

}