/* Copyright (c) 2014 Boundless and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/org/documents/edl-v10.html
 *
 * Contributors:
 * Gabriel Roldan (Boundless) - initial implementation
 */
package org.locationtech.geogig.api.hooks;

import java.util.ServiceLoader;

import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;

import org.locationtech.geogig.api.AbstractGeoGigOp;

/**
 * An interface that defines hooks for {@link AbstractGeoGigOp command} written in Java as opposed
 * to a scripting language.
 * <p>
 * Implementations of this interface are discovered using the standard Java {@link ServiceLoader}
 * SPI lookup, by looking for implementing class names at
 * {@code META-INF/services/org.locationtech.geogig.api.hooks.CommandHook} resources.
 * <p>
 * Implementations must have a default constructor (or no explicit constructor at all), and must be
 * thread safe.
 */
@ThreadSafe
public interface CommandHook {

    public <C extends AbstractGeoGigOp<?>> C pre(C command)
            throws CannotRunGeogigOperationException;

    public <T> T post(AbstractGeoGigOp<T> command, @Nullable Object retVal,
            @Nullable RuntimeException exception) throws Exception;

    public boolean appliesTo(Class<? extends AbstractGeoGigOp<?>> clazz);
}