/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2011, Red Hat, Inc., and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jboss.as.protocol.mgmt;

import org.jboss.threads.AsyncFuture;
import org.xnio.Cancellable;

/**
 * Encapsulates information about a currently active operation, which
 * can require multiple messages exchanged between the client and the
 * server.
 *
 * An attachment is optional, but can be used to maintain a shared state between multiple requests.
 * It can be accessed using the {@link org.jboss.as.protocol.mgmt.ManagementRequestContext#getAttachment()}
 * from the request handler.
 *
 * An operation is seen as active until one of the methods on the {@link ActiveOperation.ResultHandler} are called.
 *
 * @param <T> the result type
 * @param <A> the attachment type
 *
 * @author Emanuel Muckenhuber
 */
public interface ActiveOperation<T, A> {

    /**
     * Get the batch id.
     *
     * @return the batch id
     */
    Integer getOperationId();

    /**
     * Get the result handler for this request.
     *
     * @return the result handler
     */
    ResultHandler<T> getResultHandler();

    /**
     * Get the attachment.
     *
     * @return the attachment
     */
    A getAttachment();

    /**
     * Get the result.
     *
     * @return the future result
     */
    AsyncFuture<T> getResult();

    /**
     * Add a cancellation handler.
     *
     * @param cancellable the cancel handler
     */
    void addCancellable(final Cancellable cancellable);

    /**
     * Handler for the operation result or to mark the operation as cancelled or failed.
     *
     * @param <T> the result type
     */
    interface ResultHandler<T> {

        /**
         * Set the result.
         *
         * @return {@code true} if the result was successfully set, or {@code false} if a result was already set
         * @param result the result
         */
        boolean done(T result);

        /**
         * Mark the operation as failed.
         *
         * @return {@code true} if the result was successfully set, or {@code false} if a result was already set
         * @param t the exception
         */
        boolean failed(Throwable t);

        /**
         * Cancel the operation.
         */
        void cancel();
    }

    /**
     * A callback indicating when an operation is complete. This is not part of the ActiveOperation API itself,
     * but rather is often provided by callers that trigger instantiation of an ActiveOperation in a process.
     *
     * @param <T> the result type
     */
    interface CompletedCallback<T> {

        /**
         * The operation completed successfully.
         *
         * @param result the result
         */
        void completed(T result);

        /**
         * The operation failed.
         *
         * @param e the failure
         */
        void failed(Exception e);

        /**
         * The operation was cancelled before being able to complete.
         */
        void cancelled();
    }

}