/*
 * Copyright 2007-2010 Sun Microsystems, Inc.
 *
 * This file is part of Project Darkstar Server.
 *
 * Project Darkstar Server is free software: you can redistribute it
 * and/or modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation and
 * distributed hereunder to you.
 *
 * Project Darkstar Server 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Sun designates this particular file as subject to the "Classpath"
 * exception as provided by Sun in the LICENSE file that accompanied
 * this code.
 *
 * --
 */

package com.sun.sgs.protocol;

/**
 * An exception indicating that processing a request has failed, and
 * therefore that request has been dropped.  The {@link
 * Throwable#getMessage getMessage} method returns a detail message
 * containing an explanation for the failure (possibly {@code
 * null}), the {@link #getReason getReason} method returns the
 * failure reason, and if the failure reason is {@link
 * FailureReason#OTHER}, the {@link Throwable#getCause getCause}
 * method returns the possibly-{@code null} cause of the failure.
 */
public class RequestFailureException extends Exception {
    
    /** The serial version for this class. */
    private static final long serialVersionUID = 1L;

    /** The reason for the failure */
    private final FailureReason reason;

    /**
     * Reasons why a request fails.
     */
    public enum FailureReason {
	/** The associated client session has not completed login. */
	LOGIN_PENDING,
	/** The client session is relocating to another node. */
	RELOCATE_PENDING,
	/** The client session is disconnecting from the local node. */
	DISCONNECT_PENDING,
	/** Other operational failure (see exception {@link
	 * Throwable#getCause cause} for detail). */ 
	OTHER
    };
    
    /**
     * Constructs an instance with the specified detail {@code message}
     * and {@code reason}.
     *
     * @param	message a detail message, or {@code null}
     * @param	reason a reason why the request failed
     */
    public RequestFailureException(String message, FailureReason reason) {
	super(message);
	if (reason == null) {
	    throw new NullPointerException("null reason");
	}
	this.reason = reason;
    }
    
    /**
     * Constructs an instance with the specified detail {@code message}
     * and {@code cause}.
     *
     * @param	message a detail message, or {@code null}
     * @param	cause the cause of this exception, or {@code null}
     */
    public RequestFailureException(String message, Throwable cause)
    {
	super(message, cause);
	this.reason = FailureReason.OTHER;
    }

    /**
     * Returns a failure reason.  If the returned reason is {@link
     * FailureReason#OTHER}, then the {@link Throwable#getCause cause} may
     * contain an exception that caused the failure.
     *
     * @return a failure reason
     */
    public FailureReason getReason() {
	return reason;
    }
}