/*
 * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.eclipse.jgit.internal.transport.sshd.auth;

import java.io.Closeable;

/**
 * An {@code AuthenticationHandler} encapsulates a possibly multi-step
 * authentication protocol. Intended usage:
 *
 * <pre>
 * setParams(something);
 * start();
 * sendToken(getToken());
 * while (!isDone()) {
 * 	setParams(receiveMessageAndExtractParams());
 * 	process();
 * 	Object t = getToken();
 * 	if (t != null) {
 * 		sendToken(t);
 * 	}
 * }
 * </pre>
 *
 * An {@code AuthenticationHandler} may be stateful and therefore is a
 * {@link Closeable}.
 *
 * @param <ParameterType>
 *            defining the parameter type for {@link #setParams(Object)}
 * @param <TokenType>
 *            defining the token type for {@link #getToken()}
 */
public interface AuthenticationHandler<ParameterType, TokenType>
		extends Closeable {

	/**
	 * Produces the initial authentication token that can be then retrieved via
	 * {@link #getToken()}.
	 *
	 * @throws Exception
	 *             if an error occurs
	 */
	void start() throws Exception;

	/**
	 * Produces the next authentication token, if any.
	 *
	 * @throws Exception
	 *             if an error occurs
	 */
	void process() throws Exception;

	/**
	 * Sets the parameters for the next token generation via {@link #start()} or
	 * {@link #process()}.
	 *
	 * @param input
	 *            to set, may be {@code null}
	 */
	void setParams(ParameterType input);

	/**
	 * Retrieves the last token generated.
	 *
	 * @return the token, or {@code null} if there is none
	 * @throws Exception
	 *             if an error occurs
	 */
	TokenType getToken() throws Exception;

	/**
	 * Tells whether is authentication mechanism is done (successfully or
	 * unsuccessfully).
	 *
	 * @return whether this authentication is done
	 */
	boolean isDone();

	@Override
	void close();
}