/*
 * Copyright (c) 2020, 2021 Contributors to Eclipse Foundation. All rights reserved.
 * Copyright (c) 1997, 2020 Oracle and/or its affiliates and others.
 * All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package jakarta.security.auth.message;

import javax.security.auth.Subject;

/**
 * An implementation of this interface is used to secure service request messages, and validate received service
 * response messages.
 *
 * @see MessageInfo
 * @see Subject
 */
public interface ClientAuth {

    /**
     * Secure a service request message before sending it to the service.
     *
     * <p>
     * This method is called to transform the request message acquired by calling getRequestMessage (on messageInfo) into
     * the mechanism-specific form to be sent by the runtime.
     *
     * <p>
     * This method conveys the outcome of its message processing either by returning an AuthStatus value or by throwing an
     * AuthException.
     *
     * @param messageInfo A contextual object that encapsulates the client request and server response objects, and that may
     * be used to save state across a sequence of calls made to the methods of this interface for the purpose of completing
     * a secure message exchange.
     *
     * @param clientSubject A Subject that represents the source of the service request, or null. It may be used by the
     * method implementation as the source of Principals or credentials to be used to secure the request. If the Subject is
     * not null, the method implementation may add additional Principals or credentials (pertaining to the source of the
     * service request) to the Subject.
     *
     * @return An AuthStatus object representing the completion status of the processing performed by the method. The
     * AuthStatus values that may be returned by this method are defined as follows:
     * <ul>
     *   <li>AuthStatus.SUCCESS when the application request message was successfully secured. The secured request message may
     *       be obtained by calling getRequestMessage on messageInfo.
     *
     *   <li>AuthStatus.SEND_CONTINUE to indicate that the application request message (within messageInfo) was replaced with
     *       a security message that should elicit a security-specific response from the peer security system. This status value
     *       also indicates that the application message has not yet been secured.
     *
     *       This status value serves to inform the calling runtime that (to successfully complete the message exchange) it will
     *       need to be capable of continuing the message dialog by conducting at least one additional request/response exchange
     *       after having received the security-specific response elicited by sending the security message.
     *
     *       When this status value is returned, the corresponding invocation of <code>validateResponse</code> must be able to
     *       obtain the original application request message.
     *
     *   <li>AuthStatus.FAILURE to indicate that a failure occured while securing the request message, and that an appropriate
     *       failure response message is available by calling getResponseMessage on messageInfo.
     * </ul>
     *
     * @exception AuthException When the message processing failed without establishing a failure response message (in
     * messageInfo).
     */
    AuthStatus secureRequest(MessageInfo messageInfo, Subject clientSubject) throws AuthException;

    /**
     * Validate a received service response.
     *
     * <p>
     * This method is called to transform the mechanism-specific response message acquired by calling getResponseMessage (on
     * messageInfo) into the validated application message to be returned to the message processing runtime. If the response
     * message is a (mechanism-specific) meta-message, the method implementation must attempt to transform the meta-message
     * into the next mechanism-specific request message to be sent by the runtime.
     *
     * <p>
     * This method conveys the outcome of its message processing either by returning an AuthStatus value or by throwing an
     * AuthException.
     *
     * @param messageInfo A contextual object that encapsulates the client request and server response objects, and that may
     * be used to save state across a sequence of calls made to the methods of this interface for the purpose of completing
     * a secure message exchange.
     *
     * @param clientSubject A Subject that represents the recipient of the service response, or null. It may be used by the
     * method implementation as the source of Principals or credentials to be used to validate the response. If the Subject
     * is not null, the method implementation may add additional Principals or credentials (pertaining to the recipient of
     * the service request) to the Subject.
     *
     * @param serviceSubject A Subject that represents the source of the service response, or null. If the Subject is not
     * null, the method implementation may add additional Principals or credentials (pertaining to the source of the service
     * response) to the Subject.
     *
     * @return An AuthStatus object representing the completion status of the processing performed by the method. The
     * AuthStatus values that may be returned by this method are defined as follows:
     * <ul>
     *   <li>AuthStatus.SUCCESS when the application response message was successfully validated. The validated message is
     *       available by calling getResponseMessage on messageInfo.
     *
     *   <li>AuthStatus.SEND_CONTINUE to indicate that response validation is incomplete, and that a continuation request was
     *       returned as the request message within messageInfo.
     *
     *       This status value serves to inform the calling runtime that (to successfully complete the message exchange) it will
     *       need to be capable of continuing the message dialog by conducting at least one additional request/response exchange.
     *
     *   <li>AuthStatus.FAILURE to indicate that validation of the response failed, and that a failure response message has
     *       been established in messageInfo.
     * </ul>
     *
     * @exception AuthException When the message processing failed without establishing a failure response message (in
     * messageInfo).
     */
    default AuthStatus validateResponse(MessageInfo messageInfo, Subject clientSubject, Subject serviceSubject) throws AuthException {
        return AuthStatus.SUCCESS;
    }

    /**
     * Remove implementation specific principals and credentials from the subject.
     *
     * @param messageInfo A contextual object that encapsulates the client request and server response objects, and that may
     * be used to save state across a sequence of calls made to the methods of this interface for the purpose of completing
     * a secure message exchange.
     *
     * @param subject The Subject instance from which the Principals and credentials are to be removed.
     *
     * @exception AuthException If an error occurs during the Subject processing.
     */
    default void cleanSubject(MessageInfo messageInfo, Subject subject) throws AuthException {

    }
}
