/*

 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.security.spec;

import java.security.InvalidParameterException;

import java.util.Objects;

import java.util.Optional;

/**

 * A class used to specify EdDSA signature and verification parameters. All

 * algorithm modes in <a href="https://tools.ietf.org/html/rfc8032">RFC 8032:

 * Edwards-Curve Digital Signature Algorithm (EdDSA)</a> can be specified using

 * combinations of the settings in this class.

 *

 * <ul>

 * <li>If prehash is true, then the mode is Ed25519ph or Ed448ph</li>

 * <li>Otherwise, if a context is present, the mode is Ed25519ctx or Ed448</li>

 * <li>Otherwise, the mode is Ed25519 or Ed448</li>

 * </ul>

 *

 * @since 15

 */

public class EdDSAParameterSpec implements AlgorithmParameterSpec {

    private final boolean prehash;

    private final byte[] context;

    /**

     * Construct an {@code EdDSAParameterSpec} by specifying whether the prehash mode

     * is used. No context is provided so this constructor specifies a mode

     * in which the context is null. Note that this mode may be different

     * than the mode in which an empty array is used as the context.

     *

     * @param prehash whether the prehash mode is specified.

     */

    public EdDSAParameterSpec(boolean prehash) {

        this.prehash = prehash;

        this.context = null;

    }

    /**

     * Construct an {@code EdDSAParameterSpec} by specifying a context and whether the

     * prehash mode is used. The context may not be null, but it may be an

     * empty array. The mode used when the context is an empty array may not be

     * the same as the mode used when the context is absent.

     *

     * @param prehash whether the prehash mode is specified.

     * @param context the context is copied and bound to the signature.

     * @throws NullPointerException if context is null.

     * @throws InvalidParameterException if context length is greater than 255.

     */

    public EdDSAParameterSpec(boolean prehash, byte[] context) {

        Objects.requireNonNull(context, "context may not be null");

        if (context.length > 255) {

            throw new InvalidParameterException("context length cannot be " +

                "greater than 255");

        }

        this.prehash = prehash;

        this.context = context.clone();

    }

    /**

     * Get whether the prehash mode is specified.

     *

     * @return whether the prehash mode is specified.

     */

    public boolean isPrehash() {

        return prehash;

    }

    /**

     * Get the context that the signature will use.

     *

     * @return {@code Optional} contains a copy of the context or empty

     * if context is null.

     */

    public Optional<byte[]> getContext() {

        if (context == null) {

            return Optional.empty();

        } else {

            return Optional.of(context.clone());

        }

    }

}