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package java.security.spec;

import java.math.BigInteger;

import java.util.Objects;

/**

 * An elliptic curve point used to specify keys as defined by

 * <a href="https://tools.ietf.org/html/rfc8032">RFC 8032: Edwards-Curve

 * Digital Signature Algorithm (EdDSA)</a>. These points are distinct from the

 * points represented by {@code ECPoint}, and they are intended for use with

 * algorithms based on RFC 8032 such as the EdDSA {@code Signature} algorithm.

 * <p>

 * An EdEC point is specified by its y-coordinate value and a boolean that

 * indicates whether the x-coordinate is odd. The y-coordinate is an

 * element of the field of integers modulo some value p that is determined by

 * the algorithm parameters. This field element is represented by a

 * {@code BigInteger}, and implementations that consume objects of this class

 * may reject integer values which are not in the range [0, p).

 *

 * @since 15

 */

public final class EdECPoint {

    private final boolean xOdd;

    private final BigInteger y;

    /**

     * Construct an EdECPoint.

     *

     * @param xOdd whether the x-coordinate is odd.

     * @param y the y-coordinate, represented using a {@code BigInteger}.

     *

     * @throws NullPointerException if {@code y} is null.

     */

    public EdECPoint(boolean xOdd, BigInteger y) {

        Objects.requireNonNull(y, "y must not be null");

        this.xOdd = xOdd;

        this.y = y;

    }

    /**

     * Get whether the x-coordinate of the point is odd.

     *

     * @return a boolean indicating whether the x-coordinate is odd.

     */

    public boolean isXOdd() {

        return xOdd;

    }

    /**

     * Get the y-coordinate of the point.

     *

     * @return the y-coordinate, represented using a {@code BigInteger}.

     */

    public BigInteger getY() {

        return y;

    }

}