/*
 * Copyright (c) 2018, 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 sun.security.ec;

import sun.security.ec.point.*;
import sun.security.util.ArrayUtil;
import sun.security.util.Function;
import sun.security.util.Optional;
import sun.security.util.math.*;
import static sun.security.ec.ECOperations.IntermediateValueException;

import java.security.ProviderException;
import java.security.spec.*;

public class ECDSAOperations {

    public static class Seed {
        private final byte[] seedValue;

        public Seed(byte[] seedValue) {
            this.seedValue = seedValue;
        }

        public byte[] getSeedValue() {
            return seedValue;
        }
    }

    public static class Nonce {
        private final byte[] nonceValue;

        public Nonce(byte[] nonceValue) {
            this.nonceValue = nonceValue;
        }

        public byte[] getNonceValue() {
            return nonceValue;
        }
    }

    private final ECOperations ecOps;
    private final AffinePoint basePoint;

    public ECDSAOperations(ECOperations ecOps, ECPoint basePoint) {
        this.ecOps = ecOps;
        this.basePoint = toAffinePoint(basePoint, ecOps.getField());
    }

    public ECOperations getEcOperations() {
        return ecOps;
    }

    public AffinePoint basePointMultiply(byte[] scalar) {
        return ecOps.multiply(basePoint, scalar).asAffine();
    }

    public static AffinePoint toAffinePoint(ECPoint point,
        IntegerFieldModuloP field) {

        ImmutableIntegerModuloP affineX = field.getElement(point.getAffineX());
        ImmutableIntegerModuloP affineY = field.getElement(point.getAffineY());
        return new AffinePoint(affineX, affineY);
    }

    public static
    Optional<ECDSAOperations> forParameters(final ECParameterSpec ecParams) {
        Optional<ECOperations> curveOps =
            ECOperations.forParameters(ecParams);
        return curveOps.map(new Function<ECOperations, ECDSAOperations>() {
            @Override
            public ECDSAOperations apply(ECOperations ops) {
                return new ECDSAOperations(ops, ecParams.getGenerator());
            }
        });
    }

    
Sign a digest using the provided private key and seed.
IMPORTANT: The private key is a scalar represented using a
little-endian byte array. This is backwards from the conventional
representation in ECDSA. The routines that produce and consume this
value uses little-endian, so this deviation from convention removes
the requirement to swap the byte order. The returned signature is in
the conventional byte order.
Params:
privateKey – the private key scalar as a little-endian byte array
digest – the digest to be signed
seed – the seed that will be used to produce the nonce. This object
            should contain an array that is at least 64 bits longer than
            the number of bits required to represent the group order.
Throws:
IntermediateValueException – if the signature cannot be produced
     due to an unacceptable intermediate or final value. If this
     exception is thrown, then the caller should discard the nonnce and
     try again with an entirely new nonce value.
Returns:
the ECDSA signature value/**
     *
     * Sign a digest using the provided private key and seed.
     * IMPORTANT: The private key is a scalar represented using a
     * little-endian byte array. This is backwards from the conventional
     * representation in ECDSA. The routines that produce and consume this
     * value uses little-endian, so this deviation from convention removes
     * the requirement to swap the byte order. The returned signature is in
     * the conventional byte order.
     *
     * @param privateKey the private key scalar as a little-endian byte array
     * @param digest the digest to be signed
     * @param seed the seed that will be used to produce the nonce. This object
     *             should contain an array that is at least 64 bits longer than
     *             the number of bits required to represent the group order.
     * @return the ECDSA signature value
     * @throws IntermediateValueException if the signature cannot be produced
     *      due to an unacceptable intermediate or final value. If this
     *      exception is thrown, then the caller should discard the nonnce and
     *      try again with an entirely new nonce value.
     */
    public byte[] signDigest(byte[] privateKey, byte[] digest, Seed seed)
        throws IntermediateValueException {

        byte[] nonceArr = ecOps.seedToScalar(seed.getSeedValue());

        Nonce nonce = new Nonce(nonceArr);
        return signDigest(privateKey, digest, nonce);
    }

    
Sign a digest using the provided private key and nonce.
IMPORTANT: The private key and nonce are scalars represented by a
little-endian byte array. This is backwards from the conventional
representation in ECDSA. The routines that produce and consume these
values use little-endian, so this deviation from convention removes
the requirement to swap the byte order. The returned signature is in
the conventional byte order.
Params:
privateKey – the private key scalar as a little-endian byte array
digest – the digest to be signed
nonce – the nonce object containing a little-endian scalar value.
Throws:
IntermediateValueException – if the signature cannot be produced
     due to an unacceptable intermediate or final value. If this
     exception is thrown, then the caller should discard the nonnce and
     try again with an entirely new nonce value.
Returns:
the ECDSA signature value/**
     *
     * Sign a digest using the provided private key and nonce.
     * IMPORTANT: The private key and nonce are scalars represented by a
     * little-endian byte array. This is backwards from the conventional
     * representation in ECDSA. The routines that produce and consume these
     * values use little-endian, so this deviation from convention removes
     * the requirement to swap the byte order. The returned signature is in
     * the conventional byte order.
     *
     * @param privateKey the private key scalar as a little-endian byte array
     * @param digest the digest to be signed
     * @param nonce the nonce object containing a little-endian scalar value.
     * @return the ECDSA signature value
     * @throws IntermediateValueException if the signature cannot be produced
     *      due to an unacceptable intermediate or final value. If this
     *      exception is thrown, then the caller should discard the nonnce and
     *      try again with an entirely new nonce value.
     */
    public byte[] signDigest(byte[] privateKey, byte[] digest, Nonce nonce)
        throws IntermediateValueException {

        IntegerFieldModuloP orderField = ecOps.getOrderField();
        int orderBits = orderField.getSize().bitLength();
        if (orderBits % 8 != 0 && orderBits < digest.length * 8) {
            // This implementation does not support truncating digests to
            // a length that is not a multiple of 8.
            throw new ProviderException("Invalid digest length");
        }

        byte[] k = nonce.getNonceValue();
        // check nonce length
        int length = (orderField.getSize().bitLength() + 7) / 8;
        if (k.length != length) {
            throw new ProviderException("Incorrect nonce length");
        }

        MutablePoint R = ecOps.multiply(basePoint, k);
        IntegerModuloP r = R.asAffine().getX();
        // put r into the correct field by fully reducing to an array
        byte[] temp = new byte[length];
        r.asByteArray(temp);
        r = orderField.getElement(temp);
        // store r in result
        r.asByteArray(temp);
        byte[] result = new byte[2 * length];
        ArrayUtil.reverse(temp);
        System.arraycopy(temp, 0, result, 0, length);
        // compare r to 0
        if (ECOperations.allZero(temp)) {
            throw new IntermediateValueException();
        }

        IntegerModuloP dU = orderField.getElement(privateKey);
        int lengthE = Math.min(length, digest.length);
        byte[] E = new byte[lengthE];
        System.arraycopy(digest, 0, E, 0, lengthE);
        ArrayUtil.reverse(E);
        IntegerModuloP e = orderField.getElement(E);
        IntegerModuloP kElem = orderField.getElement(k);
        IntegerModuloP kInv = kElem.multiplicativeInverse();
        MutableIntegerModuloP s = r.mutable();
        s.setProduct(dU).setSum(e).setProduct(kInv);
        // store s in result
        s.asByteArray(temp);
        ArrayUtil.reverse(temp);
        System.arraycopy(temp, 0, result, length, length);
        // compare s to 0
        if (ECOperations.allZero(temp)) {
            throw new IntermediateValueException();
        }

        return result;

    }

}