/*
    * GordianKnot: Security Suite
    * Copyright 2026. Tony Washer
    *
    * Licensed under the Apache License, Version 2.0 (the "License"); you may not
    * use this file except in compliance with the License.  You may obtain a copy
    * of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations under
   * the License.
   */
  
  package io.github.tonywasher.joceanus.gordianknot.impl.bc.sign;
  
  import io.github.tonywasher.joceanus.gordianknot.api.base.GordianException;
  import io.github.tonywasher.joceanus.gordianknot.api.sign.GordianNewSignParams;
  import io.github.tonywasher.joceanus.gordianknot.api.sign.spec.GordianSignatureSpec;
  import io.github.tonywasher.joceanus.gordianknot.impl.bc.keypair.BouncyEllipticKeyPair.BouncyECPrivateKey;
  import io.github.tonywasher.joceanus.gordianknot.impl.bc.keypair.BouncyEllipticKeyPair.BouncyECPublicKey;
  import io.github.tonywasher.joceanus.gordianknot.impl.bc.keypair.BouncyKeyPair;
  import io.github.tonywasher.joceanus.gordianknot.impl.bc.sign.BouncySignature.BouncyDERCoder;
  import io.github.tonywasher.joceanus.gordianknot.impl.core.base.GordianBaseFactory;
  import org.bouncycastle.crypto.DSA;
  import org.bouncycastle.crypto.params.ParametersWithRandom;
  
  import java.math.BigInteger;
  
  /**
   * EC signer.
   */
  public class BouncyECSignature
          extends BouncyDigestSignature {
      /**
       * The Signer.
       */
      private final DSA theSigner;
  
      /**
       * The Coder.
       */
      private final BouncyDERCoder theCoder;
  
      /**
       * Constructor.
       *
       * @param pFactory the factory
       * @param pSpec    the signatureSpec.
       * @throws GordianException on error
       */
      BouncyECSignature(final GordianBaseFactory pFactory,
                        final GordianSignatureSpec pSpec) throws GordianException {
          /* Initialise underlying class */
          super(pFactory, pSpec);
  
          /* Create the signer and Coder */
          theSigner = BouncySignature.getDSASigner(pFactory, pSpec);
          theCoder = new BouncyDERCoder();
      }
  
      @Override
      public void initForSigning(final GordianNewSignParams pParams) throws GordianException {
          /* Initialise detail */
          super.initForSigning(pParams);
          final BouncyKeyPair myPair = getKeyPair();
          BouncyKeyPair.checkKeyPair(myPair);
  
          /* Initialise and set the signer */
          final BouncyECPrivateKey myPrivate = (BouncyECPrivateKey) myPair.getPrivateKey();
          final ParametersWithRandom myParms = new ParametersWithRandom(myPrivate.getPrivateKey(), getRandom());
          theSigner.init(true, myParms);
      }
  
      @Override
      public void initForVerify(final GordianNewSignParams pParams) throws GordianException {
          /* Initialise detail */
          super.initForVerify(pParams);
          final BouncyKeyPair myPair = getKeyPair();
          BouncyKeyPair.checkKeyPair(myPair);
  
          /* Initialise and set the signer */
          final BouncyECPublicKey myPublic = (BouncyECPublicKey) myPair.getPublicKey();
          theSigner.init(false, myPublic.getPublicKey());
      }
  
      @Override
      public byte[] sign() throws GordianException {
          /* Check that we are in signing mode */
          checkMode(GordianSignatureMode.SIGN);
  
          /* Sign the message */
          final BigInteger[] myValues = theSigner.generateSignature(getDigest());
          return theCoder.dsaEncode(myValues[0], myValues[1]);
      }
  
     @Override
     public boolean verify(final byte[] pSignature) throws GordianException {
         /* Check that we are in verify mode */
         checkMode(GordianSignatureMode.VERIFY);
 
         /* Verify the message */
         final BigInteger[] myValues = theCoder.dsaDecode(pSignature);
         return theSigner.verifySignature(getDigest(), myValues[0], myValues[1]);
     }
 }