/*
    * GordianKnot: Security Suite
    * Copyright 2012-2026. 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.ext.macs;
  
  import io.github.tonywasher.joceanus.gordianknot.impl.ext.digests.GordianSkeinBase;
  import io.github.tonywasher.joceanus.gordianknot.impl.ext.params.GordianSkeinParameters;
  import io.github.tonywasher.joceanus.gordianknot.impl.ext.params.GordianSkeinParameters.GordianSkeinParametersBuilder;
  import org.bouncycastle.crypto.CipherParameters;
  import org.bouncycastle.crypto.Mac;
  import org.bouncycastle.crypto.engines.ThreefishEngine;
  import org.bouncycastle.crypto.params.KeyParameter;
  
  /**
   * Implementation of the Skein parameterised MAC function in 256, 512 and 1024 bit block sizes,
   * based on the {@link ThreefishEngine Threefish} tweakable block cipher.
   * <p>
   * This is the 1.3 version of Skein defined in the Skein hash function submission to the NIST SHA-3
   * competition in October 2010.
   * <p>
   * Skein was designed by Niels Ferguson - Stefan Lucks - Bruce Schneier - Doug Whiting - Mihir
   * Bellare - Tadayoshi Kohno - Jon Callas - Jesse Walker.
   *
   * @see GordianSkeinBase
   * @see GordianSkeinParameters
   */
  public class GordianSkeinMac
          implements Mac {
      /**
       * 256 bit block size - Skein MAC-256.
       */
      public static final int SKEIN_256 = GordianSkeinBase.SKEIN_256;
  
      /**
       * 512 bit block size - Skein MAC-512.
       */
      public static final int SKEIN_512 = GordianSkeinBase.SKEIN_512;
  
      /**
       * 1024 bit block size - Skein MAC-1024.
       */
      public static final int SKEIN_1024 = GordianSkeinBase.SKEIN_1024;
  
      /**
       * The engine.
       */
      private final GordianSkeinBase theEngine;
  
      /**
       * Constructs a Skein MAC with an internal state size and output size.
       *
       * @param stateSizeBits  the internal state size in bits - one of {@link #SKEIN_256}, {@link #SKEIN_512} or
       *                       {@link #SKEIN_1024}.
       * @param digestSizeBits the output/MAC size to produce in bits, which must be an integral number of bytes.
       */
      public GordianSkeinMac(final int stateSizeBits,
                             final int digestSizeBits) {
          this.theEngine = new GordianSkeinBase(stateSizeBits, digestSizeBits);
      }
  
      /**
       * Copy constructor.
       *
       * @param mac the source mac
       */
      public GordianSkeinMac(final GordianSkeinMac mac) {
          this.theEngine = new GordianSkeinBase(mac.theEngine);
      }
  
      /**
       * Obtain the lgorithm name.
       *
       * @return the name
       */
      public String getAlgorithmName() {
          return "Skein-MAC-" + (theEngine.getBlockSize() * Byte.SIZE) + "-" + (theEngine.getOutputSize() * Byte.SIZE);
      }
  
      /**
       * Initialises the Skein digest with the provided parameters.<br>
       * See {@link GordianSkeinParameters} for details on the parameterisation of the Skein hash function.
       *
       * @param params an instance of {@link GordianSkeinParameters} or {@link KeyParameter}.
       */
      public void init(final CipherParameters params)
              throws IllegalArgumentException {
         final GordianSkeinParameters skeinParameters;
         if (params instanceof GordianSkeinParameters) {
             skeinParameters = (GordianSkeinParameters) params;
         } else if (params instanceof KeyParameter) {
             skeinParameters = new GordianSkeinParametersBuilder().setKey(((KeyParameter) params).getKey()).build();
         } else {
             throw new IllegalArgumentException("Invalid parameter passed to Skein MAC init - "
                     + params.getClass().getName());
         }
         if (skeinParameters.getKey() == null) {
             throw new IllegalArgumentException("Skein MAC requires a key parameter.");
         }
         theEngine.init(skeinParameters);
     }
 
     @Override
     public int getMacSize() {
         return theEngine.getOutputSize();
     }
 
     @Override
     public void reset() {
         theEngine.reset();
     }
 
     @Override
     public void update(final byte in) {
         theEngine.update(in);
     }
 
     @Override
     public void update(final byte[] in,
                        final int inOff,
                        final int len) {
         theEngine.update(in, inOff, len);
     }
 
     @Override
     public int doFinal(final byte[] out,
                        final int outOff) {
         return theEngine.doFinal(out, outOff);
     }
 }