/*
    * 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.digests;
  
  import io.github.tonywasher.joceanus.gordianknot.impl.ext.params.GordianSkeinParameters;
  import org.bouncycastle.crypto.ExtendedDigest;
  import org.bouncycastle.crypto.engines.ThreefishEngine;
  import org.bouncycastle.util.Memoable;
  
  /**
   * Implementation of the Skein parameterised hash 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 GordianSkeinDigest
          implements ExtendedDigest, Memoable {
      /**
       * 256 bit block size - Skein-256.
       */
      public static final int SKEIN_256 = GordianSkeinBase.SKEIN_256;
      /**
       * 512 bit block size - Skein-512.
       */
      public static final int SKEIN_512 = GordianSkeinBase.SKEIN_512;
      /**
       * 1024 bit block size - Skein-1024.
       */
      public static final int SKEIN_1024 = GordianSkeinBase.SKEIN_1024;
  
      /**
       * The underlying engine.
       */
      private GordianSkeinBase engine;
  
      /**
       * Constructs a Skein digest 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/digest size to produce in bits, which must be an integral number of
       *                       bytes.
       */
      public GordianSkeinDigest(final int stateSizeBits, final int digestSizeBits) {
          this.engine = new GordianSkeinBase(stateSizeBits, digestSizeBits);
          init(null);
      }
  
      /**
       * Constructor.
       *
       * @param digest the digest to copy
       */
      public GordianSkeinDigest(final GordianSkeinDigest digest) {
          this.engine = new GordianSkeinBase(digest.engine);
      }
  
      @Override
      public void reset(final Memoable other) {
          final GordianSkeinDigest d = (GordianSkeinDigest) other;
          engine.reset(d.engine);
      }
  
      @Override
      public Memoable copy() {
          return new GordianSkeinDigest(this);
      }
  
      @Override
      public String getAlgorithmName() {
          return "Skein-" + (engine.getBlockSize() * Byte.SIZE) + "-" + (engine.getOutputSize() * Byte.SIZE);
      }
  
      @Override
      public int getDigestSize() {
          return engine.getOutputSize();
      }
  
     @Override
     public int getByteLength() {
         return engine.getBlockSize();
     }
 
     /**
      * Obtain the base.
      *
      * @return the base
      */
     GordianSkeinBase getBase() {
         return engine;
     }
 
     /**
      * Optionally initialises the Skein digest with the provided parameters.<br>
      * See {@link GordianSkeinParameters} for details on the parameterisation of the Skein hash function.
      *
      * @param params the parameters to apply to this engine, or <code>null</code> to use no parameters.
      */
     public void init(final GordianSkeinParameters params) {
         engine.init(params);
     }
 
     @Override
     public void reset() {
         engine.reset();
     }
 
     @Override
     public void update(final byte in) {
         engine.update(in);
     }
 
     @Override
     public void update(final byte[] in, final int inOff, final int len) {
         engine.update(in, inOff, len);
     }
 
     @Override
     public int doFinal(final byte[] out, final int outOff) {
         return engine.doFinal(out, outOff);
     }
 }