/*
    * 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 org.bouncycastle.util.Memoable;
  import org.bouncycastle.util.Pack;
  
  /**
   * Blake2s digest.
   */
  @SuppressWarnings("checkstyle:MagicNumber")
  public class GordianBlake2sDigest
          extends GordianBlake2Base {
      /**
       * Number of Rounds.
       */
      private static final int ROUNDS = 10;
  
      /**
       * Block length.
       */
      private static final int BLOCK_LENGTH_BYTES = NUMWORDS * Integer.BYTES << 1;
  
      /**
       * Blake2s Initialization Vector.
       */
      private static final int[] IV = {
              // Produced from the square root of primes 2, 3, 5, 7, 11, 13, 17, 19.
              // The same as SHA-256 IV.
  
              0x6a09e667, 0xbb67ae85, 0x3c6ef372,
              0xa54ff53a, 0x510e527f, 0x9b05688c,
              0x1f83d9ab, 0x5be0cd19
      };
  
      /**
       * The state.
       */
      private final int[] theH = new int[NUMWORDS];
  
      /**
       * The workBuffer.
       */
      private final int[] theV = new int[NUMWORDS << 1];
  
      /**
       * The messageBuffer.
       */
      private final int[] theM = new int[NUMWORDS << 1];
  
      /**
       * Low Counter.
       */
      private int t0;
  
      /**
       * High Counter.
       */
      private int t1;
  
      /**
       * Constructor.
       */
      public GordianBlake2sDigest() {
          /* Default to 256 bits */
          this(256);
      }
  
      /**
       * Constructor.
       *
       * @param pLength the digest length in bits.
       */
      public GordianBlake2sDigest(final int pLength) {
          /* Initialise underlying class */
          super(ROUNDS, BLOCK_LENGTH_BYTES);
  
          /* Check digest length */
          if ((pLength % Byte.SIZE) != 0 || pLength < 0 || pLength > 256) {
              throw new IllegalArgumentException("Incorrect digest length");
          }
          setDigestLength(pLength / Byte.SIZE);
          activateH();
      }
  
     /**
      * Constructor.
      *
      * @param pSource the source digest.
      */
     private GordianBlake2sDigest(final GordianBlake2sDigest pSource) {
         /* Initialise underlying class */
         super(pSource);
 
         /* Initialise from source */
         reset((Memoable) pSource);
     }
 
     @Override
     public String getAlgorithmName() {
         return "Blake2s-" + getDigestSize() * Byte.SIZE;
     }
 
     @Override
     public int getByteLength() {
         return BLOCK_LENGTH_BYTES;
     }
 
     @Override
     public void reset() {
         /* Reset counter */
         t0 = 0;
         t1 = 0;
 
         /* reset underlying class */
         super.reset();
     }
 
     @Override
     public void reset(final Memoable pSource) {
         /* Access source */
         final GordianBlake2sDigest mySource = (GordianBlake2sDigest) pSource;
 
         /* reset underlying class */
         super.reset(mySource);
 
         /* Reset counter */
         t0 = mySource.t0;
         t1 = mySource.t1;
 
         /* Copy state */
         System.arraycopy(mySource.theH, 0, theH, 0, theH.length);
     }
 
     @Override
     public GordianBlake2sDigest copy() {
         return new GordianBlake2sDigest(this);
     }
 
     @Override
     void adjustCounter(final int pCount) {
         t0 += pCount;
         if (t0 == 0) {
             t1++;
         }
     }
 
     @Override
     void completeCounter(final int pCount) {
         t0 += pCount;
         if (pCount > 0 && t0 == 0) {
             t1++;
         }
     }
 
     @Override
     void outputDigest(final byte[] pOut,
                       final int pOutOffset) {
         /* Loop to provide the output */
         final int myDigestLen = getDigestSize();
         for (int i = 0, j = 0; i < NUMWORDS && j < myDigestLen; i++, j += Integer.BYTES) {
             /* Convert the next word to bytes */
             final byte[] bytes = Pack.intToLittleEndian(theH[i]);
 
             if (j + Integer.BYTES < myDigestLen) {
                 System.arraycopy(bytes, 0, pOut, pOutOffset + j, Integer.BYTES);
             } else {
                 System.arraycopy(bytes, 0, pOut, pOutOffset + j, myDigestLen - j);
             }
         }
     }
 
     @Override
     protected void activateH() {
         /* Initialise from IV */
         System.arraycopy(IV, 0, theH, 0, IV.length);
 
         /* Initialise first word */
         theH[0] ^= getDigestSize() | (getKeyLen() << Byte.SIZE);
         theH[0] ^= (getFanOut() | (getMaxDepth() << Byte.SIZE)) << Short.SIZE;
 
         /* Initialise second word */
         theH[1] ^= getLeafLen();
 
         /* Initialise third word */
         theH[2] ^= getNodeOffset();
 
         /* Initialise fourth word */
         theH[3] ^= getXofLen();
         theH[3] ^= (getNodeDepth() | (getInnerLen() << Byte.SIZE)) << Short.SIZE;
 
         /* Build salt section */
         final byte[] mySalt = getSalt();
         if (mySalt != null) {
             theH[4] ^= Pack.littleEndianToInt(mySalt, 0);
             theH[5] ^= Pack.littleEndianToInt(mySalt, Integer.BYTES);
         }
 
         /* Build personalisation section */
         final byte[] myPersonal = getPersonal();
         if (myPersonal != null) {
             theH[6] ^= Pack.littleEndianToInt(myPersonal, 0);
             theH[7] ^= Pack.littleEndianToInt(myPersonal, Integer.BYTES);
         }
 
         /* Initialise any keyBlock */
         initKeyBlock();
     }
 
     @Override
     protected void initV() {
         /* Copy in H and IV */
         System.arraycopy(theH, 0, theV, 0, NUMWORDS);
         System.arraycopy(IV, 0, theV, NUMWORDS, NUMWORDS);
 
         /* Fold in counters */
         theV[12] ^= t0;
         theV[13] ^= t1;
 
         /* Fold in finalisation flags */
         if (isLastBlock()) {
             theV[14] ^= -1;
             if (isLastNode()) {
                 theV[15] ^= -1;
             }
         }
     }
 
     @Override
     protected void initM(final byte[] pMessage,
                          final int pMsgPos) {
         /* Copy message bytes into word array */
         for (int i = 0; i < NUMWORDS << 1; i++) {
             theM[i] = Pack.littleEndianToInt(pMessage, pMsgPos + i * Integer.BYTES);
         }
     }
 
     @Override
     protected void adjustH() {
         /* Combine V into H */
         for (int i = 0; i < NUMWORDS; i++) {
             theH[i] ^= theV[i] ^ theV[i + NUMWORDS];
         }
     }
 
     @Override
     protected void mixG(final int msgIdx1,
                         final int msgIdx2,
                         final int posA,
                         final int posB,
                         final int posC,
                         final int posD) {
         /* Perform the Round */
         theV[posA] += theV[posB] + theM[msgIdx1];
         theV[posD] = rotr32(theV[posD] ^ theV[posA], 16);
         theV[posC] += theV[posD];
         theV[posB] = rotr32(theV[posB] ^ theV[posC], 12);
         theV[posA] += theV[posB] + theM[msgIdx2];
         theV[posD] = rotr32(theV[posD] ^ theV[posA], 8);
         theV[posC] += theV[posD];
         theV[posB] = rotr32(theV[posB] ^ theV[posC], 7);
     }
 
     /**
      * Rotate an int right.
      *
      * @param x   the value to rotate
      * @param rot the number of bits to rotate
      * @return the result
      */
     private static int rotr32(final int x,
                               final int rot) {
         return x >>> rot | (x << (Integer.SIZE - rot));
     }
 }