/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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
    *
    *      https://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 org.apache.commons.codec.digest;
  
  import java.util.Arrays;
  import java.util.Objects;
  
  /**
   * Implements the Blake3 algorithm providing a {@linkplain #initHash() hash function} with extensible output (XOF), a
   * {@linkplain #initKeyedHash(byte[]) keyed hash function} (MAC, PRF), and a
   * {@linkplain #initKeyDerivationFunction(byte[]) key derivation function} (KDF). Blake3 has a 128-bit security level
   * and a default output length of 256 bits (32 bytes) which can extended up to 2<sup>64</sup> bytes.
   * <h2>Hashing</h2>
   * <p>
   * Hash mode calculates the same output hash given the same input bytes and can be used as both a message digest and
   * and extensible output function.
   * </p>
   * <pre>{@code
   *      Blake3 hasher = Blake3.initHash();
   *      hasher.update("Hello, world!".getBytes(StandardCharsets.UTF_8));
   *      byte[] hash = new byte[32];
   *      hasher.doFinalize(hash);
   * }</pre>
   * <h2>Keyed Hashing</h2>
   * <p>
   * Keyed hashes take a 32-byte secret key and calculates a message authentication code on some input bytes. These
   * also work as pseudo-random functions (PRFs) with extensible output similar to the extensible hash output. Note that
   * Blake3 keyed hashes have the same performance as plain hashes; the key is used in initialization in place of a
   * standard initialization vector used for plain hashing.
   * </p>
   * <pre>{@code
   *      SecureRandom random = SecureRandom.getInstanceStrong();
   *      byte[] key = new byte[32];
   *      random.nextBytes(key);
   *      Blake3 hasher = Blake3.initKeyedHash(key);
   *      hasher.update("Hello, Alice!".getBytes(StandardCharsets.UTF_8));
   *      byte[] mac = new byte[32];
   *      hasher.doFinalize(mac);
   * }</pre>
   * <h2>Key Derivation</h2>
   * <p>
   * A specific hash mode for deriving session keys and other derived keys in a unique key derivation context
   * identified by some sequence of bytes. These context strings should be unique but do not need to be kept secret.
   * Additional input data is hashed for key material which can be finalized to derive subkeys. To derive multiple subkeys,
   * request their combined length in one finalization and split the output. Repeated finalizations start at the beginning
   * of the same output and do not derive new subkeys.
   * </p>
   * <pre>{@code
   *      String context = "org.apache.commons.codec.digest.Blake3Example";
   *      byte[] sharedSecret = ...;
   *      byte[] senderId = ...;
   *      byte[] recipientId = ...;
   *      Blake3 kdf = Blake3.initKeyDerivationFunction(context.getBytes(StandardCharsets.UTF_8));
   *      kdf.update(sharedSecret);
   *      kdf.update(senderId);
   *      kdf.update(recipientId);
   *      byte[] keys = kdf.doFinalize(64);
   *      byte[] txKey = Arrays.copyOfRange(keys, 0, 32);
   *      byte[] rxKey = Arrays.copyOfRange(keys, 32, 64);
   * }</pre>
   * <p>
   * Adapted from the ISC-licensed O(1) Cryptography library by Matt Sicker and ported from the reference public domain
   * implementation by Jack O'Connor.
   * </p>
   *
   * @see <a href="https://github.com/BLAKE3-team/BLAKE3">BLAKE3 hash function</a>
   * @since 1.16
   */
  public final class Blake3 {
  
      private static final class ChunkState {
  
          private int[] chainingValue;
          private final long chunkCounter;
          private final int flags;
  
          private final byte[] block = new byte[BLOCK_LEN];
          private int blockLength;
          private int blocksCompressed;
  
          private ChunkState(final int[] key, final long chunkCounter, final int flags) {
              chainingValue = key;
              this.chunkCounter = chunkCounter;
              this.flags = flags;
          }
 
         private int length() {
             return BLOCK_LEN * blocksCompressed + blockLength;
         }
 
         private Output output() {
             final int[] blockWords = unpackInts(block, BLOCK_INTS);
             final int outputFlags = flags | startFlag() | CHUNK_END;
             return new Output(chainingValue, blockWords, chunkCounter, blockLength, outputFlags);
         }
 
         private int startFlag() {
             return blocksCompressed == 0 ? CHUNK_START : 0;
         }
 
         private void update(final byte[] input, int offset, int length) {
             while (length > 0) {
                 if (blockLength == BLOCK_LEN) {
                     // If the block buffer is full, compress it and clear it. More
                     // input is coming, so this compression is not CHUNK_END.
                     final int[] blockWords = unpackInts(block, BLOCK_INTS);
                     chainingValue = Arrays.copyOf(
                             compress(chainingValue, blockWords, BLOCK_LEN, chunkCounter, flags | startFlag()),
                             CHAINING_VALUE_INTS);
                     blocksCompressed++;
                     blockLength = 0;
                     Arrays.fill(block, (byte) 0);
                 }
 
                 final int want = BLOCK_LEN - blockLength;
                 final int take = Math.min(want, length);
                 System.arraycopy(input, offset, block, blockLength, take);
                 blockLength += take;
                 offset += take;
                 length -= take;
             }
         }
     }
     private static final class EngineState {
         private final int[] key;
         private final int flags;
         // Space for 54 subtree chaining values: 2^54 * CHUNK_LEN = 2^64
         // No more than 54 entries can ever be added to this stack (after updating 2^64 bytes and not finalizing any)
         // so we preallocate the stack here. This can be smaller in environments where the data limit is expected to
         // be much lower.
         private final int[][] cvStack = new int[54][];
         private int stackLen;
         private ChunkState state;
 
         private EngineState(final int[] key, final int flags) {
             this.key = key;
             this.flags = flags;
             state = new ChunkState(key, 0, flags);
         }
 
         // Section 5.1.2 of the BLAKE3 spec explains this algorithm in more detail.
         private void addChunkCV(final int[] firstCV, final long totalChunks) {
             // This chunk might complete some subtrees. For each completed subtree,
             // its left child will be the current top entry in the CV stack, and
             // its right child will be the current value of `newCV`. Pop each left
             // child off the stack, merge it with `newCV`, and overwrite `newCV`
             // with the result. After all these merges, push the final value of
             // `newCV` onto the stack. The number of completed subtrees is given
             // by the number of trailing 0-bits in the new total number of chunks.
             int[] newCV = firstCV;
             long chunkCounter = totalChunks;
             while ((chunkCounter & 1) == 0) {
                 newCV = parentChainingValue(popCV(), newCV, key, flags);
                 chunkCounter >>= 1;
             }
             pushCV(newCV);
         }
 
         private void inputData(final byte[] in, int offset, int length) {
             while (length > 0) {
                 // If the current chunk is complete, finalize it and reset the
                 // chunk state. More input is coming, so this chunk is not ROOT.
                 if (state.length() == CHUNK_LEN) {
                     final int[] chunkCV = state.output().chainingValue();
                     final long totalChunks = state.chunkCounter + 1;
                     addChunkCV(chunkCV, totalChunks);
                     state = new ChunkState(key, totalChunks, flags);
                 }
 
                 // Compress input bytes into the current chunk state.
                 final int want = CHUNK_LEN - state.length();
                 final int take = Math.min(want, length);
                 state.update(in, offset, take);
                 offset += take;
                 length -= take;
             }
         }
 
         private void outputHash(final byte[] out, final int offset, final int length) {
             // Starting with the Output from the current chunk, compute all the
             // parent chaining values along the right edge of the tree, until we
             // have the root Output.
             Output output = state.output();
             int parentNodesRemaining = stackLen;
             while (parentNodesRemaining-- > 0) {
                 final int[] parentCV = cvStack[parentNodesRemaining];
                 output = parentOutput(parentCV, output.chainingValue(), key, flags);
             }
             output.rootOutputBytes(out, offset, length);
         }
 
         private int[] popCV() {
             return cvStack[--stackLen];
         }
 
         private void pushCV(final int[] cv) {
             cvStack[stackLen++] = cv;
         }
 
         private void reset() {
             stackLen = 0;
             Arrays.fill(cvStack, null);
             state = new ChunkState(key, 0, flags);
         }
     }
 
     /**
      * Represents the state just prior to either producing an eight word chaining value or any number of output bytes
      * when the ROOT flag is set.
      */
     private static final class Output {
 
         private final int[] inputChainingValue;
         private final int[] blockWords;
         private final long counter;
         private final int blockLength;
         private final int flags;
 
         private Output(final int[] inputChainingValue, final int[] blockWords, final long counter, final int blockLength, final int flags) {
             this.inputChainingValue = inputChainingValue;
             this.blockWords = blockWords;
             this.counter = counter;
             this.blockLength = blockLength;
             this.flags = flags;
         }
 
         private int[] chainingValue() {
             return Arrays.copyOf(compress(inputChainingValue, blockWords, blockLength, counter, flags), CHAINING_VALUE_INTS);
         }
 
         private void rootOutputBytes(final byte[] out, int offset, int length) {
             int outputBlockCounter = 0;
             while (length > 0) {
                 int chunkLength = Math.min(OUT_LEN * 2, length);
                 length -= chunkLength;
                 final int[] words = compress(inputChainingValue, blockWords, blockLength, outputBlockCounter++, flags | ROOT);
                 int wordCounter = 0;
                 while (chunkLength > 0) {
                     final int wordLength = Math.min(Integer.BYTES, chunkLength);
                     packInt(words[wordCounter++], out, offset, wordLength);
                     offset += wordLength;
                     chunkLength -= wordLength;
                 }
             }
         }
     }
 
     private static final int BLOCK_LEN = 64;
     private static final int BLOCK_INTS = BLOCK_LEN / Integer.BYTES;
     private static final int KEY_LEN = 32;
     private static final int KEY_INTS = KEY_LEN / Integer.BYTES;
     private static final int OUT_LEN = 32;
     private static final int CHUNK_LEN = 1024;
     private static final int CHAINING_VALUE_INTS = 8;
 
     /**
      * Standard hash key used for plain hashes; same initialization vector as Blake2s.
      */
     private static final int[] IV = { 0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19 };
 
     // domain flags
     private static final int CHUNK_START = 1;
     private static final int CHUNK_END = 1 << 1;
     private static final int PARENT = 1 << 2;
     private static final int ROOT = 1 << 3;
     private static final int KEYED_HASH = 1 << 4;
     private static final int DERIVE_KEY_CONTEXT = 1 << 5;
     private static final int DERIVE_KEY_MATERIAL = 1 << 6;
 
     /**
      * Pre-permuted for all 7 rounds; the second row (2,6,3,...) indicates the base permutation.
      */
     // @formatter:off
     private static final byte[][] MSG_SCHEDULE = {
             { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
             { 2, 6, 3, 10, 7, 0, 4, 13, 1, 11, 12, 5, 9, 14, 15, 8 },
             { 3, 4, 10, 12, 13, 2, 7, 14, 6, 5, 9, 0, 11, 15, 8, 1 },
             { 10, 7, 12, 9, 14, 3, 13, 15, 4, 0, 11, 2, 5, 8, 1, 6 },
             { 12, 13, 9, 11, 15, 10, 14, 8, 7, 2, 5, 3, 0, 1, 6, 4 },
             { 9, 14, 11, 5, 8, 12, 15, 1, 13, 3, 0, 10, 2, 6, 4, 7 },
             { 11, 15, 5, 0, 1, 9, 8, 6, 14, 10, 2, 12, 3, 4, 7, 13 }
     };
     // @formatter:on
 
     private static void checkBufferArgs(final byte[] buffer, final int offset, final int length) {
         Objects.requireNonNull(buffer, "buffer");
         if (offset < 0) {
             throw new IndexOutOfBoundsException("Offset must be non-negative");
         }
         if (length < 0) {
             throw new IndexOutOfBoundsException("Length must be non-negative");
         }
         final int bufferLength = buffer.length;
         if (offset > bufferLength - length) {
             throw new IndexOutOfBoundsException("Offset " + offset + " and length " + length + " out of bounds with buffer length " + bufferLength);
         }
     }
 
     private static int[] compress(final int[] chainingValue, final int[] blockWords, final int blockLength, final long counter, final int flags) {
         final int[] state = Arrays.copyOf(chainingValue, BLOCK_INTS);
         System.arraycopy(IV, 0, state, 8, 4);
         state[12] = (int) counter;
         state[13] = (int) (counter >> Integer.SIZE);
         state[14] = blockLength;
         state[15] = flags;
         for (int i = 0; i < 7; i++) {
             final byte[] schedule = MSG_SCHEDULE[i];
             round(state, blockWords, schedule);
         }
         for (int i = 0; i < state.length / 2; i++) {
             state[i] ^= state[i + 8];
             state[i + 8] ^= chainingValue[i];
         }
         return state;
     }
 
     /**
      * The mixing function, G, which mixes either a column or a diagonal.
      */
     private static void g(final int[] state, final int a, final int b, final int c, final int d, final int mx, final int my) {
         state[a] += state[b] + mx;
         state[d] = Integer.rotateRight(state[d] ^ state[a], 16);
         state[c] += state[d];
         state[b] = Integer.rotateRight(state[b] ^ state[c], 12);
         state[a] += state[b] + my;
         state[d] = Integer.rotateRight(state[d] ^ state[a], 8);
         state[c] += state[d];
         state[b] = Integer.rotateRight(state[b] ^ state[c], 7);
     }
 
     /**
      * Calculates the Blake3 hash of the provided data.
      *
      * @param data source array to absorb data from.
      * @return 32-byte hash squeezed from the provided data.
      * @throws NullPointerException Thrown if data is null.
      */
     public static byte[] hash(final byte[] data) {
         return initHash().update(data).doFinalize(OUT_LEN);
     }
 
     /**
      * Constructs a fresh Blake3 hash function. The instance returned functions as an arbitrary length message digest.
      *
      * @return fresh Blake3 instance in hashed mode.
      */
     public static Blake3 initHash() {
         return new Blake3(IV, 0);
     }
 
     /**
      * Constructs a fresh Blake3 key derivation function using the provided key derivation context byte string.
      * The instance returned functions as a key-derivation function which can further absorb additional context data
      * before squeezing derived key data.
      *
      * @param kdfContext A globally unique key-derivation context byte string to separate key derivation contexts from each other.
      * @return fresh Blake3 instance in key derivation mode.
      * @throws NullPointerException Thrown if kdfContext is null.
      */
     public static Blake3 initKeyDerivationFunction(final byte[] kdfContext) {
         Objects.requireNonNull(kdfContext, "kdfContext");
         final EngineState kdf = new EngineState(IV, DERIVE_KEY_CONTEXT);
         kdf.inputData(kdfContext, 0, kdfContext.length);
         final byte[] key = new byte[KEY_LEN];
         kdf.outputHash(key, 0, key.length);
         return new Blake3(unpackInts(key, KEY_INTS), DERIVE_KEY_MATERIAL);
     }
 
     /**
      * Constructs a fresh Blake3 keyed hash function. The instance returned functions as a pseudorandom function (PRF) or as a
      * message authentication code (MAC).
      *
      * @param key 32-byte secret key.
      * @return fresh Blake3 instance in keyed mode using the provided key.
      * @throws NullPointerException     Thrown if key is null.
      * @throws IllegalArgumentException Thrown if key is not 32 bytes.
      */
     public static Blake3 initKeyedHash(final byte[] key) {
         Objects.requireNonNull(key, "key");
         if (key.length != KEY_LEN) {
             throw new IllegalArgumentException("Blake3 keys must be 32 bytes");
         }
         return new Blake3(unpackInts(key, KEY_INTS), KEYED_HASH);
     }
 
     /**
      * Calculates the Blake3 keyed hash (MAC) of the provided data.
      *
      * @param key  32-byte secret key.
      * @param data source array to absorb data from.
      * @return 32-byte mac squeezed from the provided data.
      * @throws NullPointerException Thrown if key or data are null.
      */
     public static byte[] keyedHash(final byte[] key, final byte[] data) {
         return initKeyedHash(key).update(data).doFinalize(OUT_LEN);
     }
 
     private static void packInt(final int value, final byte[] dst, final int off, final int len) {
         for (int i = 0; i < len; i++) {
             dst[off + i] = (byte) (value >>> i * Byte.SIZE);
         }
     }
 
     private static int[] parentChainingValue(final int[] leftChildCV, final int[] rightChildCV, final int[] key, final int flags) {
         return parentOutput(leftChildCV, rightChildCV, key, flags).chainingValue();
     }
 
     private static Output parentOutput(final int[] leftChildCV, final int[] rightChildCV, final int[] key, final int flags) {
         final int[] blockWords = Arrays.copyOf(leftChildCV, BLOCK_INTS);
         System.arraycopy(rightChildCV, 0, blockWords, 8, CHAINING_VALUE_INTS);
         return new Output(key.clone(), blockWords, 0, BLOCK_LEN, flags | PARENT);
     }
 
     private static void round(final int[] state, final int[] msg, final byte[] schedule) {
         // Mix the columns.
         g(state, 0, 4, 8, 12, msg[schedule[0]], msg[schedule[1]]);
         g(state, 1, 5, 9, 13, msg[schedule[2]], msg[schedule[3]]);
         g(state, 2, 6, 10, 14, msg[schedule[4]], msg[schedule[5]]);
         g(state, 3, 7, 11, 15, msg[schedule[6]], msg[schedule[7]]);
 
         // Mix the diagonals.
         g(state, 0, 5, 10, 15, msg[schedule[8]], msg[schedule[9]]);
         g(state, 1, 6, 11, 12, msg[schedule[10]], msg[schedule[11]]);
         g(state, 2, 7, 8, 13, msg[schedule[12]], msg[schedule[13]]);
         g(state, 3, 4, 9, 14, msg[schedule[14]], msg[schedule[15]]);
     }
 
     private static int unpackInt(final byte[] buf, final int off) {
         return buf[off] & 0xFF | (buf[off + 1] & 0xFF) << 8 | (buf[off + 2] & 0xFF) << 16 | (buf[off + 3] & 0xFF) << 24;
     }
 
     private static int[] unpackInts(final byte[] buf, final int nrInts) {
         final int[] values = new int[nrInts];
         for (int i = 0, off = 0; i < nrInts; i++, off += Integer.BYTES) {
             values[i] = unpackInt(buf, off);
         }
         return values;
     }
 
     private final EngineState engineState;
 
     private Blake3(final int[] key, final int flags) {
         engineState = new EngineState(key, flags);
     }
 
     /**
      * Finalizes hash output into the provided array.
      *
      * <p>
      * This method does not change the hash state. Each invocation starts at the beginning of the output for the bytes supplied to {@code update()}.
      * Repeated invocations without additional input produce the same output prefix. Additional calls to {@code update()} append input to the existing hash
      * state, even after finalization.
      * </p>
      *
      * @param out destination array to finalize bytes into.
      * @return {@code this} instance.
      * @throws NullPointerException Thrown if out is null.
      */
     public Blake3 doFinalize(final byte[] out) {
         return doFinalize(out, 0, out.length);
     }
 
     /**
      * Finalizes hash output into a region of the provided array.
      *
      * <p>
      * This method does not change the hash state. Each invocation starts at the beginning of the output for the bytes supplied to {@code update()}.
      * Repeated invocations without additional input produce the same output prefix. The offset selects the destination array position, not a position in
      * the hash output. Additional calls to {@code update()} append input to the existing hash state, even after finalization.
      * </p>
      *
      * @param out    destination array to finalize bytes into.
      * @param offset where in the array to begin writing bytes to.
      * @param length number of bytes to finalize.
      * @return {@code this} instance.
      * @throws NullPointerException      Thrown if out is null.
      * @throws IndexOutOfBoundsException Thrown if offset or length are negative or if offset + length is greater than the
      *                                   length of the provided array.
      */
     public Blake3 doFinalize(final byte[] out, final int offset, final int length) {
         checkBufferArgs(out, offset, length);
         engineState.outputHash(out, offset, length);
         return this;
     }
 
     /**
      * Finalizes hash output into a new array.
      *
      * <p>
      * This method does not change the hash state. Each invocation starts at the beginning of the output for the bytes supplied to {@code update()}.
      * Repeated invocations without additional input produce the same output prefix. Additional calls to {@code update()} append input to the existing hash
      * state, even after finalization.
      * </p>
      *
      * @param nrBytes number of bytes to finalize.
      * @return requested number of finalized bytes.
      * @throws IllegalArgumentException Thrown if nrBytes is negative.
      */
     public byte[] doFinalize(final int nrBytes) {
         if (nrBytes < 0) {
             throw new IllegalArgumentException("Requested bytes must be non-negative");
         }
         final byte[] hash = new byte[nrBytes];
         doFinalize(hash);
         return hash;
     }
 
     /**
      * Resets this instance back to its initial state when it was first constructed.
      *
      * @return {@code this} instance.
      */
     public Blake3 reset() {
         engineState.reset();
         return this;
     }
 
     /**
      * Updates this hash state using the provided bytes.
      *
      * <p>
      * Input is appended to the existing hash state, including after finalization. Call {@link #reset()} first to start a new message.
      * </p>
      *
      * @param in source array to update data from.
      * @return {@code this} instance.
      * @throws NullPointerException Thrown if in is null.
      */
     public Blake3 update(final byte[] in) {
         return update(in, 0, in.length);
     }
 
     /**
      * Updates this hash state using the provided bytes at an offset.
      *
      * <p>
      * Input is appended to the existing hash state, including after finalization. Call {@link #reset()} first to start a new message.
      * </p>
      *
      * @param in     source array to update data from.
      * @param offset where in the array to begin reading bytes.
      * @param length number of bytes to update.
      * @return {@code this} instance.
      * @throws NullPointerException      Thrown if in is null.
      * @throws IndexOutOfBoundsException Thrown if offset or length are negative or if offset + length is greater than the
      *                                   length of the provided array.
      */
     public Blake3 update(final byte[] in, final int offset, final int length) {
         checkBufferArgs(in, offset, length);
         engineState.inputData(in, offset, length);
         return this;
     }
 
 }