/*
    * 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
    *
   *   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 org.apache.maven.buildcache.hash;
  
  import java.nio.charset.StandardCharsets;
  
  /**
   * HexUtils
   */
  @SuppressWarnings("checkstyle:MagicNumber")
  public class HexUtils {
  
      private static final byte[] ENC_ARRAY;
      private static final byte[] DEC_ARRAY;
  
      static {
          ENC_ARRAY = new byte[16];
          DEC_ARRAY = new byte[256];
          for (byte i = 0; i < 10; i++) {
              ENC_ARRAY[i] = (byte) ('0' + i);
              DEC_ARRAY['0' + i] = i;
          }
          for (byte i = 10; i < 16; i++) {
              ENC_ARRAY[i] = (byte) ('a' + i - 10);
              DEC_ARRAY['a' + i - 10] = i;
              DEC_ARRAY['A' + i - 10] = i;
          }
      }
  
      public static String encode(byte[] hash) {
          byte[] hexChars = new byte[hash.length * 2];
          for (int j = 0; j < hash.length; j++) {
              int v = hash[j] & 0xFF;
              hexChars[j * 2] = ENC_ARRAY[v >>> 4];
              hexChars[j * 2 + 1] = ENC_ARRAY[v & 0x0F];
          }
          return new String(hexChars, StandardCharsets.US_ASCII);
      }
  
      public static byte[] decode(String hex) {
          int size = hex.length();
          if (size % 2 != 0) {
              throw new IllegalArgumentException("String length should be even");
          }
          byte[] bytes = new byte[size / 2];
          int idx = 0;
          for (int i = 0; i < size; i += 2) {
              bytes[idx++] = (byte) (DEC_ARRAY[hex.charAt(i)] << 4 | DEC_ARRAY[hex.charAt(i + 1)]);
          }
          return bytes;
      }
  
      public static byte[] toByteArray(long value) {
          byte[] result = new byte[8];
          for (int i = 7; i >= 0; i--) {
              result[i] = (byte) (value & 0xFF);
              value >>= 8;
          }
          return result;
      }
  }