/*
 * ToroDB
 * Copyright © 2014 8Kdata Technology (www.8kdata.com)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.torodb.common.util;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.primitives.UnsignedBytes;

import java.util.Collection;

import javax.annotation.Nonnull;

/**
 *
 */
public class HexUtils {

  private static final char[] BYTE_HEX_VALUES = new char[256 << 1];

  static {
    for (int i = 0; i < 256; i++) {
      int high = i >>> 4;
      int low = i & 0x0F;
      BYTE_HEX_VALUES[i << 1] = high < 10 ? (char) ('0' + high) : (char) ('A' + high - 10);
      BYTE_HEX_VALUES[(i << 1) + 1] = low < 10 ? (char) ('0' + low) : (char) ('A' + low - 10);
    }
  }

  public static String bytes2Hex(@Nonnull byte[] bytes) {
    checkNotNull(bytes, "bytes");

    final int length = bytes.length;
    final char[] chars = new char[length << 1];
    int index;
    int charPos = 0;
    for (int i = 0; i < length; i++) {
      index = (bytes[i] & 0xFF) << 1;
      chars[charPos++] = BYTE_HEX_VALUES[index++];
      chars[charPos++] = BYTE_HEX_VALUES[index];
    }

    return new String(chars);
  }

  public static String bytes2Hex(@Nonnull Collection<Byte> bytes) {
    checkNotNull(bytes, "bytes");

    final int length = bytes.size();
    final char[] chars = new char[length << 1];
    int index;
    int charPos = 0;
    for (Byte b : bytes) {
      index = (b & 0xFF) << 1;
      chars[charPos++] = BYTE_HEX_VALUES[index++];
      chars[charPos++] = BYTE_HEX_VALUES[index];
    }

    return new String(chars);
  }

  public static void bytes2Hex(@Nonnull byte[] bytes, StringBuilder output) {
    checkNotNull(bytes, "bytes");

    int index;
    for (Byte b : bytes) {
      index = (b & 0xFF) << 1;
      output.append(BYTE_HEX_VALUES[index++]);
      output.append(BYTE_HEX_VALUES[index]);
    }
  }

  public static byte[] hex2Bytes(@Nonnull String value) {
    checkNotNull(value);
    checkArgument(value.length() % 2 == 0, "A string with a even lenght was expected");

    final int size = value.length();
    int r = 0;
    byte[] result = new byte[size / 2];
    for (int i = 0; i < size; i += 2) {
      assert r == i / 2;

      String substring = value.substring(i, i + 2);
      assert substring.length() == 2;
      result[r] = UnsignedBytes.parseUnsignedByte(substring, 16);

      r++;
    }
    return result;
  }
}