/*
 * 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.calcite.avatica.util;

import com.fasterxml.jackson.annotation.JsonValue;

import java.io.IOException;
import java.io.Serializable;
import java.util.Arrays;

/**
 * Collection of bytes.
 *
 * <p>ByteString is to bytes what {@link String} is to chars: It is immutable,
 * implements equality ({@link #hashCode} and {@link #equals}),
 * comparison ({@link #compareTo}) and
 * {@link Serializable serialization} correctly.</p>
 */
public class ByteString implements Comparable<ByteString>, Serializable {
  private final byte[] bytes;

  /** An empty byte string. */
  public static final ByteString EMPTY = new ByteString(new byte[0], false);

  private static final char[] DIGITS = {
      '0', '1', '2', '3', '4', '5', '6', '7',
      '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
  };

  /**
   * Creates a ByteString.
   *
   * @param bytes Bytes
   */
  public ByteString(byte[] bytes) {
    this(bytes.clone(), false);
  }

  // private constructor that does not copy
  private ByteString(byte[] bytes, boolean dummy) {
    this.bytes = bytes;
  }

  @Override public int hashCode() {
    return Arrays.hashCode(bytes);
  }

  @Override public boolean equals(Object obj) {
    return this == obj
        || obj instanceof ByteString
        && Arrays.equals(bytes, ((ByteString) obj).bytes);
  }

  public int compareTo(ByteString that) {
    final byte[] v1 = bytes;
    final byte[] v2 = that.bytes;
    final int n = Math.min(v1.length, v2.length);
    for (int i = 0; i < n; i++) {
      int c1 = v1[i] & 0xff;
      int c2 = v2[i] & 0xff;
      if (c1 != c2) {
        return c1 - c2;
      }
    }
    return v1.length - v2.length;
  }

  /**
   * Returns this byte string in hexadecimal format.
   *
   * @return Hexadecimal string
   */
  @Override public String toString() {
    return toString(16);
  }

  /**
   * Returns this byte string in a given base.
   *
   * @return String in given base
   */
  public String toString(int base) {
    return toString(bytes, base);
  }

  /**
   * Returns the given byte array in hexadecimal format.
   *
   * <p>For example, <code>toString(new byte[] {0xDE, 0xAD})</code>
   * returns {@code "DEAD"}.</p>
   *
   * @param bytes Array of bytes
   * @param base Base (2 or 16)
   * @return String
   */
  public static String toString(byte[] bytes, int base) {
    char[] chars;
    int j = 0;
    switch (base) {
    case 2:
      chars = new char[bytes.length * 8];
      for (byte b : bytes) {
        chars[j++] = DIGITS[(b & 0x80) >> 7];
        chars[j++] = DIGITS[(b & 0x40) >> 6];
        chars[j++] = DIGITS[(b & 0x20) >> 5];
        chars[j++] = DIGITS[(b & 0x10) >> 4];
        chars[j++] = DIGITS[(b & 0x08) >> 3];
        chars[j++] = DIGITS[(b & 0x04) >> 2];
        chars[j++] = DIGITS[(b & 0x02) >> 1];
        chars[j++] = DIGITS[b & 0x01];
      }
      break;
    case 16:
      chars = new char[bytes.length * 2];
      for (byte b : bytes) {
        chars[j++] = DIGITS[(b & 0xF0) >> 4];
        chars[j++] = DIGITS[b & 0x0F];
      }
      break;
    default:
      throw new IllegalArgumentException("bad base " + base);
    }
    return new String(chars, 0, j);
  }

  /**
   * Returns this byte string in Base64 format.
   *
   * @return Base64 string
   */
  public String toBase64String() {
    return Base64.encodeBytes(bytes);
  }

  /**
   * Creates a byte string from a hexadecimal or binary string.
   *
   * <p>For example, <code>of("DEAD", 16)</code>
   * returns the same as {@code ByteString(new byte[] {0xDE, 0xAD})}.
   *
   * @param string Array of bytes
   * @param base Base (2 or 16)
   * @return String
   */
  public static ByteString of(String string, int base) {
    final byte[] bytes = parse(string, base);
    return new ByteString(bytes, false);
  }

  /**
   * Parses a hexadecimal or binary string to a byte array.
   *
   * @param string Hexadecimal or binary string
   * @param base Base (2 or 16)
   * @return Byte array
   */
  public static byte[] parse(String string, int base) {
    char[] chars = string.toCharArray();
    byte[] bytes;
    int j = 0;
    byte b = 0;
    switch (base) {
    case 2:
      bytes = new byte[chars.length / 8];
      for (char c : chars) {
        b <<= 1;
        if (c == '1') {
          b |= 0x1;
        }
        if (j % 8 == 7) {
          bytes[j / 8] = b;
          b = 0;
        }
        ++j;
      }
      break;
    case 16:
      if (chars.length % 2 != 0) {
        throw new IllegalArgumentException("hex string has odd length");
      }
      bytes = new byte[chars.length / 2];
      for (char c : chars) {
        b <<= 4;
        byte i = decodeHex(c);
        b |= i & 0x0F;
        if (j % 2 == 1) {
          bytes[j / 2] = b;
          b = 0;
        }
        ++j;
      }
      break;
    default:
      throw new IllegalArgumentException("bad base " + base);
    }
    return bytes;
  }

  private static byte decodeHex(char c) {
    if (c >= '0' && c <= '9') {
      return (byte) (c - '0');
    }
    if (c >= 'a' && c <= 'f') {
      return (byte) (c - 'a' + 10);
    }
    if (c >= 'A' && c <= 'F') {
      return (byte) (c - 'A' + 10);
    }
    throw new IllegalArgumentException("invalid hex character: " + c);
  }

  /**
   * Creates a byte string from a Base64 string.
   *
   * @param string Base64 string
   * @return Byte string
   */
  public static ByteString ofBase64(String string) {
    final byte[] bytes = parseBase64(string);
    return new ByteString(bytes, false);
  }

  /**
   * Parses a Base64 to a byte array.
   *
   * @param string Base64 string
   * @return Byte array
   */
  public static byte[] parseBase64(String string) {
    try {
      return Base64.decode(string);
    } catch (IOException e) {
      throw new IllegalArgumentException("bad base64 string", e);
    }
  }

  @SuppressWarnings({
      "CloneDoesntCallSuperClone",
      "CloneDoesntDeclareCloneNotSupportedException"
      })
  @Override public Object clone() {
    return this;
  }

  /**
   * Returns the number of bytes in this byte string.
   *
   * @return Length of this byte string
   */
  public int length() {
    return bytes.length;
  }

  /**
   * Returns the byte at a given position in the byte string.
   *
   * @param i Index
   * @throws  IndexOutOfBoundsException if the <code>index</code> argument is
   *          negative or not less than <code>length()</code>
   * @return Byte at given position
   */
  public byte byteAt(int i) {
    return bytes[i];
  }

  /**
   * Returns a ByteString that consists of a given range.
   *
   * @param start Start of range
   * @param end Position after end of range
   * @return Substring
   */
  public ByteString substring(int start, int end) {
    byte[] bytes = Arrays.copyOfRange(this.bytes, start, end);
    return new ByteString(bytes, false);
  }

  /**
   * Returns a ByteString that starts at a given position.
   *
   * @param start Start of range
   * @return Substring
   */
  public ByteString substring(int start) {
    return substring(start, length());
  }

  /**
   * Returns a copy of the byte array.
   */
  @JsonValue
  public byte[] getBytes() {
    return bytes.clone();
  }

  /**
   * Returns a ByteString consisting of the concatenation of this and another
   * string.
   *
   * @param other Byte string to concatenate
   * @return Combined byte string
   */
  public ByteString concat(ByteString other) {
    int otherLen = other.length();
    if (otherLen == 0) {
      return this;
    }
    int len = bytes.length;
    byte[] buf = Arrays.copyOf(bytes, len + otherLen);
    System.arraycopy(other.bytes, 0, buf, len, other.bytes.length);
    return new ByteString(buf, false);
  }

  /** Returns the position at which {@code seek} first occurs in this byte
   * string, or -1 if it does not occur. */
  public int indexOf(ByteString seek) {
    return indexOf(seek, 0);
  }

  /** Returns the position at which {@code seek} first occurs in this byte
   * string, starting at the specified index, or -1 if it does not occur. */
  public int indexOf(ByteString seek, int start) {
  iLoop:
    for (int i = start; i < bytes.length - seek.bytes.length + 1; i++) {
      for (int j = 0;; j++) {
        if (j == seek.bytes.length) {
          return i;
        }
        if (bytes[i + j] != seek.bytes[j]) {
          continue iLoop;
        }
      }
    }
    return -1;
  }
}

// End ByteString.java