/**
 *
 * 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.hadoop.hbase.filter;

import java.nio.ByteBuffer;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.util.ByteBufferUtils;
import org.apache.hadoop.hbase.util.Bytes;


/** Base class for byte array comparators */
@InterfaceAudience.Public
// TODO Now we are deviating a lot from the actual Comparable<byte[]> what this implements, by
// adding special compareTo methods. We have to clean it. Deprecate this class and replace it
// with a more generic one which says it compares bytes (not necessary a byte array only)
// BytesComparable implements Comparable<Byte> will work?
public abstract class ByteArrayComparable implements Comparable<byte[]> {

  byte[] value;

  /**
   * Constructor.
   * @param value the value to compare against
   */
  public ByteArrayComparable(byte [] value) {
    this.value = value;
  }

  public byte[] getValue() {
    return value;
  }

  /**
   * @return The comparator serialized using pb
   */
  public abstract byte [] toByteArray();

  /**
   * @param pbBytes A pb serialized {@link ByteArrayComparable} instance
   * @return An instance of {@link ByteArrayComparable} made from <code>bytes</code>
   * @throws DeserializationException
   * @see #toByteArray
   */
  public static ByteArrayComparable parseFrom(final byte [] pbBytes)
  throws DeserializationException {
    throw new DeserializationException(
      "parseFrom called on base ByteArrayComparable, but should be called on derived type");
  }

  /**
   * @param other
   * @return true if and only if the fields of the comparator that are serialized
   * are equal to the corresponding fields in other.  Used for testing.
   */
  boolean areSerializedFieldsEqual(ByteArrayComparable other) {
    if (other == this) return true;

    return Bytes.equals(this.getValue(), other.getValue());
  }

  @Override
  public int compareTo(byte [] value) {
    return compareTo(value, 0, value.length);
  }

  /**
   * Special compareTo method for subclasses, to avoid
   * copying byte[] unnecessarily.
   * @param value byte[] to compare
   * @param offset offset into value
   * @param length number of bytes to compare
   * @return a negative integer, zero, or a positive integer as this object
   *         is less than, equal to, or greater than the specified object.
   */
  public abstract int compareTo(byte [] value, int offset, int length);

  /**
   * Special compareTo method for subclasses, to avoid copying bytes unnecessarily.
   * @param value bytes to compare within a ByteBuffer
   * @param offset offset into value
   * @param length number of bytes to compare
   * @return a negative integer, zero, or a positive integer as this object
   *         is less than, equal to, or greater than the specified object.
   */
  public int compareTo(ByteBuffer value, int offset, int length) {
    // For BC, providing a default implementation here which is doing a bytes copy to a temp byte[]
    // and calling compareTo(byte[]). Make sure to override this method in subclasses to avoid
    // copying bytes unnecessarily.
    byte[] temp = new byte[length];
    ByteBufferUtils.copyFromBufferToArray(temp, value, offset, 0, length);
    return compareTo(temp);
  }
}