/*
 * 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.io;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * A byte sequence that is usable as a key or value. Based on
 * {@link org.apache.hadoop.io.BytesWritable} only this class is NOT resizable and DOES NOT
 * distinguish between the size of the sequence and the current capacity as
 * {@link org.apache.hadoop.io.BytesWritable} does. Hence its comparatively 'immutable'. When
 * creating a new instance of this class, the underlying byte [] is not copied, just referenced. The
 * backing buffer is accessed when we go to serialize.
 */
@InterfaceAudience.Public
@edu.umd.cs.findbugs.annotations.SuppressWarnings(
    value = "EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS",
    justification = "It has been like this forever")
public class ImmutableBytesWritable implements WritableComparable<ImmutableBytesWritable> {
  private byte[] bytes;
  private int offset;
  private int length;

  /**
   * Create a zero-size sequence.
   */
  public ImmutableBytesWritable() {
    super();
  }

  /**
   * Create a ImmutableBytesWritable using the byte array as the initial value.
   * @param bytes This array becomes the backing storage for the object.
   */
  public ImmutableBytesWritable(byte[] bytes) {
    this(bytes, 0, bytes.length);
  }

  /**
   * Set the new ImmutableBytesWritable to the contents of the passed <code>ibw</code>.
   * @param ibw the value to set this ImmutableBytesWritable to.
   */
  public ImmutableBytesWritable(final ImmutableBytesWritable ibw) {
    this(ibw.get(), ibw.getOffset(), ibw.getLength());
  }

  /**
   * Set the value to a given byte range
   * @param bytes  the new byte range to set to
   * @param offset the offset in newData to start at
   * @param length the number of bytes in the range
   */
  public ImmutableBytesWritable(final byte[] bytes, final int offset, final int length) {
    this.bytes = bytes;
    this.offset = offset;
    this.length = length;
  }

  /**
   * Get the data from the BytesWritable.
   * @return The data is only valid between offset and offset+length.
   */
  public byte[] get() {
    if (this.bytes == null) {
      throw new IllegalStateException(
        "Uninitialiized. Null constructor " + "called w/o accompaying readFields invocation");
    }
    return this.bytes;
  }

  /** Use passed bytes as backing array for this instance. */
  public void set(final byte[] b) {
    set(b, 0, b.length);
  }

  /** Use passed bytes as backing array for this instance. */
  public void set(final byte[] b, final int offset, final int length) {
    this.bytes = b;
    this.offset = offset;
    this.length = length;
  }

  /** Returns the number of valid bytes in the buffer */
  public int getLength() {
    if (this.bytes == null) {
      throw new IllegalStateException(
        "Uninitialiized. Null constructor " + "called w/o accompaying readFields invocation");
    }
    return this.length;
  }

  /** Return the offset into the buffer. */
  public int getOffset() {
    return this.offset;
  }

  @Override
  public void readFields(final DataInput in) throws IOException {
    this.length = in.readInt();
    this.bytes = new byte[this.length];
    in.readFully(this.bytes, 0, this.length);
    this.offset = 0;
  }

  @Override
  public void write(final DataOutput out) throws IOException {
    out.writeInt(this.length);
    out.write(this.bytes, this.offset, this.length);
  }

  // Below methods copied from BytesWritable

  @Override
  public int hashCode() {
    int hash = 1;
    for (int i = offset; i < offset + length; i++)
      hash = (31 * hash) + (int) bytes[i];
    return hash;
  }

  /**
   * Define the sort order of the BytesWritable.
   * @param that The other bytes writable
   * @return Positive if left is bigger than right, 0 if they are equal, and negative if left is
   *         smaller than right.
   */
  @Override
  public int compareTo(ImmutableBytesWritable that) {
    return WritableComparator.compareBytes(this.bytes, this.offset, this.length, that.bytes,
      that.offset, that.length);
  }

  /**
   * Compares the bytes in this object to the specified byte array
   * @return Positive if left is bigger than right, 0 if they are equal, and negative if left is
   *         smaller than right.
   */
  public int compareTo(final byte[] that) {
    return WritableComparator.compareBytes(this.bytes, this.offset, this.length, that, 0,
      that.length);
  }

  @Override
  public boolean equals(Object right_obj) {
    if (right_obj instanceof byte[]) {
      return compareTo((byte[]) right_obj) == 0;
    }
    if (right_obj instanceof ImmutableBytesWritable) {
      return compareTo((ImmutableBytesWritable) right_obj) == 0;
    }
    return false;
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder(3 * this.length);
    final int endIdx = this.offset + this.length;
    for (int idx = this.offset; idx < endIdx; idx++) {
      sb.append(' ');
      String num = Integer.toHexString(0xff & this.bytes[idx]);
      // if it is only one digit, add a leading 0.
      if (num.length() < 2) {
        sb.append('0');
      }
      sb.append(num);
    }
    return sb.length() > 0 ? sb.substring(1) : "";
  }

  /** A Comparator optimized for ImmutableBytesWritable. */
  @InterfaceAudience.Public
  public static class Comparator extends WritableComparator {
    private BytesWritable.Comparator comparator = new BytesWritable.Comparator();

    public Comparator() {
      super(ImmutableBytesWritable.class);
    }

    @Override
    public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
      return comparator.compare(b1, s1, l1, b2, s2, l2);
    }
  }

  static { // register this comparator
    WritableComparator.define(ImmutableBytesWritable.class, new Comparator());
  }

  /**
   * Convert a list of byte arrays into an array of byte arrays
   * @param array List of byte [].
   * @return Array of byte [].
   */
  public static byte[][] toArray(final List<byte[]> array) {
    // List#toArray doesn't work on lists of byte [].
    byte[][] results = new byte[array.size()][];
    for (int i = 0; i < array.size(); i++) {
      results[i] = array.get(i);
    }
    return results;
  }

  /** Returns a copy of the bytes referred to by this writable */
  public byte[] copyBytes() {
    return Arrays.copyOfRange(bytes, offset, offset + length);
  }
}