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/*
 * Copyright (C) 2014-2024 Philip Helger (www.helger.com)
 * philip[at]helger[dot]com
 *
 * Licensed 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 com.helger.security.messagedigest;

import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.WillClose;
import javax.annotation.concurrent.Immutable;

import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.Nonempty;
import com.helger.commons.annotation.ReturnsMutableObject;
import com.helger.commons.hashcode.HashCodeGenerator;
import com.helger.commons.io.ByteArrayWrapper;
import com.helger.commons.io.IHasByteArray;
import com.helger.commons.io.stream.StreamHelper;
import com.helger.commons.string.ToStringGenerator;

/**
 * Represents a single message digest value as the combination of the algorithm
 * and the digest bytes.
 *
 * @author Philip Helger
 */
@Immutable
public class MessageDigestValue implements IHasByteArray
{
  public static final boolean DEFAULT_COPY_NEEDED = true;

  private final EMessageDigestAlgorithm m_eAlgorithm;
  private final ByteArrayWrapper m_aBytes;

  public MessageDigestValue (@Nonnull final EMessageDigestAlgorithm eAlgorithm, @Nonnull @Nonempty final byte [] aDigestBytes)
  {
    this (eAlgorithm, aDigestBytes, DEFAULT_COPY_NEEDED);
  }

  public MessageDigestValue (@Nonnull final EMessageDigestAlgorithm eAlgorithm,
                             @Nonnull @Nonempty final byte [] aDigestBytes,
                             final boolean bIsCopyNeeded)
  {
    ValueEnforcer.notNull (eAlgorithm, "Algorithm");
    ValueEnforcer.notEmpty (aDigestBytes, "DigestBytes");
    m_eAlgorithm = eAlgorithm;
    m_aBytes = new ByteArrayWrapper (aDigestBytes, bIsCopyNeeded);
  }

  /**
   * @return The message digest algorithm used. Never null.
   */
  @Nonnull
  public EMessageDigestAlgorithm getAlgorithm ()
  {
    return m_eAlgorithm;
  }

  public boolean isCopy ()
  {
    return m_aBytes.isCopy ();
  }

  /**
   * @return The message digest bytes. The length depends on the used algorithm.
   *         Never null.
   * @since 9.1.3
   */
  @Nonnull
  @Nonempty
  @ReturnsMutableObject
  public byte [] bytes ()
  {
    return m_aBytes.bytes ();
  }

  @Nonnegative
  public int size ()
  {
    return m_aBytes.size ();
  }

  @Nonnegative
  public int getOffset ()
  {
    return 0;
  }

  /**
   * @return The hex-encoded String of the message digest bytes. Never
   *         null.
   */
  @Nonnull
  @Nonempty
  public String getHexEncodedDigestString ()
  {
    return m_aBytes.getHexEncoded ();
  }

  @Override
  public boolean equals (final Object o)
  {
    if (o == this)
      return true;
    if (o == null || !getClass ().equals (o.getClass ()))
      return false;
    final MessageDigestValue rhs = (MessageDigestValue) o;
    return m_eAlgorithm.equals (rhs.m_eAlgorithm) && m_aBytes.equals (rhs.m_aBytes);
  }

  @Override
  public int hashCode ()
  {
    return new HashCodeGenerator (this).append (m_eAlgorithm).append (m_aBytes).getHashCode ();
  }

  @Override
  public String toString ()
  {
    return new ToStringGenerator (this).append ("Algorithm", m_eAlgorithm).append ("Bytes", m_aBytes).getToString ();
  }

  /**
   * Create a new {@link MessageDigestValue} object based on the passed source
   * byte array
   *
   * @param aBytes
   *        The byte array to create the hash value from. May not be
   *        null.
   * @param eAlgorithm
   *        The algorithm to be used. May not be null.
   * @return Never null.
   */
  @Nonnull
  public static MessageDigestValue create (@Nonnull final byte [] aBytes, @Nonnull final EMessageDigestAlgorithm eAlgorithm)
  {
    final MessageDigest aMD = eAlgorithm.createMessageDigest ();
    aMD.update (aBytes);
    // aMD goes out of scope anyway, so no need to copy byte[]
    return new MessageDigestValue (eAlgorithm, aMD.digest (), false);
  }

  /**
   * Create a new {@link MessageDigestValue} object based on the passed source
   * {@link InputStream}.
   *
   * @param aIS
   *        The input stream to read from. May not be null.
   * @param eAlgorithm
   *        The algorithm to be used. May not be null.
   * @return Never null.
   * @throws IOException
   *         In case reading throws an IOException
   */
  @Nonnull
  public static MessageDigestValue create (@Nonnull @WillClose final InputStream aIS,
                                           @Nonnull final EMessageDigestAlgorithm eAlgorithm) throws IOException
  {
    final MessageDigest aMD = eAlgorithm.createMessageDigest ();
    StreamHelper.readUntilEOF (aIS, (aBytes, nBytes) -> aMD.update (aBytes, 0, nBytes));
    // aMD goes out of scope anyway, so no need to copy byte[]
    return new MessageDigestValue (eAlgorithm, aMD.digest (), false);
  }
}