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/**
 * Copyright (C) 2013-2019 Regents of the University of California.
 * @author: Jeff Thompson 
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see .
 * A copy of the GNU Lesser General Public License is in the file COPYING.
 */

package net.named_data.jndn;

import net.named_data.jndn.util.Blob;
import net.named_data.jndn.util.ChangeCountable;
import net.named_data.jndn.util.ChangeCounter;

public class KeyLocator implements ChangeCountable {
  /**
   * Create a new KeyLocator with default values.
   */
  public KeyLocator()
  {
  }

  /**
   * Create a new KeyLocator with a copy of the fields in keyLocator.
   * @param keyLocator The KeyLocator to copy.
   */
  public KeyLocator(KeyLocator keyLocator)
  {
    type_ = keyLocator.type_;
    keyData_ = keyLocator.keyData_;
    keyName_.set(new Name(keyLocator.getKeyName()));
  }

  public final KeyLocatorType
  getType() { return type_; }

  public final Blob
  getKeyData() { return keyData_; }

  public final Name
  getKeyName() { return (Name)keyName_.get(); }

  public final void
  setType(KeyLocatorType type)
  {
    type_ = type;
    ++changeCount_;
  }

  public final void
  setKeyData(Blob keyData)
  {
    keyData_ = (keyData == null ? new Blob() : keyData);
    ++changeCount_;
  }

  public final void
  setKeyName(Name keyName)
  {
    keyName_.set(keyName == null ? new Name() : new Name(keyName));
    ++changeCount_;
  }

  /**
   * Clear fields and reset to default values.
   */
  public final void
  clear()
  {
    type_ = KeyLocatorType.NONE;
    keyData_ = new Blob();
    keyName_.set(new Name());
    ++changeCount_;
  }

  /**
   * Check if this key locator has the same values as the given key locator.
   * @param other The other key locator to check.
   * @return true if the key locators are equal, otherwise false.
   */
  public boolean
  equals(KeyLocator other)
  {
    if (type_ != other.type_)
      return false;

    if (type_ == KeyLocatorType.KEYNAME) {
      if (!getKeyName().equals(other.getKeyName()))
        return false;
    }
    else if (type_ == KeyLocatorType.KEY_LOCATOR_DIGEST) {
      if (!getKeyData().equals(other.getKeyData()))
        return false;
    }

    return true;
  }

  public boolean
  equals(Object other)
  {
    if (!(other instanceof KeyLocator))
      return false;

    return equals((KeyLocator)other);
  }

  /**
   * If the signature is a type that has a KeyLocator (so that
   * getFromSignature will succeed), return true.
   * Note: This is a static method of KeyLocator instead of a method of
   * Signature so that the Signature base class does not need to be overloaded
   * with all the different kinds of information that various signature
   * algorithms may use.
   * @param signature An object of a subclass of Signature.
   * @return True if the signature is a type that has a KeyLocator, otherwise
   * false.
   */
  public static boolean
  canGetFromSignature(Signature signature)
  {
    return signature instanceof Sha256WithRsaSignature ||
           signature instanceof Sha256WithEcdsaSignature ||
           signature instanceof HmacWithSha256Signature;
  }

  /**
   * If the signature is a type that has a KeyLocator, then return it. Otherwise
   * throw an error. To check if the signature has a KeyLocator without throwing
   * an error, you can use canGetFromSignature().
   * @param signature An object of a subclass of Signature.
   * @return The signature's KeyLocator. It is an error if signature doesn't
   * have a KeyLocator.
   */
  public static KeyLocator
  getFromSignature(Signature signature)
  {
    if (signature instanceof Sha256WithRsaSignature)
      return ((Sha256WithRsaSignature)signature).getKeyLocator();
    else if (signature instanceof Sha256WithEcdsaSignature)
      return ((Sha256WithEcdsaSignature)signature).getKeyLocator();
    else if (signature instanceof HmacWithSha256Signature)
      return ((HmacWithSha256Signature)signature).getKeyLocator();
    else
      throw new Error
        ("KeyLocator.getFromSignature: Signature type does not have a KeyLocator");
  }

  /**
   * Get the change count, which is incremented each time this object
   * (or a child object) is changed.
   * @return The change count.
   */
  public final long
  getChangeCount()
  {
    if (keyName_.checkChanged())
      // A child object has changed, so update the change count.
      ++changeCount_;

    return changeCount_;
  }

  private KeyLocatorType type_ = KeyLocatorType.NONE;
  private Blob keyData_ = new Blob(); /**< A Blob for the key data as follows:
    * If type_ is KeyLocatorType.KEY_LOCATOR_DIGEST, the digest data.
    */
  private final ChangeCounter keyName_ =
    new ChangeCounter(new Name()); /**< The key name (only used if
                                        type_ KeyLocatorType.KEYNAME.) */
  private long changeCount_ = 0;
}