/*
    * The contents of this file are subject to the terms of the Common Development and
    * Distribution License (the License). You may not use this file except in compliance with the
    * License.
    *
    * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
    * specific language governing permission and limitations under the License.
    *
    * When distributing Covered Software, include this CDDL Header Notice in each file and include
   * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
   * Header, with the fields enclosed by brackets [] replaced by your own identifying
   * information: "Portions copyright [year] [name of copyright owner]".
   *
   * Copyright 2016 ForgeRock AS.
   */
  
  package org.forgerock.json.jose.jwe.handlers.encryption;
  
  import java.security.Key;
  
  import org.forgerock.json.jose.exceptions.JweDecryptionException;
  import org.forgerock.json.jose.jwe.EncryptionMethod;
  import org.forgerock.json.jose.jwe.JweEncryption;
  import org.forgerock.util.annotations.VisibleForTesting;
  
  /**
   * Supports direct encryption using a shared symmetric key.
   */
  public final class DirectEncryptionHandler implements EncryptionHandler {
      private final ContentEncryptionHandler contentEncryptionHandler;
  
      /**
       * Constructs the direct encryption handler for the given content encryption method.
       *
       * @param encryptionMethod the content encryption method.
       */
      public DirectEncryptionHandler(final EncryptionMethod encryptionMethod) {
          this(ContentEncryptionHandler.getInstance(encryptionMethod));
      }
  
      @VisibleForTesting
      DirectEncryptionHandler(ContentEncryptionHandler contentEncryptionHandler) {
          this.contentEncryptionHandler = contentEncryptionHandler;
      }
  
      @Override
      public Key getContentEncryptionKey() {
          return null;
      }
  
      @Override
      public byte[] generateJWEEncryptedKey(final Key key, final Key contentEncryptionKey) {
          // As per https://tools.ietf.org/html/rfc7518#section-4.5 an empty octet sequence is used as the JWE
          // Encrypted Key value when using direct encryption.
          return new byte[0];
      }
  
      @Override
      public byte[] generateInitialisationVector() {
          return contentEncryptionHandler.generateInitialisationVector();
      }
  
      @Override
      public JweEncryption encryptPlaintext(final Key contentEncryptionKey, final byte[] initialisationVector,
              final byte[] plaintext, final byte[] additionalAuthenticatedData) {
          return contentEncryptionHandler.encrypt(contentEncryptionKey, initialisationVector, plaintext,
                  additionalAuthenticatedData);
      }
  
      @Override
      public Key decryptContentEncryptionKey(final Key key, final byte[] encryptedContentEncryptionKey) {
          if (encryptedContentEncryptionKey != null && encryptedContentEncryptionKey.length != 0) {
              throw new JweDecryptionException();
          }
          return key;
      }
  
      @Override
      public byte[] decryptCiphertext(final Key contentEncryptionKey, final byte[] initialisationVector,
              final byte[] ciphertext,
              final byte[] authenticationTag, final byte[] additionalAuthenticatedData) {
          return contentEncryptionHandler.decrypt(contentEncryptionKey, initialisationVector,
                  new JweEncryption(ciphertext, authenticationTag), additionalAuthenticatedData);
      }
  }