/*
    * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
    *
    * 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 de.smartics.properties.api.core.security;
  
  import static de.smartics.properties.api.core.security.SecurityConfigurationLoader.SECURITY_ID;
  import static de.smartics.properties.api.core.security.SecurityConfigurationLoader.SECURITY_ALGORITHM;
  import static de.smartics.properties.api.core.security.SecurityConfigurationLoader.SECURITY_KEY;
  import static de.smartics.properties.api.core.security.SecurityConfigurationLoader.SECURITY_PROVIDER;
  import static de.smartics.properties.api.core.security.SecurityConfigurationLoader.SECURITY_TRANSFORMATION;
  
  import java.util.Properties;
  
  import javax.crypto.Cipher;
  import javax.crypto.SecretKey;
  import javax.crypto.spec.SecretKeySpec;
  
  import org.apache.commons.codec.binary.Base64;
  import org.apache.commons.lang.StringUtils;
  
  import de.smartics.properties.api.core.domain.PropertyDescriptor;
  
  /**
   * Base implementation based on Java security, loading configuration values from
   * a properties file stored in
   * {@link SecurityConfigurationLoader#CLASSPATH_LOCATION}.
   */
  public class PropertiesBasedPropertyValueSecurity extends
      AbstractPropertyValueSecurity
  
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The class version identifier.
     */
    private static final long serialVersionUID = 1L;
  
    // --- members --------------------------------------------------------------
  
    /**
     * The security properties to create key and cipher.
     *
     * @serial
     */
    private final Properties properties;
  
    /**
     * The symmetric key to en- and decrypt property values.
     *
     * @serial
     */
    private final SecretKey key;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     */
    public PropertiesBasedPropertyValueSecurity()
    {
      properties = loadProperties();
      key = createKey(properties);
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    private Properties loadProperties()
    {
      try
      {
        final SecurityConfigurationLoader loader =
            new SecurityConfigurationLoader();
        return loader.load();
      }
      catch (final IllegalStateException e)
      {
        throw new SecurityException(new SecurityMessageBean(
            SecurityCode.LOADING_SECURITY_PROPERTIES_FAILED, e,
           properties.getProperty(SECURITY_ID)));
     }
   }
 
   /**
    * Creates the symmetric key instance.
    *
    * @param descriptor the descriptor of the property whose value is to be
    *          secured.
    * @return the symmetric key instance ready to be used.
    * @throws SecurityException on any problem creating the symmetric key
    *           instance.
    */
   private SecretKey createKey(final Properties properties)
     throws SecurityException
   {
     final String key = properties.getProperty(SECURITY_KEY);
     final String encryptAlgorithm = properties.getProperty(SECURITY_ALGORITHM);
 
     try
     {
       final byte[] decodedKey = Base64.decodeBase64(key);
 
       final SecretKeySpec secretKey =
           new SecretKeySpec(decodedKey, encryptAlgorithm);
       return secretKey;
     }
     catch (final Exception e)
     {
       throw new SecurityException(new SecurityMessageBean(
           SecurityCode.INIT_KEY_GENERATION_FAILED, e,
           properties.getProperty(SECURITY_ID)));
     }
   }
 
   // --- get&set --------------------------------------------------------------
 
   // --- business -------------------------------------------------------------
 
   @Override
   public String decrypt(final PropertyDescriptor descriptor,
       final String encryptedValue) throws NullPointerException,
     SecurityException
   {
     final Cipher cipher = createCipher();
     return decrypt(descriptor, encryptedValue, key, cipher);
   }
 
   @Override
   public String encrypt(final PropertyDescriptor descriptor,
       final String plainValue) throws NullPointerException, SecurityException
   {
     final Cipher cipher = createCipher();
     return encrypt(descriptor, plainValue, key, cipher);
   }
 
   private Cipher createCipher() throws SecurityException
   {
     final String transformation =
         properties.getProperty(SECURITY_TRANSFORMATION);
     final String provider = properties.getProperty(SECURITY_PROVIDER);
 
     try
     {
       if (StringUtils.isNotEmpty(provider))
       {
         return Cipher.getInstance(transformation, provider);
       }
       else
       {
         return Cipher.getInstance(transformation);
       }
     }
     catch (final Exception e)
     {
       throw new SecurityException(new SecurityMessageBean(
           SecurityCode.INIT_CIPHER_GENERATION_FAILED, e,
           properties.getProperty(SECURITY_ID)));
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }