/*

  * 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.spi.config.proxy;

 import de.smartics.properties.api.config.domain.SerializableConfigurationProperties;

 import de.smartics.properties.api.core.annotations.PropertySet;

 /**

  * This factory creates a implementation object via a java dynamic proxy for a

  * given properties interface. Using this object it is possible to access the

  * properties and when defined in the given interface the keys and property

  * descriptions can be accessed.

  */

 public final class PropertyConfigurationObjectBuilder

 {

   // ********************************* Fields *********************************

   // --- constants ------------------------------------------------------------

   // --- members --------------------------------------------------------------

   // ****************************** Initializer *******************************

   // ****************************** Constructors ******************************

   /**

    * The default message suffix.

    */

   private static final String MESSAGE =

       "Only classes that represent an"

           + " interface and that interface must have a 'PropertySet'"

           + " annotation are allowed.";

   /**

    * Default constructor.

    */

   public PropertyConfigurationObjectBuilder()

   {

   }

   // ****************************** Inner Classes *****************************

   // ********************************* Methods ********************************

   // --- init -----------------------------------------------------------------

   // --- get&set --------------------------------------------------------------

   // --- business -------------------------------------------------------------

   /**

    * Build the object that contains the properties information for the given

    * properties interface. The interface must be provided through its class

    * object and has to have a {@link PropertySet} annotation.

    *

    * @param propertiesInterface the properties interface as class object with an

    *          {@link PropertySet} annotation.

    * @param configurationProperties the configuration properties that shall be

    *          used to access the properties.

    * @param <T> to provide a type safe access to the properties the returned

    *          object implements the given properties interface.

    * @return the object that contains the properties information for the given

    *         properties interface.

    * @throws NotAPropertySetAnnotatedInterfaceException when the given class

    *           does not represent an interface and this interface is not

    *           annotated with {@link PropertySet} or when null.

    */

   public <T> T build(final Class<T> propertiesInterface,

       final SerializableConfigurationProperties configurationProperties)

     throws NotAPropertySetAnnotatedInterfaceException

   {

     checkForValidPropertiesInterface(propertiesInterface);

     final T propertiesObject =

         buildObject(propertiesInterface, configurationProperties);

     return propertiesObject;

   }

   @SuppressWarnings("unchecked")

   private <T> T buildObject(final Class<T> propertiesInterface,

       final SerializableConfigurationProperties configurationProperties)

   {

     final T propertiesObject =

         (T) java.lang.reflect.Proxy.newProxyInstance(

             propertiesInterface.getClassLoader(),

             new Class[] { propertiesInterface },

             new PropertiesProxyInvocationHandler(configurationProperties));

     return propertiesObject;

   }

   private <T> void checkForValidPropertiesInterface(

       final Class<T> propertiesInterface)

   {

     checkNull(propertiesInterface);

     checkIfInterface(propertiesInterface);

     checkIfCorrectAnnotated(propertiesInterface);

   }

   private <T> void checkNull(final Class<T> propertiesInterface)

   {

     if (propertiesInterface == null)

     {

       throw new NotAPropertySetAnnotatedInterfaceException(

           "Null is not allowed." + MESSAGE);

     }

   }

   private <T> void checkIfInterface(final Class<T> propertiesInterface)

   {

     if (!propertiesInterface.isInterface())

     {

       throw new NotAPropertySetAnnotatedInterfaceException("Not an interface."

                                                            + MESSAGE);

     }

   }

   private <T> void checkIfCorrectAnnotated(final Class<T> propertiesInterface)

   {

     final PropertySet propertySetAnnotation =

         propertiesInterface.getAnnotation(PropertySet.class);

     if (propertySetAnnotation == null)

     {

       throw new NotAPropertySetAnnotatedInterfaceException(

           "Not a valid annotated interface." + MESSAGE);

     }

   }

   // --- object basics --------------------------------------------------------

 }