package org.trails.builder;

 import org.trails.exception.TrailsRuntimeException;

 import java.lang.reflect.Constructor;

 import java.util.HashMap;

 import java.util.Map;

 /**

  * Fulfils the "Director" role in the Trails implementation of

  * GOF's <a href="http://en.wikipedia.org/wiki/Builder_pattern">Builder pattern</a>

  *

  * Constructs an object using the Builder interface 

  */

 public class BuilderDirector

 {

         Map<Class, Builder> map = new HashMap<Class, Builder>();

         /**

          * Create a new instance of an object of class 'type' using a Builder.

          *

          * @param type is a class whose instance should be created

          * @return a newly created object

          */

         public <T> T createNewInstance(final Class<T> type)

         {

                 Builder<T> builder = (Builder<T>) map.get(type);

                 if (builder != null)

                 {

                         return builder.build();

                 } else

                 {

                         return createNewInstanceFromEmptyConstructor(type);

                 }

         }

         /**

          * Create a new instance of an object of class 'type' using an empty constructor.

          *

          * @param type is a class whose instance should be created

          * @return a newly created object

          */

         private <T> T createNewInstanceFromEmptyConstructor(final Class<T> type)

         {

                 try

                 {

                         Constructor constructor = type.getDeclaredConstructor();

                         constructor.setAccessible(true);

                         return (T) constructor.newInstance();

                 } catch (Exception ex)

                 {

                         throw new TrailsRuntimeException(ex, type);

                 }

         }

 }