/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.collections.functors;
  
  import java.io.Serializable;
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  
  import org.apache.commons.collections.FunctorException;
  import org.apache.commons.collections.Transformer;
  
  /**
   * Transformer implementation that creates a new object instance by reflection.
   *
   * @since 3.0
   * @version $Id: InstantiateTransformer.java 1435965 2013-01-20 21:13:18Z tn $
   */
  public class InstantiateTransformer<T> implements Transformer<Class<? extends T>, T>, Serializable {
  
      /** The serial version */
      private static final long serialVersionUID = 3786388740793356347L;
  
      /** Singleton instance that uses the no arg constructor */
      public static final Transformer<Class<?>, ?> NO_ARG_INSTANCE = new InstantiateTransformer<Object>();
  
      /** The constructor parameter types */
      private final Class<?>[] iParamTypes;
      /** The constructor arguments */
      private final Object[] iArgs;
  
      /**
       * Get a typed no-arg instance.
       *
       * @param <T>  the type of the objects to be created
       * @return Transformer<Class<? extends T>, T>
       */
      public static <T> Transformer<Class<? extends T>, T> instantiateTransformer() {
          return new InstantiateTransformer<T>();
      }
  
      /**
       * Transformer method that performs validation.
       *
       * @param <T>  the type of the objects to be created
       * @param paramTypes  the constructor parameter types
       * @param args  the constructor arguments
       * @return an instantiate transformer
       */
      public static <T> Transformer<Class<? extends T>, T> instantiateTransformer(Class<?>[] paramTypes, Object[] args) {
          if (((paramTypes == null) && (args != null))
              || ((paramTypes != null) && (args == null))
              || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) {
              throw new IllegalArgumentException("Parameter types must match the arguments");
          }
  
          if (paramTypes == null || paramTypes.length == 0) {
              return new InstantiateTransformer<T>();
          }
          paramTypes = paramTypes.clone();
          args = args.clone();
          return new InstantiateTransformer<T>(paramTypes, args);
      }
  
      /**
       * Constructor for no arg instance.
       */
      private InstantiateTransformer() {
          super();
          iParamTypes = null;
          iArgs = null;
      }
  
      /**
       * Constructor that performs no validation.
       * Use <code>getInstance</code> if you want that.
       *
       * @param paramTypes  the constructor parameter types, not cloned
       * @param args  the constructor arguments, not cloned
       */
      public InstantiateTransformer(final Class<?>[] paramTypes, final Object[] args) {
          super();
          iParamTypes = paramTypes;
          iArgs = args;
      }
  
     /**
      * Transforms the input Class object to a result by instantiation.
      *
      * @param input  the input object to transform
      * @return the transformed result
      */
     public T transform(final Class<? extends T> input) {
         try {
             if (input == null) {
                 throw new FunctorException(
                     "InstantiateTransformer: Input object was not an instanceof Class, it was a null object");
             }
             final Constructor<? extends T> con = input.getConstructor(iParamTypes);
             return con.newInstance(iArgs);
         } catch (final NoSuchMethodException ex) {
             throw new FunctorException("InstantiateTransformer: The constructor must exist and be public ");
         } catch (final InstantiationException ex) {
             throw new FunctorException("InstantiateTransformer: InstantiationException", ex);
         } catch (final IllegalAccessException ex) {
             throw new FunctorException("InstantiateTransformer: Constructor must be public", ex);
         } catch (final InvocationTargetException ex) {
             throw new FunctorException("InstantiateTransformer: Constructor threw an exception", ex);
         }
     }
 
 }