/*

  * 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.functor.core.collection;

 import java.util.Iterator;

 import org.apache.commons.functor.UnaryFunction;

 /**

  * Iterator that transforms another Iterator by applying a UnaryFunction to each returned element.

  * @version $Revision: 1156793 $ $Date: 2011-08-11 22:06:24 +0200 (Thu, 11 Aug 2011) $

  * @author Rodney Waldhoff

  */

 public final class TransformedIterator<E, T> implements Iterator<T> {

     // attributes

     // ------------------------------------------------------------------------

     private final UnaryFunction<? super E, ? extends T> function;

     private final Iterator<? extends E> iterator;

     // constructor

     // ------------------------------------------------------------------------

     /**

      * Create a new TransformedIterator.

      * @param iterator Iterator to decorate

      * @param function to apply

      */

     public TransformedIterator(Iterator<? extends E> iterator, UnaryFunction<? super E, ? extends T> function) {

         if (null == iterator) {

             throw new IllegalArgumentException("Iterator argument was null");

         }

         if (null == function) {

             throw new IllegalArgumentException("filtering UnaryFunction argument was null");

         }

         this.function = function;

         this.iterator = iterator;

     }

     // iterator methods

     // ------------------------------------------------------------------------

     /**

      * {@inheritDoc}

      * @see java.util.Iterator#hasNext()

      */

     public boolean hasNext() {

         return iterator.hasNext();

     }

     /**

      * {@inheritDoc}

      * @see java.util.Iterator#next()

      */

     public T next() {

         return function.evaluate(iterator.next());

     }

     /**

      * {@inheritDoc}

      * @see java.util.Iterator#remove()

      */

     public void remove() {

         iterator.remove();

     }

     /**

      * {@inheritDoc}

      */

     public boolean equals(Object obj) {

         if (obj == this) {

             return true;

         }

         if (!(obj instanceof TransformedIterator<?, ?>)) {

             return false;

         }

         TransformedIterator<?, ?> that = (TransformedIterator<?, ?>) obj;

         return function.equals(that.function) && iterator.equals(that.iterator);

     }

     /**

      * {@inheritDoc}

      */

     public int hashCode() {

         int hash = "TransformedIterator".hashCode();

         hash <<= 2;

         hash ^= function.hashCode();

         hash <<= 2;

         hash ^= iterator.hashCode();

         return hash;

     }

     /**

      * {@inheritDoc}

      */

     public String toString() {

         return "TransformedIterator<" + iterator + "," + function + ">";

     }

     // class methods

     // ------------------------------------------------------------------------

     /**

      * Get a Transformed Iterator instance.

      * @param iter to decorate, if null result is null

      * @param func transforming function, cannot be null

      * @return Iterator<T>

      */

     public static <E, T> Iterator<T> transform(Iterator<? extends E> iter, UnaryFunction<? super E, ? extends T> func) {

         if (null == iter) {

             return null;

         }

         return new TransformedIterator<E, T>(iter, func);

     }

     /**

      * Get an Iterator instance that may be transformed.

      * @param iter to decorate, if null result is null

      * @param func transforming function, if null result is iter

      * @return Iterator<?>

      */

     public static <E> Iterator<?> maybeTransform(Iterator<? extends E> iter, UnaryFunction<? super E, ?> func) {

         return null == func ? (null == iter ? null : iter) : new TransformedIterator<E, Object>(iter, func);

     }

 }