/*

  * 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.composite;

 import java.io.Serializable;

 import org.apache.commons.functor.BinaryFunction;

 /**

  * A {@link BinaryFunction BinaryFunction} composed of

  * three binary functions, <i>f</i>, <i>g</i> and <i>h</i>,

  * evaluating the ordered parameters <i>x</i>, <i>y</i>

  * to <code><i>f</i>(<i>g</i>(<i>x</i>,<i>y</i>),<i>h</i>(<i>x</i>,<i>y</i>))</code>.

  * <p>

  * Note that although this class implements

  * {@link Serializable}, a given instance will

  * only be truly <code>Serializable</code> if all the

  * underlying functors are.  Attempts to serialize

  * an instance whose delegates are not all

  * <code>Serializable</code> will result in an exception.

  * </p>

  * @version $Revision: 1171154 $ $Date: 2011-09-15 17:58:38 +0200 (Thu, 15 Sep 2011) $

  * @author Rodney Waldhoff

  */

 public class BinaryCompositeBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {

     /**

      * serialVersionUID declaration.

      */

     private static final long serialVersionUID = 2570517284319064043L;

     /** Base hash integer used to shift hash */

     private static final int HASH_SHIFT = 4;

     /**

      * Type-remembering Helper

      *

      * @param <G>

      * @param <H>

      */

     private static class Helper<G, H, L, R, T> implements BinaryFunction<L, R, T>, Serializable {

         /**

          * serialVersionUID declaration.

          */

         private static final long serialVersionUID = 6013646799505641592L;

         private BinaryFunction<? super G, ? super H, ? extends T> f;

         private BinaryFunction<? super L, ? super R, ? extends G> g;

         private BinaryFunction<? super L, ? super R, ? extends H> h;

         /**

          * Create a new Helper.

          * @param f final BinaryFunction to evaluate

          * @param g left preceding BinaryFunction

          * @param h right preceding BinaryFunction

          */

         public Helper(BinaryFunction<? super G, ? super H, ? extends T> f,

                 BinaryFunction<? super L, ? super R, ? extends G> g,

                 BinaryFunction<? super L, ? super R, ? extends H> h) {

             this.f = f;

             this.g = g;

             this.h = h;

         }

         /**

          * {@inheritDoc}

          */

         public T evaluate(L left, R right) {

             return f.evaluate(g.evaluate(left, right), h.evaluate(left, right));

         }

     }

     private final Helper<?, ?, L, R, T> helper;

     // constructor

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

     /**

      * Create a new BinaryCompositeBinaryFunction.

      * @param f final BinaryFunction to evaluate

      * @param g left preceding BinaryFunction

      * @param h right preceding BinaryFunction

      */

     public <G, H> BinaryCompositeBinaryFunction(BinaryFunction<? super G, ? super H, ? extends T> f,

             BinaryFunction<? super L, ? super R, ? extends G> g, BinaryFunction<? super L, ? super R, ? extends H> h) {

         if (f == null || g == null || h == null) {

             throw new IllegalArgumentException("BinaryFunction arguments may not be null");

         }

         this.helper = new Helper<G, H, L, R, T>(f, g, h);

     }

     // function interface

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

     /**

      * {@inheritDoc}

      */

     public final T evaluate(L left, R right) {

         return helper.evaluate(left, right);

     }

     /**

      * {@inheritDoc}

      */

     public final boolean equals(Object that) {

         return that == this || (that instanceof BinaryCompositeBinaryFunction<?, ?, ?>

                                     && equals((BinaryCompositeBinaryFunction<?, ?, ?>) that));

     }

     /**

      * Learn whether another BinaryCompositeBinaryFunction is equal to this.

      * @param that BinaryCompositeBinaryFunction to test

      * @return boolean

      */

     public final boolean equals(BinaryCompositeBinaryFunction<?, ?, ?> that) {

         return null != that

                 && helper.f.equals(that.helper.f)

                 && helper.g.equals(that.helper.g)

                 && helper.h.equals(that.helper.h);

     }

     /**

      * {@inheritDoc}

      */

     public int hashCode() {

         int hash = "BinaryCompositeBinaryFunction".hashCode();

             hash <<= HASH_SHIFT;

             hash ^= helper.f.hashCode();

             hash <<= HASH_SHIFT;

             hash ^= helper.g.hashCode();

             hash <<= HASH_SHIFT;

             hash ^= helper.h.hashCode();

         return hash;

     }

     /**

      * {@inheritDoc}

      */

     public String toString() {

         return "BinaryCompositeBinaryFunction<" + helper.f + ";" + helper.g + ";" + helper.h + ">";

     }

 }