/*

  * 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;

 import org.apache.commons.functor.BinaryPredicate;

 /**

  * A {@link BinaryFunction BinaryFunction}

  * similiar to Java's "ternary"

  * or "conditional" operator (<code>&#x3F; &#x3A;</code>).

  * Given a {@link BinaryPredicate predicate}

  * <i>p</i> and {@link BinaryFunction functions}

  * <i>f</i> and <i>g</i>, {@link #evaluate evaluates}

  * to

  * <code>p.test(x,y) ? f.evaluate(x,y) : g.evaluate(x,y)</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: 1166381 $ $Date: 2011-09-07 22:19:48 +0200 (Wed, 07 Sep 2011) $

  * @author Rodney Waldhoff

  */

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

     /**

      * serialVersionUID declaration.

      */

     private static final long serialVersionUID = -994698971284481482L;

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

     private static final int HASH_SHIFT = 4;

     // attributes

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

     private final BinaryPredicate<? super L, ? super R> ifPred;

     private final BinaryFunction<? super L, ? super R, ? extends T> thenFunc;

     private final BinaryFunction<? super L, ? super R, ? extends T> elseFunc;

     // constructor

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

     /**

      * Create a new ConditionalBinaryFunction.

      * @param ifPred if

      * @param thenFunc then

      * @param elseFunc else

      */

     public ConditionalBinaryFunction(BinaryPredicate<? super L, ? super R> ifPred,

             BinaryFunction<? super L, ? super R, ? extends T> thenFunc,

             BinaryFunction<? super L, ? super R, ? extends T> elseFunc) {

         if (ifPred == null) {

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

         }

         if (thenFunc == null || elseFunc == null) {

             throw new IllegalArgumentException("One or more BinaryFunction arguments was null");

         }

         this.ifPred = ifPred;

         this.thenFunc = thenFunc;

         this.elseFunc = elseFunc;

     }

     // predicate interface

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

     /**

      * {@inheritDoc}

      */

     public T evaluate(L left, R right) {

         if (ifPred.test(left, right)) {

             return thenFunc.evaluate(left, right);

         } else {

             return elseFunc.evaluate(left, right);

         }

     }

     /**

      * {@inheritDoc}

      */

     public boolean equals(Object that) {

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

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

     }

     /**

      * Learn whether another ConditionalBinaryFunction is equal to this.

      * @param that ConditionalBinaryFunction to test

      * @return boolean

      */

     public boolean equals(ConditionalBinaryFunction<?, ?, ?> that) {

         return null != that

                 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))

                 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc))

                 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc));

     }

     /**

      * {@inheritDoc}

      */

     public int hashCode() {

         int hash = "ConditionalBinaryFunction".hashCode();

         if (null != ifPred) {

             hash <<= HASH_SHIFT;

             hash ^= ifPred.hashCode();

         }

         if (null != thenFunc) {

             hash <<= HASH_SHIFT;

             hash ^= thenFunc.hashCode();

         }

         if (null != elseFunc) {

             hash <<= HASH_SHIFT;

             hash ^= elseFunc.hashCode();

         }

         return hash;

     }

     /**

      * {@inheritDoc}

      */

     public String toString() {

         return "ConditionalBinaryFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";

     }

 }