/*

  * 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.algorithm;

 import java.io.Serializable;

 import org.apache.commons.functor.BinaryFunction;

 import org.apache.commons.functor.UnaryPredicate;

 import org.apache.commons.functor.UnaryProcedure;

 import org.apache.commons.functor.generator.Generator;

 /**

  * Return the index of the first Object in a {@link Generator} matching a {@link UnaryPredicate}, or -1 if not found.

  *

  * @version $Revision: 1156337 $ $Date: 2011-08-10 21:44:54 +0200 (Wed, 10 Aug 2011) $

  */

 public final class IndexOfInGenerator<T>

     implements BinaryFunction<Generator<? extends T>, UnaryPredicate<? super T>, Number>, Serializable {

     /**

      * serialVersionUID declaration.

      */

     private static final long serialVersionUID = -11365986575536471L;

     private static final IndexOfInGenerator<Object> INSTANCE = new IndexOfInGenerator<Object>();

     /**

      * Helper procedure.

      */

     private static class IndexProcedure<T> implements UnaryProcedure<T> {

         private final Generator<? extends T> generator;

         private final UnaryPredicate<? super T> pred;

         private long index = -1L;

         private long current = 0L;

         /**

          * Create a new IndexProcedure.

          * @pred test

          */

         IndexProcedure(Generator<? extends T> generator, UnaryPredicate<? super T> pred) {

             this.generator = generator;

             this.pred = pred;

         }

         /**

          * {@inheritDoc}

          */

         public void run(T obj) {

             if (index < 0 && pred.test(obj)) {

                 index = current;

                 generator.stop();

             }

             current++;

         }

     }

     /**

      * {@inheritDoc}

      * @param left Generator

      * @param right UnaryPredicate

      */

     public Number evaluate(Generator<? extends T> left, UnaryPredicate<? super T> right) {

         IndexProcedure<T> findProcedure = new IndexProcedure<T>(left, right);

         left.run(findProcedure);

         return findProcedure.index;

     }

     /**

      * {@inheritDoc}

      */

     public boolean equals(Object obj) {

         return obj == this || obj != null && obj.getClass().equals(getClass());

     }

     /**

      * {@inheritDoc}

      */

     public int hashCode() {

         return System.identityHashCode(INSTANCE);

     }

     /**

      * Get a static {@link IndexOfInGenerator} instance.

      * @return {@link IndexOfInGenerator}

      */

     public static IndexOfInGenerator<Object> instance() {

         return INSTANCE;

     }

 }