/*

 * 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.collections4.functors;

import java.io.Serializable;

import org.apache.commons.collections4.Predicate;

import org.apache.commons.collections4.Transformer;

/**

 * Transformer implementation that will call one of two closures based on whether a predicate evaluates

 * as true or false.

 *

 * @param <I> The input type for the transformer

 * @param <O> The output type for the transformer

 *

 * @since 4.1

 */

public class IfTransformer<I, O> implements Transformer<I, O>, Serializable {

    /** Serial version UID */

    private static final long serialVersionUID = 8069309411242014252L;

    /** The test */

    private final Predicate<? super I> iPredicate;

    /** The transformer to use if true */

    private final Transformer<? super I, ? extends O> iTrueTransformer;

    /** The transformer to use if false */

    private final Transformer<? super I, ? extends O> iFalseTransformer;

    /**

     * Factory method that performs validation.

     *

     * @param <I>  input type for the transformer

     * @param <O>  output type for the transformer

     * @param predicate  predicate to switch on

     * @param trueTransformer  transformer used if true

     * @param falseTransformer  transformer used if false

     * @return the <code>if</code> transformer

     * @throws NullPointerException if either argument is null

     */

    public static <I, O> Transformer<I, O> ifTransformer(final Predicate<? super I> predicate,

                                                         final Transformer<? super I, ? extends O> trueTransformer,

                                                         final Transformer<? super I, ? extends O> falseTransformer) {

        if (predicate == null) {

            throw new NullPointerException("Predicate must not be null");

        }

        if (trueTransformer == null || falseTransformer == null) {

            throw new NullPointerException("Transformers must not be null");

        }

        return new IfTransformer<>(predicate, trueTransformer, falseTransformer);

    }

    /**

     * Factory method that performs validation.

     * <p>

     * This factory creates a transformer that just returns the input object when

     * the predicate is false.

     *

     * @param <T>  input and output type for the transformer

     * @param predicate  predicate to switch on

     * @param trueTransformer  transformer used if true

     * @return the <code>if</code> transformer

     * @throws NullPointerException if either argument is null

     */

    public static <T> Transformer<T, T> ifTransformer(

            final Predicate<? super T> predicate,

            final Transformer<? super T, ? extends T> trueTransformer) {

        if (predicate == null) {

            throw new NullPointerException("Predicate must not be null");

        }

        if (trueTransformer == null) {

            throw new NullPointerException("Transformer must not be null");

        }

        return new IfTransformer<>(predicate, trueTransformer, NOPTransformer.<T>nopTransformer());

    }

    /**

     * Constructor that performs no validation.

     * Use the static factory method <code>ifTransformer</code> if you want that.

     *

     * @param predicate  predicate to switch on, not null

     * @param trueTransformer  transformer used if true, not null

     * @param falseTransformer  transformer used if false, not null

     */

    public IfTransformer(final Predicate<? super I> predicate,

        final Transformer<? super I, ? extends O> trueTransformer,

        final Transformer<? super I, ? extends O> falseTransformer) {

        super();

        iPredicate = predicate;

        iTrueTransformer = trueTransformer;

        iFalseTransformer = falseTransformer;

    }

    /**

     * Transforms the input using the true or false transformer based to the result of the predicate.

     *

     * @param input  the input object to transform

     * @return the transformed result

     */

    @Override

    public O transform(final I input) {

        if(iPredicate.evaluate(input)){

            return iTrueTransformer.transform(input);

        }

        return iFalseTransformer.transform(input);

    }

    /**

     * Gets the predicate.

     *

     * @return the predicate

     */

    public Predicate<? super I> getPredicate(){

        return iPredicate;

    }

    /**

     * Gets the transformer used when true.

     *

     * @return the transformer

     */

    public Transformer<? super I, ? extends O> getTrueTransformer() {

        return iTrueTransformer;

    }

    /**

     * Gets the transformer used when false.

     *

     * @return the transformer

     */

    public Transformer<? super I, ? extends O> getFalseTransformer() {

        return iFalseTransformer;

    }

}