/*

 * 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 java.util.Map;

import org.apache.commons.collections4.Transformer;

/**

 * Transformer implementation that returns the value held in a specified map

 * using the input parameter as a key.

 *

 * @since 3.0

 */

public final class MapTransformer<I, O> implements Transformer<I, O>, Serializable {

    /** Serial version UID */

    private static final long serialVersionUID = 862391807045468939L;

    /** The map of data to lookup in */

    private final Map<? super I, ? extends O> iMap;

    /**

     * Factory to create the transformer.

     * <p>

     * If the map is null, a transformer that always returns null is returned.

     *

     * @param <I>  the input type

     * @param <O>  the output type

     * @param map the map, not cloned

     * @return the transformer

     */

    public static <I, O> Transformer<I, O> mapTransformer(final Map<? super I, ? extends O> map) {

        if (map == null) {

            return ConstantTransformer.<I, O>nullTransformer();

        }

        return new MapTransformer<>(map);

    }

    /**

     * Constructor that performs no validation.

     * Use <code>mapTransformer</code> if you want that.

     *

     * @param map  the map to use for lookup, not cloned

     */

    private MapTransformer(final Map<? super I, ? extends O> map) {

        super();

        iMap = map;

    }

    /**

     * Transforms the input to result by looking it up in a <code>Map</code>.

     *

     * @param input  the input object to transform

     * @return the transformed result

     */

    @Override

    public O transform(final I input) {

        return iMap.get(input);

    }

    /**

     * Gets the map to lookup in.

     *

     * @return the map

     * @since 3.1

     */

    public Map<? super I, ? extends O> getMap() {

        return iMap;

    }

}