/*

 * 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.collection;

import java.util.ArrayList;

import java.util.Collection;

import java.util.List;

import org.apache.commons.collections4.Transformer;

/**

 * Decorates another {@link Collection} to transform objects that are added.

 * <p>

 * The add methods are affected by this class.

 * Thus objects must be removed or searched for using their transformed form.

 * For example, if the transformation converts Strings to Integers, you must

 * use the Integer form to remove objects.

 * </p>

 * <p>

 * This class is Serializable from Commons Collections 3.1.

 * </p>

 *

 * @param <E> the type of the elements in the collection

 * @since 3.0

 */

public class TransformedCollection<E> extends AbstractCollectionDecorator<E> {

    /** Serialization version */

    private static final long serialVersionUID = 8692300188161871514L;

    /** The transformer to use */

    protected final Transformer<? super E, ? extends E> transformer;

    /**

     * Factory method to create a transforming collection.

     * <p>

     * If there are any elements already in the collection being decorated, they

     * are NOT transformed.

     * Contrast this with {@link #transformedCollection(Collection, Transformer)}.

     *

     * @param <E> the type of the elements in the collection

     * @param coll  the collection to decorate, must not be null

     * @param transformer  the transformer to use for conversion, must not be null

     * @return a new transformed collection

     * @throws NullPointerException if collection or transformer is null

     * @since 4.0

     */

    public static <E> TransformedCollection<E> transformingCollection(final Collection<E> coll,

            final Transformer<? super E, ? extends E> transformer) {

        return new TransformedCollection<>(coll, transformer);

    }

    /**

     * Factory method to create a transforming collection that will transform

     * existing contents of the specified collection.

     * <p>

     * If there are any elements already in the collection being decorated, they

     * will be transformed by this method.

     * Contrast this with {@link #transformingCollection(Collection, Transformer)}.

     *

     * @param <E> the type of the elements in the collection

     * @param collection  the collection to decorate, must not be null

     * @param transformer  the transformer to use for conversion, must not be null

     * @return a new transformed Collection

     * @throws NullPointerException if collection or transformer is null

     * @since 4.0

     */

    public static <E> TransformedCollection<E> transformedCollection(final Collection<E> collection,

            final Transformer<? super E, ? extends E> transformer) {

        final TransformedCollection<E> decorated = new TransformedCollection<>(collection, transformer);

        // null collection & transformer are disallowed by the constructor call above

        if (collection.size() > 0) {

            @SuppressWarnings("unchecked") // collection is of type E

            final E[] values = (E[]) collection.toArray(); // NOPMD - false positive for generics

            collection.clear();

            for (final E value : values) {

                decorated.decorated().add(transformer.transform(value));

            }

        }

        return decorated;

    }

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

    /**

     * Constructor that wraps (not copies).

     * <p>

     * If there are any elements already in the collection being decorated, they

     * are NOT transformed.

     *

     * @param coll  the collection to decorate, must not be null

     * @param transformer  the transformer to use for conversion, must not be null

     * @throws NullPointerException if collection or transformer is null

     */

    protected TransformedCollection(final Collection<E> coll, final Transformer<? super E, ? extends E> transformer) {

        super(coll);

        if (transformer == null) {

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

        }

        this.transformer = transformer;

    }

    /**

     * Transforms an object.

     * <p>

     * The transformer itself may throw an exception if necessary.

     *

     * @param object  the object to transform

     * @return a transformed object

     */

    protected E transform(final E object) {

        return transformer.transform(object);

    }

    /**

     * Transforms a collection.

     * <p>

     * The transformer itself may throw an exception if necessary.

     *

     * @param coll  the collection to transform

     * @return a transformed object

     */

    protected Collection<E> transform(final Collection<? extends E> coll) {

        final List<E> list = new ArrayList<>(coll.size());

        for (final E item : coll) {

            list.add(transform(item));

        }

        return list;

    }

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

    @Override

    public boolean add(final E object) {

        return decorated().add(transform(object));

    }

    @Override

    public boolean addAll(final Collection<? extends E> coll) {

        return decorated().addAll(transform(coll));

    }

}