/*

 * 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;

import java.util.ArrayList;

import java.util.Enumeration;

import java.util.List;

import java.util.StringTokenizer;

import org.apache.commons.collections4.iterators.EnumerationIterator;

/**

 * Provides utility methods for {@link Enumeration} instances.

 *

 * @since 3.0

 */

public class EnumerationUtils {

    /**

     * EnumerationUtils is not normally instantiated.

     */

    private EnumerationUtils() {}

    /**

     * Returns the <code>index</code>-th value in the {@link Enumeration}, throwing

     * <code>IndexOutOfBoundsException</code> if there is no such element.

     * <p>

     * The Enumeration is advanced to <code>index</code> (or to the end, if

     * <code>index</code> exceeds the number of entries) as a side effect of this method.

     *

     * @param e  the enumeration to get a value from

     * @param index  the index to get

     * @param <T> the type of object in the {@link Enumeration}

     * @return the object at the specified index

     * @throws IndexOutOfBoundsException if the index is invalid

     * @throws IllegalArgumentException if the object type is invalid

     * @since 4.1

     */

    public static <T> T get(final Enumeration<T> e, final int index) {

        int i = index;

        CollectionUtils.checkIndexBounds(i);

        while (e.hasMoreElements()) {

            i--;

            if (i == -1) {

                return e.nextElement();

            }

            e.nextElement();

        }

        throw new IndexOutOfBoundsException("Entry does not exist: " + i);

    }

    /**

     * Creates a list based on an enumeration.

     *

     * <p>As the enumeration is traversed, an ArrayList of its values is

     * created. The new list is returned.</p>

     *

     * @param <E> the element type

     * @param enumeration  the enumeration to traverse, which should not be <code>null</code>.

     * @return a list containing all elements of the given enumeration

     * @throws NullPointerException if the enumeration parameter is <code>null</code>.

     */

    public static <E> List<E> toList(final Enumeration<? extends E> enumeration) {

        return IteratorUtils.toList(new EnumerationIterator<>(enumeration));

    }

    /**

     * Override toList(Enumeration) for StringTokenizer as it implements Enumeration<Object>

     * for the sake of backward compatibility.

     *

     * @param stringTokenizer  the tokenizer to convert to a {@link List}<{@link String}>

     * @return a list containing all tokens of the given StringTokenizer

     */

    public static List<String> toList(final StringTokenizer stringTokenizer) {

        final List<String> result = new ArrayList<>(stringTokenizer.countTokens());

        while (stringTokenizer.hasMoreTokens()) {

            result.add(stringTokenizer.nextToken());

        }

        return result;

    }

}