/*

 * 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.iterators;

import org.apache.commons.collections4.MapIterator;

import org.apache.commons.collections4.Unmodifiable;

/**

 * Decorates a map iterator such that it cannot be modified.

 * <p>

 * Attempts to modify it will result in an UnsupportedOperationException.

 * </p>

 *

 * @param <K> the type of keys

 * @param <V> the type of mapped values

 * @since 3.0

 */

public final class UnmodifiableMapIterator<K, V> implements MapIterator<K, V>, Unmodifiable {

    /** The iterator being decorated */

    private final MapIterator<? extends K, ? extends V> iterator;

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

    /**

     * Decorates the specified iterator such that it cannot be modified.

     *

     * @param <K>  the key type

     * @param <V>  the value type

     * @param iterator  the iterator to decorate

     * @return a new unmodifiable map iterator

     * @throws NullPointerException if the iterator is null

     */

    public static <K, V> MapIterator<K, V> unmodifiableMapIterator(

            final MapIterator<? extends K, ? extends V> iterator) {

        if (iterator == null) {

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

        }

        if (iterator instanceof Unmodifiable) {

            @SuppressWarnings("unchecked") // safe to upcast

            final MapIterator<K, V> tmpIterator = (MapIterator<K, V>) iterator;

            return tmpIterator;

        }

        return new UnmodifiableMapIterator<>(iterator);

    }

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

    /**

     * Constructor.

     *

     * @param iterator  the iterator to decorate

     */

    private UnmodifiableMapIterator(final MapIterator<? extends K, ? extends V> iterator) {

        super();

        this.iterator = iterator;

    }

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

    @Override

    public boolean hasNext() {

        return iterator.hasNext();

    }

    @Override

    public K next() {

        return iterator.next();

    }

    @Override

    public K getKey() {

        return iterator.getKey();

    }

    @Override

    public V getValue() {

        return iterator.getValue();

    }

    @Override

    public V setValue(final V value) {

        throw new UnsupportedOperationException("setValue() is not supported");

    }

    @Override

    public void remove() {

        throw new UnsupportedOperationException("remove() is not supported");

    }

}