/*

 * 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.map;

import java.lang.reflect.Array;

import java.util.Collection;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.function.Predicate;

import org.apache.commons.collections4.Unmodifiable;

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

import org.apache.commons.collections4.keyvalue.AbstractMapEntryDecorator;

import org.apache.commons.collections4.set.AbstractSetDecorator;

/**

 * Decorates a map entry <code>Set</code> to ensure it can't be altered.

 * <p>

 * Attempts to modify it will result in an UnsupportedOperationException.

 * </p>

 *

 * @param <K> the type of the keys in the map

 * @param <V> the type of the values in the map

 *

 * @since 3.0

 */

public final class UnmodifiableEntrySet<K, V>

        extends AbstractSetDecorator<Map.Entry<K, V>> implements Unmodifiable {

    /** Serialization version */

    private static final long serialVersionUID = 1678353579659253473L;

    /**

     * Factory method to create an unmodifiable set of Map Entry objects.

     *

     * @param <K>  the key type

     * @param <V>  the value type

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

     * @return a new unmodifiable entry set

     * @throws NullPointerException if set is null

     * @since 4.0

     */

    public static <K, V> Set<Map.Entry<K, V>> unmodifiableEntrySet(final Set<Map.Entry<K, V>> set) {

        if (set instanceof Unmodifiable) {

            return set;

        }

        return new UnmodifiableEntrySet<>(set);

    }

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

    /**

     * Constructor that wraps (not copies).

     *

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

     * @throws NullPointerException if set is null

     */

    private UnmodifiableEntrySet(final Set<Map.Entry<K, V>> set) {

        super(set);

    }

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

    @Override

    public boolean add(final Map.Entry<K, V> object) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean addAll(final Collection<? extends Map.Entry<K, V>> coll) {

        throw new UnsupportedOperationException();

    }

    @Override

    public void clear() {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean remove(final Object object) {

        throw new UnsupportedOperationException();

    }

    /**

     * @since 4.4

     */

    @Override

    public boolean removeIf(Predicate<? super Map.Entry<K, V>> filter) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean removeAll(final Collection<?> coll) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean retainAll(final Collection<?> coll) {

        throw new UnsupportedOperationException();

    }

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

    @Override

    public Iterator<Map.Entry<K, V>> iterator() {

        return new UnmodifiableEntrySetIterator(decorated().iterator());

    }

    @Override

    @SuppressWarnings("unchecked")

    public Object[] toArray() {

        final Object[] array = decorated().toArray();

        for (int i = 0; i < array.length; i++) {

            array[i] = new UnmodifiableEntry((Map.Entry<K, V>) array[i]);

        }

        return array;

    }

    @Override

    @SuppressWarnings("unchecked")

    public <T> T[] toArray(final T[] array) {

        Object[] result = array;

        if (array.length > 0) {

            // we must create a new array to handle multi-threaded situations

            // where another thread could access data before we decorate it

            result = (Object[]) Array.newInstance(array.getClass().getComponentType(), 0);

        }

        result = decorated().toArray(result);

        for (int i = 0; i < result.length; i++) {

            result[i] = new UnmodifiableEntry((Map.Entry<K, V>) result[i]);

        }

        // check to see if result should be returned straight

        if (result.length > array.length) {

            return (T[]) result;

        }

        // copy back into input array to fulfill the method contract

        System.arraycopy(result, 0, array, 0, result.length);

        if (array.length > result.length) {

            array[result.length] = null;

        }

        return array;

    }

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

    /**

     * Implementation of an entry set iterator.

     */

    private class UnmodifiableEntrySetIterator extends AbstractIteratorDecorator<Map.Entry<K, V>> {

        protected UnmodifiableEntrySetIterator(final Iterator<Map.Entry<K, V>> iterator) {

            super(iterator);

        }

        @Override

        public Map.Entry<K, V> next() {

            return new UnmodifiableEntry(getIterator().next());

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

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

    /**

     * Implementation of a map entry that is unmodifiable.

     */

    private class UnmodifiableEntry extends AbstractMapEntryDecorator<K, V> {

        protected UnmodifiableEntry(final Map.Entry<K, V> entry) {

            super(entry);

        }

        @Override

        public V setValue(final V obj) {

            throw new UnsupportedOperationException();

        }

    }

}