/*

 * 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.set;

import java.util.Collection;

import java.util.Iterator;

import java.util.Set;

import java.util.function.Predicate;

import org.apache.commons.collections4.Unmodifiable;

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

/**

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

 * <p>

 * This class is Serializable from Commons Collections 3.1.

 * </p>

 * <p>

 * Attempts to modify it will result in an UnsupportedOperationException.

 * </p>

 *

 * @param <E> the type of the elements in this set

 * @since 3.0

 */

public final class UnmodifiableSet<E>

        extends AbstractSerializableSetDecorator<E>

        implements Unmodifiable {

    /** Serialization version */

    private static final long serialVersionUID = 6499119872185240161L;

    /**

     * Factory method to create an unmodifiable set.

     *

     * @param <E> the element type

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

     * @return a new unmodifiable set

     * @throws NullPointerException if set is null

     * @since 4.0

     */

    public static <E> Set<E> unmodifiableSet(final Set<? extends E> set) {

        if (set instanceof Unmodifiable) {

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

            final Set<E> tmpSet = (Set<E>) set;

            return tmpSet;

        }

        return new UnmodifiableSet<>(set);

    }

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

    /**

     * Constructor that wraps (not copies).

     *

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

     * @throws NullPointerException if set is null

     */

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

    private UnmodifiableSet(final Set<? extends E> set) {

        super((Set<E>) set);

    }

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

    @Override

    public Iterator<E> iterator() {

        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());

    }

    @Override

    public boolean add(final E object) {

        throw new UnsupportedOperationException();

    }

    @Override

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

        throw new UnsupportedOperationException();

    }

    @Override

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

        throw new UnsupportedOperationException();

    }

    @Override

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

        throw new UnsupportedOperationException();

    }

}