/*

 * 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.Collection;

import java.util.Iterator;

import java.util.function.Predicate;

import org.apache.commons.collections4.Unmodifiable;

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

/**

 * Decorates another {@link Collection} 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 the collection

 * @since 3.0

 */

public final class UnmodifiableCollection<E>

        extends AbstractCollectionDecorator<E>

        implements Unmodifiable {

    /** Serialization version */

    private static final long serialVersionUID = -239892006883819945L;

    /**

     * Factory method to create an unmodifiable collection.

     * <p>

     * If the collection passed in is already unmodifiable, it is returned.

     *

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

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

     * @return an unmodifiable collection

     * @throws NullPointerException if collection is null

     * @since 4.0

     */

    public static <T> Collection<T> unmodifiableCollection(final Collection<? extends T> coll) {

        if (coll instanceof Unmodifiable) {

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

            final Collection<T> tmpColl = (Collection<T>) coll;

            return tmpColl;

        }

        return new UnmodifiableCollection<>(coll);

    }

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

    /**

     * Constructor that wraps (not copies).

     *

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

     * @throws NullPointerException if collection is null

     */

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

    private UnmodifiableCollection(final Collection<? extends E> coll) {

        super((Collection<E>) coll);

    }

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

    @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(final 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();

    }

}