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/*
 * #%L
 * fujion
 * %%
 * Copyright (C) 2018 Fujion Framework
 * %%
 * Licensed 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.
 *
 * #L%
 */
package org.fujion.common;

import java.util.Collection;
import java.util.Iterator;

/**
 * Wraps a collection and delegates implementations for add and remove operations to an external
 * implementation.
 *
 * @param  The element type.
 */
public class ProxiedCollection implements Collection {

    /**
     * Mutator operations for a proxied collection.
     *
     * @param  The element type.
     */
    public interface IProxiedCollectionOperations {

        boolean add(T element, Collection delegate);

        boolean remove(Object element, Collection delegate);

        default void remove(T element, Iterator iterator) {
            throw new UnsupportedOperationException();
        }
    }

    protected final Collection delegate;

    private final IProxiedCollectionOperations operations;

    public ProxiedCollection(Collection delegate, IProxiedCollectionOperations operations) {
        this.delegate = delegate;
        this.operations = operations;
    }

    @Override
    public int size() {
        return delegate.size();
    }

    @Override
    public boolean isEmpty() {
        return delegate.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
        return delegate.contains(o);
    }

    @Override
    public Iterator iterator() {
        final Iterator iterator = delegate.iterator();

        return new Iterator() {

            private T current;

            @Override
            public boolean hasNext() {
                return iterator.hasNext();
            }

            @Override
            public T next() {
                return current = iterator.next();
            }

            @Override
            public void remove() {
                operations.remove(current, iterator);
            }
        };
    }

    @Override
    public Object[] toArray() {
        return delegate.toArray();
    }

    @Override
    public  S[] toArray(S[] a) {
        return delegate.toArray(a);
    }

    @Override
    public final boolean add(T element) {
        return operations.add(element, delegate);
    }

    @Override
    public final boolean remove(Object element) {
        return operations.remove(element, delegate);
    }

    @Override
    public final boolean containsAll(Collection c) {
        return delegate.containsAll(c);
    }

    @Override
    public final boolean addAll(Collection c) {
        boolean changed = false;

        for (T element : c) {
            changed |= add(element);
        }

        return changed;
    }

    @Override
    public final boolean removeAll(Collection c) {
        boolean changed = false;

        for (Object element : c) {
            changed |= remove(element);
        }

        return changed;
    }

    @Override
    public final boolean retainAll(Collection c) {
        boolean changed = false;
        Iterator iter = iterator();

        while (iter.hasNext()) {
            T element = iter.next();

            if (!c.contains(element)) {
                iter.remove();
                changed = true;
            }
        }

        return changed;
    }

    @Override
    public final void clear() {
        Iterator iter = iterator();

        while (iter.hasNext()) {
            iter.next();
            iter.remove();
        }
    }

}