/*
 * Copyright (C) 2007 The Guava Authors
 *
 * 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.
 */

package com.google.common.collect;

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

import javax.annotation.Nullable;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;

/**
 * A multiset which forwards all its method calls to another multiset.
 * Subclasses should override one or more methods to modify the behavior of the
 * backing multiset as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator
 * pattern</a>.
 *
 * <p>
 * <b>Warning:</b> The methods of {@code ForwardingMultiset} forward
 * <b>indiscriminately</b> to the methods of the delegate. For example,
 * overriding {@link #add(Object, int)} alone <b>will not</b> change the
 * behavior of {@link #add(Object)}, which can lead to unexpected behavior. In
 * this case, you should override {@code add(Object)} as well, either providing
 * your own implementation, or delegating to the provided {@code standardAdd}
 * method.
 *
 * <p>
 * The {@code standard} methods and any collection views they return are not
 * guaranteed to be thread-safe, even when all of the methods that they depend
 * on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0 (imported from Google Collections Library)
 */
@GwtCompatible
public abstract class ForwardingMultiset<E> extends ForwardingCollection<E> implements Multiset<E> {

	/** Constructor for use by subclasses. */
	protected ForwardingMultiset() {
	}

	@Override
	protected abstract Multiset<E> delegate();

	@Override
	public int count(Object element) {
		return delegate().count(element);
	}

	@Override
	public int add(E element, int occurrences) {
		return delegate().add(element, occurrences);
	}

	@Override
	public int remove(Object element, int occurrences) {
		return delegate().remove(element, occurrences);
	}

	@Override
	public Set<E> elementSet() {
		return delegate().elementSet();
	}

	@Override
	public Set<Entry<E>> entrySet() {
		return delegate().entrySet();
	}

	@Override
	public boolean equals(@Nullable Object object) {
		return object == this || delegate().equals(object);
	}

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

	@Override
	public int setCount(E element, int count) {
		return delegate().setCount(element, count);
	}

	@Override
	public boolean setCount(E element, int oldCount, int newCount) {
		return delegate().setCount(element, oldCount, newCount);
	}

	/**
	 * A sensible definition of {@link #contains} in terms of {@link #count}. If you
	 * override {@link #count}, you may wish to override {@link #contains} to
	 * forward to this implementation.
	 * 
	 * @since 7.0
	 */
	@Override
	protected boolean standardContains(@Nullable Object object) {
		return count(object) > 0;
	}

	/**
	 * A sensible definition of {@link #clear} in terms of the {@code iterator}
	 * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish
	 * to override {@link #clear} to forward to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	protected void standardClear() {
		Iterators.clear(entrySet().iterator());
	}

	/**
	 * A sensible, albeit inefficient, definition of {@link #count} in terms of
	 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
	 * override {@link #count} to forward to this implementation.
	 * 
	 * @since 7.0
	 */
	@Beta
	protected int standardCount(@Nullable Object object) {
		for (Entry<?> entry : this.entrySet()) {
			if (Objects.equal(entry.getElement(), object)) {
				return entry.getCount();
			}
		}
		return 0;
	}

	/**
	 * A sensible definition of {@link #add(Object)} in terms of
	 * {@link #add(Object, int)}. If you override {@link #add(Object, int)}, you may
	 * wish to override {@link #add(Object)} to forward to this implementation.
	 * 
	 * @since 7.0
	 */
	protected boolean standardAdd(E element) {
		add(element, 1);
		return true;
	}

	/**
	 * A sensible definition of {@link #addAll(Collection)} in terms of
	 * {@link #add(Object)} and {@link #add(Object, int)}. If you override either of
	 * these methods, you may wish to override {@link #addAll(Collection)} to
	 * forward to this implementation.
	 * 
	 * @since 7.0
	 */
	@Beta
	@Override
	protected boolean standardAddAll(Collection<? extends E> elementsToAdd) {
		return Multisets.addAllImpl(this, elementsToAdd);
	}

	/**
	 * A sensible definition of {@link #remove(Object)} in terms of
	 * {@link #remove(Object, int)}. If you override {@link #remove(Object, int)},
	 * you may wish to override {@link #remove(Object)} to forward to this
	 * implementation.
	 * 
	 * @since 7.0
	 */
	@Override
	protected boolean standardRemove(Object element) {
		return remove(element, 1) > 0;
	}

	/**
	 * A sensible definition of {@link #removeAll} in terms of the {@code
	 * removeAll} method of {@link #elementSet}. If you override
	 * {@link #elementSet}, you may wish to override {@link #removeAll} to forward
	 * to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	protected boolean standardRemoveAll(Collection<?> elementsToRemove) {
		return Multisets.removeAllImpl(this, elementsToRemove);
	}

	/**
	 * A sensible definition of {@link #retainAll} in terms of the {@code
	 * retainAll} method of {@link #elementSet}. If you override
	 * {@link #elementSet}, you may wish to override {@link #retainAll} to forward
	 * to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	protected boolean standardRetainAll(Collection<?> elementsToRetain) {
		return Multisets.retainAllImpl(this, elementsToRetain);
	}

	/**
	 * A sensible definition of {@link #setCount(Object, int)} in terms of
	 * {@link #count(Object)}, {@link #add(Object, int)}, and
	 * {@link #remove(Object, int)}. {@link #entrySet()}. If you override any of
	 * these methods, you may wish to override {@link #setCount(Object, int)} to
	 * forward to this implementation.
	 * 
	 * @since 7.0
	 */
	protected int standardSetCount(E element, int count) {
		return Multisets.setCountImpl(this, element, count);
	}

	/**
	 * A sensible definition of {@link #setCount(Object, int, int)} in terms of
	 * {@link #count(Object)} and {@link #setCount(Object, int)}. If you override
	 * either of these methods, you may wish to override
	 * {@link #setCount(Object, int, int)} to forward to this implementation.
	 *
	 * @since 7.0
	 */
	protected boolean standardSetCount(E element, int oldCount, int newCount) {
		return Multisets.setCountImpl(this, element, oldCount, newCount);
	}

	/**
	 * A sensible implementation of {@link Multiset#elementSet} in terms of the
	 * following methods: {@link ForwardingMultiset#clear},
	 * {@link ForwardingMultiset#contains}, {@link ForwardingMultiset#containsAll},
	 * {@link ForwardingMultiset#count}, {@link ForwardingMultiset#isEmpty}, the
	 * {@link Set#size} and {@link Set#iterator} methods of
	 * {@link ForwardingMultiset#entrySet}, and
	 * {@link ForwardingMultiset#remove(Object, int)}. In many situations, you may
	 * wish to override {@link ForwardingMultiset#elementSet} to forward to this
	 * implementation or a subclass thereof.
	 *
	 * @since 10.0
	 */
	@Beta
	protected class StandardElementSet extends Multisets.ElementSet<E> {
		/** Constructor for use by subclasses. */
		public StandardElementSet() {
		}

		@Override
		Multiset<E> multiset() {
			return ForwardingMultiset.this;
		}
	}

	/**
	 * A sensible definition of {@link #iterator} in terms of {@link #entrySet} and
	 * {@link #remove(Object)}. If you override either of these methods, you may
	 * wish to override {@link #iterator} to forward to this implementation.
	 * 
	 * @since 7.0
	 */
	protected Iterator<E> standardIterator() {
		return Multisets.iteratorImpl(this);
	}

	/**
	 * A sensible, albeit inefficient, definition of {@link #size} in terms of
	 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
	 * override {@link #size} to forward to this implementation.
	 * 
	 * @since 7.0
	 */
	protected int standardSize() {
		return Multisets.sizeImpl(this);
	}

	/**
	 * A sensible, albeit inefficient, definition of {@link #size} in terms of
	 * {@code entrySet().size()} and {@link #count}. If you override either of these
	 * methods, you may wish to override {@link #size} to forward to this
	 * implementation.
	 *
	 * @since 7.0
	 */
	protected boolean standardEquals(@Nullable Object object) {
		return Multisets.equalsImpl(this, object);
	}

	/**
	 * A sensible definition of {@link #hashCode} as {@code entrySet().hashCode()} .
	 * If you override {@link #entrySet}, you may wish to override {@link #hashCode}
	 * to forward to this implementation.
	 *
	 * @since 7.0
	 */
	protected int standardHashCode() {
		return entrySet().hashCode();
	}

	/**
	 * A sensible definition of {@link #toString} as {@code entrySet().toString()} .
	 * If you override {@link #entrySet}, you may wish to override {@link #toString}
	 * to forward to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	protected String standardToString() {
		return entrySet().toString();
	}
}
