/*
 * 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.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.SortedSet;

import javax.annotation.Nullable;

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

/**
 * A sorted set which forwards all its method calls to another sorted set.
 * Subclasses should override one or more methods to modify the behavior of the
 * backing sorted set as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator
 * pattern</a>.
 *
 * <p>
 * <i>Warning:</i> The methods of {@code ForwardingSortedSet} forward
 * <i>indiscriminately</i> to the methods of the delegate. For example,
 * overriding {@link #add} alone <i>will not</i> change the behavior of
 * {@link #addAll}, which can lead to unexpected behavior. In this case, you
 * should override {@code addAll} as well, either providing your own
 * implementation, or delegating to the provided {@code standardAddAll} method.
 *
 * <p>
 * Each of the {@code standard} methods, where appropriate, uses the set's
 * comparator (or the natural ordering of the elements, if there is no
 * comparator) to test element equality. As a result, if the comparator is not
 * consistent with equals, some of the standard implementations may violate the
 * {@code Set} contract.
 *
 * <p>
 * The {@code standard} methods and the 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 Mike Bostock
 * @author Louis Wasserman
 * @since 2.0 (imported from Google Collections Library)
 */
@GwtCompatible
public abstract class ForwardingSortedSet<E> extends ForwardingSet<E> implements SortedSet<E> {

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

	@Override
	public Comparator<? super E> comparator() {
		return delegate().comparator();
	}

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

	@Override
	public E first() {
		return delegate().first();
	}

	@Override
	public SortedSet<E> headSet(E toElement) {
		return delegate().headSet(toElement);
	}

	@Override
	public E last() {
		return delegate().last();
	}

	/**
	 * A sensible definition of {@link #contains} in terms of the {@code first()}
	 * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish to
	 * override {@link #contains} to forward to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	@Beta
	protected boolean standardContains(@Nullable Object object) {
		try {
			// any ClassCastExceptions are caught
			@SuppressWarnings("unchecked")
			SortedSet<Object> self = (SortedSet<Object>) this;
			Object ceiling = self.tailSet(object).first();
			return unsafeCompare(ceiling, object) == 0;
		} catch (ClassCastException e) {
			return false;
		} catch (NoSuchElementException e) {
			return false;
		} catch (NullPointerException e) {
			return false;
		}
	}

	/**
	 * A sensible definition of {@link #remove} in terms of the {@code iterator()}
	 * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish to
	 * override {@link #remove} to forward to this implementation.
	 *
	 * @since 7.0
	 */
	@Override
	@Beta
	protected boolean standardRemove(@Nullable Object object) {
		try {
			// any ClassCastExceptions are caught
			@SuppressWarnings("unchecked")
			SortedSet<Object> self = (SortedSet<Object>) this;
			Iterator<Object> iterator = self.tailSet(object).iterator();
			if (iterator.hasNext()) {
				Object ceiling = iterator.next();
				if (unsafeCompare(ceiling, object) == 0) {
					iterator.remove();
					return true;
				}
			}
		} catch (ClassCastException e) {
			return false;
		} catch (NullPointerException e) {
			return false;
		}
		return false;
	}

	/**
	 * A sensible default implementation of {@link #subSet(Object, Object)} in terms
	 * of {@link #headSet(Object)} and {@link #tailSet(Object)}. In some situations,
	 * you may wish to override {@link #subSet(Object, Object)} to forward to this
	 * implementation.
	 *
	 * @since 7.0
	 */
	@Beta
	protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
		return tailSet(fromElement).headSet(toElement);
	}

	@Override
	public SortedSet<E> subSet(E fromElement, E toElement) {
		return delegate().subSet(fromElement, toElement);
	}

	@Override
	public SortedSet<E> tailSet(E fromElement) {
		return delegate().tailSet(fromElement);
	}

	// unsafe, but worst case is a CCE is thrown, which callers will be expecting
	@SuppressWarnings("unchecked")
	private int unsafeCompare(Object o1, Object o2) {
		Comparator<? super E> comparator = comparator();
		return (comparator == null) ? ((Comparable<Object>) o1).compareTo(o2)
				: ((Comparator<Object>) comparator).compare(o1, o2);
	}
}
