/*
 * Copyright 2015-present Open Networking Laboratory
 *
 * 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 org.onosproject.store.service;

/**
 * Transactional Set data structure.
 * <p>
 * A TransactionalSet is implemented with the help of TransactionalMap data structure.
 * All operations performed on this set within a transaction boundary are invisible externally
 * until the point when the transaction commits. A commit usually succeeds in the absence of conflicts.
 *
 * @param <E> type of element.
 */
public interface TransactionalSet<E> {

    /**
     * Adds the specified element to this set if it is not already present
     * (optional operation).  More formally, adds the specified element
     * <tt>e</tt> to this set if the set contains no element <tt>e2</tt>
     * such that
     * <tt>(e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))</tt>.
     * If this set already contains the element, the call leaves the set
     * unchanged and returns <tt>false</tt>.  In combination with the
     * restriction on constructors, this ensures that sets never contain
     * duplicate elements.
     *
     * @param e element to be added to this set
     * @return <tt>true</tt> if this set did not already contain the specified
     *         element
     */
    boolean add(E e);

    /**
     * Removes the specified element from this set if it is present
     * (optional operation).  More formally, removes an element <tt>e</tt>
     * such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>, if
     * this set contains such an element.  Returns <tt>true</tt> if this set
     * contained the element (or equivalently, if this set changed as a
     * result of the call).  (This set will not contain the element once the
     * call returns.)
     *
     * @param e element to be removed to this set
     * @return <tt>true</tt> if this set contained the specified element
     */
    boolean remove(E e);

    /**
     * Returns <tt>true</tt> if this set contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this set
     * contains an element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     *
     * @param e element whose presence in this set is to be tested
     * @return <tt>true</tt> if this set contains the specified element
     * @throws ClassCastException if the type of the specified element
     *         is incompatible with this set
     * @throws NullPointerException if the specified element is null and this
     *         set does not permit null elements
     */
    boolean contains(E e);
}