hazelcast-master/hazelcast/src/main/java/com/hazelcast/cp/IAtomicReference.java
/*
 * Copyright (c) 2008-2023, Hazelcast, Inc. All Rights Reserved.
 *
 * 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.hazelcast.cp;

import com.hazelcast.config.cp.CPSubsystemConfig;
import com.hazelcast.core.DistributedObject;
import com.hazelcast.core.IFunction;

import java.util.concurrent.CompletionStage;

/**
 * IAtomicReference is a redundant and highly available distributed alternative
 * to the {@link java.util.concurrent.atomic.AtomicReference}.
 * <p>
 * Asynchronous variants have been introduced in version 3.7.
 * Async methods immediately return a {@link CompletionStage} from which
 * the operation's result can be obtained either in a blocking manner or by
 * registering a callback to be executed upon completion. For example:
 * <pre>
 * CompletionStage&lt;E&gt; future = atomicRef.getAsync();
 * future.whenCompleteAsync((v, throwable) -&gt; {
 *     if (throwable == null) {
 *         // do something with the old value returned by put operation
 *     } else {
 *         // handle failure
 *     }
 * });
 * </pre>
 * <p>
 * Actions supplied for dependent completions of default non-async methods and async methods
 * without an explicit {@link java.util.concurrent.Executor} argument are performed
 * by the {@link java.util.concurrent.ForkJoinPool#commonPool()} (unless it does not
 * support a parallelism level of at least 2, in which case a new {@code Thread} is
 * created per task).
 * <p>
 * IAtomicReference is accessed via {@link CPSubsystem#getAtomicReference(String)}.
 * It works on top of the Raft consensus algorithm.
 * It offers linearizability during crash failures and network
 * partitions. It is CP with respect to the CAP principle. If a network
 * partition occurs, it remains available on at most one side of the partition.
 * <p>
 * IAtomicReference impl does not offer exactly-once / effectively-once
 * execution semantics. It goes with at-least-once execution semantics
 * by default and can cause an API call to be committed multiple times
 * in case of CP member failures. It can be tuned to offer at-most-once
 * execution semantics. Please see
 * {@link CPSubsystemConfig#setFailOnIndeterminateOperationState(boolean)}
 *
 * @param <E> the type of object referred to by this reference
 * @see IAtomicLong
 * @since 3.2
 */
public interface IAtomicReference<E> extends DistributedObject {

    /**
     * Atomically sets the value to the given updated value
     * only if the current value {@code ==} the expected value.
     *
     * @param expect the expected value
     * @param update the new value
     * @return {@code true} if successful; or {@code false} if the actual value
     * was not equal to the expected value
     */
    boolean compareAndSet(E expect, E update);

    /**
     * Gets the current value.
     *
     * @return the current value
     */
    E get();

    /**
     * Atomically sets the given value.
     *
     * @param newValue the new value
     */
    void set(E newValue);

    /**
     * Gets the old value and sets the new value.
     *
     * @param newValue the new value
     * @return the old value
     */
    E getAndSet(E newValue);

    /**
     * Checks if the stored reference is {@code null}.
     *
     * @return {@code true} if {@code null}, {@code false} otherwise
     */
    boolean isNull();

    /**
     * Clears the current stored reference.
     */
    void clear();

    /**
     * Checks if the reference contains the value.
     *
     * @param value the value to check (is allowed to be {@code null})
     * @return {@code true} if the value is found, {@code false} otherwise
     */
    boolean contains(E value);

    /**
     * Alters the currently stored reference by applying a function on it.
     *
     * @param function the function that alters the currently stored reference
     * @throws IllegalArgumentException if function is {@code null}
     */
    void alter(IFunction<E, E> function);

    /**
     * Alters the currently stored reference by applying a function on it and
     * gets the result.
     *
     * @param function the function that alters the currently stored reference
     * @return the new value, the result of the applied function
     * @throws IllegalArgumentException if function is {@code null}
     */
    E alterAndGet(IFunction<E, E> function);

    /**
     * Alters the currently stored reference by applying a function on it on
     * and gets the old value.
     *
     * @param function the function that alters the currently stored reference
     * @return the old value, the value before the function is applied
     * @throws IllegalArgumentException if function is {@code null}
     */
    E getAndAlter(IFunction<E, E> function);

    /**
     * Applies a function on the value, the actual stored value will not
     * change.
     *
     * @param function the function applied on the value, the stored value does not change
     * @param <R> the result type of the function
     * @return the result of the function application
     * @throws IllegalArgumentException if function is {@code null}
     */
    <R> R apply(IFunction<E, R> function);

    /**
     * Atomically sets the value to the given updated value only if the
     * current value {@code ==} the expected value.
     *
     * @param expect the expected value
     * @param update the new value
     * @return {@code true} if successful; or {@code false} if the actual value
     * was not equal to the expected value
     */
    CompletionStage<Boolean> compareAndSetAsync(E expect, E update);

    /**
     * Gets the current value.
     *
     * @return the current value
     */
    CompletionStage<E> getAsync();

    /**
     * Atomically sets the given value.
     *
     * @param newValue the new value
     */
    CompletionStage<Void> setAsync(E newValue);

    /**
     * Gets the value and sets the new value.
     *
     * @param newValue the new value
     * @return the old value
     */
    CompletionStage<E> getAndSetAsync(E newValue);

    /**
     * Checks if the stored reference is {@code null}.
     *
     * @return {@code true} if {@code null}, {@code false} otherwise
     */
    CompletionStage<Boolean> isNullAsync();

    /**
     * Clears the current stored reference.
     */
    CompletionStage<Void> clearAsync();

    /**
     * Checks if the reference contains the value.
     *
     * @param expected the value to check (is allowed to be null)
     * @return {@code true} if the value is found, {@code false} otherwise
     */
    CompletionStage<Boolean> containsAsync(E expected);

    /**
     * Alters the currently stored reference by applying a function on it.
     *
     * @param function the function
     * @throws IllegalArgumentException if function is {@code null}
     */
    CompletionStage<Void> alterAsync(IFunction<E, E> function);

    /**
     * Alters the currently stored reference by applying a function on it and
     * gets the result.
     *
     * @param function the function
     * @return the new value
     * @throws IllegalArgumentException if function is {@code null}
     */
    CompletionStage<E> alterAndGetAsync(IFunction<E, E> function);

    /**
     * Alters the currently stored reference by applying a function on it on
     * and gets the old value.
     *
     * @param function the function
     * @return the old value
     * @throws IllegalArgumentException if function is {@code null}
     */
    CompletionStage<E> getAndAlterAsync(IFunction<E, E> function);

    /**
     * Applies a function on the value, the actual stored value will not
     * change.
     *
     * @param function the function
     * @param <R> the result type of the function
     * @return the result of the function application
     * @throws IllegalArgumentException if function is {@code null}
     */
    <R> CompletionStage<R> applyAsync(IFunction<E, R> function);
}
