/*
 * ============LICENSE_START=======================================================
 * policy-core
 * ================================================================================
 * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
 * Modifications Copyright (C) 2023 Nordix Foundation.
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 */

package org.onap.policy.common.capabilities;

/**
 * Interface for classes that supports start-like operations.
 */
public interface Startable {

    /**
     * Start operation. This operation starts the entity.
     * 
     * @return boolean. true if the start operation was successful, otherwise false.
     * @throws IllegalStateException if the element is in a state that conflicts with the start
     *         operation.
     */
    boolean start();

    /**
     * Stop operation. The entity can be restarted again by invoking the start operation.
     * 
     * @return boolean. true if the stop operation was successful, otherwise false.
     * @throws IllegalStateException if the element is in a state that conflicts with the stop
     *         operation.
     */
    boolean stop();

    /**
     * shutdown operation. The terminate operation yields the entity unusuable. It cannot be
     * (re)started.
     * 
     * @throws IllegalStateException if the element is in a state that conflicts with the stop
     *         operation.
     */
    void shutdown();

    /**
     * Checks if the entity is alive.
     * 
     * @return boolean. true if alive, otherwise false
     */
    boolean isAlive();
}