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/*
 * The MIT License
 *
 * Copyright 2016 Jong Soft.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.jongsoft;

public interface Startable {

    /**
     * The status enum provides information into the current state of a {@link Startable} instance.
     */
    public static enum Status {
        IDLE,           // The instance is not running at the moment
        STARTING,       // The instance is starting and not yet ready
        RUNNING,        // The instance is ready for further instructions
        RESTARTING,     // The instance is performing a restart and not yet ready
        KILLED,         // An underlying resource has been killed, the instance needs to be restarted
        FAILED,         // The startup has failed
        STOPPING        // The instance is performing a shutdown operation
    }

    /**
     * Start the entity, this should allocate any needed resources and will allow the instance to accept further instructions
     * when completed.
     *
     * @return true if the start command succeeded
     */
    boolean start();

    /**
     * Stop the instance. This call will release any allocated resources and result into a {@link #getStatus()} call returning
     * {@link Status#IDLE}.
     */
    void stop();

    /**
     * Get the current state of the instance.
     *
     * @return the status of the instance
     * @see Status
     */
    Status getStatus();

    /**
     * Attempt to perform a restart if the status is FAILED, RUNNING or RESTARTING.
     *
     * @return true if the restart succeeded, false the instance is in incorrect state or restart failed.
     */
    default boolean restart() {
        if (getStatus() == Status.FAILED || getStatus() == Status.RUNNING || getStatus() == Status.RESTARTING) {
            stop();
            return start();
        }
        return false;
    }

}