ch.openchvote.framework.services.MessagingService Maven / Gradle / Ivy

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/*
 * Copyright (C) 2024 Berner Fachhochschule https://e-voting.bfh.ch
 *
 *  - This program is free software: you can redistribute it and/or modify                           -
 *  - it under the terms of the GNU Affero General Public License as published by                    -
 *  - the Free Software Foundation, either version 3 of the License, or                              -
 *  - (at your option) any later version.                                                            -
 *  -                                                                                                -
 *  - This program is distributed in the hope that it will be useful,                                -
 *  - but WITHOUT ANY WARRANTY; without even the implied warranty of                                 -
 *  - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                                   -
 *  - GNU General Public License for more details.                                                   -
 *  -                                                                                                -
 *  - You should have received a copy of the GNU Affero General Public License                       -
 *  - along with this program. If not, see .                           -
 */
package ch.openchvote.framework.services;

import ch.openchvote.framework.communication.Message;

/**
 * A messaging service can be used by the parties participating in a protocol to exchange signed messages with other
 * protocol participants. The interface provides methods for subscribing a party to the messaging service, unsubscribing
 * a party from the messaging service, and for sending a signed {@link Message} from one subscribed party to another
 * subscribed party. Upon receiving a signed message, the receiver's method
 * {@link MessagingService.Subscriber#onMessage(Message)} is called.
 */
public interface MessagingService {

    /**
     * This sub-interface defines the sender's part of the messaging service needed for sending messages.
     */
    interface Source extends Service {

        /**
         * Sends the given signed message to the intended receiver.
         *
         * @param message The given signed message
         */
        void send(Message message);

    }

    /**
     * This sub-interface defines the subscriber's part of the messaging service. It provides methods for subscribing
     * and unsubscribing.
     */
    interface Target extends Service {

        /**
         * Subscribes the given subscriber to the messaging service. Nothing happens if the subscriber is already
         * subscribed.
         *
         * @param subscriber The given subscriber
         */
        void subscribe(MessagingService.Subscriber subscriber);

        /**
         * Unsubscribes the given subscriber from the messaging service. Nothing happens if currently the subscriber is
         * not subscribed to the messaging service.
         *
         * @param subscriber The given subscriber
         */
        void unsubscribe(MessagingService.Subscriber subscriber);

    }

    /**
     * This sub-interface defines the method that a messaging service subscriber must provide for receiving signed
     * messages.
     */
    interface Subscriber extends Service.Subscriber {

        /**
         * This method is called upon receiving an incoming signed message.
         *
         * @param message The received signed message
         */
        void onMessage(Message message);

    }

}