vincent4vx / SingleInstance

 * This file is part of SingleInstance.

 *

 * SingleInstance is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * SingleInstance 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 Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with SingleInstance.  If not, see <https://www.gnu.org/licenses/>.

 *

 * Copyright (c) 2020 Vincent Quatrevieux

 */

package fr.quatrevieux.singleinstance.ipc.consumer;

import fr.quatrevieux.singleinstance.ipc.Message;

import java.util.HashMap;

import java.util.Map;

import java.util.function.Consumer;

import java.util.function.Function;

/**

 * {@link fr.quatrevieux.singleinstance.ipc.InstanceServer} consumer implementation

 * allowing transformation of the received message, based on the message name.

 *

 * Usage:

 * <pre>{@code

 * // Create the consumer

 * MessageTransformerConsumer consumer = new MessageTransformerConsumer(message -> {

 *     // Switch on the message type

 *     if (message instanceof Foo) {

 *         // ...

 *     } else if (message instanceof Bar) {

 *         // ...

 *     } else {

 *         System.out.println("Unsupported message");

 *     }

 * });

 *

 * // Register transformers

 * consumer.register("Foo", message -> new Foo(message.data()));

 * consumer.register("Bar", message -> new Bar(message.data()));

 *

 * // Start consume messages

 * SingleInstance.onMessage(consumer);

 * }</pre>

 *

 * @see fr.quatrevieux.singleinstance.ipc.InstanceServer#consume(Consumer)

 */

final public class MessageTransformerConsumer implements Consumer<Message> {

    final private Consumer<Message> next;

    final private Map<String, Function<Message, Message>> transformers = new HashMap<>();

    public MessageTransformerConsumer(Consumer<Message> next) {

        this.next = next;

    }

    /**

     * Register a new message transformer

     *

     * Usage:

     * <pre>{@code

     * MessageTransformerConsumer consumer = xxx;

     *

     * consumer

     *     .register("Foo", message -> new Foo(message.data()))

     *     .register("Bar", message -> new Bar(message.data()))

     * ;

     * }</pre>

     *

     * @param messageName The message name {@link Message#name()}

     * @param transformer The transformer function. If the transformer returns null, the message will be ignored.

     *

     * @return this instance

     */

    public MessageTransformerConsumer register(String messageName, Function<Message, Message> transformer) {

        transformers.put(messageName, transformer);

        return this;

    }

    }

}