/* SPDX-License-Identifier: MIT */

package com.cecilia.event;

import java.util.function.Consumer;

public interface EventBus {

    /**
     * Subscribe to an event type.
     *
     * @param eventType  the event type, can be a super class of all events to subscribe.
     * @param subscriber the subscriber which will consume the events.
     * @param <T>        the event type class.
     */
    <T extends Event> void subscribe(Class<? extends T> eventType, Consumer<T> subscriber);

    /**
     * Unsubscribe from all event types.
     *
     * @param subscriber the subscriber to unsubscribe.
     */
    <T extends Event> void unsubscribe(Consumer<T> subscriber);

    /**
     * Unsubscribe from an event type.
     *
     * @param eventType  the event type, can be a super class of all events to unsubscribe.
     * @param subscriber the subscriber to unsubscribe.
     * @param <T>        the event type class.
     */
    <T extends Event> void unsubscribe(Class<? extends T> eventType, Consumer<T> subscriber);

    /**
     * Publish an event to all subscribers.
     *
     * <p>The event type is the class of <code>event</code>. The event is published to all consumers which subscribed to
     * this event type or any super class.
     *
     * @param event the event.
     */
    <T extends Event> void publish(T event);

}