"use strict";

/**
 * Base class to implement an event system in any class. Events can be dispatched and
 * subscribed/unsubscribed. Events can have multiple registered callbacks.
 */
class EventDispatcher {
    constructor() {
        this._events = {};
    }

    /**
     * Dispatch a named event. Calls all callbacks that are subscribed to this event.
     */
    dispatch(eventName, data = null) {
        if (this._events[eventName]) {
            this._events[eventName].forEach((callback) => {
                callback(data);
            });
        }
    }

    /**
     * Subscribe to an event.
     */
    on(eventName, callback) {
        if (!this._events[eventName]) {
            this._events[eventName] = [];
        }
        this._events[eventName].push(callback);
    }

    /**
     * Unsubscribe from an event. Not sure how to unsubscribe anonymous functions though.
     * If callback is not found, nothing happens.
     */
    off(eventName, callback) {
        if (this._events[eventName]) {
            this._events[eventName] = this._events[eventName].filter(item => item !== callback);
        }
    }
}