class Emitter {
	#listeners;
	constructor() {
		this.#listeners = {};
	}

	/**
	 * Registers a callback function for the specified event.
	 *
	 * @param {string} event - The name of the event.
	 * @param {Function} callback - The callback function to be executed when the event is triggered.
	 */
	on(event, callback) {
		if (!this.#listeners[event]) {
			this.#listeners[event] = [];
		}
		this.#listeners[event].push(callback);
	}

	/**
	 * Removes an event listener callback for the specified event.
	 * If no callback is provided, removes all callbacks for the event.
	 *
	 * @param {string} event - The name of the event.
	 * @param {Function} [callback] - The callback function to be removed.
	 */
	off(event, callback = undefined) {
		if (typeof event != 'string') {
			throw new TypeError('event must be a string');
			return;
		}

		if (
			!Array.isArray(this.#listeners[event]) ||
			this.#listeners[event].length === 0
		) {
			throw new TypeError(
				`listener for \`${event}\` is not an array or empty`
			);
		}

		if (!callback) {
			this.#listeners[event] = undefined;
			return;
		}

		this.#listeners[event] = this.#listeners[event].filter(
			(listener) => listener !== callback
		);
	}

	/**
	 * Emits an event and invokes all registered listeners for that event.
	 *
	 * @param {string} event - The name of the event to emit.
	 * @param {...any} args - The arguments to pass to the event listeners.
	 */
	emit(event, ...args) {
		if (!this.#listeners[event]) {
			return;
		}

		for (const callback of this.#listeners[event]) {
			callback(this, ...args);
		}
	}
}

export default Emitter;