import { IListenerMap } from "./listener-map";

/**
 * Basic event emitter implementation.
 *
 * @export
 * @class EventEmitter
 */
export class EventEmitter {
    private listeners: IListenerMap = {};

    /**
     * Adds a new event listener.
     *
     * @param {string} event Event type.
     * @param {(data?: any) => void} listener Event listener.
     * @memberof EventEmitter
     */
    public on(event: string, listener: (data?: any) => void) {
        let bucket = this.listeners[event];

        if (bucket == null) {
            this.listeners[event] = bucket = [];
        }

        bucket.push(listener);
    }

    /**
     * Triggers all listeners by event type.
     *
     * @param {string} event Event type.
     * @param {*} [data] Event data.
     * @memberof EventEmitter
     */
    public trigger(event: string, data?: any) {
        const bucket = this.listeners[event];

        if (bucket != null) {
            for (const listener of bucket) {
                listener(data);
            }
        }
    }

    /**
     * Clears all listeners.
     *
     * @memberof EventEmitter
     */
    public off() {
        this.listeners = {};
    }
}