class EventEmitter
{

    //--------------------------
    // constructor
    //--------------------------
    constructor()
    {
        this.listeners = new Map();
    }
    //--------------------------
    // methods
    //--------------------------
    addListener(label, callback) {
        this.listeners.has(label) || this.listeners.set(label, []);
        this.listeners.get(label).push(callback);
    }

    removeListener(label, callback) {
        var isFunction = function(obj) {
            return typeof obj == 'function' || false;
        };

        var listeners = this.listeners.get(label),
            index;

        if (listeners && listeners.length) {
            index = listeners.reduce((i, listener, index) => {
                return (isFunction(listener) && listener === callback)
                    ? i = index
                    : i;
            }, -1);

            if (index > -1) {
                listeners.splice(index, 1);
                this.listeners.set(label, listeners);
                return true;
            }
        }
        return false;
    }

    emitEvent(label, ...args) {
        var listeners = this.listeners.get(label);
        if (listeners && listeners.length) {
            listeners.forEach((listener) => {
                listener(...args);
            });
            return true;
        }
        return false;
    }
    //--------------------------
    // event handlers
    //--------------------------
}
export default EventEmitter