function E() {
  // Keep this empty so it's easier to inherit from
  // (via https://github.com/lipsmack from https://github.com/scottcorgan/tiny-emitter/issues/3)
}

E.prototype = {
  on (name, callback, ctx) {
    let e = this.e || (this.e = {});

    (e[name] || (e[name] = [])).push({
      fn: callback,
      ctx,
    });

    return this;
  },

  once (name, callback, ctx) {
    let self = this;
    function listener() {
      self.off(name, listener);
      callback.apply(ctx, arguments);
    }

    listener._ = callback;
    return this.on(name, listener, ctx);
  },

  emit (name) {
    let data = [].slice.call(arguments, 1);
    let evtArr = ((this.e || (this.e = {}))[name] || []).slice();
    let i = 0;
    let len = evtArr.length;

    for (i; i < len; i++) {
      evtArr[i].fn.apply(evtArr[i].ctx, data);
    }

    return this;
  },

  off (name, callback) {
    let e = this.e || (this.e = {});
    let evts = e[name];
    let liveEvents = [];

    if (evts && callback) {
      for (let i = 0, len = evts.length; i < len; i++) {
        if (evts[i].fn !== callback && evts[i].fn._ !== callback) liveEvents.push(evts[i]);
      }
    }

    // Remove event from queue to prevent memory leak
    // Suggested by https://github.com/lazd
    // Ref: https://github.com/scottcorgan/tiny-emitter/commit/c6ebfaa9bc973b33d110a84a307742b7cf94c953#commitcomment-5024910

    liveEvents.length ? (e[name] = liveEvents) : delete e[name];

    return this;
  },
};

export default E;