'use strict';

var has = Object.prototype.hasOwnProperty;

/**
 * An auto incrementing id which we can use to create "unique" Ultron instances
 * so we can track the event emitters that are added through the Ultron
 * interface.
 *
 * @type {Number}
 * @private
 */
var id = 0;

/**
 * Ultron is high-intelligence robot. It gathers intelligence so it can start improving
 * upon his rudimentary design. It will learn from your EventEmitting patterns
 * and exterminate them.
 *
 * @constructor
 * @param {EventEmitter} ee EventEmitter instance we need to wrap.
 * @api public
 */
function Ultron(ee) {
  if (!(this instanceof Ultron)) return new Ultron(ee);

  this.id = id++;
  this.ee = ee;
}

/**
 * Register a new EventListener for the given event.
 *
 * @param {String} event Name of the event.
 * @param {Functon} fn Callback function.
 * @param {Mixed} context The context of the function.
 * @returns {Ultron}
 * @api public
 */
Ultron.prototype.on = function on(event, fn, context) {
  fn.__ultron = this.id;
  this.ee.on(event, fn, context);

  return this;
};
/**
 * Add an EventListener that's only called once.
 *
 * @param {String} event Name of the event.
 * @param {Function} fn Callback function.
 * @param {Mixed} context The context of the function.
 * @returns {Ultron}
 * @api public
 */
Ultron.prototype.once = function once(event, fn, context) {
  fn.__ultron = this.id;
  this.ee.once(event, fn, context);

  return this;
};

/**
 * Remove the listeners we assigned for the given event.
 *
 * @returns {Ultron}
 * @api public
 */
Ultron.prototype.remove = function remove() {
  var args = arguments
    , ee = this.ee
    , event;

  //
  // When no event names are provided we assume that we need to clear all the
  // events that were assigned through us.
  //
  if (args.length === 1 && 'string' === typeof args[0]) {
    args = args[0].split(/[, ]+/);
  } else if (!args.length) {
    if (ee.eventNames) {
      args = ee.eventNames();
    } else if (ee._events) {
      args = [];

      for (event in ee._events) {
        if (has.call(ee._events, event)) args.push(event);
      }

      if (Object.getOwnPropertySymbols) {
        args = args.concat(Object.getOwnPropertySymbols(ee._events));
      }
    }
  }

  for (var i = 0; i < args.length; i++) {
    var listeners = ee.listeners(args[i]);

    for (var j = 0; j < listeners.length; j++) {
      event = listeners[j];

      //
      // Once listeners have a `listener` property that stores the real listener
      // in the EventEmitter that ships with Node.js.
      //
      if (event.listener) {
        if (event.listener.__ultron !== this.id) continue;
      } else if (event.__ultron !== this.id) {
        continue;
      }

      ee.removeListener(args[i], event);
    }
  }

  return this;
};

/**
 * Destroy the Ultron instance, remove all listeners and release all references.
 *
 * @returns {Boolean}
 * @api public
 */
Ultron.prototype.destroy = function destroy() {
  if (!this.ee) return false;

  this.remove();
  this.ee = null;

  return true;
};

//
// Expose the module.
//
module.exports = Ultron;