define(function(require,exports,module){

    var Events=function(){

        var array = [];

        var push = array.push;

        var slice = array.slice;

        var splice = array.splice;

        var Events  = {

            // Bind an event to a `callback` function. Passing `"all"` will bind

            // the callback to all events fired.

            on: function(name, callback, context) {

                if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this;

                this._events || (this._events = {});

                var events = this._events[name] || (this._events[name] = []);

                events.push({callback: callback, context: context, ctx: context || this});

                return this;

            },

            // Bind an event to only be triggered a single time. After the first time

            // the callback is invoked, it will be removed.

            once: function(name, callback, context) {

                if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this;

                var self = this;

                var once = _.once(function() {

                    self.off(name, once);

                    callback.apply(this, arguments);

                });

                once._callback = callback;

                return this.on(name, once, context);

            },

            // Remove one or many callbacks. If `context` is null, removes all

            // callbacks with that function. If `callback` is null, removes all

            // callbacks for the event. If `name` is null, removes all bound

            // callbacks for all events.

            off: function(name, callback, context) {

                var retain, ev, events, names, i, l, j, k;

                if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this;

                if (!name && !callback && !context) {

                    this._events = {};

                    return this;

                }

                names = name ? [name] : _.keys(this._events);

                for (i = 0, l = names.length; i < l; i++) {

                    name = names[i];

                    if (events = this._events[name]) {

                        this._events[name] = retain = [];

                        if (callback || context) {

                            for (j = 0, k = events.length; j < k; j++) {

                                ev = events[j];

                                if ((callback && callback !== ev.callback && callback !== ev.callback._callback) ||

                                    (context && context !== ev.context)) {

                                    retain.push(ev);

                                }

                            }

                        }

                        if (!retain.length) delete this._events[name];

                    }

                }

                return this;

            },

            // Trigger one or many events, firing all bound callbacks. Callbacks are

            // passed the same arguments as `trigger` is, apart from the event name

            // (unless you're listening on `"all"`, which will cause your callback to

            // receive the true name of the event as the first argument).

            trigger: function(name) {

                if (!this._events) return this;

                var args = slice.call(arguments, 1);

                if (!eventsApi(this, 'trigger', name, args)) return this;

                var events = this._events[name];

                var allEvents = this._events.all;

                if (events) triggerEvents(events, args);

                if (allEvents) triggerEvents(allEvents, arguments);

                return this;

            },

            // Tell this object to stop listening to either specific events ... or

            // to every object it's currently listening to.

            stopListening: function(obj, name, callback) {

                var listeners = this._listeners;

                if (!listeners) return this;

                var deleteListener = !name && !callback;

                if (typeof name === 'object') callback = this;

                if (obj) (listeners = {})[obj._listenerId] = obj;

                for (var id in listeners) {

                    listeners[id].off(name, callback, this);

                    if (deleteListener) delete this._listeners[id];

                }

                return this;

            }

        };

        // Regular expression used to split event strings.

        var eventSplitter = /\s+/;

        // Implement fancy features of the Events API such as multiple event

        // names `"change blur"` and jQuery-style event maps `{change: action}`

        // in terms of the existing API.

        var eventsApi = function(obj, action, name, rest) {

            if (!name) return true;

            // Handle event maps.

            if (typeof name === 'object') {

                for (var key in name) {

                    obj[action].apply(obj, [key, name[key]].concat(rest));

                }

                return false;

            }

            // Handle space separated event names.

            if (eventSplitter.test(name)) {

                var names = name.split(eventSplitter);

                for (var i = 0, l = names.length; i < l; i++) {

                    obj[action].apply(obj, [names[i]].concat(rest));

                }

                return false;

            }

            return true;

        };

        // A difficult-to-believe, but optimized internal dispatch function for

        // triggering events. Tries to keep the usual cases speedy (most internal

        // Backbone events have 3 arguments).

        var triggerEvents = function(events, args) {

            var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];

            switch (args.length) {

                case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;

                case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;

                case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;

                case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;

                default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args);

            }

        };

        // Aliases for backwards compatibility.

        Events.bind   = Events.on;

        Events.unbind = Events.off;

        return Events;

    }()

module.exports=Events

})