source: Dev/trunk/src/client/dojo/request/notify.js

define(['../Evented', '../_base/lang', './util'], function(Evented, lang, util){
        // module:
        //              dojo/request/notify
        // summary:
        //              Global notification API for dojo/request. Notifications will
        //              only be emitted if this module is required.
        //
        //              | require('dojo/request', 'dojo/request/notify',
        //              |     function(request, notify){
        //              |         notify('load', function(response){
        //              |             if(response.url === 'someUrl.html'){
        //              |                 console.log('Loaded!');
        //              |             }
        //              |         });
        //              |         request.get('someUrl.html');
        //              |     }
        //              | );

        var pubCount = 0,
                slice = [].slice;

        var hub = lang.mixin(new Evented, {
                onsend: function(data){
                        if(!pubCount){
                                this.emit('start');
                        }
                        pubCount++;
                },
                _onload: function(data){
                        this.emit('done', data);
                },
                _onerror: function(data){
                        this.emit('done', data);
                },
                _ondone: function(data){
                        if(--pubCount <= 0){
                                pubCount = 0;
                                this.emit('stop');
                        }
                },
                emit: function(type, event){
                        var result = Evented.prototype.emit.apply(this, arguments);

                        // After all event handlers have run, run _on* handler
                        if(this['_on' + type]){
                                this['_on' + type].apply(this, slice.call(arguments, 1));
                        }
                        return result;
                }
        });

        function notify(type, listener){
                // summary:
                //              Register a listener to be notified when an event
                //              in dojo/request happens.
                // type: String?
                //              The event to listen for. Events emitted: "start", "send",
                //              "load", "error", "done", "stop".
                // listener: Function?
                //              A callback to be run when an event happens.
                // returns:
                //              A signal object that can be used to cancel the listener.
                //              If remove() is called on this signal object, it will
                //              stop the listener from being executed.
                return hub.on(type, listener);
        }
        notify.emit = function(type, event, cancel){
                return hub.emit(type, event, cancel);
        };

        // Attach notify to dojo/request/util to avoid
        // try{ require('./notify'); }catch(e){}
        return util.notify = notify;
});