define([
	'../errors/RequestError',
	'./watch',
	'./handlers',
	'./util',
	'../has'/*=====,
	'../request',
	'../_base/declare' =====*/
], function(RequestError, watch, handlers, util, has/*=====, request, declare =====*/){
	has.add('native-xhr', function(){
		// if true, the environment has a native XHR implementation
		return typeof XMLHttpRequest !== 'undefined';
	});
	has.add('dojo-force-activex-xhr', function(){
		return has('activex') && window.location.protocol === 'file:';
	});

	has.add('native-xhr2', function(){
		if(!has('native-xhr') || has('dojo-force-activex-xhr')){ return; }
		var x = new XMLHttpRequest();
		return typeof x['addEventListener'] !== 'undefined' &&
			(typeof opera === 'undefined' || typeof x['upload'] !== 'undefined');
	});

	has.add('native-formdata', function(){
		// if true, the environment has a native FormData implementation
		return typeof FormData !== 'undefined';
	});

	has.add('native-blob', function(){
		// if true, the environment has a native Blob implementation
		return typeof Blob !== 'undefined';
	});

	has.add('native-arraybuffer', function(){
		// if true, the environment has a native ArrayBuffer implementation
		return typeof ArrayBuffer !== 'undefined';
	});

	has.add('native-response-type', function(){
		return has('native-xhr') && typeof new XMLHttpRequest().responseType !== 'undefined';
	});

	has.add('native-xhr2-blob', function(){
		if(!has('native-response-type')){ return; }
		var x = new XMLHttpRequest();
		// The URL used here does not have to be reachable as the XHR's `send` method is never called.
		// It does need to be parsable/resolvable in all cases, so it should be an absolute URL.
		// XMLHttpRequest within a Worker created from a Blob does not support relative URL paths.
		x.open('GET', 'https://dojotoolkit.org/', true);
		x.responseType = 'blob';
		// will not be set if unsupported
		var responseType = x.responseType;
		x.abort();
		return responseType === 'blob';
	});

	// Google Chrome doesn't support "json" response type
	// up to version 30, so it's intentionally not included here
	var nativeResponseTypes = {
		'blob': has('native-xhr2-blob') ? 'blob' : 'arraybuffer',
		'document': 'document',
		'arraybuffer': 'arraybuffer'
	};

	function handleResponse(response, error){
		var _xhr = response.xhr;
		response.status = response.xhr.status;

		try {
			// Firefox throws an error when trying to access
			// xhr.responseText if response isn't text
			response.text = _xhr.responseText;
		} catch (e) {}

		if(response.options.handleAs === 'xml'){
			response.data = _xhr.responseXML;
		}

		var handleError;
		if(error){
			this.reject(error);
		}else{
			try{
				handlers(response);
			}catch(e){
				handleError = e;
			}
			if(util.checkStatus(_xhr.status)){
				if(!handleError){
					this.resolve(response);
				}else{
					this.reject(handleError);
				}
			}else{
				if(!handleError){
					error = new RequestError('Unable to load ' + response.url + ' status: ' + _xhr.status, response);
					this.reject(error);
				}else{
					error = new RequestError('Unable to load ' + response.url + ' status: ' + _xhr.status +
						' and an error in handleAs: transformation of response', response);
					this.reject(error);
				}
			}
		}
	}

	var isValid, isReady, addListeners, cancel;
	if(has('native-xhr2')){
		// Any platform with XHR2 will only use the watch mechanism for timeout.

		isValid = function(response){
			// summary:
			//		Check to see if the request should be taken out of the watch queue
			return !this.isFulfilled();
		};
		cancel = function(dfd, response){
			// summary:
			//		Canceler for deferred
			response.xhr.abort();
		};
		addListeners = function(_xhr, dfd, response, uploadProgress){
			// summary:
			//		Adds event listeners to the XMLHttpRequest object
			function onLoad(evt){
				dfd.handleResponse(response);
			}
			function onError(evt){
				var _xhr = evt.target;
				var error = new RequestError('Unable to load ' + response.url + ' status: ' + _xhr.status, response);
				dfd.handleResponse(response, error);
			}

			function onProgress(transferType, evt){
				response.transferType = transferType;
				if(evt.lengthComputable){
					response.loaded = evt.loaded;
					response.total = evt.total;
					dfd.progress(response);
				} else if(response.xhr.readyState === 3){
					response.loaded = ('loaded' in evt) ? evt.loaded : evt.position;
					dfd.progress(response);
				}
			}

			function onDownloadProgress(evt) {
				return onProgress('download', evt);
			}

			function onUploadProgress(evt) {
				return onProgress('upload', evt);
			}

			_xhr.addEventListener('load', onLoad, false);
			_xhr.addEventListener('error', onError, false);
			_xhr.addEventListener('progress', onDownloadProgress, false);

			if (uploadProgress && _xhr.upload) {
				_xhr.upload.addEventListener('progress', onUploadProgress, false);
			}

			return function(){
				_xhr.removeEventListener('load', onLoad, false);
				_xhr.removeEventListener('error', onError, false);
				_xhr.removeEventListener('progress', onDownloadProgress, false);
				_xhr.upload.removeEventListener('progress', onUploadProgress, false);
				_xhr = null;
			};
		};
	}else{
		isValid = function(response){
			return response.xhr.readyState; //boolean
		};
		isReady = function(response){
			return 4 === response.xhr.readyState; //boolean
		};
		cancel = function(dfd, response){
			// summary:
			//		canceller function for util.deferred call.
			var xhr = response.xhr;
			var _at = typeof xhr.abort;
			if(_at === 'function' || _at === 'object' || _at === 'unknown'){
				xhr.abort();
			}
		};
	}

	function getHeader(headerName){
		return this.xhr.getResponseHeader(headerName);
	}

	var undefined,
		defaultOptions = {
			data: null,
			query: null,
			sync: false,
			method: 'GET'
		};
	function xhr(url, options, returnDeferred){
		var isFormData = has('native-formdata') && options && options.data && options.data instanceof FormData;
		var response = util.parseArgs(
			url,
			util.deepCreate(defaultOptions, options),
			isFormData
		);
		url = response.url;
		options = response.options;
		var hasNoData = !options.data && options.method !== 'POST' && options.method !== 'PUT';

		if(has('ie') <= 10){
			// older IE breaks point 9 in http://www.w3.org/TR/XMLHttpRequest/#the-open()-method and sends fragment, so strip it
			url = url.split('#')[0];
		}

		var remover,
			last = function(){
				remover && remover();
			};

		//Make the Deferred object for this xhr request.
		var dfd = util.deferred(
			response,
			cancel,
			isValid,
			isReady,
			handleResponse,
			last
		);
		var _xhr = response.xhr = xhr._create();

		if(!_xhr){
			// If XHR factory somehow returns nothings,
			// cancel the deferred.
			dfd.cancel(new RequestError('XHR was not created'));
			return returnDeferred ? dfd : dfd.promise;
		}

		response.getHeader = getHeader;

		if(addListeners){
			remover = addListeners(_xhr, dfd, response, options.uploadProgress);
		}

		// IE11 treats data: undefined different than other browsers
		var data = typeof(options.data) === 'undefined' ? null : options.data,
			async = !options.sync,
			method = options.method;

		try{
			// IE6 won't let you call apply() on the native function.
			_xhr.open(method, url, async, options.user || undefined, options.password || undefined);

			if(options.withCredentials){
				_xhr.withCredentials = options.withCredentials;
			}

			if(has('native-response-type') && options.handleAs in nativeResponseTypes) {
				_xhr.responseType = nativeResponseTypes[options.handleAs];
			}

			var headers = options.headers,
				contentType = (isFormData || hasNoData) ? false : 'application/x-www-form-urlencoded';
			if(headers){
				for(var hdr in headers){
					if(hdr.toLowerCase() === 'content-type'){
						contentType = headers[hdr];
					}else if(headers[hdr]){
						//Only add header if it has a value. This allows for instance, skipping
						//insertion of X-Requested-With by specifying empty value.
						_xhr.setRequestHeader(hdr, headers[hdr]);
					}
				}
			}

			if(contentType && contentType !== false){
				_xhr.setRequestHeader('Content-Type', contentType);
			}
			if(!headers || !('X-Requested-With' in headers)){
				_xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
			}

			if(util.notify){
				util.notify.emit('send', response, dfd.promise.cancel);
			}
			_xhr.send(data);
		}catch(e){
			dfd.reject(e);
		}

		watch(dfd);
		_xhr = null;

		return returnDeferred ? dfd : dfd.promise;
	}

	/*=====
	xhr = function(url, options){
		// summary:
		//		Sends a request using XMLHttpRequest with the given URL and options.
		// url: String
		//		URL to request
		// options: dojo/request/xhr.__Options?
		//		Options for the request.
		// returns: dojo/request.__Promise
	};
	xhr.__BaseOptions = declare(request.__BaseOptions, {
		// sync: Boolean?
		//		Whether to make a synchronous request or not. Default
		//		is `false` (asynchronous).
		// data: String|Object|FormData?
		//		Data to transfer. This is ignored for GET and DELETE
		//		requests.
		// headers: Object?
		//		Headers to use for the request.
		// user: String?
		//		Username to use during the request.
		// password: String?
		//		Password to use during the request.
		// withCredentials: Boolean?
		//		For cross-site requests, whether to send credentials
		//		or not.
		// uploadProgress: Boolean?
		//		Upload progress events cause preflighted requests. This
		//		option enables upload progress event support but also
		//		causes all requests to be preflighted.
	});
	xhr.__MethodOptions = declare(null, {
		// method: String?
		//		The HTTP method to use to make the request. Must be
		//		uppercase. Default is `"GET"`.
	});
	xhr.__Options = declare([xhr.__BaseOptions, xhr.__MethodOptions]);

	xhr.get = function(url, options){
		// summary:
		//		Send an HTTP GET request using XMLHttpRequest with the given URL and options.
		// url: String
		//		URL to request
		// options: dojo/request/xhr.__BaseOptions?
		//		Options for the request.
		// returns: dojo/request.__Promise
	};
	xhr.post = function(url, options){
		// summary:
		//		Send an HTTP POST request using XMLHttpRequest with the given URL and options.
		// url: String
		//		URL to request
		// options: dojo/request/xhr.__BaseOptions?
		//		Options for the request.
		// returns: dojo/request.__Promise
	};
	xhr.put = function(url, options){
		// summary:
		//		Send an HTTP PUT request using XMLHttpRequest with the given URL and options.
		// url: String
		//		URL to request
		// options: dojo/request/xhr.__BaseOptions?
		//		Options for the request.
		// returns: dojo/request.__Promise
	};
	xhr.del = function(url, options){
		// summary:
		//		Send an HTTP DELETE request using XMLHttpRequest with the given URL and options.
		// url: String
		//		URL to request
		// options: dojo/request/xhr.__BaseOptions?
		//		Options for the request.
		// returns: dojo/request.__Promise
	};
	=====*/
	xhr._create = function(){
		// summary:
		//		does the work of portably generating a new XMLHTTPRequest object.
		throw new Error('XMLHTTP not available');
	};
	if(has('native-xhr') && !has('dojo-force-activex-xhr')){
		xhr._create = function(){
			return new XMLHttpRequest();
		};
	}else if(has('activex')){
		try{
			new ActiveXObject('Msxml2.XMLHTTP');
			xhr._create = function(){
				return new ActiveXObject('Msxml2.XMLHTTP');
			};
		}catch(e){
			try{
				new ActiveXObject('Microsoft.XMLHTTP');
				xhr._create = function(){
					return new ActiveXObject('Microsoft.XMLHTTP');
				};
			}catch(e){}
		}
	}

	util.addCommonMethods(xhr);

	return xhr;
});