define([
	"dojo/aspect",
	"dojo/_base/declare", // declare
	"dojo/dom", // domAttr.get dom.isDescendant
	"dojo/dom-attr", // domAttr.get dom.isDescendant
	"dojo/dom-construct", // connect to domConstruct.empty, domConstruct.destroy
	"dojo/Evented",
	"dojo/_base/lang", // lang.hitch
	"dojo/on",
	"dojo/ready",
	"dojo/sniff", // has("ie")
	"dojo/Stateful",
	"dojo/_base/unload", // unload.addOnWindowUnload
	"dojo/_base/window", // win.body
	"dojo/window", // winUtils.get
	"./a11y",	// a11y.isTabNavigable
	"./registry",	// registry.byId
	"./main"		// to set dijit.focus
], function(aspect, declare, dom, domAttr, domConstruct, Evented, lang, on, ready, has, Stateful, unload, win, winUtils,
			a11y, registry, dijit){

	// module:
	//		dijit/focus

	var FocusManager = declare([Stateful, Evented], {
		// summary:
		//		Tracks the currently focused node, and which widgets are currently "active".
		//		Access via require(["dijit/focus"], function(focus){ ... }).
		//
		//		A widget is considered active if it or a descendant widget has focus,
		//		or if a non-focusable node of this widget or a descendant was recently clicked.
		//
		//		Call focus.watch("curNode", callback) to track the current focused DOMNode,
		//		or focus.watch("activeStack", callback) to track the currently focused stack of widgets.
		//
		//		Call focus.on("widget-blur", func) or focus.on("widget-focus", ...) to monitor when
		//		when widgets become active/inactive
		//
		//		Finally, focus(node) will focus a node, suppressing errors if the node doesn't exist.

		// curNode: DomNode
		//		Currently focused item on screen
		curNode: null,

		// activeStack: dijit/_WidgetBase[]
		//		List of currently active widgets (focused widget and it's ancestors)
		activeStack: [],

		constructor: function(){
			// Don't leave curNode/prevNode pointing to bogus elements
			var check = lang.hitch(this, function(node){
				if(dom.isDescendant(this.curNode, node)){
					this.set("curNode", null);
				}
				if(dom.isDescendant(this.prevNode, node)){
					this.set("prevNode", null);
				}
			});
			aspect.before(domConstruct, "empty", check);
			aspect.before(domConstruct, "destroy", check);
		},

		registerIframe: function(/*DomNode*/ iframe){
			// summary:
			//		Registers listeners on the specified iframe so that any click
			//		or focus event on that iframe (or anything in it) is reported
			//		as a focus/click event on the `<iframe>` itself.
			// description:
			//		Currently only used by editor.
			// returns:
			//		Handle with remove() method to deregister.
			return this.registerWin(iframe.contentWindow, iframe);
		},

		registerWin: function(/*Window?*/targetWindow, /*DomNode?*/ effectiveNode){
			// summary:
			//		Registers listeners on the specified window (either the main
			//		window or an iframe's window) to detect when the user has clicked somewhere
			//		or focused somewhere.
			// description:
			//		Users should call registerIframe() instead of this method.
			// targetWindow:
			//		If specified this is the window associated with the iframe,
			//		i.e. iframe.contentWindow.
			// effectiveNode:
			//		If specified, report any focus events inside targetWindow as
			//		an event on effectiveNode, rather than on evt.target.
			// returns:
			//		Handle with remove() method to deregister.

			// TODO: make this function private in 2.0; Editor/users should call registerIframe(),

			var _this = this;
			var mousedownListener = function(evt){
				_this._justMouseDowned = true;
				setTimeout(function(){ _this._justMouseDowned = false; }, 0);

				// workaround weird IE bug where the click is on an orphaned node
				// (first time clicking a Select/DropDownButton inside a TooltipDialog)
				if(has("ie") && evt && evt.srcElement && evt.srcElement.parentNode == null){
					return;
				}

				_this._onTouchNode(effectiveNode || evt.target || evt.srcElement, "mouse");
			};

			// Listen for blur and focus events on targetWindow's document.
			// Using attachEvent()/addEventListener() rather than on() to try to catch mouseDown events even
			// if other code calls evt.stopPropagation().  But rethink for 2.0 since that doesn't work for attachEvent(),
			// which watches events at the bubbling phase rather than capturing phase, like addEventListener(..., false).
			// Connect to <html> (rather than document) on IE to avoid memory leaks, but document on other browsers because
			// (at least for FF) the focus event doesn't fire on <html> or <body>.
			var doc = has("ie") ? targetWindow.document.documentElement : targetWindow.document;
			if(doc){
				if(has("ie")){
					targetWindow.document.body.attachEvent('onmousedown', mousedownListener);
					var focusinListener = function(evt){
						// IE reports that nodes like <body> have gotten focus, even though they have tabIndex=-1,
						// ignore those events
						var tag = evt.srcElement.tagName.toLowerCase();
						if(tag == "#document" || tag == "body"){ return; }

						// Previous code called _onTouchNode() for any activate event on a non-focusable node.   Can
						// probably just ignore such an event as it will be handled by onmousedown handler above, but
						// leaving the code for now.
						if(a11y.isTabNavigable(evt.srcElement)){
							_this._onFocusNode(effectiveNode || evt.srcElement);
						}else{
							_this._onTouchNode(effectiveNode || evt.srcElement);
						}
					};
					doc.attachEvent('onfocusin', focusinListener);
					var focusoutListener =  function(evt){
						_this._onBlurNode(effectiveNode || evt.srcElement);
					};
					doc.attachEvent('onfocusout', focusoutListener);

					return {
						remove: function(){
							targetWindow.document.detachEvent('onmousedown', mousedownListener);
							doc.detachEvent('onfocusin', focusinListener);
							doc.detachEvent('onfocusout', focusoutListener);
							doc = null;	// prevent memory leak (apparent circular reference via closure)
						}
					};
				}else{
					doc.body.addEventListener('mousedown', mousedownListener, true);
					doc.body.addEventListener('touchstart', mousedownListener, true);
					var focusListener = function(evt){
						_this._onFocusNode(effectiveNode || evt.target);
					};
					doc.addEventListener('focus', focusListener, true);
					var blurListener = function(evt){
						_this._onBlurNode(effectiveNode || evt.target);
					};
					doc.addEventListener('blur', blurListener, true);

					return {
						remove: function(){
							doc.body.removeEventListener('mousedown', mousedownListener, true);
							doc.body.removeEventListener('touchstart', mousedownListener, true);
							doc.removeEventListener('focus', focusListener, true);
							doc.removeEventListener('blur', blurListener, true);
							doc = null;	// prevent memory leak (apparent circular reference via closure)
						}
					};
				}
			}
		},

		_onBlurNode: function(/*DomNode*/ node){
			// summary:
			//		Called when focus leaves a node.
			//		Usually ignored, _unless_ it *isn't* followed by touching another node,
			//		which indicates that we tabbed off the last field on the page,
			//		in which case every widget is marked inactive

			// If the blur event isn't followed by a focus event, it means the user clicked on something unfocusable,
			// so clear focus.
			if(this._clearFocusTimer){
				clearTimeout(this._clearFocusTimer);
			}
			this._clearFocusTimer = setTimeout(lang.hitch(this, function(){
				this.set("prevNode", this.curNode);
				this.set("curNode", null);
			}), 0);

			if(this._justMouseDowned){
				// the mouse down caused a new widget to be marked as active; this blur event
				// is coming late, so ignore it.
				return;
			}

			// If the blur event isn't followed by a focus or touch event then mark all widgets as inactive.
			if(this._clearActiveWidgetsTimer){
				clearTimeout(this._clearActiveWidgetsTimer);
			}
			this._clearActiveWidgetsTimer = setTimeout(lang.hitch(this, function(){
				delete this._clearActiveWidgetsTimer;
				this._setStack([]);
			}), 0);
		},

		_onTouchNode: function(/*DomNode*/ node, /*String*/ by){
			// summary:
			//		Callback when node is focused or mouse-downed
			// node:
			//		The node that was touched.
			// by:
			//		"mouse" if the focus/touch was caused by a mouse down event

			// ignore the recent blurNode event
			if(this._clearActiveWidgetsTimer){
				clearTimeout(this._clearActiveWidgetsTimer);
				delete this._clearActiveWidgetsTimer;
			}

			// compute stack of active widgets (ex: ComboButton --> Menu --> MenuItem)
			var newStack=[];
			try{
				while(node){
					var popupParent = domAttr.get(node, "dijitPopupParent");
					if(popupParent){
						node=registry.byId(popupParent).domNode;
					}else if(node.tagName && node.tagName.toLowerCase() == "body"){
						// is this the root of the document or just the root of an iframe?
						if(node === win.body()){
							// node is the root of the main document
							break;
						}
						// otherwise, find the iframe this node refers to (can't access it via parentNode,
						// need to do this trick instead). window.frameElement is supported in IE/FF/Webkit
						node=winUtils.get(node.ownerDocument).frameElement;
					}else{
						// if this node is the root node of a widget, then add widget id to stack,
						// except ignore clicks on disabled widgets (actually focusing a disabled widget still works,
						// to support MenuItem)
						var id = node.getAttribute && node.getAttribute("widgetId"),
							widget = id && registry.byId(id);
						if(widget && !(by == "mouse" && widget.get("disabled"))){
							newStack.unshift(id);
						}
						node=node.parentNode;
					}
				}
			}catch(e){ /* squelch */ }

			this._setStack(newStack, by);
		},

		_onFocusNode: function(/*DomNode*/ node){
			// summary:
			//		Callback when node is focused

			if(!node){
				return;
			}

			if(node.nodeType == 9){
				// Ignore focus events on the document itself.  This is here so that
				// (for example) clicking the up/down arrows of a spinner
				// (which don't get focus) won't cause that widget to blur. (FF issue)
				return;
			}

			// There was probably a blur event right before this event, but since we have a new focus, don't
			// do anything with the blur
			if(this._clearFocusTimer){
				clearTimeout(this._clearFocusTimer);
				delete this._clearFocusTimer;
			}

			this._onTouchNode(node);

			if(node == this.curNode){ return; }
			this.set("prevNode", this.curNode);
			this.set("curNode", node);
		},

		_setStack: function(/*String[]*/ newStack, /*String*/ by){
			// summary:
			//		The stack of active widgets has changed.  Send out appropriate events and records new stack.
			// newStack:
			//		array of widget id's, starting from the top (outermost) widget
			// by:
			//		"mouse" if the focus/touch was caused by a mouse down event

			var oldStack = this.activeStack;
			this.set("activeStack", newStack);

			// compare old stack to new stack to see how many elements they have in common
			for(var nCommon=0; nCommon<Math.min(oldStack.length, newStack.length); nCommon++){
				if(oldStack[nCommon] != newStack[nCommon]){
					break;
				}
			}

			var widget;
			// for all elements that have gone out of focus, set focused=false
			for(var i=oldStack.length-1; i>=nCommon; i--){
				widget = registry.byId(oldStack[i]);
				if(widget){
					widget._hasBeenBlurred = true;		// TODO: used by form widgets, should be moved there
					widget.set("focused", false);
					if(widget._focusManager == this){
						widget._onBlur(by);
					}
					this.emit("widget-blur", widget, by);
				}
			}

			// for all element that have come into focus, set focused=true
			for(i=nCommon; i<newStack.length; i++){
				widget = registry.byId(newStack[i]);
				if(widget){
					widget.set("focused", true);
					if(widget._focusManager == this){
						widget._onFocus(by);
					}
					this.emit("widget-focus", widget, by);
				}
			}
		},

		focus: function(node){
			// summary:
			//		Focus the specified node, suppressing errors if they occur
			if(node){
				try{ node.focus(); }catch(e){/*quiet*/}
			}
		}
	});

	var singleton = new FocusManager();

	// register top window and all the iframes it contains
	ready(function(){
		var handle = singleton.registerWin(winUtils.get(win.doc));
		if(has("ie")){
			unload.addOnWindowUnload(function(){
				if(handle){	// because this gets called twice when doh.robot is running
					handle.remove();
					handle = null;
				}
			});
		}
	});

	// Setup dijit.focus as a pointer to the singleton but also (for backwards compatibility)
	// as a function to set focus.   Remove for 2.0.
	dijit.focus = function(node){
		singleton.focus(node);	// indirection here allows dijit/_base/focus.js to override behavior
	};
	for(var attr in singleton){
		if(!/^_/.test(attr)){
			dijit.focus[attr] = typeof singleton[attr] == "function" ? lang.hitch(singleton, attr) : singleton[attr];
		}
	}
	singleton.watch(function(attr, oldVal, newVal){
		dijit.focus[attr] = newVal;
	});

	return singleton;
});